Ok, I'm ready to beg for help. E34 won't stay running.

[Bin_jammin]

I've got a 1990 e34 535i automatic. The car came to me with a dead engine (jumped time) and a lot of miles. I found an e32 parts car that I'm told had been running years ago before it was wrecked, and it only had 89,000 on it. My car has been sitting for about a year. I've completely sandblasted and painted the engine, tranny, and rear from the e32, blasted and painted the engine bay on the e34, and now everything is installed.

The problem is that it won't run. I have a code 1222. The car won't idle. If you crank the starter and keep your foot in it it will catch and run, but if you try to let it idle it will stall. Depending on the mood it's in I can hold it running between ~500-1000rpm. It pulls around 15hg at 1k. I can't test it at idle because... well obviously. I have 45lbs of fuel pressure. My plugs are gapped to .35 and I've adjusted the valves. The only gasket not replaced on the engine was the head gasket, but the engine runs smooth when it's running, compression feels decent. I've even put dry gas and new gas in the tank thinking that might help.

I have two mafs, one's off the parts car, and they both test good according to Mitchell on Demand. I removed and installed both the crank sensor, and the throttle position switch. All fuses test good, and I can't think of any relays that would cause this sort of behavior. Oh, and the spark plugs are new. Antifreeze is full. Plugs are a little black, but they don't foul out.

I just tested the idle air controller and it seems to be working alright also.

I replaced the 179 ecu with a 150 ecu, only because it was my only spare. Didn't make a difference. Unplugging the tps and the o2 sensor made no difference in running.


I can't think of anything else to check, or anything else I HAVE checked. Not to say I haven't, I just don't recall, other than it doesn't seem like there's any vacuum leaks anywhere, not even the dipstick tube.


So basically, please, if you have any answers or suggestions they will be welcomed with open ears.

[Ross]

First thing I would look for is vacuum hoses disconnected or improperly connected. Idle valve stuck?

[Bin_jammin]

No, All vacuum lines have been replaced and are not leaking. I plan on smoking the motor tomorrow to see if I can find a leak just to triple check my triple checking. Idle valve seems to be working just fine.

[BIGRED]

Will your fuel pressure hold once its you stop cranking it? Maybe a mity-vac test to the fuel pressure regulator to see if it holds vacuum? (being you can't check it at idle).

Don

[Bin_jammin]

that's an interesting idea, I'll try that in the morning and post the results. I assume you're asking if the valve that holds pressure in the line for fast restarts is functioning, but that's not the issue as it won't start at all unless I hold the throttle. I am going to test the fpr though.

Good idea.

[BIGRED]

that's an interesting idea, I'll try that in the morning and post the results. I assume you're asking if the valve that holds pressure in the line for fast restarts is functioning, but that's not the issue as it won't start at all unless I hold the throttle. I am going to test the fpr though.

Good idea.

There is a check valve in the pump to keep the fuel from backing up. The FPR provides in part the same function. Idea is to lock the fuel pressure in the rail for quick starts. But if the pressure is either way high because the FRP won't let it drain back to the tank (dumps all that fuel in the engine) or is stuck open and wont let the pressure build high enough to allow it to get enough fuel into the engine.

When ours acted up it was sporadic. It was at times near impossible to get started and I had to keep it floored. Then it would stumble and if I was lucky it would start. When I ran our pressure test I had 50ish psi running and it dropped back slowly - out of spec.

I tried to figure out where my problem(s) were and narrowed it down to the FP and FPR. I replaced both and along with it the filters because I didn't want to risk having my wife stuck on the road with our kids. My gut was telling me it was only the FPR.

Good luck

[Bin_jammin]

I don't have a wife and/or kids, nor am I looking for a set of my own at the moment. I'm also pretty sure you're not going to loan me yours for the purpose of getting stuck on the side of the road in my car, so I suppose I'll just go about changing my filters. At work now, but I'm babysitting the dealership today, so I'll have to wait a little bit before I can run out and check my fpr.

Thanks for the advice so far, even if it's not the problem, it will be one more thing on a long list that it won't be

[Barney Paull-Edwards]

FPR or, try holding the revs steady at wherever and spray the engine with Easystart or Ether Diesel starter, if revs go up you have a vacuum or inlet leak, my bet is cold start regulator.

[Bin_jammin]

that I don't have a vacuum leak. At least not one on the engine. Every gasket is brand new and properly tightened. Also I'm a bit apprehensive about spraying cleaner on my engine as everything has paint on it that I'd like to let cure a while longer. I can't imagine anything sucking worse than having all the new paint on my engine dissolving and running.

Having said that, I'll see if I can find some type of benign cleaner to try that with. Or maybe I can thread a compression test fitting into the valve cover, pressurize the engine, drop the car into a lake, and look for the bubbles.


I'll have to look around and see what we've got for spray.

[Ross]

If you still want to fish around for vac leaks you can use a propane torch and a hose, that should preserve your fresh paint.
I tend to agree a vac leak sounds unlikely at this point. Do you suspect it's too rich or lean? Maybe too much fuel? How does the exhaust look while this is going on?
You are sure the ignition is up to snuff. ??