'91 L98 6-Speed Running Rich

I have a '91 L98 w/ 84k that I recently changed the ignition module, cap, rotor, wires, plugs, with no engine codes and the thing is still running very rich.. can smell it. It has also recently stalled a few
times on me and I cannot start it until I let it sit for a few minutes, almost like it's flooded. The idle also fluctuates frequently between 800-1000 rpms at idle. Someone had suggested a new EGR valve. Any suggestions would be appreciated. Thanks.
Eric
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You may have a sensor telling the computer that the engine is running cold and it is in effect choking it (adding more fuel). If that is so it will eventually shut you down by flooding it out. How's your fuel mileage? My guess it that it sucks, (in a bad way ;-)).
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Dad wrote:

Good to see you back, Dad. It was too 'f'ing quiet in here without you...
TomC '90ZR1
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Dad wrote:

Fuel mileage is not as good for sure, but nothing horrible. If a sensor was bad, wouldn't the computer put out a code... there's nothing in the computer that says anything is wrong. Any other suggestions? I do get some popping in the exhaust occasionally when down-shifting as well.
Eric
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No more suggestions, but I just went through this same scenario with my sons 91 and we changed all of the stuff you did and more before we thought it was fixed. Ran good when I left and while it was a cold engine. Right after we "fixed it" it left him setting in the bank drive up window on Friday afternoon. Had it scanned and it showed a faulty temperature sensor. Changed it and it now runs like a charm. Is that your problem, don't know, discount it if you want it never threw a code.
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Dad is right , check the water temperature sensore first. And check your fuel pressure regulator. A ruptured diaphragm could cause the problem. RPM fluctuation could indicate an intake leak.

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To Dad and tom_I_35806, What would the water temperature sensor have to do with anything? Mine works fine as far as I know it, temperature seems accurate. As far as the intake, you're referring to the intake manifold I suppose. How would I diagnose that? The idle fluctuation gets worse if I throw the AC on... don't think the AC has anything to do with it, just think that the AC exaggerates whatever problem it is. Thanks again.
Eric
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the weather pack connection is the one for the SENSOR that reports back to the ECM (electronic control module), the single wire connector is the one for the temperature gauge SENDER. as far as the fuel pressure regulator, just pull the vacuum line off of it and engage the fuel pump by turning the ignition switch to the run position. it should give the fuel pump a 3 second burst. if it is bad it will pump fuel out of the regulator. there are a lot of things that can make it run rich that MAY not set a code or turn the SES (service engine soon) light on. O2 sensor, CTS (coolant temperature sensor) MAF (mass airflow sensor) bad injectors, rupture in the fuel pressure regulator. find some one who has a scan tool (and understands what they are looking at) and look at the data stream for the swing on the O2 and CTS voltage, look at the data stream for the MAF. more than likely Dad and Tom are right on the money on this one. look for any stored DTC (diagnostic trouble codes) while you are in there.
PS, glad to see you did not stay away to long Dad, i have always enjoyed your posts and your vast depth of knowledge. now where the hell is Diode?????? Greg Nettles
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Sensor can give a erroneous bit of information to the computer and therefore sends an incorrect request for more fuel. The sending unit for your coolant temperature gage may not be the same as the one used to control your fuel. Do you have more than one temperature sensor and did you have a scan tool check it? It don't have to set a code that would appear in your DIC to be a faulty sensor. Sorry, I can't look it up, I no longer have a manual for my '92 which may be different anyway with the LT1 and its reverse flow coolant.
Dad
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A bad O2 sensor can also make the engine rich.
Al
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