Give Gas=Stalls/backfires

[Kirby]

Very nasty! Those need to be replaced, and certainly are not helping. After you replace this stuff, if it still has the problems you describe, unplug the connector on the Mass Air Flow Sensor. It might stumble for a bit for a few seconds after you unplug it, but if it then gets better after you unplug the MAF, it's DEFINITELY a bad MAF.

 

[E30m42cab]

Yeah, we don't need to tell you to replace those two things now do we?

Kirby, I bet half the e30's on the road have a garbage MAF and they don't run like that, and they certainly don't start misfiring like that all of a sudden when the MAF quits.

 

[Doughnut]

Your cap and rotor is fail.
Your injectors could be a cause, as well as your throttle position switch under the throttle body.

 

[RBThompsonV]

alright, replaced cap and rotor... NO CHANGE....

tps? got a pic or can ya tell me how to troubleshoot it?
should i try junk parts at this time just to make it cost effective to troubleshoot (not to mention time involved as it's my only car right now)

 

[RBThompsonV]

not sure how to test the TPS but... unplugged it, tried to start the car.. fires for half a second and dies... plug it back in, fires up... but no change in how it runs... unplug again and fire up while giving it gas, car turns over, let out of gas and car runs EXACTLY the way it did before even with TPS unplugged... plug it back in while running, no change, unplug it, no change...

 

[Doughnut]

not sure how to test the TPS but... unplugged it, tried to start the car.. fires for half a second and dies... plug it back in, fires up... but no change in how it runs... unplug again and fire up while giving it gas, car turns over, let out of gas and car runs EXACTLY the way it did before even with TPS unplugged... plug it back in while running, no change, unplug it, no change...

Thats how i would have checked it (unplugging it)
Is it possible for you to get a second hand throttle body? or borrow one?

Sorry, have to ask the obvious... Whats your air filter like?

 

[RBThompsonV]

well, what does that mean though? if I unplug it and it makes absolutely no difference.. what have i proven? that it's faulty or that it's not the problem?

air filer is K&N.. was a little dirty but cleaned it out. during this period though (once it was in the garage) i bypassed the filter (opened the cone on one half). I can get a throttle body tomorrow at the junk-yard (gotta go to pick up some parts just to start tossing things in and see if there's a change....)
actually... my shopping list is as follows:

TCP (2 or 3)
O2 sensor (2 or 3)
and now.. another throttle body

anything else i should grab to check?

no need for another MAF (i've got an extra one in my garage)

 

[Doughnut]

well, what does that mean though? if I unplug it and it makes absolutely no difference.. what have i proven? that it's faulty or that it's not the problem?

Well, thats a good question...
I spose that if you unplug it and it does nothing, it might well be the tps.
Shopping list looks good, thats what I'd get.

 

[RBThompsonV]

No Joy

changed with 2 TPS s... no change.....
changed O2 sensor... no change...
unplugged O2 sensor... no change....
change MAF box... no change

the ONLY tweak that even remotely helped was tinkering with the Air Flow sensor (small siver cylinder on passenger side) and even that only let me get it up to around 1500 RPMs before it does the same thing (stops it from being able to idle though... it'll die out on idle).... so... any other suggestions?
I'm left with thinking timing belt.... mostly cuz i'm out of ideas....

 

[Zdaneman]

What about ....

Idle Air Stabilizer Valve (Idle Control Unit) or Idle Speed Control Unit under the MCU (BRAIN)?

I had the same problem last year and took it to a BMW mechanic and he kept telling me it was the O2 sensor! Yeah right![shake]

So, I replace the Idle control Valve and ISCU and it ran fine! Not sure which one was really the problem...might be worth a shot?


Zdaneman sends

 

[RBThompsonV]

Timing Belt replaced.... NO HELP!!! and I mean, if anything, it may have made it just a little rougher on idle... but other than that.. absolutely no difference... I need more suggestions....

 

[Kirby]

I am beginning to wonder if the problem is actually ECU related, based on the stuff you have done so far.

I had a problem similar but not identical to yours on my 87 Volvo. Rough idle, sometimes it ran fine, other times it would just die on the highway. It turned out to be the ignition "Pulse Module". This goes by various names, but essentially it is a heavy duty transistor that takes a 5 volt pulse signal from the ECU and allows a large 12 volt current to flow from the battery to the coil, creating the spark energy in the coil.

On my Volvo this was external to the ECU, and easy to change for about $25. I tried to find this for your car, but it appears it may be internal to the ECU.

This site might help you with troubleshooting, this is specific to Motronic 1.0, not sure what you have? He talks about troubleshooting ICV, MAF, etc.

Also, this site talks about issues with the E30 M3 ECU and specifically the pulse transistors. It's electronic techie in nature, but it might help you.

Pelican Parts has some general DME info that might help This is primarily E36, but good general info. They claim a bad power relay supplying power TO the DME can cause problems.

Can't say any of this will solve the problem, but it's another place to start eliminating possibilities....

 

[Doughnut]

I am beginning to wonder if the problem is actually ECU related, based on the stuff you have done so far.

Yeah, try a different ecu...
Don't really know how they fail, or how any ecu fails for that matter, though this could be your problem.

This has turned into a nightmare for you, I'm really suprised you are continuing to try to diagnose the problem. Kudo's to you!