'87 325is engine issues

[Spaz!]

Ok a while back my car decided to stop idling properly, it would hunt from 1k to 2k on about 1 sec cycles. I pulled in and checked everything over and found nothing out of place. I have since managed to get it to idle by adjusting the throttle plate and unplugging the IACV. It also exhibits very poor acceleration with the IACV unplugged, cannot use more than ~1/3 throttle. With the IACV plugged in the car will not exceed 3k in any gear, it will rev in neutral but stumbles. Either way the car will stumble and back fire if I open the throttle to much. In the course of trouble shooting this I discovered my in tank pump was out and that the main pump was failing. They have been replaced with a walbro gss340 now but I still only show between 30 and 40 psi at the rail, even when I blow on the FPR vac line. I have tried swapping the AFM since I have several spares but no luck. I have also replaced the throttle body gasket and installed all new silicone vac lines. The intake bellows looks a bit cracked but holds air/smoke.

Any pointers guys?

TIA, Jon

[89 e30]

Try replacing the fuel pressure regulator

[Spaz!]

Is there a way to test it? I hate to spend money on things without knowing they're bad. I would assume it should produce x psi at y mmhg?

[jlevie]

With the engine idling the rail pressure should be 35-38psi. If you disconnect the vacuum hose the pressure should rise to 43-45psi. If the pressure is low and filter hasn't been changed in a while, replace the filter and see if that helps.

There is a good chance that at least some of the problems care caused by intake leaks. Have a shop run a smoke test and repair as indicated. Also check the idle & WOT switches to see if they are working. A meter or test light is the only valid test.

[Spaz!]

Cool TY Jlevie,
I guess my fuel pressure is ok then since thats about what I get. I didnt replace the fuel filter because it is still fairly new, though I did blow it out. My tank is actually sparkling clean inside...literally! I smoke tested the intake after I installed the new vac lines and gaskets and everything showed good there so I guess its on to the TPS. The idle and WOT "switches" are integral to the TPS correct? I should get x ohms at idle or x volts etc?

[Spaz!]

Ok I've checked the AFM, ICV, TPS, and O2 sensors. I smoke tested the intake and I have replaced all of the vac lines and still the idle cycles up and down. The only thing that has helped at all was when I cleaned the cap and rotor and now the idle only shifts up and down about 5-700 rpm or so. They were pretty degraded so I will pick up a new set but surely that isnt the only thing causing this? Also I hooked up my stoichometer and at low rpm it reads LEAN, wont even show on the gauge, at high rpm it reads stoich.

Any more ideas?

[catuned]

I have a car in our shop with the same problem. We found 2 of his injectors leaking.
And also low compression on those 2 cylinders.

Have you checked your compression?

[UserError]

Cap and rotor could definitely cause the problem, since demand on the ignition system gets much higher as the RPMs increase. Another couple weak points could be the plugs or coil. Try swapping for a known good coil, and pull a plug or two, to see if they're looking worn.

[Spaz!]

CAtuned:
I have not checked compression #s yet, I will give that a shot and see what it shows.

User Error:
Plugs are brand new, I put them in right before my last post. Old plugs were fouled but I saw no difference with the new plugs in. I will try swapping coils but the only one I have as a spare is an MSD blaster II and I dont think its safe for use with bimmer ignition systems. Any one have a known good coil lying around?

[Spaz!]

Oh and whats the difference between Eta and I injectors? I have a spare set of Eta ones sitting here I could drop in and see.

[UserError]

Eta injectors have the wrong resistance to use with the I injector drivers. I think the I injectors might also be slightly bigger, though i could definitely be mistaken on that.

[PNWDan]

Ok a while back my car decided to stop idling properly, it would hunt from 1k to 2k on about 1 sec cycles. I pulled in and checked everything over and found nothing out of place. I have since managed to get it to idle by adjusting the throttle plate and unplugging the IACV. It also exhibits very poor acceleration with the IACV unplugged, cannot use more than ~1/3 throttle. With the IACV plugged in the car will not exceed 3k in any gear, it will rev in neutral but stumbles. Either way the car will stumble and back fire if I open the throttle to much. In the course of trouble shooting this I discovered my in tank pump was out and that the main pump was failing. They have been replaced with a walbro gss340 now but I still only show between 30 and 40 psi at the rail, even when I blow on the FPR vac line. I have tried swapping the AFM since I have several spares but no luck. I have also replaced the throttle body gasket and installed all new silicone vac lines. The intake bellows looks a bit cracked but holds air/smoke.

Any pointers guys?

TIA, Jon

Had this happen twice on mine. First I'll say that unless it was ever adjusted before, dont change the idle stop screw. Now that you have youll have to adjust it back to spec when you fix the issue.

The first time this happened it was my TPS. It tested bad so I replaced it and all was well after that. A year later I had just got home, went inside, then came back out and started the E30 again and bam the same issue. Did all the tests you did just to not get any answers. On a whim I swapped the DME with a buddies and bam, all better. If you have the 153 DME and can get one to try, I would do that too.

[jlevie]

Ok I've checked the AFM, ICV, TPS, and O2 sensors. I smoke tested the intake and I have replaced all of the vac lines and still the idle cycles up and down. The only thing that has helped at all was when I cleaned the cap and rotor and now the idle only shifts up and down about 5-700 rpm or so. They were pretty degraded so I will pick up a new set but surely that isnt the only thing causing this? Also I hooked up my stoichometer and at low rpm it reads LEAN, wont even show on the gauge, at high rpm it reads stoich.

Lean at idle and normal above idle just about has to be one of the things you've tested, intake leaks, or the DME. Although you say that a smoke test has been run, I'm curious as to whether it was run properly. The exhaust should have been plugged and oil smoke introduced through an adapter that replaced the AFM. The smoke pressure should have been 2-4psi and that pressure maintained for five minutes or more. Was that the procedure used?

If in fact the things you tested are truly good and the smoke test was run properly, I'd swap DME's.

[jlevie]

Ok I've checked the AFM, ICV, TPS, and O2 sensors. I smoke tested the intake and I have replaced all of the vac lines and still the idle cycles up and down. The only thing that has helped at all was when I cleaned the cap and rotor and now the idle only shifts up and down about 5-700 rpm or so. They were pretty degraded so I will pick up a new set but surely that isnt the only thing causing this? Also I hooked up my stoichometer and at low rpm it reads LEAN, wont even show on the gauge, at high rpm it reads stoich.

Lean at idle and normal above idle just about has to be one of the things you've tested, intake leaks, or the DME. Although you say that a smoke test has been run, I'm curious as to whether it was run properly. The exhaust should have been plugged and oil smoke introduced through an adapter that replaced the AFM. The smoke pressure should have been 2-4psi and that pressure maintained for five minutes or more. Was that the procedure used?

If in fact the things you tested are truly good and the smoke test was run properly, I'd swap DME's.

[Spaz!]

PNW Danine:
Mine was barely noticeable until I drove it one evening came home and parked then got up the next morning and it was really bad.

Maybe this is a good time to swap to the 173 DME? Any body have one for sale?

Catuned:
Any pointers on checking the injectors? I cant find my comp. tester yet.