[alkjoe]

My 1987 engine has a very rough idle. The engine also sounds like it is misfiring or skipping at all speeds. I replaced the wiring harness distributor cap, rotor and the spark plugs. None of these had any effect. The car has about 220,000 miles on the odometer. Since my kids drive the car I don't know if this happened suddenly or was a progressive problem. I checked and replaced the air filter all hoses and sprayed oil around the injectors to check for vacumn leaks. It is a little worse when the engine is cold but the problem continues with a warm engine. Strangely the car seems to have normal or near normal acceleration. Has anybody experienced a similar problem? Any ideas as to the source of the problem? I am off to check the compression now.

Well I was going to ck the comp. but since the car was cold,I decided to unplug the wiring harness to the AMM. I read somewhere here, that action would put it in the "limp home" mode and it sure improved the way the engine ran. With the Air Mass Meter unplugged the car runs much better at idle and seems to also run much smoother at higher rpm. I tried to drive it with the AMM disconnected but driveability(starting from a stop) was very poor. With the AMM hooked up driveability was better but the rough idle and missing returned. I have the Bentley manual and will see if it has a electrical test for that part. Has anyone had this problem?

 

[Tech]

Sounds like a bad mass flow sensor.That is most likely the problem.

 

[alkjoe]

QUOTE(Tech @ Feb 21 2005, 05:34 PM)Sounds like a bad mass flow sensor.That is most likely the problem.

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Thanks I am going over the test for the mass flow sensor. If I do it right I should verify if it is good or bad.

 

[Tech]

Sounds good let me know how you make out.

 

[alkjoe]

QUOTE(Tech @ Feb 21 2005, 09:55 PM)Sounds good let me know how you make out.

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I tested the air mass meter with the following results: Tested between white/red and yellow/green contacts and got a reading of 2.9 ohms the tolerance in the Bentley book for the LH-2.2 system is 3.5-4.0 ohms. Bentley says if outside that range to replace the AMM. I also checked the idle mixture screw to see if it worked according to the procedure and it was good.
I have two questions: Where should I buy the AMM (rebuilts are much cheaper than new on line). Any good sites(inexpensive/relativly) that you reccommend? Secondly when I get the new unit will I have to adjust the plugged idle mixture screw? Thanks

 

[Tech]

First thing to do is see if you can find a used one in the junk yard.If not then try a new one.I don't think you wil have to adjust the screw any most of the time they are preset.Then if they go to far out of range then they are adjusted.