LOW RPM STUMBLE! FOR ALL THAT HAVE SOLVED OR HAVE FACTS INSIDE PLEASE! ?'s
#1
Registered User
Thread Starter
Join Date: Oct 1999
Location: Atlantic City, New Jersey (south jersey)
Posts: 418
LOW RPM STUMBLE! FOR ALL THAT HAVE SOLVED OR HAVE FACTS INSIDE PLEASE! ?'s
Okay... I have a 94 Z28. Right now it has Bosch Platinum Plugs and Taylor wires brand new Borg Warner Coil and GM wire. Anywhere from 1000-2500 RPM's it will stumble and hesitate badly.
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more please help
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more please help
#2
Hey, My opti did the same exact thing. Low RPM stumble only when warm but boy was it nasty sounding! Its pretty much a spark related problem but sounds like an Opti to me. Call Jason Cromer @ Sam Taylor for a new GM opti at a damn good price. 850-994-4277
#4
being you noticed that your stumble occurs around 180 degrees i would assume your O2 sensors are going. if you get a scanner...you will be able to see fairly easily if they are working properly. the reason i would suspect O2s is b/c the only real difference between open loop and closed loop functioning is when a car goes into closed loop...it starts to recieve feedback from the O2 sensors. this all happens around 140 degrees. my car has a bad idle and i guess a slight hesistation and i KNOW i have a bad O2. just havent gotten around to fixing my problem yet
#8
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
#10
Originally posted by CJ Black LS1 Z28 M6
shoebox
Can the ignition control module be replaced? The coild only has 500 miles on it.
shoebox
Can the ignition control module be replaced? The coild only has 500 miles on it.
Make sure you have checked the connection at the opti for any corrosion on the plug or down inside the connector on the opti, itself.
#12
My vote is to suspect O2s. Full throttle = Power Enrichment Mode. I think if > 80%(somewhere in that vincinity) throttle, O2 feedback is ignored by the PCM. So, if it runs well at WOT, but stumbles at part throttle, bad O2(s) is/are a distinct possibility.
#13
Re: LOW RPM STUMBLE! FOR ALL THAT HAVE SOLVED OR HAVE FACTS INSIDE PLEASE! ?'s
Originally posted by CJ Black LS1 Z28 M6
Okay... I have a 94 Z28. Right now it has Bosch Platinum Plugs and Taylor wires brand new Borg Warner Coil and GM wire. Anywhere from 1000-2500 RPM's it will stumble and hesitate badly.
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more please help
Okay... I have a 94 Z28. Right now it has Bosch Platinum Plugs and Taylor wires brand new Borg Warner Coil and GM wire. Anywhere from 1000-2500 RPM's it will stumble and hesitate badly.
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more please help
#14
Let me chime in, about 3 weeks ago I installed 30# SVO injectors to compensate for the 94% duty cycle my stock ones were giving me with my LT4 conversion. When we did a scan we noticed that my MAP reading was high and the left 02 sensor failed, well I installed new 02 sensors and the car still feels like it wants to stall when I start it. I contacted Bryan @ PCMforless and he said he viewed the scan and told me one of the fuel cells is dumping a large amount of fuel in, he said that I might have un-metered air going in somewhere when I did the injector install, perhaps I didn't seat one of the injectors fully. What do you gurus think? Also, would it be a good idea to get new spark plugs, I'm running NGK TR55VX plugs, is there a better plug to run. Any help is greatly appreciated. I'm getting very frustrated to where it's not fun driving anymore.
#15
I had a low RPM stumble to about 1800 rpms? When it hit 1800 rpms it felt like somone turned on a switch to make it run better again. I also had a high rpm miss (bad!), even in first gear my car would run past 5200 rpm's. The low rpm stumble was the EGR system. The high rpm miss was the coil. Lucky I got them my first try huh?