Car accelerates by itself / high idle

[CalmGuy]

The car is '93 E36 with M42.

In most cases the car doesn't start on the 1st attempt. Still, I could perfectly live with that as long as it starts on the 2nd one. But the problem is that when I start the engine, at the beginning it runs like a crap (not always, but very often). But then the car starts to accelerate by itself and idles at ~2000rpm like a champ.
If I switch off the engine while it does this crazy stuff, I have some trouble to start it again. Basically what I need to do then is to switch off fuel pump and only then crank the engine. When it starts, I switch fuel pump back on and the car continues to idle high.

Here is my video http://youtu.be/Sdpmq3TVQlA.
I need to mention, that at 1:36 and 1:40 I barely pushed the throttle and high idle even increased.

However, all of this doesn't happen all the time, in most cases only after starting the engine. If I let her to idle for some time/drive it/restart the engine couple of times/disconnect the battery over night, the idle suddenly drops and the car runs perfectly that day.


What have I done?
*Cleaned idle control valve, also replaced it with used one.
*Replaced coolant temperature sensor (Diagnostics showed its error so I replaced it with brand new one. That day the car was running great, there were no problems at all. But the following morning - same problems... Checked voltage in the sensor's plug - 5V, which is OK according to the Bentley manual.)
*Checked for vaacum leaks
*Tested throttle position sensor's resistance.
*Checked whether ECU is dry or not. It is.

Well, I'm out of moves. Don't know what else I can do. Any ideas would be greatly appreciated!!!

[DesktopDave]

You checked everything I'd have looked at...the only other idea I have is to check the throttle cable.  They have a tendency to crack at the ferrule mount on the TB bracket and stick open a bit, especially when they're cold.

BMW issued a small steel clip to bind the cable and ferrule together even if they have broken.  I found one in the scrapyard in an '89 525i.

[accota]

You checked everything I'd have looked at...the only other idea I have is to check the throttle cable.  They have a tendency to crack at the ferrule mount on the TB bracket and stick open a bit, especially when they're cold.

BMW issued a small steel clip to bind the cable and ferrule together even if they have broken.  I found one in the scrapyard in an '89 525i.

You got the part# of the small steel clip?

[colin86325]

35 40 1 165 393

http://web.archive.org/web/20080524064505/http://e30m3performance.com/installs/installs-1/throttle_clips/clips1.htm

[keflaman]

I'm going to keep an eye out for those in the junkyard.  15-20 dollars a piece is crazy!

[CalmGuy]

Well, both the throttle cable and throttle body are moving as they should. Nothing wrong there...

[DesktopDave]

Did you check the resistance of the CLT (coolant temp sensor)?  The 5VDC supply voltage is important but the DME reads resistance in ohms to calibrate warm-up sequence off the CLT and IAT (intake air temp).  Once that resistance goes low enough, the car should switch to closed-loop running, lean out the fuel mixture, and begin to read the O2 sensor (if installed).  Early E36 cars also have two sensors - one for the gauge and one for the DME - be sure a previous owner didn't help you out by switching them around - double check to be sure they're wired the right way.  The one with a single pin is the gauge sensor and grounds through the head (usually it has a blue connector and is installed further back in the head IIRC).

I'd also check the fuel pressure at the fuel rail, or off a t-fitting on the supply side (high pressure line from the fuel pump).  A bad FPR or a flaky fuel pump can cause a lot of frustration tracking down seemingly random problems.

I've also resolved similar problems by overhauling injectors, cleaning the throttle body, cleaning the MAF flap & checking the intake air temp (IAT) sensor.  The M42 is pretty famous for sucking a lot of oil into the intake but I'd assume it run rough instead of idle high.

[CalmGuy]

Sensors are in right places, connection plugs look clean... Yeah, I have checked the resistance of CLT many times. Even put one of them into water and boiled it. Resistance was changing perfectly. Also got another brand new sensor - no effect at all. So I assume that CLT is not a cause of my problems.

Fuel pressure regulator and pump? Haven't checked these, but I will. However, I have a feeling that it is some kind of electronic problem. :/

EDIT: Just did a quick research online and found that in some cases high (fast) idle may be caused by wrong ignition timing. Does it make sense? Since the ignition timing is adjusted by crankshaft and camshaft sensors (correct me if I'm wrong) would it be a good idea to check/replace them?

[colin86325]

I'm going to keep an eye out for those in the junkyard.  15-20 dollars a piece is crazy!

Somebody posted a cheaper option!  


http://www.s14.net/forums/showthread.php?58780-Throttle-Cable-Clips&p=553071#post553071