What do these symptoms sound like?

[Guest]

Ok - e28 noob here. My e12 is an M10 kJet car, so this is very foreign to me...

Car is an 86 535i exec. Sometimes it pulls as it should - long and strong to the rev limiter. Today (in the heat), it was .. well. it felt like the ol' 4 cyl e12. It's done this before, and I pulled over, had a listen, no clatter or catastrophe, so gave it a few revs. Suddenly its back to life. Today the same trick didn't work. In the cool evening, its alive again, though that could be coincidence.

My initial feeling is AFM. It idles pretty rich, but is super smooth from 1000rpm up. I wonder if I have a sticky AFM? Is there a good FAQon the AFM? Am I barking up the wrong tree?

[Shawn D.]

I'd check the in-tank pump for proper operation. If it isn't working, you can get vapor lock. Note that the in-tank pump is a supplemental pump, not the main pump; thus, even if it is inoperative, the car will run fine under most conditions.

[Tjn182]

I know when my car is usually hot, the fan clutch kicks in which puts a pretty decent drag on the engine. But I doubt it puts THAT much drag on an engine.

[Josh in BrewCity]

Check the air filter maybe ???

[booker]

Here is a good tutorial about the AFM. May be able to at least rule that out.

[Robert in STL]

I've had a distributor cap cause similar problems; fine when cool ambient temps, but rough when warmer. Check for corrosion, etc.

[Mike E]

A thought... Could it be the Fuel filter? Where are they on this car?

I recall the new fuel filter waking up the e12 from a long slumber...

[Shawn D.]

[QUOTE="Mike E"]A thought... Could it be the Fuel filter? Where are they on this car?[/QUOTE]
The fuel filter resides above the right axle shaft and is very easy to access.

[Mike E]

[QUOTE="Shawn D."]I'd check the in-tank pump for proper operation. If it isn't working, you can get vapor lock. Note that the in-tank pump is a supplemental pump, not the main pump; thus, even if it is inoperative, the car will run fine under most conditions.[/QUOTE]

How does one check this pump for proper operation?

[Shawn D.]

[QUOTE="Shawn D."]I'd check the in-tank pump for proper operation.[/QUOTE]

[QUOTE="Mike E"]How does one check this pump for proper operation?[/QUOTE]
Isolate (i.e. disconnect) the main pump.
1) Can you hear the aux pump running? If yes, it's probably OK.
2) If you cannot hear it running, is it getting voltage?
3) If it is not getting voltage, why is it not getting voltage?
4) Continue with "standard" malfunction analysis!

[Tim in N FL]

Hmm...sounds familiar.
I like the idea of checking the fuel pumps...easy to do.
Also check that NO unmetered air is getting past the AFM...can wreak havoc
Check that the rubber boot is secured all around...
Cheers,
Tim