Okay I give up, my 1994 MGM has run rough or is missing ever since I filled up with gas in Colorado Springs on a trip. I happened right after I filled up so 1st thought was bad gas so I went through that tank of gas and replaced the fuel filter, had the sytem treated and the injectors and TB flushed and cleaned out. It still runs rough and backfires in the TB. I replaced the Mass Airflow Sensor prior to this problem which fixed the hard start and poor running and cleared the check engine light. We read the error codes and had one for the the Throttle positioning sensor and I replaced that. I checked the plugs the are all fresh and I replaced one of the coil packs... Still running rough, I bought the car recently and it only had 68K on it now it has 73,000. It ran GREAT after I replaced the MAS for about 2 weeks. What should I check or replace next, any ideas??[img]smileys/smiley6.gif[/img]

I think it has happened because of some bad gas which have affected your engine.

you can get all the injectors checked for free at a autozone if there is one near you. Check out any parts store to do it fot you. i think it is one of two things. A different coil or even the new one. and it is probably dirty injectors. the only way to clean injectors is to take them off and to have them ultrasound cleaned.

Sorry, i ment to say get the coils checked for free....not the injectors.





You either have a bad coil and a bad injector. try pulling off a spark plug wire for each cylinder wile it is running. if it stays the same when that one is pulled off, then it is probably the bad one. the motor should run worse when a wire is pulled off. this might help you narrow down the bad and good ones sometimes

sometimes you can also pull off the injector harness on each injector when it is running. like the coils, it should run worse when pulled off. it it runs the same then you have a bad injector. If no luck then it could still mean that they are dirty. this is probably what is going on. summer fuel is cheaper and more dirty then winter fuel

I think the altitude in Col. may have messed with your computer telling it to richen and lean the fuel mixture. TPS sounds like the culprit but you say you changed it. Did you reset the computer?

Hi guys, thanks for the responses.. I live at 7000 ft. so I don''t think the alt was/is a problem. I did have the fuel system/injectors flushed there in CO Springs after it happened. I have reset the computer several times-when I replaced the MAS, TPS and the coil.


The fuel injector suggestion sounds good and I will try that next. Mostof the shops arouond here want ~$100 just to hook it up to their computer for diagnosis'' and of course they want to make more $ off the repairs so please keep the suggestions coming and I will update you with the fuel injector update.


Thanks again!

For a lean/rich fuel mix... it is not affected. the computer will adjust this several times a day. changing altitudes does not perm. affect the computer. It is programed to change. there is no need to reset the computer for this suggestion

How many miles on the plugs? make sure that a plug was not affected when you went through higher altitudes. the computer would not be affected, but if it ws needing a tune up and it was running rich for 30 seconds, then it is possible that a plug was fouled out when the computer compensated for the altitude. The computer is fine. It is the plug, coil or injector. i am 90% sure of this

when you said you checked the plugs.. How? did you just look at them or did you check them with a tester? you need to see if the plugs are sparking. a clean plug can still mean that it is fouled out. see ifit is getting the proper spark. most likely if it is not then you would then check the coil for the amount of spark and resistence. a new coil does not mean it is working properly. most aftermarket coils are junk anyway. you need to check these with a meter at least and not check them offf the list becasue they are new or look good.

90% sure are some good odds. I think you should listen to one of jason''s 10 responses. Did it really have no probs for two weeks after a MAF sensor? I mean not just an improvement but a cure? Let me know.

It was 6 responses. Conan312. The reason for the seperate is that this site only gives you 30 seconds to type. I have to do them in different resonses to finish a complete response. it was more anoying for me to retype it and do it all over again and again then it was for you to read them in different response boxes.

Hey guys, just a FYI the car was getting about 18 mpg when I bought it-check engine light was going on and off-and ran rough until I replaced the MAFS and then it jumped to 25-26 mpg on my regular commute. I was getting 26.5 on my trip to CO Springs and was well over 400 miles on that tank of gas. Then I filled up and it dropped to 20 mpg on my trip back home running rough again but no engine light.


Keep the suggestions coming I''ll get a chance to work on it soon.


Thanks!!

Maybe you got a defective sensor. It was a cure-all, then the prob returned. I''m going with mass air flow sensor failure.

yes, I agree. Those remaufactured MAF sensors are junk. bring it back before your 90 day warranty is up.


I would go with a brand new unit. it cost more, but well worth it because you wil have no more headaches

Hey guys,


Okay this is the 3rd MAS I''ve replaced and it didn''t fix the problem even with the new upgraded one. I was hoping that was going to fix it. [img]smileys/smiley6.gif[/img]I''m going to be out of town for the next couple weeks so I guess it''s going to have to wait for our next steps.


Thanks again for the input.

Your car is starting to annoy me. [img]smileys/smiley7.gif[/img]

The reason I say a new and not new remanufactured MAF is, That I had a similar problem. I went through 4 MAF ( remaufactured ones) They were all faulty. My code was going off and every MAf unit sent a different code??? one unit sent a low voltage at idle and the others sent a high voltage at idle and 1700 rpm''s. This was only figures out ater my buddy putit on the machine for about an hour at the dealer.Were did you get the MAF from?It was not fixed until I replaced it with a brand new unit.

Hey guys, I meant to reply back to you sometime ago, sorry. Well we hooked the car up to a really nice computer andthe resultscame back with no issues at all even though the car was still running rough. The tech that checked it out for us said change the plug wires. So we did and found 2 of them to be bad so that was the whole friggin problem. 2 spark plug wires just happened to go bad right after filling the tank up with gas.....? I feel bad for not even checking them first...dah....


Thanks for all your suggestions gents!!!!


Happy New Year