85 325e Idle Issue

[85Eta]

I have a 1985 325e which has had a bit of a high idle since I purchased the car (about 1050-1100). However over the past few weeks the idle had become increasingly higher (about 1400-1500). The car idles perfectly when cold (about 850-900), however the idle steadily increases as the engine warms up. Pulling the dipstick tube out a little drops the idle back down to about 1000-1100). The idle had never been perfectly smooth and I would really like to get it all straightened out. I would appreciate any advice on what to do next. Below are the links to two videos I took to try and assist diagnosis.

http://youtu.be/GTPYKp9PU4Y

This video shows the advanced position of the AMF dial and the effects that removal of the dipstick has on the idle. There is nothing of significance after the first 30-40 seconds.

http://youtu.be/qCT8EIPu_g8

This video begins with a quick rev, but demonstrates how long it takes for the idle to settle back down.

Steps taken
1. Smoke test (revealed leaking intake elbow hose)
2. Replaced hose and retested with no further leaks
3. Cleaned throttle body and ICV
4. Inspected breather hose running from ICV to intake elbow hose
5. Inspected short hose attached to other side of ICV
6. Tested TPS for “clicks” and ohms
7. Cleaned oil out of TPS
8. Checked AMF flap for full range of motion

Further observations
1. Unplugging ICV results in greatly increased idle speed
2. Unplugging TPS has no observable difference at idle
3. The AMF dial observably moved no nearly half throttle position once engine is warm
4. For reasons that I do not understand, the idle surges from time to time

[LateFan]

We did more smoke tests to find all the vac leaks as we fixed them. We cleaned the ICV and tested it, but sometimes the carb cleaners etc you use make it worse - ours rattled and tested just fine, but the new one was much looser when shaken.

Search here for JLevie and his patented list of where to find the problem.

[85Eta]

Thanks for the tip. I found one of his posts here , http://www.r3vlimited.com/board/showthread.php?t=231989, and have completed steps 1-6. However, I am rather stuck at this part, "With the engine at normal operating temperature disconnect the ICV and adjust the throttle stop for an idle of 950rpm. Then shut down the engine and adjust the TPS so that the idle switch closes when the throttle arm is 0.030-0.060" off the stop screw. Reconnect the ICV and turn the ignition on. If the ICV isn't buzzing it, the ICV is bad, there's a problem in the wiring, or the ICM or DME is bad. Otherwise crank the engine and the idle should stabilize at 750rpm." My engine won't get anywhere near 950 rpms with the ICV unplugged. It's much closer to 2000 unplugged. The shop which did the smoke test for me has done other work for me in the past and is a reputable BMW service center so I'm relatively confident that their findings are correct, but I suppose I can take it elsewhere for a second opinion.

[LateFan]

Here's another list, that we used…

http://www.r3vlimited.com/board/showthread.php?p=4123043#post4123043

Plus the Bentley troubleshooting chapters, which send you to specific tests for each system.

Our ICV buzzed, it rattled, and it showed the correct test numbers, but it was bad. We also had the AFM rebuilt.

But ours had other problems too - it would just randomly not start at all, then run perfectly. We eventually changed out the DME and fixed it, but everything on the Jim Levie list needed to be done as well.

[jlevie]

Thanks for the tip. I found one of his posts here , http://www.r3vlimited.com/board/showthread.php?t=231989, and have completed steps 1-6. However, I am rather stuck at this part, "With the engine at normal operating temperature disconnect the ICV and adjust the throttle stop for an idle of 950rpm. Then shut down the engine and adjust the TPS so that the idle switch closes when the throttle arm is 0.030-0.060" off the stop screw. Reconnect the ICV and turn the ignition on. If the ICV isn't buzzing it, the ICV is bad, there's a problem in the wiring, or the ICM or DME is bad. Otherwise crank the engine and the idle should stabilize at 750rpm." My engine won't get anywhere near 950 rpms with the ICV unplugged. It's much closer to 2000 unplugged. The shop which did the smoke test for me has done other work for me in the past and is a reputable BMW service center so I'm relatively confident that their findings are correct, but I suppose I can take it elsewhere for a second opinion.

The high idle, and even higher idle when the ICV is unplugged that doesn't respond to backing off the idle stop screw suggests to me that air is getting into the intake after the throttle body. I.E., intake leaks.