LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Rough idle and runs rich

Old 01-26-2015, 02:53 PM
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Rough idle and runs rich

Hi new member. I purchased a 1994 Z about 6 months ago and have been slowly fixing little issues with it. But since I have owned it the car has had a rough idle and running rich issue. Only getting up to 12 to 14 mpg and smell of gas out tailpipe. The cat has been removed it does have an exhaust leak were the cat was removed. I am getting no codes the opti spark, plugs, wires were replaced.
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Old 01-26-2015, 04:26 PM
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Re: Rough idle and runs rich

you still have 02's?

if you have a exhaust leak pre-02's, PCM reads lean and commands more fuel which = running rich
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Old 01-26-2015, 04:57 PM
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Re: Rough idle and runs rich

Best thing you can do is run a data log of the PCM while operating under the conditions you describe. One of us can review the data log and look for possible causes. Could be a faulty coolant temp sensor, the misfires themselves, as mentioned above exhaust leaks before the O2 sensor (or an open exhaust near the O2 sensor), problems with EGR, faulty O2 sensor or sensor wiring, etc.

Free software download..... all you need it to but a cable. Ready-made cable preferred to do-it-yourself, since the quality of the Chines-made components is becoming a problem.

And obviously, removing the cat is going to make the exhaust smell.
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