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Last year I installed a Kenne Bell supercharger in my 2006 GT. There were a few hiccups along the way, but overall it seemed to go pretty well. However, the first morning I drove the car, I nearly got into an accident when I pulled out into traffic and the engine bogged and sputtered, then finally took off, sending me sideways. I immediately contacted Kenne Bell and started trying to troubleshoot the problem.
I am going to give a detailed history of what I went through before revealing what we finally discovered. I have had posts on this issue in the past year, both here and on Mustangforums.com, so some might find this whole thread familiar.
When I first ordered the supercharger, it was sort of a special deal, which I won't get into detail about. The result was a little confusion about the intake setup. I ordered it with the 90mm MAF and cannister filter, and it showed up with the "california emissions" stock airbox setup. I figured I would get it installed and then work out the problems later. The supercharger arrived way sooner than I expected, right before the Memorial day weekend, so I was a little rushed. I had just had the gears changed from 4.10s to 3.73s and didn't even have 10 miles on them, and because I ordered the polished supercharger, I wanted to powdercoat the valve covers. When the gears were being done, I had my friend install a bung for the wideband gauge as well. So that first day, I started by pulling the valve covers to get them prepped. While they were at my friend's shop getting powder coated, I started the install. I got the covers back just before the weekend (Friday at 6 pm) and now I had everything I needed to have it running before Monday.
Everything went together pretty well, and I was very meticulous in doing it by the book. Once all done, I fired it up and drove it out of boost to make sure it ran right, and all seemed perfect. I got into boost a couple quick times and then pulled back into the garage. I then finished the install on the AF gauge and took it for another drive to make sure all was well. I got into boost and the AF was almost 14:1! Not good. It was Sunday, so I had to wait til Monday to call KB and figure out what was wrong.
So I got in touch with them, and when talking, I asked if maybe the snafu with the intake setup was the cause, and sure enough, they had sent the tune for the 90mm MAF, but I had the factory MAF with the Diablo MAFia. They sent the right intake setup out, and a few days later it arrived. I swapped it out, and since I had the right tune already, I hit the road. The AF was now a nice 11.5ish at WOT, and I figured all was well.
The next morning, I drove the car cold, and that was when the bogging was first noticed. I gave it gas and it bogged severely, then took off. The AF gauge read off the chart lean.
I contacted KB and the first thing they recommended was checking for vacuum leaks. I went over the install from start to finish and didn't see anywhere that I could have added a vacuum leak. After describing the problem on the forums, it was suggested that the MAF was probably bad, so I had KB send me a new one. No change.
At this point I had another problem. Once the engine was very warm, the power was just GONE. I opened the intercooler reservoir, and it didn't seem like there was any flow of water. So I pulled the bumper off again and when I loosened the pump intake line, the vaporlock released and the pump started pumping. I had been running without an intercooler working! The next day, the pump wasn't running again, so I had to pull the bumper AGAIN, and re-route the intake line to the pump to prevent vapor lock, and that fixed the issue.
So now it was running well when warm, but when cold it was almost undriveable. Because the AF gauge was reading lean when it bogged, we suspected either we didn't have enough spark and maybe when cold we were dumping unburnt fuel into the exhaust, which would read lean because the O2 sensors look for unburnt oxygen, they don't actually read the fuel to air mix. If unburnt mix goes past the o2 sensor, it will read lean. So I swapped back to my factory plugs after re-gapping them. No change.
Now I was noticing that the idle was going whacky under certain driving conditions. It would go as low as 200 rpm and even stall sometimes. Now I suspected a throttle body issue. I cleaned the TB and inspected it, but no change. I finally bought a used one from someone and swapped it out. No change.
Then I went on the highway, and it was surging. Also, when I pushed in the clutch, it would stall. This was all very discouraging, and at this point I started to question if it was worth it to buy the supercharger. I did some research, and there is a TSB for the 05-06 Mustang GT with the fuel pump after highway use where air bubbles will form around the intake of the pump and cause it to stall when the throttle is released. I figured for sure this was the problem, so I acquired a used fuel pump from a forum member, and swapped it out. At first I thought it helped, but further testing proved it was no change.
So I got a little more serious and picked up a Diablosport tuner to use for datalogging. The same week I bought it, the tuner at Kenne Bell, Ken Christly, sent me an SCT X3 tuner with some tunes to try out, and some instructions on what to datalog for him to check things out. One of the things he tried was to make it run in closed loop when cold, to see if the feedback from the O2 sensors would help ease the bogging issue. Normally when cold, it runs purely on the MAF table for AF ratio, and the PCM can't see if anything is wrong. He also richened the mixture a little. Unfortunately, while the tunes seemed to help a little, it wasn't solving the problem. Ken was telling me there was no way the tune was the problem as they had this very same tune on thousands of mustangs and never saw this problem - it had to be mechanical.
The problem I was having was any mechanic I took it to told me it had to be in the tune. I disagreed and continued to troubleshoot it on my own. During datalogging, I spotted a point where it bogged down and the fuel pressure dropped significantly. I figured this had to mean it was a fuel delivery issue, so I started looking at it that way. I changed the fuel filter - no change. I then picked up a set of used 39lb injectors and swapped them all out - no change. When doing the injector swap, I found that the fuel line from the drivers side to the passenger side rails was pinched a little and replaced it with a new fuel line, which did improve the difference in Long Term Fuel Trims from left to right bank. Still no change on the bogging. I also played with the Boost-a-Pump, even going so far as to remove it and drive out of boost the next morning, with no change. Aside from changing the Fuel pressure sensor, which looked like it was reading fine, or the fuel pump driver module, which is solid state and unlikely to allow the car to run at all if faulty, I had done about all I could on the fuel side.
We turned our attention back to vacuum. I borrowed a good engine smoker, and hooked it up. Immediately, we discovered a huge vacuum leak behind the supercharger. Turned out there was a bolt hole in the back of the intake plenum where it bolts to the supercharger that didn't get a good gasket from the factory. After talking to KB about it, I pulled the supercharger and pulled off the plenum, added new gasket maker and put it back together. I smoked the engine excessively, and found a couple pinhole leaks that I fixed up. I was convinced that was the problem.
I gave the gasket maker time to set, then took it for a drive. Still bogged when I gave it gas before the engine was warm. The next morning, I smoked the engine while it was stone cold, and still no visible vacuum leaks. Not a vacuum issue as far as I was concerned.
I had about run out of options and was getting deperate. I talked to Ken at Kenne Bell again and reviewed everything I had done to date. He noticed that I was still running the HT0 plugs and recommended I try the Brisks. They had seen some issues with the HT0's. So I bought a set of Brisks and tried them out. No change.
About 2 months had passed, and I was starting to think that my engine just wasn't going to run right when cold. I decided to try to adjust the tune where I could and see if it made a difference. I had been running the test tune that was a little rich, and the LTFT's were always at -18 to -12 %, indicating that the tune was very rich. So with the Diablo tuner, I downloaded the tune from the PCM and adjusted the MAF table by 3%. I drove around, engine warm, and the LTFTs were now very nice. However, when I gave it a little gas pedal, it was leaning out and bogging a little, even though the engine was warm! I reinstalled the original Kenne Bell standard tune, and sure enough, when warm, it was bogging on accelleration. I was starting to lose it.
The next week, we had a big mustang show, and we got a mobile dyno in. I was first in line. I put down 440 hp at 6300 rpm and 401 ftlbs of torque. The curve was excellent and power was spot on for what I expected. That confused the issue even more because if it is making good power, then what the heck could be wrong? I ended up packing the car into storage a few weeks later for the long cold winter.
This spring, I took the car out, and started fresh on the troubleshooting. Through the course of the last summer, I had discovered that the 3.73 gears I had installed were noisy, and I wanted to get at least one thing working right, so I went to a mechanic who had a good reputation for doing rear ends, and had him do it from scratch - new gears, new shims, everything. I paid a premium, but he had guaranteed he would make the rear end silent, and he did a fantastic job. That eased the burden a little, but I still had the issues of the bogging, and the highway driving.
Fixing the one major vacuum leak had really helped on the highway driving, at least on the surging side. Idle was still an issue, and on the highway it was a guarantee that pushing in the clutch was going to cause a stall. I contacted Ken Christly again and started talking about the issues. On a hunch, I mentioned that I did not have a factory bumper, and the Kenne Bell supercharger has the intake down in the passenger side bumper. On mine, a big vent right in front of it meant that the intake filter was exposed to direct airflow - something I figured was good. Ken immediately told me that it would cause turbulence in the MAF housing and wreak havoc on the fuel trims as the MAF would be all over the place.
I went out and got some aluminum sheeting and fabricated an air dam around the front and bottom of the filter. I took it on the highway and not only was it driving perfectly smooth and getting 27 mpg, the idle was perfect now at any speed.
Now I had all but the bogging problem solved. I reviewed what I had done to date to try to fix it: Tried 3 sets of plugs, replaced injectors, fixed vacuum leaks, replaced MAF sensor, replaced Throttle Body, Replaced fuel filter and fuel pump, and datalogged a ton. It just didn't make any sense. I was starting to think that maybe when I first installed the supercharger with the wrong MAF setup, perhaps the lean condition caused damage and burned a valve or something. So I took it to my friend's shop and just ahnded him the keys and told him to start over and let me know what he finds.
He datalogged a little and drove it a bit and called me and said "It acts like it doesn't have enough accellerator pump, if it had a carburator." I agreed, and that is one way I had been describing the problem to other mechanics. So I contacted Ken Christly at Kenne Bell again and asked if he could add more fuel at tip in on the tune. He was willing to help, even though he was convinced it was still a mechanical problem. He sent me a new tune a couple days later, and I loaded it up. Initially, it made a HUGE difference. However, after a while of driving, the fuel trims were getting way out of whack again, and when cold, it was just as bad as before.
I was about to hand the car over to a tuner to do a complete tune from scratch. Thing is, even after adjusting the tip in, the problem would come back, and seem to get worse. Of everything we had tried, nothing made complete sense.
So I gave the car back to my mechanic on Monday. He wanted to check a few things that I had already checked, just to see if I missed anything. Yesterday I went to pick it up, and he says "it just acts like there is a 3/8 inch vacuum leak after the MAF."
We popped the hood and he looks at the vacuum line going from the passenger valve cover to the intake tube (just before the Throttle Body). He says "Why did they do this? Is this right?" I tell him as far as I know it was like that from the factory. The PCV is on the drivers side and this passenger side must be where it can suck in air so that the PCV can suck all the evaporated oil and any gas fumes that blow by the pistons out of the crank case. He thinks about it for a second and asks if there is a valve in there. I tell him I would imagine so, but it must be above the little windage tray they have in the valve cover, so I didn't see anything when I pulled the valve covers. That was when it dawned on us. We baked the valve covers to powder coat them. There has to be a valve in there that allows air to go into the crank case (sucking in filtered air from the intake tube) but prevents air from coming back out. If the valve was damaged by baking the valve covers, then it would let air from the crank case into the intake tube, and in effect be a 3/8 inch vacuum leak.
So when idling, the throttle blades are almost totally closed. There is little vacuum in the intake tube, but on the other side of the throttle body, there is 20 inches of vacuum. When you give it gas, the throttle blades open and suddenly you have vacuum in the intake tube, but vacuum drops on the other side of the throttle body (and in the manifold). So the PCV side is not sucking as much air from the crank case, but there is now vacuum in the intake tube. The passenger side crank case vent should have a valve to keep from having the higher pressure in the crank case from venting air back to the intake tube, which has low pressure when you first give it gas. Once the pressure equalizes, the PCV side is pulling air out of the crank case, and the vent side is letting air go in. However, if the valve is bad in the passenger side, it will act like a vacuum leak for a short time, causing the lean condition, and causing it to bog. When cold, the blow by is much worse, and much more air can come in, allowing it to really lean out and bog until the pressure stabilizes enough to no longer be a vacuum leak, which is when it finally takes off.
So with an "intermittent vacuum leak" like this, the short term fuel trims and long term fuel trims were all over the place, causing just poor running in closed loop mode. When going wide open throttle, the trims are ignored and the maf table is all it pays attention to, and it ran great.
All in all, the problem ended up being a bad vent valve in the valve cover - surely a result of baking the powdercoat on the valve cover. I closed off the 3/8 fitting on the intake tube and attached a basic crank case vent filter to the valve cover, and the problem is GONE. Fuel trims are always near zero now, the bogging is gone, and even cold it runs like it should. I am back to the standard Kenne Bell tune and all is well.
So I posted this not just to tell my long troubleshooting story, but also to warn people that powdercoating the valve covers is a bad idea. I didn't see a way to pull the vent valve on the passenger side, or even the PCV valve on the drivers side, and as far as I know, both could be a problem now. Since I just have an open vent on one side, the system still does what it needs to do - pull fumes out of the crank case and relieve pressure in there from blow-by.
I am going to give a detailed history of what I went through before revealing what we finally discovered. I have had posts on this issue in the past year, both here and on Mustangforums.com, so some might find this whole thread familiar.
When I first ordered the supercharger, it was sort of a special deal, which I won't get into detail about. The result was a little confusion about the intake setup. I ordered it with the 90mm MAF and cannister filter, and it showed up with the "california emissions" stock airbox setup. I figured I would get it installed and then work out the problems later. The supercharger arrived way sooner than I expected, right before the Memorial day weekend, so I was a little rushed. I had just had the gears changed from 4.10s to 3.73s and didn't even have 10 miles on them, and because I ordered the polished supercharger, I wanted to powdercoat the valve covers. When the gears were being done, I had my friend install a bung for the wideband gauge as well. So that first day, I started by pulling the valve covers to get them prepped. While they were at my friend's shop getting powder coated, I started the install. I got the covers back just before the weekend (Friday at 6 pm) and now I had everything I needed to have it running before Monday.
Everything went together pretty well, and I was very meticulous in doing it by the book. Once all done, I fired it up and drove it out of boost to make sure it ran right, and all seemed perfect. I got into boost a couple quick times and then pulled back into the garage. I then finished the install on the AF gauge and took it for another drive to make sure all was well. I got into boost and the AF was almost 14:1! Not good. It was Sunday, so I had to wait til Monday to call KB and figure out what was wrong.
So I got in touch with them, and when talking, I asked if maybe the snafu with the intake setup was the cause, and sure enough, they had sent the tune for the 90mm MAF, but I had the factory MAF with the Diablo MAFia. They sent the right intake setup out, and a few days later it arrived. I swapped it out, and since I had the right tune already, I hit the road. The AF was now a nice 11.5ish at WOT, and I figured all was well.
The next morning, I drove the car cold, and that was when the bogging was first noticed. I gave it gas and it bogged severely, then took off. The AF gauge read off the chart lean.
I contacted KB and the first thing they recommended was checking for vacuum leaks. I went over the install from start to finish and didn't see anywhere that I could have added a vacuum leak. After describing the problem on the forums, it was suggested that the MAF was probably bad, so I had KB send me a new one. No change.
At this point I had another problem. Once the engine was very warm, the power was just GONE. I opened the intercooler reservoir, and it didn't seem like there was any flow of water. So I pulled the bumper off again and when I loosened the pump intake line, the vaporlock released and the pump started pumping. I had been running without an intercooler working! The next day, the pump wasn't running again, so I had to pull the bumper AGAIN, and re-route the intake line to the pump to prevent vapor lock, and that fixed the issue.
So now it was running well when warm, but when cold it was almost undriveable. Because the AF gauge was reading lean when it bogged, we suspected either we didn't have enough spark and maybe when cold we were dumping unburnt fuel into the exhaust, which would read lean because the O2 sensors look for unburnt oxygen, they don't actually read the fuel to air mix. If unburnt mix goes past the o2 sensor, it will read lean. So I swapped back to my factory plugs after re-gapping them. No change.
Now I was noticing that the idle was going whacky under certain driving conditions. It would go as low as 200 rpm and even stall sometimes. Now I suspected a throttle body issue. I cleaned the TB and inspected it, but no change. I finally bought a used one from someone and swapped it out. No change.
Then I went on the highway, and it was surging. Also, when I pushed in the clutch, it would stall. This was all very discouraging, and at this point I started to question if it was worth it to buy the supercharger. I did some research, and there is a TSB for the 05-06 Mustang GT with the fuel pump after highway use where air bubbles will form around the intake of the pump and cause it to stall when the throttle is released. I figured for sure this was the problem, so I acquired a used fuel pump from a forum member, and swapped it out. At first I thought it helped, but further testing proved it was no change.
So I got a little more serious and picked up a Diablosport tuner to use for datalogging. The same week I bought it, the tuner at Kenne Bell, Ken Christly, sent me an SCT X3 tuner with some tunes to try out, and some instructions on what to datalog for him to check things out. One of the things he tried was to make it run in closed loop when cold, to see if the feedback from the O2 sensors would help ease the bogging issue. Normally when cold, it runs purely on the MAF table for AF ratio, and the PCM can't see if anything is wrong. He also richened the mixture a little. Unfortunately, while the tunes seemed to help a little, it wasn't solving the problem. Ken was telling me there was no way the tune was the problem as they had this very same tune on thousands of mustangs and never saw this problem - it had to be mechanical.
The problem I was having was any mechanic I took it to told me it had to be in the tune. I disagreed and continued to troubleshoot it on my own. During datalogging, I spotted a point where it bogged down and the fuel pressure dropped significantly. I figured this had to mean it was a fuel delivery issue, so I started looking at it that way. I changed the fuel filter - no change. I then picked up a set of used 39lb injectors and swapped them all out - no change. When doing the injector swap, I found that the fuel line from the drivers side to the passenger side rails was pinched a little and replaced it with a new fuel line, which did improve the difference in Long Term Fuel Trims from left to right bank. Still no change on the bogging. I also played with the Boost-a-Pump, even going so far as to remove it and drive out of boost the next morning, with no change. Aside from changing the Fuel pressure sensor, which looked like it was reading fine, or the fuel pump driver module, which is solid state and unlikely to allow the car to run at all if faulty, I had done about all I could on the fuel side.
We turned our attention back to vacuum. I borrowed a good engine smoker, and hooked it up. Immediately, we discovered a huge vacuum leak behind the supercharger. Turned out there was a bolt hole in the back of the intake plenum where it bolts to the supercharger that didn't get a good gasket from the factory. After talking to KB about it, I pulled the supercharger and pulled off the plenum, added new gasket maker and put it back together. I smoked the engine excessively, and found a couple pinhole leaks that I fixed up. I was convinced that was the problem.
I gave the gasket maker time to set, then took it for a drive. Still bogged when I gave it gas before the engine was warm. The next morning, I smoked the engine while it was stone cold, and still no visible vacuum leaks. Not a vacuum issue as far as I was concerned.
I had about run out of options and was getting deperate. I talked to Ken at Kenne Bell again and reviewed everything I had done to date. He noticed that I was still running the HT0 plugs and recommended I try the Brisks. They had seen some issues with the HT0's. So I bought a set of Brisks and tried them out. No change.
About 2 months had passed, and I was starting to think that my engine just wasn't going to run right when cold. I decided to try to adjust the tune where I could and see if it made a difference. I had been running the test tune that was a little rich, and the LTFT's were always at -18 to -12 %, indicating that the tune was very rich. So with the Diablo tuner, I downloaded the tune from the PCM and adjusted the MAF table by 3%. I drove around, engine warm, and the LTFTs were now very nice. However, when I gave it a little gas pedal, it was leaning out and bogging a little, even though the engine was warm! I reinstalled the original Kenne Bell standard tune, and sure enough, when warm, it was bogging on accelleration. I was starting to lose it.
The next week, we had a big mustang show, and we got a mobile dyno in. I was first in line. I put down 440 hp at 6300 rpm and 401 ftlbs of torque. The curve was excellent and power was spot on for what I expected. That confused the issue even more because if it is making good power, then what the heck could be wrong? I ended up packing the car into storage a few weeks later for the long cold winter.
This spring, I took the car out, and started fresh on the troubleshooting. Through the course of the last summer, I had discovered that the 3.73 gears I had installed were noisy, and I wanted to get at least one thing working right, so I went to a mechanic who had a good reputation for doing rear ends, and had him do it from scratch - new gears, new shims, everything. I paid a premium, but he had guaranteed he would make the rear end silent, and he did a fantastic job. That eased the burden a little, but I still had the issues of the bogging, and the highway driving.
Fixing the one major vacuum leak had really helped on the highway driving, at least on the surging side. Idle was still an issue, and on the highway it was a guarantee that pushing in the clutch was going to cause a stall. I contacted Ken Christly again and started talking about the issues. On a hunch, I mentioned that I did not have a factory bumper, and the Kenne Bell supercharger has the intake down in the passenger side bumper. On mine, a big vent right in front of it meant that the intake filter was exposed to direct airflow - something I figured was good. Ken immediately told me that it would cause turbulence in the MAF housing and wreak havoc on the fuel trims as the MAF would be all over the place.
I went out and got some aluminum sheeting and fabricated an air dam around the front and bottom of the filter. I took it on the highway and not only was it driving perfectly smooth and getting 27 mpg, the idle was perfect now at any speed.
Now I had all but the bogging problem solved. I reviewed what I had done to date to try to fix it: Tried 3 sets of plugs, replaced injectors, fixed vacuum leaks, replaced MAF sensor, replaced Throttle Body, Replaced fuel filter and fuel pump, and datalogged a ton. It just didn't make any sense. I was starting to think that maybe when I first installed the supercharger with the wrong MAF setup, perhaps the lean condition caused damage and burned a valve or something. So I took it to my friend's shop and just ahnded him the keys and told him to start over and let me know what he finds.
He datalogged a little and drove it a bit and called me and said "It acts like it doesn't have enough accellerator pump, if it had a carburator." I agreed, and that is one way I had been describing the problem to other mechanics. So I contacted Ken Christly at Kenne Bell again and asked if he could add more fuel at tip in on the tune. He was willing to help, even though he was convinced it was still a mechanical problem. He sent me a new tune a couple days later, and I loaded it up. Initially, it made a HUGE difference. However, after a while of driving, the fuel trims were getting way out of whack again, and when cold, it was just as bad as before.
I was about to hand the car over to a tuner to do a complete tune from scratch. Thing is, even after adjusting the tip in, the problem would come back, and seem to get worse. Of everything we had tried, nothing made complete sense.
So I gave the car back to my mechanic on Monday. He wanted to check a few things that I had already checked, just to see if I missed anything. Yesterday I went to pick it up, and he says "it just acts like there is a 3/8 inch vacuum leak after the MAF."
We popped the hood and he looks at the vacuum line going from the passenger valve cover to the intake tube (just before the Throttle Body). He says "Why did they do this? Is this right?" I tell him as far as I know it was like that from the factory. The PCV is on the drivers side and this passenger side must be where it can suck in air so that the PCV can suck all the evaporated oil and any gas fumes that blow by the pistons out of the crank case. He thinks about it for a second and asks if there is a valve in there. I tell him I would imagine so, but it must be above the little windage tray they have in the valve cover, so I didn't see anything when I pulled the valve covers. That was when it dawned on us. We baked the valve covers to powder coat them. There has to be a valve in there that allows air to go into the crank case (sucking in filtered air from the intake tube) but prevents air from coming back out. If the valve was damaged by baking the valve covers, then it would let air from the crank case into the intake tube, and in effect be a 3/8 inch vacuum leak.
So when idling, the throttle blades are almost totally closed. There is little vacuum in the intake tube, but on the other side of the throttle body, there is 20 inches of vacuum. When you give it gas, the throttle blades open and suddenly you have vacuum in the intake tube, but vacuum drops on the other side of the throttle body (and in the manifold). So the PCV side is not sucking as much air from the crank case, but there is now vacuum in the intake tube. The passenger side crank case vent should have a valve to keep from having the higher pressure in the crank case from venting air back to the intake tube, which has low pressure when you first give it gas. Once the pressure equalizes, the PCV side is pulling air out of the crank case, and the vent side is letting air go in. However, if the valve is bad in the passenger side, it will act like a vacuum leak for a short time, causing the lean condition, and causing it to bog. When cold, the blow by is much worse, and much more air can come in, allowing it to really lean out and bog until the pressure stabilizes enough to no longer be a vacuum leak, which is when it finally takes off.
So with an "intermittent vacuum leak" like this, the short term fuel trims and long term fuel trims were all over the place, causing just poor running in closed loop mode. When going wide open throttle, the trims are ignored and the maf table is all it pays attention to, and it ran great.
All in all, the problem ended up being a bad vent valve in the valve cover - surely a result of baking the powdercoat on the valve cover. I closed off the 3/8 fitting on the intake tube and attached a basic crank case vent filter to the valve cover, and the problem is GONE. Fuel trims are always near zero now, the bogging is gone, and even cold it runs like it should. I am back to the standard Kenne Bell tune and all is well.
So I posted this not just to tell my long troubleshooting story, but also to warn people that powdercoating the valve covers is a bad idea. I didn't see a way to pull the vent valve on the passenger side, or even the PCV valve on the drivers side, and as far as I know, both could be a problem now. Since I just have an open vent on one side, the system still does what it needs to do - pull fumes out of the crank case and relieve pressure in there from blow-by.
