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Discussion Starter #1 (Edited)
Recently finished my 72mm build and after it driving pretty decent without a tune it just got pretty bad. Anything under WOT it bucks and stumbles, once it goes WOT its slowly clears up and takes off like it should with what it seems like no loss of power. Fuel pressure is set at 40, timing is 10 degrees spout out, Autolite 23's are gapped to .032" ,1 year old ford racing 9mm plug wires, 1 year old MSD 6al, brand new coil, stock distributor with a msd cap and rotor(should be changed but arent THAT bad). Plugs are greyish and seem fine. Fuel filter is fine, gas doesn't have water in it. This just happened all of the sudden basicly, drove it 60 miles out of state and back and wasent bad at all then over the weekend it started doing this but is now at a point where it is completely undrivable.
 

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Discussion Starter #3
The 60 mile out of state trip was to the tuner, had wastegate problems so I didnt get to far with the tune. I dont want to bring my tuner a car that cant even run, its not just the tune.
 

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Close your plug gap a bit, try your timing locked out at 15-16*, it seems like you are not running enough timing
 

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Close the gap to .020 or close to it then recheck the plugs. Drive the car and as soon as it starts to break up cut it off then pull the plugs to give you a better idea of whats going on.
 

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Discussion Starter #6 (Edited)
Well I tried for the hell of it to turn up the fuel pressure because it seemed a little lean and it was WAY worse couldn't even move 10 feet, so I brought it down to around 37-38 from 40 and it seems to drive perfect went around the block with no problems. Seems very odd that was the problem though so for the moment I am going to keep a eye on it and throw my buddies wideband on it this weekend to see whats really going on.

EDIT:Checked the timing and it was actually at 8 instead of 10 no clue how but it was.
 

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Discussion Starter #7 (Edited)
Of course screwing with the FP didnt actually fixed the problem. Same thing is going on now but if I can manage to get it to around 3500 rpm it just drives like normal. Thinking the pickup inside of the distributor could be shot. Also if I hold the throttle in a certain spot say 2k, it will stay there for a few seconds then wander up and down not really like its breaking up though just reving up and down. Any ideas?
 

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Discussion Starter #9
Threw on a set of plug wires didn't fix it. So I was reading on here that the EGR valve could be stuck wide open or completely. While it was running I unplugged the vacuum line to the EGR and it drove away perfectly fine, it has actually never ran better then this untuned. Left the line unplugged and capped it. Now I just have to figure out how to get these headers to seal up and I'll be all set.
 

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Discussion Starter #10
Well the EGR unplugged didnt fix the problem its still there just havent replied for awhile. Ive now changed, coil,cap and rotor, plugs, wires, by passed the 6al, put in a new distributor and tfi module still the same problem. When it is breaking up the boost/vaccum gauge goes to 0 and bounces around some if that matters. Also if it is stumbling I can shut the car down and start it back up and it wont do it again for about 20 seconds or so. Any clues?
 

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Im not sure if this is any help but my brother has an mass air 86 that when it was cold, it ran fine. after a few miles it would start bucking. It would start at higher rpms and then gradually go lower as you would drive it. If you shut it off for a minute then it would run fine for a little bit and start all over again. turned out to be the computer. Got a new one and put on hundreds of trouble free miles since then. Just some ideas. Im not sure if your car is acting the same. Also, a friend of mine just bought a 92 gt with a single turbo setup and after owning it for a few months it starting running badly bucking around and the boost guage was all over and you could hear the wastegate slamming shut and opening. We realized as long as you keep the tank over half full it runs fine. Im assuming that fuel was sloshing past the pickup or somehting broke inside the tank. Just some ideas Hope it helps!!
 

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Maybe try clearing the KAMRFs. That 60mi trip would have given the ecc enough time for adaptive learning to occur. Could have been rich at cruise speed and now the eec is pulling fuel. Try disconnecting the battery and holding the brake pedal down for 1 min to clear the eec's memory. Its worth a shot.
 

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Discussion Starter #15
Well I just tried something new. Put it on a jack to see if it would do the same thing while just sitting. It did the same thing it would when driving down the street. I already tried diconnecting the mass air meter(pmas 3" pro tube) and it just idled crappy but I never tried driving it unplugged. Did the same thing on jackstands and it didnt seem to do it. Took it up the street and it was fine, got back to the driveway plugged it in and went back up the street about 30 seconds after plugging it back in it did the same thing. Top of the street unplugged it ran fine. So now Iam figuring its the mass air meter or possibly the wiring.
 

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Discussion Starter #16
Tried another thing to make sure thats the problem. Put the rear on a jack and had my dad put it in 4th so it had a load on it, held it at a certain rpm until it fell on its face. Right in the middle of it breaking up I unplugged the meter and it reved to the moon. Sounds like the mass air is junk right?
 

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Discussion Starter #17
Ok, called pmas today and they told me what I was telling them sounded like the meter was fine and I have other issues. Baisicly what they said was because the car is untuned and both o2 sensors are in one downpipe my fuel curve is all over the place(no wideband) which is deff what it seems like to me. So my plan is to unplug the o2 sensors and just run off the mass air meter and see what happens. The car is getting tuned as soon as I get all this straightend out. Already talked to the tuner and he can tune it without the o2 sensors. Anyone running no o2 sensors out there?
 

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I'm fighting this same exact issue right now - my car has been tuned but it's a hit or miss everytime you turn the key. 1 minute it runs perfect - 5 minutes later, runs like #### and will not move under 2000 rpms, vacuum goes to 0 and the popping and stumbling starts. I just swapped a PCM and thought that fixed it but I just fired it up a few hours ago (after just sitting all night) no go.

I think mine might be wiring but i've ran all the tests I can possible find to do and they pointed to a bad PCM - swapped it and, again, no go.
 

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Discussion Starter #20
Completely forgot about this thread. Here is the update:

Turns out the problem was the fact my o2 sensors were in the same downpipe just like PMAS said. Unplugged them and it ran perfect, just got it tuned a few weekends ago and it runs great. Very happy with the turbo over the s trim.
 
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