1991 E350 High Idle problem
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1991 E350 High Idle problem
Vehicle is a 1991 E350 Passenger van, 5.8l V8, 130K miles, currently demon possessed....
Over the past month, this van has had a recurring (becoming more frequent) problem with a very high idle. We're talking 2500 RPM and it is not the normal high idle at startup (then dropping off). The only way we (mechanic and me) have been able to get the idle to drop is to disconnect the vacuum hose from the MAS sensor (of course, it runs like a pig).
There are no diagnostic codes.
The throttle body has been cleaned.
The throttle cable is not sticking.
The TPS and a variety of other components have been checked.
The IAC valve has been replaced as it was deemed the most likely culprit.
Still, the demon lives! Any suggestions at this point are greatfully accepted. This is the main family transport vehicle, so it's important to get it back to its normal self.
Over the past month, this van has had a recurring (becoming more frequent) problem with a very high idle. We're talking 2500 RPM and it is not the normal high idle at startup (then dropping off). The only way we (mechanic and me) have been able to get the idle to drop is to disconnect the vacuum hose from the MAS sensor (of course, it runs like a pig).
There are no diagnostic codes.
The throttle body has been cleaned.
The throttle cable is not sticking.
The TPS and a variety of other components have been checked.
The IAC valve has been replaced as it was deemed the most likely culprit.
Still, the demon lives! Any suggestions at this point are greatfully accepted. This is the main family transport vehicle, so it's important to get it back to its normal self.
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From: Oak Harbor, OH
there is a coolant temp sensor that tells the computer when the engine is warm, and how warm it is so it can adjust the air/fuel mixture properly. Its part fo the "speed density" fuel managment.
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This is very interesting.... I have either a slightly leaking head gasket or a small coolant leak somewhere... I had to add 2 gallons of coolant... that was probably lost over the past 6 months... I think I'd rather have the sensor problem somewhere else though.... head gasket issues aren't fun....
I'll keep you posted..... going outside to start the van with the coolant ...
I'll keep you posted..... going outside to start the van with the coolant ...
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The first thing to check for is vacuum leaks however, I would figure your mechanic has already done this.
If not then you can do it yourself with can of carb cleaner or even better propane. Spray around the throttle body, intake manifold , vacuum hose connections .. etc..
With an idle that high you probably have a very bad leak. Maybe someone forgot to connect a vacuum hose during maintenance.
If not then you can do it yourself with can of carb cleaner or even better propane. Spray around the throttle body, intake manifold , vacuum hose connections .. etc..
With an idle that high you probably have a very bad leak. Maybe someone forgot to connect a vacuum hose during maintenance.
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It must be a bad leak somewhere...
but would not a leak that bad trigger some kind of error code? We still have very good vacuum, so if there is a leak it must be localized. Worse, when this started happening, it would do it intermittently - say 20% of the time.
Now it does it nearly continuously. But, it idles smooth
The mechanic wants to see it again after letting it sit overnight.... it has to be something weird.
Searching through the boards, I came across some comments about 10 pin connectors on the 5.0l engines. Does the 5.8l have the 10 pin connectors?
Thanks for the suggestions.
Now it does it nearly continuously. But, it idles smooth
The mechanic wants to see it again after letting it sit overnight.... it has to be something weird.
Searching through the boards, I came across some comments about 10 pin connectors on the 5.0l engines. Does the 5.8l have the 10 pin connectors?
Thanks for the suggestions.
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>>but would not a leak that bad trigger some kind of error code?>>
Not always. The computer compensates for the leak by adding extra fuel, much in the same way as opening the throttle which is really just a controlled vacuum leak. I'm not saying it must be a bad leak, only this is a very common cause. With todays models and their tight engine compartments its very easy to forget soemthing silly like a vacuum hose.
It's funny you should mention the smooth idle. After doing some work on my fathers car, he mentioned that it never idled this good. For months I never touched it again. As it turned out I had done exactly that, left off a hose causing the idle to run slightly higher than normal, smoothing out the regular rough idle..
Not always. The computer compensates for the leak by adding extra fuel, much in the same way as opening the throttle which is really just a controlled vacuum leak. I'm not saying it must be a bad leak, only this is a very common cause. With todays models and their tight engine compartments its very easy to forget soemthing silly like a vacuum hose.
It's funny you should mention the smooth idle. After doing some work on my fathers car, he mentioned that it never idled this good. For months I never touched it again. As it turned out I had done exactly that, left off a hose causing the idle to run slightly higher than normal, smoothing out the regular rough idle..
Last edited by bigbadjs; Sep 28, 2003 at 08:07 PM.
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I just bought a 1990 F150 4x4 today. It has the 5.0L. It idles anywhere from 1500 to 2500 rpm constantly. It's up and down sporatically and I cleaned the TB and lubed everything also. No vaccum leaks so far that I can see or hear, but will be looking into it more tomorrow.
Very interesting to have the same problem though. The guy I bought it off of said it ran fine when he had it on propane, but he took the propane kit off it, and has had the problem ever since. I changed the timing thinking that your timing has to be a little bit advanced for propane, and the rpm's did come down a little bit, but runs rough now. I will be checking my coolant sensor in the morning though. Keep me informed of any progress and I'll do the same.
Very interesting to have the same problem though. The guy I bought it off of said it ran fine when he had it on propane, but he took the propane kit off it, and has had the problem ever since. I changed the timing thinking that your timing has to be a little bit advanced for propane, and the rpm's did come down a little bit, but runs rough now. I will be checking my coolant sensor in the morning though. Keep me informed of any progress and I'll do the same.
Last edited by FastFordGord; Sep 30, 2003 at 12:47 AM.
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Well, after having this in the shop for three days, we lived with the problem for a while.... then bit the bullet and took it into the dealership. They took a look at everything and replaced the idle control valve... high idle problem resolved. Interestingly, the service manager asked my wife, "Exactly who has been working on your van?" He was polite not to laugh, but he indicated things just looked a little weird under there...
Next comes the check engine light which is now indicating some kind of condition.....
He was polite not to laugh, but he indicated things just looked a little weird under there...Next comes the check engine light which is now indicating some kind of condition.....
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