E36 Cold start erratic

[Pyropete82]

1996 328I vert, every morning for the last 4 years I start the car, idle jumps to ~1500RPM sticks for 2 seconds, then starts jumping up and down by approximately 500rpm and then drops down to about 1k for roughly 20 more seconds, then normal ~750ish. Always happens on cold start, warm days nothing. Is this a bad
1. TPS
2. ICV
3. Temp sensor on engine block/radiator?
4. Vanos????
I cleaned out the ICV, no change
I replaced the CCV, no change
Cleaned the butterfly on TB, no change
.....what now? Intake boot clean, air filter new.

[Pyropete82]

Bump, looking for legit answer...

[MarcoZandrini]

Are there any codes? The first see is to check for codes.

[Pyropete82]

Nope no codes getting thrown out on the obc. It's the weirdest thing. I did sim out the SAP, is it possible that the blue tube running to the muffler is causing me the grief? The flap is stuck open, I'm not sure if my mechanic plugged up the tube. But a vacuum leak would erratic all the time right? I will get a golf tee up in there this weekend

[LacktheBoost]

Codes wouldn't be shown on the OBC, plug in an OBD2 reader and check for codes there. But yes, when I changed my muffler and left the flapper valve vacuum hose unplugged I did get a rough idle, though it wasn't as extreme as you described.

[Pyropete82]

So I have had this issue for 4 years and had diagnostics ran at least 3 times, 1 by my mechanic and 2 by the dealer, the only code they are getting back is my passenger airbag pad fault. I have the reset tool for that. For some reason the reset is no longer working nor is the sim attachment for it! But that is another issue.

Is there a cold start valve in the bimmer, and if that is faulty, would it normally throw a code?

[Pyropete82]

Bump, any other ideas out there? Should I post a video?

[bucs19]

@op

95 m3 does similar to what you are describing here... Usually what I do is hold my foot on the pedal just enough to smooth out the idle (you follow?) so like 900ish rpm. Give it like 20 seconds and it goes away... I also don't winter drive the car so I suppose my situation isn't a real "cold" start...
This is my November technique before I put it away for the winter.

[Pyropete82]

Yeah this happens summer or winter, always when it's colder, ie morning. I think I'm going to post a video tomorrow. But the car isn't throwing codes, so I don't know what help a video will be. Could a spark plug be misfiring potentially? Like at initial start for the first minute until things get warm internally?

[spoonerDee]

Auxiliary fan? Usually kicks on when you first start the car. Perhaps yours inst working, has a leak etc.

[Pyropete82]

What does aux fan have to do with crazy start? I been really sick today, so I hope to post something tomorrow. And there are no leaks

[spoonerDee]

What does aux fan have to do with crazy start? I been really sick today, so I hope to post something tomorrow. And there are no leaks

Sorry I meant the secondary air pump.

[Pyropete82]

It's deleted my friend, and the idle was crazy on cold start even when it was in and working. Caught the flu, I hope to get this vid tomorrow

[Pyropete82]

Lol I recorded the video, but don't know how to upload it!?

[Pyropete82]

Uploaded to you tube, get back to me peoples! This video doesn't show a really crazy idle, it wasn't that cold, but it gets worse in really cold weather
http://youtu.be/B_gZE8dOAls

[Pyropete82]

Bump

[breakaway]

You should check the throttle cable. If it is slightly loose the engine management system has a hard time finding the correct position for the throttle.

[spyderg0d]

Check for vacuem leaks. Icv. Could be a lot of things. Need more info.

[dakar rob]

I had an issue with low idle on start up then it would bump to regular idle after it warmed a little. I found that I had a small crack in a vac line. I also found a bad connection on the dme, not sure what fixed it but it was 100% after.

[Pyropete82]

All right well, it just seems strange to me that a vacuum leak as you guys mentioned would cause this idle at only cold start. I was under the impression that a vac leak would cause idle issues all the time, what are the most common areas to start to go after 100k miles?

[fraydar]

Although I don't have a solution, I do have the same jumpy idle on cold starts. The jumps seem to be regular rather than erratic. I also have the "golf tee" mod, which is a similarity.

[15Michaeljoseph]

All right well, it just seems strange to me that a vacuum leak as you guys mentioned would cause this idle at only cold start. I was under the impression that a vac leak would cause idle issues all the time, what are the most common areas to start to go after 100k miles?

well IDK if what I say has any truth to it, but we can agree that rubber shrinks and gets harder when it's cold. so if you have any leaks/cracks in vac. lines, they'll be amplified when it's cold. thats what i think anyway.

On a similar note, my mom's 97 328is does this revving thing when it's cold, but it doesn't seem to be irratic or anything, almost like it's programmed to do that to like warm up a bit or charge the battery faster. IDK though.

[Marv17]

Have you checked the ICV? Could be all dirty and not moving smoothly to control the idling. Could also be a hole in one of the vacuum lines, like in the SAP hoses that needs a better seal since you deleted it. Maybe it's not sealed 100%?

[Pyropete82]

Well before I start pulling my whole engine apart to find a pin hole, I want to try and address this effectively and methodically. That's why I'm asking for typical wear areas.

I have cleaned the throttle body and icv thoroughly. I cannot tell whether the throttle cable is "loose". The SAP has been deleted, and all holes plugged. Again, if I had a vacuum leak my idle would go wacky all the time, this is only happening on cold start when it is cold

ICV has continuity...is there a potential fault in the fresh air intake valve that triggers the initial start of the car? There is something that forces the idle to go higher in cold start mode, I believe this to be the culprit, so where is this little devil?

[15Michaeljoseph]

Check your intake boot and brake booster connections for starters.