Annoying Idle

[swapdip]

OK guys, after replacing my timing belt, dist cap, rotor, thermostat, 6 Autolite platinum plugs, my truck runs great but idles a little strangely. With the AC comp on everything is smooth as butter, but idling without the AC on, it will stay at 800rpm, but dip down to about 650rpm once every 2 seconds or so. Cold starts are a little rougher, and every now again the engine will die if I shift into reverse too quickly. But the truck always starts right up, pulls smooth and hard throughout the powerband, gets decent MPG, MAF sensor is clean, injector cleaner passed thru every 3000 miles, so all that should be good. This isn't such a big problem but it can get annoying sometimes to always be hearing the engine dip and surge, dip and surge, and I'd like to get it worked out to how it was since before the timing belt change. I posted a timing belt video in the how to section that shows everything I did to the truck, it is a 1990 so I didn't set the timing, anyone else had this problem or have any ideas of things I should look for?

 

Thanks

[Kittamaru]

idle air control valve? Have you checked/played with the idle-adjustment screws? Maybe check/clean the MAF and T-stat? *shrugs* just what I can think of

[Kingman]

Don't mess with the idle screws on an MPFI. They're sealed from the factory...

 

Check the wiring for the MAF sensor and the sensor it's self. there's a How-To in the garage.

[swapdip]

Don't mess with the idle screws on an MPFI. They're sealed from the factory...

 

Check the wiring for the MAF sensor and the sensor it's self. there's a How-To in the garage.

 

MAF is clean, I cleaned the connections and the sensor wires with some alcohol and a qtip when I first discovered this issue. Any other thoughts?

[Chriskaw440]

MAF is clean, I cleaned the connections and the sensor wires with some alcohol and a qtip when I first discovered this issue. Any other thoughts?

 

I'm having the same sort of issue with my 1990 SE 5 spd. I posted under the 1990 year trucks "crappy idle..."

 

after replacing most EVERYTHING one can think of...and until the engine is fully warmed up....it idles like crap...like it is struggling.

 

Only thing I have not yet replaced is the EGR valve.

 

-Chris