Author Topic: Suddenly bad idle, motor dies?! (Read 4073 times)

Frankie · « **on:** June 09, 2007, 02:34:19 PM »

Well, I washed my car, but not the engine. I drove back from the garage (pretty "fast" doing quick downshifts since I changed the transmission fluids. I changed from 3-->2 with high revs and after that I stopped to lights. Then the bad idle started, but I went on and when running it worked as normal.

However, I drove to my backyard and stopped. So did the motor. Car was idling bad the rpm's varied and then it died. I started again with quite long time until she fired up. Again bad idling and it died.

Where to start? I mean the diagnose. The idle has varied little bit and I have suspected manifold gasket leak. But what about timing chain since it is keeping noise. Is it possible that it has jumped teeth and now the timing is bad? Or can it be idle valve motor?

PLEASE HELPPPPP!!

christophbmw · « **Reply #1 on:** June 09, 2007, 03:54:59 PM »

the downshifts could have torqued your motor enough to stretch the intake boot and, if was an old boot, ripped it causing a huge vacuum leak? i know this was a problem on the M20's.

ps, why do you use the motor to brake and not your brakes? motor braking puts strain on the motor, and brakes are cheaper to replace than a motor.

Frankie · « **Reply #2 on:** June 09, 2007, 04:56:00 PM »

As I said I just changed the transmission fluids due to the bad shifting in high rpm's. Its a track day car and I changed 2 weeks ago RedLine 85-W90 fluids and they did not work. They were too thick and therefore downshiting was bad. Just playing around.

Boyracer · « **Reply #3 on:** June 09, 2007, 05:27:23 PM »

Idle control valve (ICV)? It bleeds air past throttle body so engine can idle. It is electornically controlled by ECU so water can be bad for it.

ICV's are known to stuck sometimes causing bad idle or no idle at all. Take it apart and clean with fuel. It's part number 7:

If you are really unlycky you might have overrevved the engine. This can mean bent valve(s) so one or more cylinder is missing compression because valves do not seal properly to seat :eek:

How high did you rev the engine?

e30nut · « **Reply #4 on:** June 09, 2007, 06:03:11 PM »

Differential gear oil in the transmission? That's not a very good idea. The Getrag 260 calls for ATF fluid in the transmission. If you are looking for track/heat stability, use Redline MTL at best. It's a great product, and higher viscosity than ATF for sure.

I would certainly look for massive vacuum leak, which includes checking and cleaning the ICV. Although, the ICV really does not really play when engine is at temperature. Sure sounds like vacuum...next check ignition components, wires/plugs etc...possibly a bad coil? dunno, never had one fail.

I agree with the 'use up the brake pads' suggestion. Engine braking is unnecessary wear to expensive components...pads is cheap, and then you get to try new ones:D

cheers!

Frankie · « **Reply #5 on:** June 10, 2007, 02:22:49 AM »

Thanks guys for help and moral education (high revving is bad

)

Well, I used Redline MT-90 which is transmission oil, but with higher viscosity it seemed to cause slower transmission because thicker oil film causes syncro's to engage bit slower.

I did not overrevved, maybe 5500rpm max.

I used "pressure water pump"... what hell is in english a "K�rcher" machine, you know. So I might have soaked the IDV with water??

Btw, from where (within EU) I could buy BMW tools "cheaply" like http://www.technictool.com/bmwtools.htm

Frankie · « **Reply #6 on:** June 10, 2007, 03:28:46 AM »

I think I found the fault:

part 16 was ruptured totally and was hanging out. It seems that the hose has been shrinked due to old age. I fixed it with tape(?) and everything seems ok now. What is that part 16 and what is the purpose of that? I will fix it properly when I replace the manifold gasket.

Boyracer · « **Reply #7 on:** June 10, 2007, 05:02:18 AM »

Well it was ICV related fault

Not sure if pipe 16 is before or after ICV. It should take filtered air to ICV and then ICV lets certain amount of air past TB so engine can idle. At idle the TB is completely closed.

I think that pipe is before ICV. That means that air was sucked to cylinders without it going trough air metering unit. So ecu gets singnal that there is no air going to engine but in reality there is, it is just not measured. That might cause bit of a problem

Frankie · « **Reply #8 on:** June 10, 2007, 10:56:58 AM »

Here is the actual picture of the hose. I fixed it with electricians tape

works fine.

However, what is the number 2 hose, it seems that is has leaked little bit?

Number 3 is the Idle control valve, right?

e30nut · « **Reply #9 on:** June 11, 2007, 07:38:51 AM »

yes, #3 is ICV. Not sure what #2 is, as there are a couple of different throttle body (TB) set ups that I have seen on these cars, but it's most likely another vacuum line. I've seen a version of the TB that has a simple cooling plate underneath the TB, and other setups that have a small aluminum cooling manifold between the intake manifold and the TB. These TB coolers can easily be removed with no ill effects.

I just cleaned up this rat's nest of hoses. I have 2 vacuum lines that connect to the throttle body accordian. One is lower hose to the ICV. Other is valve cover vent. There are several threads that document eliminating all those silly cooling/vacuum hoses that surround the throttle body. IMHO, they are more trouble than they are worth. Make sure you use proper vacuum/fuel line (ie: oil resistant). Also, you can add an oil catcher (trap) on the valve cover vent hose to keep your intake nice and shiney (oil free) if you like....especially good to add this trap if you track the car and or run it really hard. Sounds like you do!

cheers!