ISV Issue
01-31-2015, 08:41 PM
#1
Racer
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ISV Issue
Hi All,
I have been having a bit of a strange intermittent problem with starting the silver 95 C4. It starts right away when you press the gas a little and runs and drives great. We think we have it narrowed down to a faulty ISV. We cleaned it out but it is still a bit sticky and we found it starts every time when we use a feeler gauge to open the ISV flap just a little or press the pedal down slightly. We have recently replaced the mass airflow sensor, the O2 sensor and looked for vacuum leaks. A full 120k mile service done 15k ago including plug wires and a new distributer so all maintenance is up to date. Does anyone have a spare good ISV that I can use to test or possibly buy? The part is non-serviceable and fairly expensive new. If I knew it would fix the problem, it is an easy sell but I don't want to throw the part at the problem unless I need to. Thanks for your sage advice or any other ideas on what could cause this!
Mike
I have been having a bit of a strange intermittent problem with starting the silver 95 C4. It starts right away when you press the gas a little and runs and drives great. We think we have it narrowed down to a faulty ISV. We cleaned it out but it is still a bit sticky and we found it starts every time when we use a feeler gauge to open the ISV flap just a little or press the pedal down slightly. We have recently replaced the mass airflow sensor, the O2 sensor and looked for vacuum leaks. A full 120k mile service done 15k ago including plug wires and a new distributer so all maintenance is up to date. Does anyone have a spare good ISV that I can use to test or possibly buy? The part is non-serviceable and fairly expensive new. If I knew it would fix the problem, it is an easy sell but I don't want to throw the part at the problem unless I need to. Thanks for your sage advice or any other ideas on what could cause this!
Mike
01-31-2015, 08:57 PM
#2
Mike,
The fact that you state that its still not moving smoothly, means it is not clean.
As I understand it, these things rarely need replacement. Did you clean it with brake cleaner or carb cleaner?
I ask because brake cleaner does not contain the correct solvents to break down spent hydrocarbons like the carb cleaners do.
I use two cans. One to fill enough of a small container to soak the ISV overnight to break down and dissolve the residues, and one to spray clean, air blow, spray clean, air blow...till good and clean and the flapper movement is unencumbered.
A final spritzing with WD40, and air blowing out the residue helps with smooth movement.
Hope this helps...
The fact that you state that its still not moving smoothly, means it is not clean.
As I understand it, these things rarely need replacement. Did you clean it with brake cleaner or carb cleaner?
I ask because brake cleaner does not contain the correct solvents to break down spent hydrocarbons like the carb cleaners do.
I use two cans. One to fill enough of a small container to soak the ISV overnight to break down and dissolve the residues, and one to spray clean, air blow, spray clean, air blow...till good and clean and the flapper movement is unencumbered.
A final spritzing with WD40, and air blowing out the residue helps with smooth movement.
Hope this helps...
02-01-2015, 01:50 PM
#3
6th Gear
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ISV
They can take a bit of soaking to free off fully.
I cleaned mine last year, it started out a little sooty.
Once done it should be as free as this.
Video below.
http://vid1073.photobucket.com/albums/w392/Barry_Nuttall/Mobile%20Uploads/trimBBDB931D-AC43-46EF-BA2F-091416C4EA3F_zps458fe09c.mp4
Hope yours cleans up ok.
I cleaned mine last year, it started out a little sooty.
Once done it should be as free as this.
Video below.
http://vid1073.photobucket.com/albums/w392/Barry_Nuttall/Mobile%20Uploads/trimBBDB931D-AC43-46EF-BA2F-091416C4EA3F_zps458fe09c.mp4
Hope yours cleans up ok.
02-01-2015, 05:48 PM
#6
Burning Brakes
First off, if you cannot get your ISV cleaned up enough, I have a used one that works that I can "loan" you to try. Just PM me and I'll get it off to you.
Second, you should use a strong solvent to clean up the ISV. Some will advise you to not use brake keen, but I have used that before with good success. Carb cleaner is probably a little better choice since it is slightly more aggressive than brake keen.
You need to flush the valve multiple times with whatever solvent you use. Using compressed air will help. If the ISV is finally "clean", you should be able to shake it and hear the flappers rattle loudly. The rattle sounds exactly like the marbles in a an aerosol can of paint that has been shook to mix up the canned paint until the you can hear the can "rattle".
The first time I cleaned an ISV, I thought that the valve looked perfectly clean.....but, I could not get the "rattle" can sound to come from the valve as I shook it. It took two more episodes and more than two cans of brake keen to finally get the flappers to swing freely. When it finally happened, it was very easy to get the ISV to rattle at will. When I installed the valve, my idle was rock steady and the "stalling" issue was resolved.
Lastly, the fact that you have to slightly open the valve or use the throttle to start the car sounds unusual as a symptom of a bad ISV. The ISV takes its signal from the ECU and its job is to set the idle at a fixed speed and to maintain that idle. Has there been major work done to the engine recently other than servicing?
But, cleaning the ISV is relatively easy; and, if a dirty valve is the root cause of your issues, then a good cleaning should create a positive change in things.
Second, you should use a strong solvent to clean up the ISV. Some will advise you to not use brake keen, but I have used that before with good success. Carb cleaner is probably a little better choice since it is slightly more aggressive than brake keen.
You need to flush the valve multiple times with whatever solvent you use. Using compressed air will help. If the ISV is finally "clean", you should be able to shake it and hear the flappers rattle loudly. The rattle sounds exactly like the marbles in a an aerosol can of paint that has been shook to mix up the canned paint until the you can hear the can "rattle".
The first time I cleaned an ISV, I thought that the valve looked perfectly clean.....but, I could not get the "rattle" can sound to come from the valve as I shook it. It took two more episodes and more than two cans of brake keen to finally get the flappers to swing freely. When it finally happened, it was very easy to get the ISV to rattle at will. When I installed the valve, my idle was rock steady and the "stalling" issue was resolved.
Lastly, the fact that you have to slightly open the valve or use the throttle to start the car sounds unusual as a symptom of a bad ISV. The ISV takes its signal from the ECU and its job is to set the idle at a fixed speed and to maintain that idle. Has there been major work done to the engine recently other than servicing?
But, cleaning the ISV is relatively easy; and, if a dirty valve is the root cause of your issues, then a good cleaning should create a positive change in things.
02-01-2015, 06:00 PM
#7
Kinda why I blow it out with air afterwards, but you'd know better than I...Can you please recommend a light lube that would be better suited, Ed?
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02-01-2015, 07:53 PM
#8
Rennlist Member
If one wants to use a lube, perhaps silicone. But, a clean ISV shouldn't need any foreign lubricant.
02-01-2015, 08:26 PM
#9
I don't "know any better" than anyone. But I do know that WD is a poor thing to use for about anything except maybe moisture displacement. The residue is terrible, and I'd not rely on air to blow it out.
If one wants to use a lube, perhaps silicone. But, a clean ISV shouldn't need any foreign lubricant.
If one wants to use a lube, perhaps silicone. But, a clean ISV shouldn't need any foreign lubricant.
Does the flapper pivot on brass or bronze bushings?
02-05-2015, 11:25 PM
#10
Racer
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We got the ISV cleaned overnight and it starts every time with no pedal needed! Thanks all.
Note that I also went back to the stock pulley from the RS because of my charging issue with commuting and that may have actually contributed to solving the issue.
Mike
Note that I also went back to the stock pulley from the RS because of my charging issue with commuting and that may have actually contributed to solving the issue.
Mike