QuestionQUESTION: Greetings, and thanks for your expertise, it is quite revealing. My 1996 automatic Infiniti G20 with 185,000 miles on it was running rough, no pickup when hitting the gas while already moving, idle RPMs oscillated between 500 and 900, and when pulling away from stopped, vehicle would hesitate, then take off normally. I read codes at a retail auto store and knock sensor, and/or ERG, and/or PCV were indicated as possible problems. So I replaced all three. Problem remained and car actually ran worse. I took off distributor cover and found oil, so I replaced entire distributor and tuned it up again. Now car would not even start. All I could think was timing and removing the cover showed the chain may have jumped a sprocket tooth or two. I replaced the sprockets, chain and tensioner and related parts. Now car has a clear misfire, another code read showed misfire in cylinder four, however the previous three reads did not show that issue. Car sometimes is okay when starting cold, idles nicely as it should with all new distribution parts, but after a few blocks, it starts to misfire. Sometimes it is only at low idle, other times it missed at higher RPMs. I thought maybe oil pressure, but I'm not showing a code and oil light blinks occassionally, but it's been doing that for two years. I presume I had the difficulty after changing the timing apparatus because the computer was advancing timing to compensate for the chain jumping and bad distributor. The timing steps are very detailed and easy to follow, so I'm confident timing is fine, plus it idles and drives fantastic when it's not missing. I wonder about having a dead cylinder, the injectors or even the cam. I'm not really a 'car guy' and all I can generally do is diagnose from tech notes and BBS's like this one. Any ideas? Many thanks.
ANSWER: George,
I would get a Haynes Manual and use the procudure to diagnose the mass airflow meter (MAF). Yes, I know it sounds crazy. But, your engine is the same as a Sentra and they have this strange problem with the MAF and showing a code like you mentioned. I am sure you have the timing on so if you did check it and set it look at the MAF.
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QUESTION: Timing is dead on - I followed the directions from AllData and the guy who tuned it for me is a pro-racer and internationally certified mechanic. But I don't have the pleasure of calling him at my whim, usually on the road.
Anyway, thanks for the tip - since it's at least a few hundred for the part ($500??) how do I test it?
Thanks.
AnswerGeorge,
Here is a link to Autozone's website with pictures and a description on how to test the MAF. Also, please check the fuel pressure by using a fuel pressure gague to make sure the fuel pump is not starving your engine. Lastly, replace the oil pressure sending unit as it is used by the computer to act as a failsafe if you have no oil pressure. No oil pressure and the ECM will open the relay feeding electricity to the fuel pump.
http://www.autozone.com/az/cds/en_us/0900823d/80/13/20/fe/0900823d801320fe/repai
