High Idle

H

HAMMERHEAD

Member
Yesterday a friend stopped over and wanted to go for in a ride in the Syclone. I drove around the neighborhood for a couple of blocks to warm up the engine and then pulled onto the highway to do a 1/4 mile or so run.

I boosted about 5 lbs and did a little over a 1/4 (up to about 115mph) and when I stopped to turn around I noticed the idle was around 1,000 rpm. I did one more boost launch run for him and the truck still ran great. When I got home, I left the truck in the drive way with the hood up to cool down before putting it back in the garage.

Later, when I cranked it to put it in the garage, the idle was at a steady 2,400 for about a minuite before it dropped to normal. Any one have any ideas for me to start with?
 
nello

nello

Active member
Re: High Idle

Start by resetting your IAC bro. Certainly worth a shot as it's really easy to do.

With the truck hot, ign off, jumper two top right terminals of ALDL port w/paper clip, turn ign on, listen to IAC do a diag/reset for 30 seconds, turn ign off, wait another 5-10, start truck.
 
H

HAMMERHEAD

Member
Re: High Idle

I cranked it yesterday and it idled at 1100 for about 30 seconds and dropped to 800. I noticed that my air/fuel gauge was reading from the 10's to 11's but idled real good. I guess it liked the rich idle. Then I got a check engine light. Probably a rich o2 code. I might try to lower the fuel pressure. As far as the intake gasket, It might be bad but my truck has a steady 20 lbs of vac at idle and about 18 lbs in gear. I am stumped.
 
Bill Z

Bill Z

Donating Member
Re: High Idle

Sounds like a sticking IAC. Try removing it and clean it up with some carburetor cleaner. Should fix it up so it will not happen again (for a while). One of the problems with not driving every day.
 
Mephisto

Mephisto

These trucks are cursed
Re: High Idle

I'm having the exact same problem. Mine will idle at 2400 for about a minute, the CEL comes on (code 35 IAC error), then the idle eventually drops down to normal after about 2 minutes, and the CEL light goes off. Does it if i haven't driven the truck for a few days. I just replaced the IAC valve so it shouldn't be sticking. I'll try the ALDL trick and see what happens. Definitely annoying though.
 
Mephisto

Mephisto

These trucks are cursed
Re: High Idle

just following up on this thread...

The problem is now 100% consistent... Start the truck, rpms go up to about 1800 and hold. Eventually they'll come back down to normal 600-800... but the time to do that is completely random. Sometimes it'll do it quick, other times it'll take a 3-5 minutes.

I just pulled IAC valve yesterday, cleaned it, and cleaned the connection with electrical cleaner stuff, checked all the vacuum lines... same problem. Doesn't matter if it's hold or cold... I adjusted the throttle position screw thinking maybe it was too low and the computer was over compensating for not enough air at idle... and that didn't make a difference.

this is also a problem while I'm driving... if i take my foot off the gas to slow down for a stop sign the RPMS jump all over the place and yesterday it even stalled out.

eventually it works itself out and drives normal... but it's almost like the computer is resetting itself every time i turn the truck off and has to recapture all the sensor data and adjust before it drives properly.
 
D

Damian

Member
Re: High Idle

Mine has done that since I got it. Mine stalls out sometimes when I put it into gear, of course its when a bunch of cars are behind me. My tach is jumpy at idle as well, not while driving around though.
 
Mephisto

Mephisto

These trucks are cursed
Re: High Idle

might have some other major problems now... this POS could be going over a cliff tomorrow. :squint:
 
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