Borrowed a friend's '89 E150 short van (300/C6) to pull a trailer about 1000 miles over the weekend and was really disappointed with how it was handling the 2,000-lb.-or-so trailer on the way out, so I checked and the air filter and plugs were toast. While replacing them last night a friend and I wound up cleaning the throttle body and replacing the gasket (handmade from sheet material) while we were at it - it runs much better now (probably gained 5-7 MPH at equal throttle position on flat ground) but it won't idle down to where it was before. Speed in gear is about 700 (only about 200 high IIRC) but in Park it's up around 1,500. Barring any vacuum leaks, is there anything but IAC function that could be at fault? Nothing except above mentioned parts/systems was tampered with. I'm sure my buddy soaked the IAC solenoid pretty good while cleaning the TB - the solenoid is less than a year old but may have succumbed to being drenched in carb. cleaner. Any input from somebody with more experience with Ford's speed-density systems?
Ford 300 EFI Idle Speed?
- Thread starter Alex_V
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I have an 87. Recently, I had a fluctuating fast idle.I had to remove the IAC solenoid to really clean it. The pintle had some crud on it. You should have removed it prior to cleaning TB.That's the only way to clean the IAC pintle. Some years ago I had to disassemble the TB because the hard steel throttle shaft was binding in the aluminum sleeve of the TB and I could not get it to throttle down. I burnished the aluminum lightly where the shaft contacts it as it was scored up. So you might also want to disconnect the cable and check for a binding throttle shaft. Finally, don't ever mess with the idle hard stop screw or you will never get it to work correctly. Might want to make sure the PCV didn't come out and is sucking air, increasing the speed.
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Carb. cleaner didn't show any leaks and spraying out the IAC valve didn't do any good, but upon a bit closer examination it was obvious vise grips had been on the idle stop screw not too long ago. Adjusted that and it's back to where it should be.
I may have to exercise a little less confidence in my friend's mechanical judgement in the future...
I may have to exercise a little less confidence in my friend's mechanical judgement in the future...
Originally Posted By: Alex_V
Carb. cleaner didn't show any leaks and spraying out the IAC valve didn't do any good, but upon a bit closer examination it was obvious vise grips had been on the idle stop screw not too long ago. Adjusted that and it's back to where it should be.
I may have to exercise a little less confidence in my friend's mechanical judgement in the future...
Someone fudged and tweaked it to compensate for a poorly running engine. The screw should have no influence on the idle speed whatsoever when properly adjusted.
Carb. cleaner didn't show any leaks and spraying out the IAC valve didn't do any good, but upon a bit closer examination it was obvious vise grips had been on the idle stop screw not too long ago. Adjusted that and it's back to where it should be.
I may have to exercise a little less confidence in my friend's mechanical judgement in the future...
Someone fudged and tweaked it to compensate for a poorly running engine. The screw should have no influence on the idle speed whatsoever when properly adjusted.
I understand that. Hope the van's owner isn't too insulted when I tell him the cause/effect and how his shortcut came back to cause trouble.
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