LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Please help car is stressing me out

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Old May 28, 2011 | 07:46 PM
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Default Please help car is stressing me out

First off the car is a 97 WS6 A4 73k miles with stock engine but has a few bolt ons like headers suspension etc.

Not all the time but sometimes it will not want to idle in gear and also at low rpms when you lug it it misses BAD. Once the rpms come up a bit it seems to smooth out and run great. Sounds like a 2 step taking off from a red light when its running bad like its on a lower rpm rev limiter then all of a sudden takes off like a rocket. The other night it wouldnt even start unless I pushed the gas pedal down a bit then wouldnt idle at all without giving it some gas. This morning wouldnt start or idle then all of a sudden it smoothed out and idled fine.

Put plugs in it and that didnt help, checked fuel pressure and that seems to be ok. Plug wires are not very old and look fine. Opti is also has very low miles on it and its new gm unitm as well as a new gm water pump when i put in the opti.

Seems weird to me that it does it at low rpms instead of high rpms for it to be a spark problem. I am thinking maybe its got an injector going bad and its either not opening at low rpm OR staying open at low rpm at times. Either that or maybe bad O2 sensors which dont have hardly any miles on them either.

Any advice would be greatly appreciated as I am so depressed about it I dont even feel like turning wrenches on it at this point. I really need to get this thing up and running right cause whats even more depressing is I need to sell it to pay off some debt.
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Old May 28, 2011 | 08:08 PM
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Originally Posted by Enforcerws6
First off the car is a 97 WS6 A4 73k miles with stock engine but has a few bolt ons like headers suspension etc.

Not all the time but sometimes it will not want to idle in gear and also at low rpms when you lug it it misses BAD. Once the rpms come up a bit it seems to smooth out and run great. Sounds like a 2 step taking off from a red light when its running bad like its on a lower rpm rev limiter then all of a sudden takes off like a rocket. The other night it wouldnt even start unless I pushed the gas pedal down a bit then wouldnt idle at all without giving it some gas. This morning wouldnt start or idle then all of a sudden it smoothed out and idled fine.

Put plugs in it and that didnt help, checked fuel pressure and that seems to be ok. Plug wires are not very old and look fine. Opti is also has very low miles on it and its new gm unitm as well as a new gm water pump when i put in the opti.

Seems weird to me that it does it at low rpms instead of high rpms for it to be a spark problem. I am thinking maybe its got an injector going bad and its either not opening at low rpm OR staying open at low rpm at times. Either that or maybe bad O2 sensors which dont have hardly any miles on them either.

Any advice would be greatly appreciated as I am so depressed about it I dont even feel like turning wrenches on it at this point. I really need to get this thing up and running right cause whats even more depressing is I need to sell it to pay off some debt.
Do you have an SES light on at all? I have never heard of an O2 causing a misfire. When the car starting misfire go unplug the injectors one at a time. (the miss should get worst) plug it back in and move onto the next one. If the miss does not get worst when u unplug it u have found ur cylinder with the problem.
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Old May 30, 2011 | 12:06 PM
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i got the codes pulled from it yesterday and it said bank 1 sensor 1 no activity so I guess ill be putting some o2 sensors in it. must be just loading it up with fuel on one bank which is making it not idle right and loading it up so it misses when coming off idle.
I have my fingers crossed that this fixes it
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Old May 30, 2011 | 01:59 PM
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Originally Posted by Enforcerws6
i got the codes pulled from it yesterday and it said bank 1 sensor 1 no activity so I guess ill be putting some o2 sensors in it. must be just loading it up with fuel on one bank which is making it not idle right and loading it up so it misses when coming off idle.
I have my fingers crossed that this fixes it
That does not automatically mean the O2 sensor is bad. Can you see the O2 sensor voltage with your scanner?

Al 95 Z28
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Old May 30, 2011 | 03:03 PM
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I have the same "miss" problem when cruising around at low rpms but there isn't an SES light. Plugs and wires were done last summer. Don't mean to hijack thread but was wondering what else could cause it
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Old Jun 4, 2011 | 10:05 PM
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Put on O2 sensor in it last night and drove it today and it never missed a beat and idled better then it has in a long time. I even lugged the engine at times on purpose to see it it would miss and it did not. Both the new sensor and the sensor from bank 2 seem to be reading about the same so looks like the bank 2 sensor is fine.

I guess since the sensor was not responding at all (according to the code it set) the pcm could not get that bank close enough to keep it running.

The SES light has been on in the car for a pretty long time but very few miles since I do not drive the car much at all. I have cleared it before but it has always come back on. Put some miles on the car today and it never came on.

I guess this may be another case of the Bosch O2 sensor curse.
I bet that sensor only had at most 500 miles on it even though it has been in the car for a few years. I even ran the car for awhile (forget how much but was a good amount of miles) with the new coated headers on it as recommended then replaced both sensors when i put the headers on a few years ago. But the stupid O2 did not want to work anyways.
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