Problem noticed after snow storm

[Arpegius]

So my '89 325i had not been driven for 2 weeks due to the extreme snow and ice on the roads around my area. I would run it in the driveway for about 20 minutes every couple days or so. When I went to drive it again I noticed if the car is rolling whatsoever regardless of being in gear or not, the engine idles around 1000 rpm when before it idled around 600-700 or so. However when I stop completely the idle settled to the normal speed. Anybody have any ideas?


Also I noticed a squealing sound coming from the front of the engine bay on a cold start up assuming it could just be cold belts. How long do the belts usually last on these engines? Thanks everyone.

[jlevie]

The belts last until the break or start squealing... But the should be replaced when there is evidence of cracking or glazing on the driven surfaces.

Are you saying that if the engine is idling and you just release the brakes and get the car rolling with the transmission in neutral the idle jumps up to 1000rrpm? Or do you mean that when you let off the gas and put the clutch in that the engine doesn't go below 1000rpm until after the car comes to a halt? I have no idea what might cause the former, but the latter could be a sticking throttle cable, sticking throttle body, sticky ICV, or intake leaks.

[Arpegius]

The latter. When I let off the gas, put my foot on the clutch and coast, the revs do not settle below 1000rpm. Your diagnostic sounds like it would make sense. Unfortunately I would not know where to start looking, or know how to test it without being able to have the rear wheels rolling in neutral. The problem is very consistent though. Not an occasional idle problem, but it happens every time I go to stop.

[Arpegius]

The belts last until the break or start squealing... But the should be replaced when there is evidence of cracking or glazing on the driven surfaces.

Are you saying that if the engine is idling and you just release the brakes and get the car rolling with the transmission in neutral the idle jumps up to 1000rrpm? Or do you mean that when you let off the gas and put the clutch in that the engine doesn't go below 1000rpm until after the car comes to a halt? I have no idea what might cause the former, but the latter could be a sticking throttle cable, sticking throttle body, sticky ICV, or intake leaks.

When the car is rolling. Regardless of letting off the brakes on a hill or decelerating to stop. If the car is rolling no matter what (reverse or forward)(foot on clutch or tranny in neutral), then the car idles at 1000rpm. When i come to a complete stop, then it settles back to a normal 600-700 rpm. I asked a local shop and the guy there said it sounded like a computer problem. Like from the snow storm perhaps moisture got on it and shorted it out somewhere. I really am trying to figure it out before i end up paying a hefty price. Thanks.

[jlevie]

I don't remember the DME as having a vehicle speed input. If that's the case (check the wiring diagrams for your car at http://wedophones.com/BMWManualsLead.htm) the DME can't tell if the car is moving or not. Which suggests a throttle cable or throttle problem.

As a test, find a place where you can bring the car to a stop at the top of a hill and hold the car with the parking brake with the transmission in neutral. Don't touch the brakes or accelerator and allow the idle to stabilize. Then release the parking brake and allow the car to roll down the hill and see what the idle does.

[Arpegius]

I don't remember the DME as having a vehicle speed input. If that's the case (check the wiring diagrams for your car at http://wedophones.com/BMWManualsLead.htm) the DME can't tell if the car is moving or not. Which suggests a throttle cable or throttle problem.

As a test, find a place where you can bring the car to a stop at the top of a hill and hold the car with the parking brake with the transmission in neutral. Don't touch the brakes or accelerator and allow the idle to stabilize. Then release the parking brake and allow the car to roll down the hill and see what the idle does.

ok, I tested it. Foot off brake. Foot off clutch. In neutral. Let off the parking brake, and as it rolled backward the idle went to 1000rpm. Then I pressed the brake and came to a complete stop and it settled to 600-700rpm. Does this forward and backward. I have no idea what is wrong.

[nando]

I don't remember the DME as having a vehicle speed input. If that's the case (check the wiring diagrams for your car at http://wedophones.com/BMWManualsLead.htm) the DME can't tell if the car is moving or not. Which suggests a throttle cable or throttle problem.

As a test, find a place where you can bring the car to a stop at the top of a hill and hold the car with the parking brake with the transmission in neutral. Don't touch the brakes or accelerator and allow the idle to stabilize. Then release the parking brake and allow the car to roll down the hill and see what the idle does.

Motronic does have a VSS input.

[gtdragon980]

my car has a similar issue with the idle, sometimes it will idle around 1200-1500, then go to 600-700. i cant really figure out what is triggering it to do it but its not always doing it, only sometimes. also sometimes when i press the clutch it revs higher, its just weird and makes no sense?

[Arpegius]

^ well this is silly. WHAT IS GOING ON WITH OUR CARS? an auto enthusiast drove my car and told me not to worry about it. If its off a little it isn't worth spending a bunch of money trying to find it. However I am worried about it getting bad enough to the point of it doing some real damage. The problem you seem to be having may just be a vacuum leak, but I'm no mechanic. I don't think mine is a leak related problem. Its too consistent.

[Arpegius]

Ok so today I tried something. I popped the hood while the engine was running to see if I could fiddle with anything. I would open the throttle just barely and it would rev to around 2000. There is no subtle increase in revs up to that point. I found it was really touchy. Also when I would do this and let off the throttle to settle the revs, I would hear a slight squeal or high pitched buzz coming from the ICV once the engine idles normally, at least I think its from that unit. Hopefully this will help guide any sort of help you guys might have. Thanks.

[nando]

your ICV is probably gummed up or dead. Try cleaning it with carb cleaner first, and if that doesn't help I would replace it.

[Arpegius]

I took the ICV out and cleaned it with injector and intake cleaner. I removed a lot of dirt but it didn't fix the problem. How can I tell when the ICV is bad? ALSO if the ICV isn't the problem, is there anything in the ECU that picks up if the car is moving and is it related to the air/fuel mixture that could mess with the idle?

[nando]

if the TPS switch isn't adjusted properly or isn't working, the car won't go into closed loop idle at the right time.

the AFM, O2 sensor and Coolant sensor all affect the A/F ratio, but I'd be surprised if one of those was causing a high idle. The most likely out of those three would be the AFM, if it were stuck or something. you could clean it like you cleaned the ICV.

btw, with the ignition turned on, does the ICV buzz?

[Arpegius]

The ICV seems to have an intermittent high itch buzz. It doesn't sound to be constant. It buzzes for sure when I let off the throttle and the revs settle to normal.

I also replaced the TPS a little while ago, but my idle seemed to be just fine up until a snow storm when I was unable to drive for a couple weeks. Which is when I started noticing this idle problem. I haven't checked for Vacuum leaks, but the problem is too consistent to seem like a vacuum leak. How is the TPS suppose to be positioned? Maybe i can check that.

[nando]

if you turn the ignition on but don't start the car, the ICV should have a consistent hum (between 60-80hz). If it's intermittent than either the ICV or the wiring to it is bad.