Wont run below 3000 rpm or it sputters and dies
10-30-2011, 06:54 PM
#1
Wont run below 3000 rpm or it sputters and dies Backstory: always have had a little bit of a low rpm stumble below 1000 rpm ever since I put this motor in with an 88k mile coil, makes it very difficult for anyone other than me to drive, this was 3 years and 10,000 miles ago. Last sunday and this sunday it seemed to have a little pop out of the exhaust every couple seconds, and last weekend it started having a little miss in the low rpms, but today was worse. Today put in a Walbro 255gph fuel pump, closed the hood, drove 30 minutes to the track and did a total of 4 runs. Ive been kinda plagued by missing 4th the past 3 times at the track missing 4th maybe 5 out of 15 runs, either hitting 2nd or the spot right between 4th and 2nd, but always feeling it and letting off the throttle before killing it.
All day today I kinda faught a low rpm stumble through the 60', it felt like it was only running on 6 or 7 cylinders while I would launch, then it would kick back to normal at around 4000 and run hard to the end. It idled fine at 1000, but danced the needle a little from 900-1100. After the last run (missed 4th again, what a suprise!) it felt really shitty driving to the timeslip booth, but I was able to get it to my spot without problem. Went to start it 20 minutes later, wouldnt start. 10 more minutes of dicking with it it BARELY started, wouldnt go above 500 rpm no matter how much I feathered the throttle. Smelled really rich out the exhaust, backfired through the intake a few times, with the MAF unplugged, off the car, plugged in, no matter what. FINALLY got it to start with the MAF unplugged by playing with the throttle to get it to 3000 rpm and it felt decent if I held the throttle there, it idled long enough for me to go under the hood and put the intake back on and plug the MAF back in, then I tried to leave real fast before it died but I had to bring the throttle to 4000 in order to get it moving, or it would just bog so hard it would almost stall, even with the throttle wide open. Drove the whole ******* way home keeping the rpms above 3000, burning the **** out of my clutch every time I hit a light or a stop sign because it wouldnt go from a stop unless I brought the rpms to 5000 and feathered the clutch causing it to chatter by the end, almost stalling in every intersection, but made it home. Oil pressure is fine, voltage guage is fine, temperature is fine, no knocks or ticks.
I have 2 theories: 1 is that the 255gph fuel pump is too much for the stock regulator, causing too much fuel to be put into the motor at low rpms, hence why it only runs at 3-4000 or above.
2 is that the coil or ICM is on the way out. I dont think it could be the opti because failure usually is seen in a high rpm miss.
Anybody have any ideas? Vacuum leak? Burned valve? Something bad inside? SO PISSED
DA today was -1500 yet I could only muster a best of 12.7 at 108, and was expecting a 12.4 at 111 because it sucked so bad before the 330'.
Thats my last run, me in the left lane, showing the shitty 60' due to the low RPM miss, but also showing how hard it runs after that stops. I HAD HIM, I WAS A CAR AHEAD AND THEN MISSED 4th!!! Also you can clearly see where I missed 4th and lost the race
to a full exhaust, LS6 intake, dyno tuned 00 trans am M6. Video to follow, I havnt seen it yet but I suspect you will be able to hear the miss and the missed shift. I have ET streets on salad shooters with a race weight of 3185, he has 315 sumikomos with a race weight of 3700. I normally do 1.84 60's
All day today I kinda faught a low rpm stumble through the 60', it felt like it was only running on 6 or 7 cylinders while I would launch, then it would kick back to normal at around 4000 and run hard to the end. It idled fine at 1000, but danced the needle a little from 900-1100. After the last run (missed 4th again, what a suprise!) it felt really shitty driving to the timeslip booth, but I was able to get it to my spot without problem. Went to start it 20 minutes later, wouldnt start. 10 more minutes of dicking with it it BARELY started, wouldnt go above 500 rpm no matter how much I feathered the throttle. Smelled really rich out the exhaust, backfired through the intake a few times, with the MAF unplugged, off the car, plugged in, no matter what. FINALLY got it to start with the MAF unplugged by playing with the throttle to get it to 3000 rpm and it felt decent if I held the throttle there, it idled long enough for me to go under the hood and put the intake back on and plug the MAF back in, then I tried to leave real fast before it died but I had to bring the throttle to 4000 in order to get it moving, or it would just bog so hard it would almost stall, even with the throttle wide open. Drove the whole ******* way home keeping the rpms above 3000, burning the **** out of my clutch every time I hit a light or a stop sign because it wouldnt go from a stop unless I brought the rpms to 5000 and feathered the clutch causing it to chatter by the end, almost stalling in every intersection, but made it home. Oil pressure is fine, voltage guage is fine, temperature is fine, no knocks or ticks.
I have 2 theories: 1 is that the 255gph fuel pump is too much for the stock regulator, causing too much fuel to be put into the motor at low rpms, hence why it only runs at 3-4000 or above.
2 is that the coil or ICM is on the way out. I dont think it could be the opti because failure usually is seen in a high rpm miss.
Anybody have any ideas? Vacuum leak? Burned valve? Something bad inside? SO PISSED
DA today was -1500 yet I could only muster a best of 12.7 at 108, and was expecting a 12.4 at 111 because it sucked so bad before the 330'.
Thats my last run, me in the left lane, showing the shitty 60' due to the low RPM miss, but also showing how hard it runs after that stops. I HAD HIM, I WAS A CAR AHEAD AND THEN MISSED 4th!!! Also you can clearly see where I missed 4th and lost the race
to a full exhaust, LS6 intake, dyno tuned 00 trans am M6. Video to follow, I havnt seen it yet but I suspect you will be able to hear the miss and the missed shift. I have ET streets on salad shooters with a race weight of 3185, he has 315 sumikomos with a race weight of 3700. I normally do 1.84 60's Last edited by bufmatmuslepants; 10-30-2011 at 07:01 PM.
10-30-2011, 11:34 PM
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Is it throwing any codes? Bad maf? IAC? Check the fuel pressure just because it is new doesn't make it right. Hook up a scanner look at the datastream and the TPS.
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04-05-2018, 11:08 AM
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Starts to sputter and won’t go over 3000rpm and then cut out and now won’t start. I have a 1997 Camaro z28 and wouldn’t go over 3000rpm and sputters really bad at 3000rpm then died and now won’t start. It’ll turn over but won’t fire. Any ideas on what could be the issue?? Also isn’t throwing any codes at all and was also smoking a little bit I just had the head gasket replaced about 2 weeks ago. It’s also bored 30 over on the heads I was told when the gasket was redone. Any help will be very appreciated
Last edited by 97z28-93; 04-05-2018 at 11:17 AM.
