85 318i keeps losing timing?

[Navarone]

When I first bought the car it would idle at about 1800 rpm and after messing around and getting nowhere a friend said just turn the distributor until it runs right and that worked. I timed it at idle to the mark that said 10° in the top hole of casing and it idles at 800 or so, passed smog that day just fine.

So now, 6 months later, the timing is back up around 1800 rpm. I don't remember if it just switched over or creeped up but I think it happened about the time the weather changed, or maybe the last time I took it to the car wash and I sprayed down the engine and engine bay.

I just now loosened the distributor and turned it until the idle rpm dropped to about 800. I took it on a short test drive and it seemed to drive the same, maybe a little boggy, but I didn't want to rev it up high incase it started to ping. I don't have a timing light here at home, but I'll have one in the next few days.

Also, the ICV seems to work fine, I have it turned all the way in and if I open it up the idle goes up smoothly. When I take off the oil filler cap the RPM dips by about 800 (from the high idle, haven't checked if it dies now that idle is lower), so I guess that means I have good vacuum?

So, do you think the distributor is slowly rotating out of spec or is the vacuum advance messed up? I still haven't adjusted the valves, cleaned injectors or anything else and the fuel pump sounds grumbly but seems to work. What about timing chain? Could that stretch enough to cause this?

Thanks!

[Navarone]

Got a timing light and it's still in spec.

Here's the distributed cap, see how the teeth aren't touching? Where are they supposed to be with the car off?


Here's some metal shavings inside the cap. Maybe it made contact?

[Navarone]

I also noticed that the tps doesn't click at full throttle.

[Navarone]

85 318i keeps losing timing?

Did the penny trick and that fixed it. It still isn't super peppy, kind of a dog up higher at rpm. I timed it to 10° at idle before I did the penny trick so it was at about 1800rpm. Could that by why?

The icv works, it clicks when I tap it with 12v, the plate inside closes. When I unplug it the rpm goes up. I think the plate is all gummed up and doesn't seal all the way. Maybe one day I'll clean it out.

There's some rust in the distributor and I couldn't take it apart. I took the first ring clip off and the forked wheel wouldn't come off. The black plug in the side with the metal for going into the distributed, does that energize that coil inside or is that an eddy sensor or something? Where can I find info for the theory of operation for this distributed and icv?

Thanks!

[thebutterson]

The teeth should not touch. The Bentley manual gives a spec for the gap between them.

The plug you're looking at is the RPM sensor. M10's use this rather than a Crank Position Sensor.

Get/keep timing in spec and then address the idle issue separately by dealing with the idle control system. There's a large amount of threads on this forum for idle issues for you to reference. The Bentley manual gives more numbers than just idle for timing in case you want to further check your distributor.

[Navarone]

When I had it apart I cranked the engine to see what it all did. My mental picture of what happens was totally backwards, I thought they met and touched or something but one is stationary + vacuum advance and the other is directly on the rotor off the camshaft.

I've been looking around threads and the only real answer I've found was the penny trick. I can't even find a picture of which hole to put it in, so I put it in the one facing the firewall. That fixed the idle, but I messed with timing also so I can't say for sure it's the end all fix since it's now a dog. I think the idle issue was just a gummy icv that is letting air past but I read somewhere that it's bad to clean it?! I haven't dug into the manual yet to see if the valve runs on/off of constant 12v or if it's variable voltage or something to change the opening size.

My buddy used a vacuum hand pump on the advance and it didn't hold pressure, it just pulled in then let out each time he pumped it. Even if he held it the advance would go back. Is it supposed to hold pressure or should it have a little leakage?

I should have put a timing light on it before I messed with it because now I don't know if the timing was actually off. I don't think it was, because now it's gutless at the top end. I don't know if I had set it with a little advance before, or it creeped up on it's own or I accidentally messed something else up.

Let's say the penny trick was the only variable, could that also mess with top end? And why? All it does is let less air past at idle, with the throttle wide open it shouldn't have any effect... Right?

I haven't even started messing with the high speed timing because it ran fine up high before I messed with it this time. And won't messing with the high speed also screw up the idle?

I want it to pass smog so I can sell it, then I'll go back to whatever runs best. I'm going to go advance the timing a little and put a smaller holed penny in to see if I can keep the idle the same but have a few degrees more overall timing.

Thanks for the help! I'll get that manual out and do some reading in the closet.

[Navarone]

85 318i keeps losing timing?

I just went and fiddled some more, advanced the timing just a hair and now it runs a little better. Idle went up about 200. Before (under load) it was like "are you sure you wanna go all the way to 4,000 rpm?" And now it's all "ok I guess I'll go to 5,000 if you make me... stop yelling, I'm doing my best!!" I bet I could dial in a tad more, but that's just a bandaid. I'll go do some reading about how to set high rpm timing. For some reason I remember it being stupid.

[TobyB]

I think you need a new distributor. That sort of cap damage, if the cap's seating firmly,
usually means that the bushings in the dizzy are very warm.

And yes, your vac advance is shot.

t

[Navarone]

Yay, thanks. Time to throw more money at it!!

[Navarone]

85 318i keeps losing timing?

Got a new (to me) distributor waiting for me at home. (UPS says garage but they've left stuff in trash cans before...) but I was wondering about the throttle position sensor. Mine clicks with a little bit of throttle, but there is no click at full throttle. Isn't it supposed to click at full throttle also? What does that do to the idle etc?

Thanks!