keve34
03-05-2017, 11:47 PM
I replaced the head gasket on my 1995 525i manual trans, 160K miles, took me a while but got it done successfully. Also replaced the o-rings in the Vanos, as the poor thing had been lethargic up to about 2500 rpm. Reassembled, all looking good...
It started right up but idled at about 1100. Then after it warmed up for a few minutes, it began to rev up to 1700, then die down to about 1100, up-down-up-down 10 cycles every 25 seconds. It seemed like the same cycle as the computer sets for the rich/lean cycle for the oxidation/reduction catalytic converter to work. Thought perhaps a vacuum leak, but checked all the hoses, etc. and everything seemed tight. I drove it around and the car ran great except at idle (if I had an automatic trans, this cycling would likely have killed the engine at idle).
After reading and researching more, and checking all the vacuum fittings, I decided that the symptoms indicated the idle control valve or ICV. It was indeed completely stuck - I cleaned it out with brake cleaner and PB Blaster and after a few minutes I could shake the valve and it loosened and started to move as it should. Gave it some shots of WD40, reassembled and voila - normal idle, all good! OMG - sure wish I had known to check and clean that thing before reassembly the first time!
Here's the story:
I had already reassembled everything after replacing the head gasket, of course - so I had to gain access to the ICV. I just had a feeling that it was really gunked up and stuck. I didn't want to disassemble everything, as I only needed to make some room to work...
- I removed the alternator cooler hose and the front half of the air cleaner housing to provide some more room to work,
- I removed the air intake hose from the throttle body and pulled off that end of the hose that runs between it and the ICV
- then removed the engine covers, removed the ignition coil nuts that hold down the wiring from the electrical connection tray, and carefully pried up the injector electrical connection tray - some of the plastic connectors broke a little this time but I didn't sweat it too much. I disconnected the ground wire that runs from the tray to the bolt that holds the engine hoist bracket and was able to move the tray a little out of the way.
- Next I reached under the intake manifold and carefully worked at the plastic clip that holds the other ICV air hose to the underside of the manifold, and pulled that hose away from the manifold.
- a few other things - electrical connectors for the air temperature sensor and the throttle position sensor, pushed various hoses out of their holders, etc.
- Then I removed the bolts from the intake manifold supports - those are underneath and a bit hard to get at but not too bad - then removed all the nuts that hold the manifold to the head.
- I did not take any of the fuel lines off, or the hoses or cables to the throttle body. I didn't have to move the intake manifold all that far.
- I was able to pull the manifold away from the head, and prop it up on top of the dipstick - this gave me good access to the ICV.
- Then loosened the hose clamp on the upper ICV hose (the one that clips into the intake manifold) and worked that hose off the ICV, and disconnected the electrical connector on the end of the ICV (towards the front of the car).
- Worked the ICV out of its rubber holder ring, and extracted it (along with its lower hose - the one that runs underneath to the intake air hose).
- I removed that lower hose from the ICV, looked inside the ICV and it was pretty ugly in there.
- Wow that ICV was really stuck. I used brake cleaner (as my carb cleaner can wouldn't squirt) then some PB Blaster, and set it down for a few minutes.
- Came back, started shaking the valve and suddenly it freed up and started moving inside, just like in the Youtube videos I had seen about cleaning an ICV.
Gave it some shots of WD40 - it seemed to like it...I put everything back together, connected the battery, and he started right up and idled at about 700 - Magic!!
All this took me about 3 hours. If I had to do it again (boy I hope not!) I could probably get it under 2.
Drove it - all good! Idles now at about 600. Much better low-end power after replacing the Vanos O-rings. Happy!
It started right up but idled at about 1100. Then after it warmed up for a few minutes, it began to rev up to 1700, then die down to about 1100, up-down-up-down 10 cycles every 25 seconds. It seemed like the same cycle as the computer sets for the rich/lean cycle for the oxidation/reduction catalytic converter to work. Thought perhaps a vacuum leak, but checked all the hoses, etc. and everything seemed tight. I drove it around and the car ran great except at idle (if I had an automatic trans, this cycling would likely have killed the engine at idle).
After reading and researching more, and checking all the vacuum fittings, I decided that the symptoms indicated the idle control valve or ICV. It was indeed completely stuck - I cleaned it out with brake cleaner and PB Blaster and after a few minutes I could shake the valve and it loosened and started to move as it should. Gave it some shots of WD40, reassembled and voila - normal idle, all good! OMG - sure wish I had known to check and clean that thing before reassembly the first time!
Here's the story:
I had already reassembled everything after replacing the head gasket, of course - so I had to gain access to the ICV. I just had a feeling that it was really gunked up and stuck. I didn't want to disassemble everything, as I only needed to make some room to work...
- I removed the alternator cooler hose and the front half of the air cleaner housing to provide some more room to work,
- I removed the air intake hose from the throttle body and pulled off that end of the hose that runs between it and the ICV
- then removed the engine covers, removed the ignition coil nuts that hold down the wiring from the electrical connection tray, and carefully pried up the injector electrical connection tray - some of the plastic connectors broke a little this time but I didn't sweat it too much. I disconnected the ground wire that runs from the tray to the bolt that holds the engine hoist bracket and was able to move the tray a little out of the way.
- Next I reached under the intake manifold and carefully worked at the plastic clip that holds the other ICV air hose to the underside of the manifold, and pulled that hose away from the manifold.
- a few other things - electrical connectors for the air temperature sensor and the throttle position sensor, pushed various hoses out of their holders, etc.
- Then I removed the bolts from the intake manifold supports - those are underneath and a bit hard to get at but not too bad - then removed all the nuts that hold the manifold to the head.
- I did not take any of the fuel lines off, or the hoses or cables to the throttle body. I didn't have to move the intake manifold all that far.
- I was able to pull the manifold away from the head, and prop it up on top of the dipstick - this gave me good access to the ICV.
- Then loosened the hose clamp on the upper ICV hose (the one that clips into the intake manifold) and worked that hose off the ICV, and disconnected the electrical connector on the end of the ICV (towards the front of the car).
- Worked the ICV out of its rubber holder ring, and extracted it (along with its lower hose - the one that runs underneath to the intake air hose).
- I removed that lower hose from the ICV, looked inside the ICV and it was pretty ugly in there.
- Wow that ICV was really stuck. I used brake cleaner (as my carb cleaner can wouldn't squirt) then some PB Blaster, and set it down for a few minutes.
- Came back, started shaking the valve and suddenly it freed up and started moving inside, just like in the Youtube videos I had seen about cleaning an ICV.
Gave it some shots of WD40 - it seemed to like it...I put everything back together, connected the battery, and he started right up and idled at about 700 - Magic!!
All this took me about 3 hours. If I had to do it again (boy I hope not!) I could probably get it under 2.
Drove it - all good! Idles now at about 600. Much better low-end power after replacing the Vanos O-rings. Happy!