Need help bad...
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Joined: Jan 2010
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From: Longview Texas
Need help bad...
So here is the deal. I have a 1995 base coupe with 116,xxx miles automatic trans. Last year I replaced the entire ignition system with MSD Pro billet distributor, cap, rotor, wires, coil, new plugs, new water pump, the works right... Well now I am having an issue with it running rich but throwing a lean bank code?!?!?!? I have already replaced all of the o2 sensors, which made it go away for a while. Now the issue has returned. I have already gone through and tightened up the pcv system and checked for vac leaks. I have pulled the valve covers and checked all of that out as well... I am at a loss for a solution to this issue and am now thinking of selling the car due to the issue. Anyone who may have seen this issue or dealt with it in any way before your input would be greatly appreciated.
Melting Slicks
Joined: Jan 2009
Posts: 3,181
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From: Puyallup Washington
My 1992 would give me intermittent code 44 - left bank oxygen sensor lean. I poured 2 bottles of Techron in the tank and drove it. The code seems to have gone away and the car even idles a lot smoother now.
Burning Brakes
Joined: Feb 2009
Posts: 785
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From: Richmond Virginia
Have you checked fuel pressure ? Could be a bad FPR leaking fuel to the vacuum side. If as you suspect it is running rich the O2 sensor would be steady/stuck at .9 to 1.0 volts-- the PCM would respond to the O2 via fuel trim (dialing back the "on" time of the injectors) if the PCM has adjusted as much as it can to lean out the fuel system and the o2 is still "stuck" in the 1.0 volt range--the PCM will set a "stuck lean" code. In closed loop on a correctly working system the O2 voltage should vary constantly back and forth between .1 and .9 volts. If you have access to a scan tool (not a paper clip or a code reader) you can see your self on the data list what the PCM sees from the O2s--MAF--CTS etc. May be a sensor out of range,but I'd check fuel pressure first.
BTW If I didn't make myself clear the "stuck lean" code does not mean the engine is actually running lean--it means the PCM has done everything it can to make it "leaner" and is unable system still too rich.
BTW If I didn't make myself clear the "stuck lean" code does not mean the engine is actually running lean--it means the PCM has done everything it can to make it "leaner" and is unable system still too rich.
Last edited by TWISTERUP; May 3, 2011 at 07:32 PM.
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From: Longview Texas
Yeah I have a snap-on scan tool that has OBD1.5 interface on it. The o2's are functioning properly as the milivolts are right. It is actually going into "safe mode" (open loop) after the heater cycle is already complete and the o2's are up to normal operating temperature. as it does this it feels as if it is drastically pulling the timing out and causing it to misfire. Will check the FPR and Injectors. By the way I am a serious gearhed with a nice garage... I understood well what you meant by the way. Thank you for all of the input. Keep it coming though as this may or may not be the issue.
Safety Car
Joined: Apr 2011
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Yeah I have a snap-on scan tool that has OBD1.5 interface on it. The o2's are functioning properly as the milivolts are right. It is actually going into "safe mode" (open loop) after the heater cycle is already complete and the o2's are up to normal operating temperature. as it does this it feels as if it is drastically pulling the timing out and causing it to misfire. Will check the FPR and Injectors. By the way I am a serious gearhed with a nice garage... I understood well what you meant by the way. Thank you for all of the input. Keep it coming though as this may or may not be the issue.
If it does, then start pulling plugs looking for a dirty one.
This could also come from low or inconsistant FP...plugged filter or sock.
Low voltage in the ign will make it spit and misfire. The stock ign was probably more than enough when its maintained. These aftermarket ign cause more trouble than they are worth on a semi-stock engine.Its the "placebo" effect that sells those things. Guys spend a few hundred and the car will run better....after doing that, you can't walk around saying it does not..
Vacuum leak...EGR stuck open. Easy to test with a stick-mirror and vac.
You should see an o2 sensor going out of normal range if there is a major issue with an inj thats dumping too much fuel. That would have to be drastic to send it to open loop via the o2 sensor, I'd think..
I'd be more inclined to look at air problems...leaks and other means of unmetered air entering combustion.
