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3.8L V6 Rich issues.

3K views 15 replies 4 participants last post by  145566 
#1 · (Edited)
Hello guys, I dont mean to post alot, but im just wondering if anyone can help me out here. I have an 01 3.8l Mustang that has been running very rich for the past couple of months. I have cleaned the MAF sensor, cleaned the K&N air filter, even had to change a fuel hose that goes to the filter, along with the fuel filter cause it ruptured, due to pressure. I tried to test the fuel pressure regulator, so far it seems to be working normal according to my tests. I unplugged the vacuum line, and the pressure went up by about 10psi which ive been told is a sign of normal operation, but i did notice after a while the pressure rises to about 60psi which i know is too high, that is with the vacuum line plugged in as normal. I was told to perform a test on it with a vacuum gun, which im waiting on from mityvac, then ill perform the pressure test with it on the FPR. Today, when we turned the car on, it did not want to run. We were able to get it to run with the gas pedal pushed in. It would then die out when letting go, and the engine wasnt very responsive, like if it was drowning out in fuel, due to the black smoke from the exhaust. I checked for fuel pressure, and spark, which were good. I removed spark plugs, they were all fouled black. I replaced them, i know that they are not the problem and will foul again if the problem isnt fixed, but the vehicle was able to start better, but still difficult. It was now able to idle, but giving it gas and letting go would cause it to die. Also lots of black smoke from the exhaust, along with a rotten egg smell. Any ideas on what i should do now? Also to add on, if everything checks out good, could the PCM be the issue? I am able to connect with it through the scanner, but ive noticed that no check engine light comes on. Any way i can test the PCM if it comes to that?
 
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#2 ·
Update - the vehicle did not idle well this morning. I proceeded to disconnect the MAF sensor and the vehicle began to idle pretty good, did not stall. I tested the FPR with a vacuum gauge and the fuel guage and the regulator was functioning fine. The regular pressure was 55psi and removing the vacuum line it was about 10psi higher. Could the MAF be my issue?
 
#3 ·
IMHO, scrap the K&N and replace your MAF.... it is likely contaminated with oil from the K&N Which does nothing for the engine in terms of HP/TQ, MPG, etc.)
 
#8 ·
Update. So the new MAF sensor and OEM air filter came in. I replaced the old parts with these new ones. The vehicle is now running pretty normal, but idk if it's too soon to tell since I only had it on for about 30 mins. There was a slight misfire at time but it wasnt crazy. Fuel trims were close to 0% I'll post a pic. I suspect there is an evap leak somewhere though, since the scanner told me the fuel tank pressure was 0psi. Also the fuel rail pressure showed up as 66psi. It seemed to be running fine. Is that within spec?
 

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#9 ·
66 psi is too high. It should be around 40 psi with the engine running and 35-50 with the key on and but engine off. High fuel pressure will create a rich condition.
As far as the K&N goes, unless you recently put the K&N oil on it then it wasn’t likely the problem. The problem with the K&N gauze type filters is when people clean them and then re-oil them. If too much oil is added then the oil can get on the MAF wires causing problems. If the filter wasn’t sopping wet when you installed it then oil didn’t get on the MAF. Did your hand get wet when you put the filter in? Doubtful because new filters aren’t really wet to the touch.
 
#15 ·
Well I've had the stang on for about 30 minutes or more and so far the PIDS for fuel trims are +/- 3% on the short term. Fluctuates from positive to negative in that small range. The long term is pretty stable for 0%at bank 1 and -1% at bank 2. Is it too early to tell if the issue is fixed? I will attach a photo of the PIDS.

Edit. Both Ltfts went to the negatives but between -0.75 and like -2%. Guess we gotta give it time.
 

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