Engine runs rough a few minutes after start up and then quits. - Ford Mustang Forum
 
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post #1 of 13 (permalink) Old 10-16-2007 Thread Starter
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Engine runs rough a few minutes after start up and then quits.

I have a problem with my car and I have had it for a few months. Upon starting the car it runs fine for about 30 seconds to a minute or so. Then, usually after I have started driving it, it starts missing and jumping like it is flooding or something. After driving it for a mile or so and running it at a high rpm it stops and runs fine. I have read about the oil separators and I am wondering if this may be the problem. I dont have a separator on it right now but going to install one tomorrow. Any ideas out there about what could be going on here? It happens all the time, even if the car is still warm the next time I drive it.
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post #2 of 13 (permalink) Old 10-16-2007
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I don't know about mustangs, but my friend's dodge truck did the same thing. We ended up taking it to a shop and he wasn't running on all 8 cylinders...

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post #3 of 13 (permalink) Old 10-16-2007
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Few things to check. Make sure all your plugs are torqued to 25 lb-ft. Clean your MAF sensor and throttle body. Check for intake leaks downstream of the MAF. Could also be a plugged injector or dirty fuel filter. You could have some carbon buildup, so a can of Seafoam in the gastank couldn't hurt either. Last thing would be a possible failing throttle position sensor.

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post #4 of 13 (permalink) Old 10-17-2007 Thread Starter
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Quote:
Originally Posted by stlwagon View Post
Few things to check. Make sure all your plugs are torqued to 25 lb-ft. Clean your MAF sensor and throttle body. Check for intake leaks downstream of the MAF. Could also be a plugged injector or dirty fuel filter. You could have some carbon buildup, so a can of Seafoam in the gastank couldn't hurt either. Last thing would be a possible failing throttle position sensor.
I have changed plugs, from the problem I had getting the stuck plug out when installing my cams. The problem has persisted with both the stock tb and the BBK. It was doing this before any of these things were changed. If I had a intake leak or the plugged injector or dirty filter or the throttle position sensor problem wouldnt it do what it is doing all the time, not just for a little while after starting up the car?
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Could a leaking injector leak fuel into a cylinder when the engine is not running and then when it is cranked it has all this extra fuel in the cylinder it has to clear out? The baffling thing to me is that the car starts and runs great initially and then about 2 minutes later is when the problem starts and once I get some runing time on the engine, about 30 secs to a minute, is clears up and doesnt happen again until it sits for a while and I start it and it happens all over again. If I run the engine at a higher rpm initially it clears up faster. It just seems that the engine is trying to flood and once I get what seems like the extra gas out of it, it runs great. The car is running rich at idle. I have a Bamachip tune and the smell of gas is strong when idleing (and the exhaust pipes are black and sutty looking) especially just after starting it. I have been living with the problem for months now, but is really aggravating.
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post #6 of 13 (permalink) Old 10-17-2007
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Could it possibly be the fuel pump issue? My car actually ran out of gas twice because of it. No problems since they replaced the fuel pumps.

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post #7 of 13 (permalink) Old 10-17-2007
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Check your TB voltage to ensure it's between 1.19 and 1.31 volts.

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post #8 of 13 (permalink) Old 10-17-2007
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Quote:
Originally Posted by rhbuff6622 View Post
I have changed plugs, from the problem I had getting the stuck plug out when installing my cams. The problem has persisted with both the stock tb and the BBK. It was doing this before any of these things were changed. If I had a intake leak or the plugged injector or dirty filter or the throttle position sensor problem wouldnt it do what it is doing all the time, not just for a little while after starting up the car?
I forgot about the plug nightmare!

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post #9 of 13 (permalink) Old 12-17-2007 Thread Starter
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I recently had to have my car dyno tuned because it wouldnt pass emissions testing here in TN. After the tune, this problem has gone away but has been replaced by a more agrivating one. The idle rpm is erratic. It will sit and lope nicely for a little while with the cams talking to ya nicely and then just change, normally idle rpm going up and then back down and up again. Not a big change at all but never the less it is erratic. The car dyno'ed at 339.9 rwhp and runs GREAT except for this problem. The engine light stays on all the time, which is not unusual, its been coming on and off ever since I started modifying the engine. It just normally goes off by itself after a couple of days. There are no trouble codes on my diablo. Think maybe this is the same problem I had before, just manifesting itself differently after the dyno tune? Fuel pump maybe? I also seem to notice a little rpm change just cruising like the car is surging just a little. I am going to post the dyno sheets as soon as I get a scanner, the A/F ratio seems pretty erratic on the pulls to me. Any ideas guys? By the way, the car passes the emissions testing after the tune.
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With a good dyno tune your A/F should be almost a straight line. I had mine dyno tuned a couple weeks ago and it idles smooth at 750. with cams it might be a little lopie but still shouldn't surge. I would talk to the tuner and have him look at tweeking your tune.
I have a emission tune for mine which I load when it's time to have it done. and then back to the fun tune.


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I'm puzzled about the engine light.

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post #12 of 13 (permalink) Old 12-18-2007 Thread Starter
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With a good dyno tune your A/F should be almost a straight line. I had mine dyno tuned a couple weeks ago and it idles smooth at 750. with cams it might be a little lopie but still shouldn't surge. I would talk to the tuner and have him look at tweeking your tune.
I have a emission tune for mine which I load when it's time to have it done. and then back to the fun tune.
Our state now has the equipment to plug right into the computer and see what has been done to it. Mine didnt pass because there had not been enough run time hours on the car since the last time I reloaded the canned bama chips tune trying to get the car to run right before dyno tuning. That is what the guy told me anyway. I am not sure about the light either. It has crossed my mind that there may be a vacuum leak but the car just runs so darn good everywhere but at idle I don't see how it could have a vacuum leak and it doesnt do this all the time either. My gas milage dropped from a little over 20.4 mpgs to 18.4 mpgs after the tune or perhaps it may be the cold weather and the air being so much better. I dunno. It has also crossed my mind that the problem could be something with the cam phasers working with the cams, or the BBK Tb although the tuner said that my tb was the best running one he had worked with. Like most tuners I have talked to he isnt crazy about the BBK TB. He said that 98% of the ones they have tried to tune they couldnt get to work so they put the stock ones back on the cars. He said that if they work right that they help but most dont work right. He said that most of the ones he had worked with just stopped working, the throttle wouldnt respond at all.
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Quote:
Originally Posted by rhbuff6622 View Post
Our state now has the equipment to plug right into the computer and see what has been done to it. Mine didnt pass because there had not been enough run time hours on the car since the last time I reloaded the canned bama chips tune trying to get the car to run right before dyno tuning. That is what the guy told me anyway. I am not sure about the light either. It has crossed my mind that there may be a vacuum leak but the car just runs so darn good everywhere but at idle I don't see how it could have a vacuum leak and it doesnt do this all the time either. My gas milage dropped from a little over 20.4 mpgs to 18.4 mpgs after the tune or perhaps it may be the cold weather and the air being so much better. I dunno. It has also crossed my mind that the problem could be something with the cam phasers working with the cams, or the BBK Tb although the tuner said that my tb was the best running one he had worked with. Like most tuners I have talked to he isnt crazy about the BBK TB. He said that 98% of the ones they have tried to tune they couldnt get to work so they put the stock ones back on the cars. He said that if they work right that they help but most dont work right. He said that most of the ones he had worked with just stopped working, the throttle wouldnt respond at all.
I've had several tuners tell me the same about the TB. I even pulled it off at one point when I was getting a bunch of failsafe mode errors. It's back on there now though.

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