I did search - M42 running issues.

[Mannix]

OK.  Here's the deal - 155k miles on a 91 318is, I bought it with ~115k.  Up until now, it has been very reliable.

When I got it, I immediately replaced a bunch of things - maintenance items, control arms, bushings, etc.  

I also did the timing chain (this may be relevant).  

SO, last December, here in Denver, it started to snow - and did not stop.  The car was parked for ~3 months.  It was starting to act up at that time - crappy idle, kinda shuddery, ehhhh, was not sure what was going on.  Once the snow melted, I went to drive it again.  It started right up, but started feeling funky at 4k rpm, then, once warm, 2krpm.  

Hmmm.  I've always suspected my AFM, but in this case, it does not _seem_ to be the case.  

The cam sensor is new.  Crank sensor is not, but I compared resistance to a brand new one - it may still be an issue.

Current symptoms - car starts ok, but sounds like it is running on 3 cyl.  I put new plugs in it, and it will rev to ~4k, but it sounds dead.

It sounds like the timing is waaaayyyy off.  

Back to the timing chain - could it be that the bolts on the cams came loose, and now the cams are way out of whack?  I don't THINK this is the case, but everything else is checking out OK - AFM tests fine, wires to the DME are fine, voltage increases as flapper door opens, O2 sensor is new as of 3 years ago, fuel filter has 25k miles on it, ehhhh, what the heck am I missing?  

So - I guess that's the question; is it plausible that the cam gears slipped?  Sounds odd, seems unlikely, but I'm getting down to the "unlikely" end of it.  Right now, I think I may have one of two problems.  Well, three.

1. Timing way off.  Cam gears?  I'll check that tomorrow.  Crank sensor, too - that seems likely, but I'd not expect it to run at ALL if that were dead.
2. Bad spark plugs - I put Platinum +4s in it, figured new was better than old, but I hate those things, too many horrorstories about porcelain sliding down and shrouding the center electrode.  I might yank those and put a traditional plug in it, out of principle.
3. Something Else Entirely.  

Bah.  I need to get this thing going again.  Initially, the problem was (what seems to be typical) "runs fine when cold, but won't rev over 4k, as it warms up, it won't get past 2k."  Coil packs?  

I guess I should search and figure out how to test my coil packs.

Aargh.

Any insights?  Is there a fuse that might be blown?  Main relay should be OK, all the fuses I know about are OK, why would one of these things just all of a sudden run like crap?


Thanks!



Iain

[RED IS 91]

I would put money on one or more of your coils being bad .

[Mannix]

You would lose money!

Big update. I took plugs out, cleaned everything better, stuck it all back together, and long story short, it runs 95% normally now.  

I _THINK_ that in reality, it needed a battery & some exercise.  

Now, it will turn on the CEL at steady throttle positions for >30 seconds or so - IE, sitting at a light, or if you're on the highway & the throttle does not move for a LONG time.

It also sputters at 5500rpm or so, but that's gradually getting better.

Only code is for the AFM, which I do believe is the remaining problem.

Strange, but I think it was a combination of bad gas, dead battery & sitting - I just drove it ~60 miles in the mountains, and if no one told you there was something wrong (and you did not try to rev it to 5500+), you'd not know anything was amiss.

Hmmm.


Iain

[badboypolar]

If you have a code for your AFM, it's time to change it.

[Mannix]

Agreed, the AFM is at the top of the list.  Where's the best place to get one?  Reman or "new?"  

Thanks!


Iain

[badboypolar]

"IF" you find a new it's like $500. A reman from Pelican is $182 + $80 core. You can send the core back in and get your $80 back.

I just bought one last week and it's like a brand new car.

[Mannix]

Sounds like a plan - thank you very much for the tip.  $182 sounds pretty good.

Thanks!


Iain

[RED IS 91]

If it's not running 100% how can you rule out the coils .................:confused:

good luck

[Mannix]

They all test fine, and the not-great idle + stumble at 5700 (it gained another 200rpm at lunch today:) are more indicative of fueling issues than spark issues.  

Those two items - slightly bad idle and a stumble at 5700 - are the ONLY things wrong with the car; if someone were to go drive it, they'd not think anything wrong, unless they were unusually car savvy (and kept it below 5699rpm).  

I've not ruled out the coils entirely - one could be bad, but the difference between Saturday morning and Sunday afternoon is significant.  The CEL is squawking about the airflow meter, which has been suspect since the day I bought the car, it is acting like it runs out of fuel at high rpms (but as it gets progressively better, I'm suspecting it just needs exercise), and the idle, while not *perfect*, is very good.

It needs an e-test now - it is due.  If it were not for the fact that the CEL is likely to come on during the test, while they're sitting there idling, waiting for the stuff to do it's stuff, I'd take it in - it is running very well.

I suspect the AFM will cure the rest of it completely.  

The coils check out; they do not appear to be an issue.  The wires are all in great shape - they were replaced ~1 year prior to my ownership, and it shows, they're pliable, no cracks in boots, shrug, that stuff seems OK.  

If the AFM does NOT fix it, and a coil does, I'll gladly concede - but right now, it is not looking to be coil related at all.

Thanks for the help, though - that sort of past experience is very helpful, the good thing about German cars is they seem to fail the same way every time - this time, it just seems as though it was the AFM (or DME brain, but that seems way, way less likely).



Iain