325ix running rough on start up - revving fixes issue

[D.Martijn]

I actually was able to solve it.

A friend of mine told me to check compression, got 10-11bar on all cylinders. O that wasn't the problem.
However the last few time I tried starting the car I noticed the new fuel pump getting quite loud.
I figured it might be a good idea to replace the fuel filter because why not.. it's been 5 year or so (however I do have a new tank fitted).

Well it's been idling fine when I first started it after replacing the filter!

[laidback93]

I had/have this same issue with my 325is. I did everything you have done. Smoke test (no leaks), new ICV, new TPS, coolant sensors, swapped AFMs and DMEs. Also replaced the FPR and fuel pump. I too had a very bad rich on cold start issue. To the point you would smell raw gas from the exhaust.

Flash forward to a couple weeks ago and she is running much better, not perfect from the factory, but much improved.

So here’s what helped. The C191 plug was heavily corroded. It was replaced with factory connectors. My fuel injectors were leaking pretty bad so they were replaced with new OEM. I also went back to a stock flywheel when I had the clutch redone. The PO installed a 7lb JB Racing flywheel which was just too aggressive for my E30 which I daily. And finally the kicker… turns out the fuel pump installed last year was defective. The check valve came apart. No more long ass cranks on cold start up.

Here’s the crazy part. My mechanic did a compression check when I had the clutch job done and all 6 cylinders have very low compression. Like 115-120 range. It’s hard to believe as my M20 runs very strong all the way through the power band. It doesn’t smoke or is mixing coolant and oil. He thinks this is why I still have a slight stumble off cold idle and our very warm weather is masking the problem. This would make sense at this idle issue is the worst when it’s cold outside.

Sorry for the long winded post. I could write a book about the history I have with my E30.

have you made any progress or discoveries on your E30!

[D.Martijn]

A friend of mine tried reading the ECU it's fault codes but somehow couldn't get a connection with his computer, which on this E30 worked just fine.
Last evening I started the E30 again and with the ICV connector barely connected the idle raised, I was able to repeat this a couple times but after a while I couldn't get it to do this again.. Some bad connection some where? bad engine loom..?

So I followed this trouble shooting guide from RTS auto, and everything seems to check out. Also the resistance of 40ohms to the ICV. As well as the TPS on idle is continuity and WOT too, nothing in between
https://www.rtsauto.com/ecu-pinout-a...cal-tests-e30/

[D.Martijn]

What is your charging voltage at idle?

I'd have to check. I did rebuild the alternator roughly a year ago. Installed a new rotor as well and voltage reg.

Check ohms on coolant sensor, and make sure the TPS is reading idle switch. If one/both are bad, you will run excessively rich on idle and low part throttle maps.

I replaced both sensors with new one.
There was a 400ohm difference between the old and new one.
Yeah that's next on the list!

[ForcedFirebird]

Check ohms on coolant sensor, and make sure the TPS is reading idle switch. If one/both are bad, you will run excessively rich on idle and low part throttle maps.

[ADEN]

What is your charging voltage at idle?

[D.Martijn]

Cold starts on a properly running E30 are fine. But given 30 years of use, age, and neglect, some things are going to need refreshed.

I swapped the AFM and idle control valve from my uncles iX (which starts/runs perfectly fine) to my iX and still have the same hard starting problem.
Turning the key, engine cranks over, starts up, shuts down, try starting again, need te keep cranking + add some throttle input and it fits up again.
Keeping the revs up a little and it seems to smooth out although the idle isn't still nice and constant

[nando]

Also a off brand ICV will cause idle issues. The cold start on E30's isn't known for being great (correct me if I'm wrong). My E30 has always hated the cold, but I make sure everything is in good working order and clean. So it is pretty much a manageable issue for me.

Cold starts on a properly running E30 are fine. But given 30 years of use, age, and neglect, some things are going to need refreshed.

[D.Martijn]

try swapping AFM's with another one if you have a buddy that has an E30. I had a similar issue years back, and it ended up being that.

What probably fixed your issue was cleaning your ICV, When cold idle (More fuel+throttle closed) the only air source is the ICV if not enough air gets in you will end up rich (lesser than expected air against injected fuel= disturbed Air Fuel Mixture).

Also a off brand ICV will cause idle issues. The cold start on E30's isn't known for being great (correct me if I'm wrong). My E30 has always hated the cold, but I make sure everything is in good working order and clean. So it is pretty much a manageable issue for me.

Yes, I asked my uncle if he could bring over his iX so I could swap his AFM and idle control valve.
I'll go from there. In the meantime I also changed to fuel pump since I was able to get it prertty cheap (ERA brand, 60€) and temp sensors (Blue sensor is Bosch, brown although has nothing to do with the ECU Hella) ) but that doesn't seem to fix it either

[It's Soda Not Pop]

Also a off brand ICV will cause idle issues. The cold start on E30's isn't known for being great (correct me if I'm wrong). My E30 has always hated the cold, but I make sure everything is in good working order and clean. So it is pretty much a manageable issue for me.

[ADEN]

I started the E30 again last night after letting it sit for a while because I didn't know it if I had let it sit for long enough last time.. It's definitely better, just still hunting for it's idle, after a raising the rpm a little it's fixed..

What probably fixed your issue was cleaning your ICV, When cold idle (More fuel+throttle closed) the only air source is the ICV if not enough air gets in you will end up rich (lesser than expected air against injected fuel= disturbed Air Fuel Mixture).

[audiquattrot]

try swapping AFM's with another one if you have a buddy that has an E30. I had a similar issue years back, and it ended up being that.

[D.Martijn]

I started the E30 again last night after letting it sit for a while because I didn't know it if I had let it sit for long enough last time.. It's definitely better, just still hunting for it's idle, after a raising the rpm a little it's fixed..

[D.Martijn]

If fuel pressure's not dropping, you've ruled out the injectors- which is good.

Smoke testing, also good!

Next, I'd have a look at the plugs, wires cap and rotor. Worn plugs can do this-
but usually you'd also be starting to get a misfire under heavy load as well.

Small chance it's something like the air temp sensor wiring...

t

I checked the plugs but they honestly still looked looked good
wires, cap and rotor got replacement no too long ago
Power seems good once running okay

[TobyB]

If fuel pressure's not dropping, you've ruled out the injectors- which is good.

Smoke testing, also good!

Next, I'd have a look at the plugs, wires cap and rotor. Worn plugs can do this-
but usually you'd also be starting to get a misfire under heavy load as well.

Small chance it's something like the air temp sensor wiring...

t