Seriously odd syptoms
07-23-2003, 12:49 AM
#1
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Join Date: Apr 2000
Location: northwest suburbs
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Seriously odd syptoms
I will start from the top.
Started to demod the car for a different setup. Took off a set of ported heads and put a stock set back on. Car still has a Hotcam but that is the only performance mod which involves the problem.
After stock set goes on car is stumbly down low which is likely programming, but once you hit 4500 or more rpm the car will not rev it will hit a wall pretty much and then eventually rev past it and **** but it feels as if it is cutting out due to fuel or lack of spark. It will also pop out of the into low in the rpms if you do a sudden half throttle slap.
New symptom added in to the mix tonight. Driving along and the car just wants to do as it wishes. Car still dos items listed above but decideds it wants to jump around in rpm with the throttle still in the same position. It will fluctuate about 300 rpm up or down while evenly accelerating and once you let out of throttle to cost it will come down in rpm evenly but then drop 300 and come back to were it started to drop from. On top of the car will just drop the 0 rpm while driving, tach will show zero you loose power steering (just stating the tach is correct) and then it will come back on all by itself within a second or two. Only once have i had it completely die and i needed to rekey the car to get it started. I cannot see how the car is seeing 0 rpm and restarting on its own.
The items i have looked into or tried to check on so far have been fuel pressure (dead nuts 45psi), coil, ignition module, map sensor, scanned the car no codes and 02's are ranging properly, also tried another pcm with proper programming to see if it was the pcm acting up and tuning as well, it cleared up the low rpm stumbles a bit but it still hit at wall at 4500 rpm. As for it solving the car shutting off on its own i am not sure since it did that after the tried swapping the pcms.
Please help. Next step is to throw an opti at it. I believe there is more than one problem at hand. One being the car not revving past 4500 easily and the other being it shutting off at will.
Started to demod the car for a different setup. Took off a set of ported heads and put a stock set back on. Car still has a Hotcam but that is the only performance mod which involves the problem.
After stock set goes on car is stumbly down low which is likely programming, but once you hit 4500 or more rpm the car will not rev it will hit a wall pretty much and then eventually rev past it and **** but it feels as if it is cutting out due to fuel or lack of spark. It will also pop out of the into low in the rpms if you do a sudden half throttle slap.
New symptom added in to the mix tonight. Driving along and the car just wants to do as it wishes. Car still dos items listed above but decideds it wants to jump around in rpm with the throttle still in the same position. It will fluctuate about 300 rpm up or down while evenly accelerating and once you let out of throttle to cost it will come down in rpm evenly but then drop 300 and come back to were it started to drop from. On top of the car will just drop the 0 rpm while driving, tach will show zero you loose power steering (just stating the tach is correct) and then it will come back on all by itself within a second or two. Only once have i had it completely die and i needed to rekey the car to get it started. I cannot see how the car is seeing 0 rpm and restarting on its own.
The items i have looked into or tried to check on so far have been fuel pressure (dead nuts 45psi), coil, ignition module, map sensor, scanned the car no codes and 02's are ranging properly, also tried another pcm with proper programming to see if it was the pcm acting up and tuning as well, it cleared up the low rpm stumbles a bit but it still hit at wall at 4500 rpm. As for it solving the car shutting off on its own i am not sure since it did that after the tried swapping the pcms.
Please help. Next step is to throw an opti at it. I believe there is more than one problem at hand. One being the car not revving past 4500 easily and the other being it shutting off at will.
07-23-2003, 12:55 AM
#2
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Join Date: Sep 2002
Location: Chicagoland Area
Posts: 1,158
hmmmm interesting.
I also have the Hot Cam kit on stock heads. My car doesn't have that extensive of problems, however i do experience the same upper RPM "wall" that u are describing.
I replaced the Lifters due to bad vacuum pressure. It helped the problem somewhat, but it still seems to lose power up top.
I also have the Hot Cam kit on stock heads. My car doesn't have that extensive of problems, however i do experience the same upper RPM "wall" that u are describing.
I replaced the Lifters due to bad vacuum pressure. It helped the problem somewhat, but it still seems to lose power up top.
07-23-2003, 11:38 AM
#4
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Join Date: Apr 2000
Location: northwest suburbs
Posts: 326
Everyone really likes top normally just assume and say it is the opti. The one on the car has at most 10K on it. Was a new GM unit. Yeah i guess it could go bad but i really do not want to be just throwing parts at the car.
Keep the ideas coming. TIA
Keep the ideas coming. TIA
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