$500 in parts- now have stumbling issue

[Philo]

So just for clarification, the car stumbles but the tach shows no decrease or increase in rpm? I assume your TPS is good. I've seen this thread floating around for ages so I thought i'd try and lend a hand.

[bimmerboy12]

OK-Im getting full resistance across the CTS prongs when the car is off. 799 ohms when the car is running, then 1650 after turning the car back off. Tonight it started and idled really nice, then got shitty when warmed up. Sometimes its shitty right when i start it cold. It is completely temperamental. Another thing I noticed is a really shitty throttle response when the car is cold. If you punch it right after starting there is a half second of nothing then it takes. After its warmed up this problem goes away (although I must admit the throttle response is not perfect). I double checked for any arcing in the dark and saw absolutely nothing. I know some of you said the cap and rotor look rough for how new they are. What would have caused this? These are both Bosch items.
Any other ideas?

[bimmerboy12]

haha yeah don't think so, notice it from 1K-6K. I KNEW somebody was gonna say that!
I would attribute it to all the new ignition components.

[scabzzzz]

The car drives awesome and has tons of power when you get past idle... more than ever in fact and I've been driving it since 2000.

Advanced timing!

[bimmerboy12]

I keep watching this thread and without seeing the car, I really dont know.

My bet is the timing is off a tooth and you're just not seeing it. Like maybe you marked it wrong and its lined up perfect with the wrong tooth. If it was a tooth off, I think the effects would be similiar to what you're experiencing. Amirite?

I just can't see it. The pulleys can only go on one way rotationally. I put on the belt and rotated the engine by hand two full rotations and verified both marks were hitting at the same time... dead nuts on. Although its been awhile, I have timed many motors in the past with no issue. Also, sometimes the stumbling is worse than other times. The car drives awesome and has tons of power when you get past idle... more than ever in fact and I've been driving it since 2000.

[scabzzzz]

I keep watching this thread and without seeing the car, I really dont know.

My bet is the timing is off a tooth and you're just not seeing it. Like maybe you marked it wrong and its lined up perfect with the wrong tooth. If it was a tooth off, I think the effects would be similiar to what you're experiencing. Amirite?

[bimmerboy12]

So it stumbles at all engine temps, right?

Does it stumble when you remove the harness from the temp sender?

Measure the resistance at the engine temp sender prongs.

Yes, it stumbles at all temperatures, sometimes it is worse that other times randomly. Sometimes when I start it cold it will idle so rhythmically that it will almost die when I put it in gear.
If I remember correctly, it will not stumble when you remove the CTS harness, because the idle goes up high enough to smooth it out (Im assuming). I will try again tonight and also measure the resistance across the prongs. Look for another post in 6 hrs.
Thanks again everybody.
Brian

[bmwpower]

So it stumbles at all engine temps, right?

Does it stumble when you remove the harness from the temp sender?

Measure the resistance at the engine temp sender prongs.

[bimmerboy12]

Often times the injector harness plug under the IM gets corroded.(coolant temp wires are also a part of this harness) Especially the coolant temp sensor prongs. I am heavily leaning towards that. So depending on how you are testing the sensor, if you just measure the resistance across the sensor that will not help you if one of the wires for the sensor is corroded in the harness.

OK, the car not starting was a low battery symptom, apparently having the key in the accessory position for an hour drained it enough that it would not turn over, even though it measured 12 volts??? Charged it up and its fine. That crisis averted hopefully.

I cleaned all the corrosion out of the circular harness beneath the IM, I am pretty sure that is OK. I know the coolant temp sensor is doing something, because when I unplug it while running the engine will idle high, around 1200 rpms or so. Plug it back in and it drops to around 700-800, but still stumbling.

[E30Eric]

Often times the injector harness plug under the IM gets corroded.(coolant temp wires are also a part of this harness) Especially the coolant temp sensor prongs. I am heavily leaning towards that. So depending on how you are testing the sensor, if you just measure the resistance across the sensor that will not help you if one of the wires for the sensor is corroded in the harness.

[bmwpower]

NO NOTHING. as if there wasn't even a starter there.
Is there a fusible link on this car I can check?

I *believe* there is a fusable link but never saw it. Definitely check the fuses upfront. Not sure why they would blow like that, but I'm wondering if this is getting you closer to the read problem.

[bimmerboy12]

Geez. You can't catch a break.

You sure it's 12v at the battery?? Not even a crank??

NO NOTHING. as if there wasn't even a starter there.
Is there a fusible link on this car I can check?

[bmwpower]

Geez. You can't catch a break.

You sure it's 12v at the battery?? Not even a crank??

[bimmerboy12]

ok, so now I am really pissed off. I just had the car in the garage to check that booster vacuum hose, and I reset my service indicator, and had the car on the "accessory" position for an hour to reset my radio (wrong code too many times). THATS IT. Now I try to start it and nothing happens when i turn the key! full 12 volts. NOTHING! I am so fed up with this! I feel guilty when I say I was browsing for E46's today...

[nomis3613]

my 2 cents

OK, pulled the brake booster vacuum line. Started sucking air like a bitch and idled horribly but did not die. Plugged it back in and resumed to normal shitty idle.
I have now done everything you guys have suggested. Please don't tell me its time to take it in to the stealer...

Sorry to hear you're still having problems. I know how much it sucks, I've been through a very similar saga. Got a mechanic to do timing belt (just like you did yourself), valve gaps and mixture adjustment and from then on it intermittently idled like a pig and throttle response was terrible. That was over a year ago, and various mechanics could never find the problem. But last weekend I got it back from a fine-toothed comb job at the mechanic...and...IT'S FIXED!!!

So hang in there dude, with patience and a logical approach you will get there in the end. My problems (check your PMs) turned out unrelated to original work, just coincidence that the problems started then, or perhaps it just upset the delicate mystical balance of an engine that was hanging in there despite its problems. And it will be worth it in the end, because I've rediscovered how wonderful these cars are to drive when they're running properly.

Enough pep talk, here's my conspiracy theories:
1 The Bosch ECU has a set warm-up cycle where it runs a pre-programmed sequence. Only after a certain time does it start listening to its sensors. If it runs fine when cold, then it points towards a faulty input (or input processing in the ECU). You said you changed the "sending" CTS, sorry could you confirm this is the one to the ECU, not the dash?

2 I wouldn't write off vacuum leaks just yet. Perhaps others can help here, but will stethoscope testing pick these up? FWIW My mechanic did a smoke test and found some leaks I wasn't aware of.

3 I would also check the rotor/cap. Might not be the main cause, but possibly a contributing factor.

4 Sorry if you've mentioned this, but have you tried your old plug leads?

5 Go back to basics with some testing while it is running bad. Sure this stuff will seem irrelevant considering what you changed to cause the problem but it'll help you narrow down the cause. You might need to go to a pro cause they have the tools, but if go to an independant not a dealer and just ask for a specific test then you shouldn't get bent over backwards too much! Checklist:
Fuel pressure?
Spark trace on oscilloscope?
Mixtures rich or lean?
Fault codes?

Hope ya get sorted soon.:drink:

Simon