strange misfire

[92foxchp]

My 92 lx is misfiring oddly. Idles fine, revs fine when not in gear, but when you give it gas in gear it wants to stall unless you give it a lot of gas. It feels like its running on 3 cylinders, stutters horribly, and there's a very rich gas smell. Weird thing is, some days the problem completely disappears. I've replaced the coil, the distributor and the cap, the wires, the plugs, disabled the egr, cleaned the maf, tried disabling the o2 sensors--nothing works. It passes the cylinder balance test, and the only code it gives is for the engine temp sensor.

I think it might be a grounding problem or something.. But the way the problem sometimes completely disappears (usually in freezing weather) has me stumped

Update: problem appears to be fixed. It was a stuck fuel regulator that was flooding the engine. Thanks again for the suggestions.

 

[jcgafford]

code 21? dont worry about it. mine threw it all the time if i ran codes with the engine cold. if your not running cats you will get that rich gas like smell. does the car run something like this?
turned out to be the dizzy in mine.

 

[foxbody5150]

Mine does the same exact thing one day itll doit the next it won't. I find if i let my car warm up for a while itll run fine but if i dont it spits smoke and smells like gas and it sounds like one f the pistons siezed or something i still havent figured it out. If you find anything out please let me know.

 

[jka]

Have you ever replaced the ECT sensor ?and did it give you a code 21 with a warm engine?..because if you got a code 21 with a warm engine that may be the problem. If you tested it with the engine cold it would give a 21 code anyway..but if you ran a self test wih the engine at normal temp and got this code..you have a bad ECT sensor. It can cause your engine to run lean ..and cause the computer to dump too much fuel at idle.

 

[Mustang5L5]

Code 21 on a hot engine could be your issue.


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[92foxchp]

code 21? dont worry about it. mine threw it all the time if i ran codes with the engine cold. if your not running cats you will get that rich gas like smell. does the car run something like this?
turned out to be the dizzy in mine.

No mine idles fine, it's just when you give it gas while in gear, it seems to flood the engine with fuel. It does it whether the engine is cold or hot (so i dont think its the ECU). You can drive it but its extremely rough and it gets like 5 miles to the gallon, like it's literally dumping fuel through the tailpipe.

Also, at WOT the problem completely goes away.. (so I tried disabling the o2 sensors to see if that was the problem, but no dice). My next guess is the TPS or a stuck injector, or some grounding problem.. I'll update the thread if I figure it out.

 

[jcgafford]

try putting a differnet distibutor in. your description is the same as mine was and the op of the youtube video. the video is from a guy i had to track down from a youtube account. it was his distibutor too.

 

[92foxchp]

Thanks for the suggestions. I had already replaced the dizzy with one from another car and it didn't help. Today I rewired some old frayed wires near the battery, cleaned the MAF again, along with the AIC.

None of that seemed to do anything so I took the TFI module from my old dizzy and put it on this replacement distributor, since it had a non-motorcraft one.

Then I changed the fuel filter--to my surprise some nasty stuff came out of it--it is now running considerably better but still stalling.. Of course the problem was always intermittent so I don't know if it's really any better. Still need to test the TPS and fuel pressure....

 

[jka]

Did you get the code 21 with the engine warm?..because if the ECT sensor is bad it will cause surging and stalling.

 

[ID89GT]

Replace the ECT... It probably thinks the car is cold so is making it run pig rich so it will warm up. That is what is designed to do..

 

[Bill Gordon]

Did you get the code 21 with the engine warm?..because if the ECT sensor is bad it will cause surging and stalling.

This makes sense. If the ECT is bad it will cause the ECU to dump extra fuel even if the engine is warm (kinda like a sticking choke on a carb).

 

[92foxchp]

Problem returned today worse as ever. It seems to have to do with the temperature outside-not the temp of the motor. If it's under 30 degrees, the car will run fine all day... But above that, runs like hell--I don't mean a simple stall or surge, I mean misfiring so bad its like running on 3 cylinders, and gives out white smoke. Stuttering very violently under 3k RPM, but at WOT runs beautifully. I think it's the TPS or some electrical short.

I used to run it with the ECT disconnected and it never behaved like this.. I had my intake coolant rail spring a leak and had to reroute the coolant with a hose, and haven't rerouted the temp sensor yet, but I'll definitely do that.

 

[92foxchp]

Did you get the code 21 with the engine warm?..because if the ECT sensor is bad it will cause surging and stalling.

No the 21 was in memory from when I had the ECT disconnected from the electrical plug. I've since plugged it back in and it just sits in open air. The engine acts the same with the ECT disconnected from the engine harness -- wouldn't the computer then just run on the base tables ?

 

[jka]

Yes it would cause your car to ..buck-..stutter.. surge.. run rich sometimes run lean. If your computer does not know the temp of the coolant it can not control how much fuel to give in open loop/cold engine or closed loop/normal temp warm engine. That's your problem ..even if you got that code 21 as a memory code. Well the only thing i can tell you ..is to fix the problem with the coolant tube and install a new ECT sensor and unplug both battery cables and your car should run better then..plus the memory code 21 should be gone.

 

[92foxchp]

Just an update--problem appears to be fixed. It was a stuck fuel regulator that was flooding the engine. Thanks again for the suggestions.