Keith - jumping in here.... don't to MAF **yet** (archive)

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The hot-platinum-wire mass/airflow meters are electronically managed to give their outputs, and the current through the wire is by definition regulated - it's how they measure the airmass going past the wire. What I'd suggest would be to step back a couple of issues - not always easy, I know - and consider these things:

1) what's the state of your battery WHILE RUNNING IN THE FLAT SPOT? Higher engine revs mean more current drain through loads like the injectors... I'd suggest a check both "at the battery" (maybe via the OBC functions?) and AT THE DME units, and then at the MAF sensors themselves

2) Check the outputs of the Lambda (oxygen) sensors - they will give you the REAL mixture picture. If one side is high and the other low, try swapping the MAFs side to side & check again - does the rich/lean side swap too?

3) I personally would also check all the pin voltages on each MAF before consigning one to the trash - just to make sure it's not a bad loom connection or dirt on the pins - remember, these are WEAK signals. I'd also not flinch from cleaning the "defective" MAF - probably carb cleaner on a q-tip, esp around the ends where the insulation could have been comprimised, ALSWAYS VERY GENTLY (surprise surprise, I'll stop telling you how to suck eggs now too) and then re-trying...

4) last thought that occurs is also to check all engine earths - the MAFs are isolated/insulated from any major earth return paths.

I dunno - I'd just hate to have you end up with a related mixture problem in the end but not have it be the MAF after all... hope these ideas help rather than hinder.

I replaced the bad ignition coil but still have performance issues. As I described before, when cold the car runs and idles as expected; however, after running for a while it begins to idle rough and has a big flat spot. It will sometimes regain composure for brief periods of time, but in general once it starts to run bad it continues.

I decided to check the MAF's according to the procedure described by the Bentley manual. I did not see the glowing wire as described but the voltages going to the unit were as described; except that the number 3 terminal measured about 4.5 volts instead of 5 volts. Can anyone tell me if this is a concern or not?

While checking on the MAF's I had the car running without the air filters hooked up. I noticed how much easier the car seemed to rev up and decided to take it for a spin without the air filters. It ran better than it ever has since I have had the car (1.5 years). Then after driving it for about 15 minutes it began to run flat again (it was already hot from idling when I started). However, this time, it was not as bad as typical. It is as if by removing the air filters, the engine runs a bit better.

When I had the MAF's exposed a realized how sensitive the intake is to airflow. Two fingers over one side practically shut the car down. Is it possible that the MAF's are defective and causing the car to run flat and idle rough. The thin wire inside looks to be complete (not broken). Is there any other way to test the MAF's?

By the way, while driving the car when it was running correct, the shifting became very smooth. I had forgotten how smooth it could be. It seems that when the engine is not running just right, the shift point comes earlier and becomes hard. Can anyone provide some information about this?

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