I went and cleaned my MAF, EGR, TB, and TB elbow two weeks ago. Took it all off the engine and cleaned them with the appropriate cleaners. My idle was at 550 rpm before and now its at 650 rpm but now it will surge up to 800 rpm when stopped at a light for more than a half a minuet. My only guess is that I screwed up the IAC or TPS when I cleaned everything else.

Any suggestions?

1998 5.4L 82,000 miles

 

My suggestion would be to replace the IAC, then force the EEC to re-learn idle programming.

Steve

 

junk into the seat of the IAC when you cleaned the throttle boby...remove the IAC and blow out the cavity at the top of the throttle body

 

quote: Originally posted by Raoul

Next time it won't idle try tapping the IAC a few times then try it.
This happened to me and the IAC was gummed up. When I hit it a few times it unstuck itself.

I had the IAC replaced under warranty at about 25K. It was on back order at the time and I had to carry a screwdriver for the intermittent 'no idle' condition.

 

I have cleaned my IAC twice, and both times it would idle funny for a day or so. After that, it would clear up like nothing was ever wrong. Pull it off, blast it with TB cleaner, and clean it out with a Q-tip or two. Gently pry the plunger inside up, and clean around the seal also. Make sure you get it good and dry before re-installing it. Both times my truck stopped doing the low idle thing it was doing before. I guess I should replace it, there's 86k on this one,,,,98

 

my truck is doing the same thing......but what exactly is IAC or TPS??
thanks

 

IAC is a cyndrilical sensor about 2-3 inches long, with an electrical connector mounted on top of your TB. Just replaced mine ($75 for part) The TPS (Throttle Position Sensor) is located on the drivers side of your TB. It is round and flat. Has an electrical connector as well.

I would start with the IAC first. It cleared my idle problem right up. Did have to let the computer relearn after the change, but by the time I drove it home and started it up the next a.m. it was as good as new.

John

 

..that if you took the TPS off and you didnt know that is has a certain position it sits in then you could get some idle surging if the voltage is above 1 volt.....

Neal would have to refresh this procedure... but you take the 3 wires coming out of the TPS and probe 2 of them ...you have 2 hots and a ground so to speak....one hot is around 3 volts I think (can't remember for sure) and the other wire's voltage goes up and down with the position of the TB/TPS. Slightly unscrew the TPS and rotate it until you get about .98v through the wire. Remember when you do this the ignition has to be on and the truck off. When you get to right under 1 volt tighten the screws down. Of course if you didnt take the TPS off then it should be within tolerances from the factory.

Just some helpfull info..

5.4