1988 325e Problems

[Bmwman92]

Hey guys im looking for some help. I have a 325e Seta.

I have been trying a whole bunch of different things and cant figure out the problem. You start the car and it takes about 10 seconds to start. It will sit there and idle just fine but you hit the gas and the idle just bogs and does nothing. But when i floor it it will slowly build up then rev. But nowhere else in the pedal. So i have no throttle response.

Idle control valve is buzzing with key on so im guessing its working.
tps unplugged, idle goes erratic
maf unplugged car dies.
cps replaced from 1988 325is
compression tested fine
timing is tdc. well i believe cam and crank are aligned.
no vacuum leaks.
changed cap, rotor, and plugs
tested another fuel pump from 1988 325is dont know if that one is any better than mine.
bypassed fuel filter to see if it was clogged no help.
sometimes it will backfire out of the intake


sure im missing something i have a mazda b2200 3 seater truck and i have 2 kids i really need my e30 please help me.

[Bmwman92]

I'm going to pull the valve cover in the morning because there is a small leak. and im going to pull the injectors.

[jlevie]

The list of possible causes of this has intake leaks at the top. Have a shop run a smoke test and fix the leaks it reveals.

[ForcedFirebird]

Jim is correct.

The Motronic ECU is very picky about vacuum leaks (non-metered air). If your VC gasket is leaking oil, it's not unlikely it's also leaking vacuum.

[Bmwman92]

Yes the valve cover had a leak. but wouldnt a bad vacuum leak cause erratic idle? the other 2 things i havent checked are the intake manifold and fuel injectors.

[Bmwman92]

Ok i fixed the valve cover. pulled the o2 sensor plug and it was corroded so i sprayed it clean with my tb cleaner and plugged it in and cleaned the maf sensor and it helped but still really slow response and small backfires but could be from being out of gas =P

[MrNatural]

Mine did the backfire thing and it was the cap...check your's for any cracks

[Bmwman92]

Cap is good gonna check the tps for continuity. How do you test the maf to see if its up to standard? and could the ignition coil be a part of my problem?

Edit


Let's take a break from testing things for a moment to discuss fuel pressure. This may be a little confusing so you may have to read it twice. I know I would. Proper fuel pressure is very important on the E28s. The Motronic ECU maintains control of the fuel air mixture by measuring the engine's air intake and then injecting in the proper amount of fuel. It controls fuel delivery exclusively by controlling the amount of time the fuel injectors are open (except during starting, which will be covered later). If fuel pressure is too high or too low the ECU won't know it, and at idle or full throttle it will make no attempt to compensate. Under these conditions if fuel pressure is too high the injectors will allow too much fuel to spray in because the ECU won't know to reduce the amount of time they are open. If it's too low, we have the opposite problem. The Motronic system can compensate for small variations in fuel pressure during normal driving (i.e. not during starting, warm up, idle, or high power operations). It does this via inputs from the O2 sensor. We will cover that later.

Could my o2 sensor be telling my ecu not to give the engine enough fuel? but when i cleaned mine the cel turned off.. so no cel

[paperplane94]

Cap is good gonna check the tps for continuity. How do you test the maf to see if its up to standard? and could the ignition coil be a part of my problem?

Edit


Let's take a break from testing things for a moment to discuss fuel pressure. This may be a little confusing so you may have to read it twice. I know I would. Proper fuel pressure is very important on the E28s. The Motronic ECU maintains control of the fuel air mixture by measuring the engine's air intake and then injecting in the proper amount of fuel. It controls fuel delivery exclusively by controlling the amount of time the fuel injectors are open (except during starting, which will be covered later). If fuel pressure is too high or too low the ECU won't know it, and at idle or full throttle it will make no attempt to compensate. Under these conditions if fuel pressure is too high the injectors will allow too much fuel to spray in because the ECU won't know to reduce the amount of time they are open. If it's too low, we have the opposite problem. The Motronic system can compensate for small variations in fuel pressure during normal driving (i.e. not during starting, warm up, idle, or high power operations). It does this via inputs from the O2 sensor. We will cover that later.

Could my o2 sensor be telling my ecu not to give the engine enough fuel? but when i cleaned mine the cel turned off.. so no cel

It is actually called a VAFM and not a MAF.

It can be easily tested on the bench by applying a small amount of power to it and testing that the change in resistance is smooth.

see this:
Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk

[Bmwman92]

http://youtu.be/wGtzrmbcAxk

http://www.youtube.com/watch?v=ZGOqtUBAfc4&feature=plcp&context=C4b49927VDvjVQa1PpcFMgpPQ-1DEXoDAvgKyGp04_FRstIPhZhxQ%3D

[Bmwman92]

The list of possible causes of this has intake leaks at the top. Have a shop run a smoke test and fix the leaks it reveals.

This is exactly word for word my problem:D