Hi guys, what would cause an erratic idel? (example) after driving a bit, stop at intersection.. she jumps up to 1500 rpms , then back down and up , and so on. recent head gasket, timing chain. any ideas? thanks,

 

might wanna search on this one, because a lot of things can cause it, first question I always ask is this: What does it idle at when parked and not in gear? How many RPM.

Oh and it might help a little more if we knew what engine and truck. Very few of us will look back on your previous threads to find out.

by you saying timing chain and not belt going to assume it's a 22re and not a 3vze. by the look of the tailgate in your avatar I would assume its an 89-95 pickup.

Therefore gonna make a "edumacated" assumption that your truck is an 89-95 pickup with a 22re.

 

The most common is that your idle adjustment screw is set too high, once the brakes are applied the computer tries to cut the idle, and goes into a confused loop.

Rotate the adjustment screw counter clockwise down to about 800 RPM after its been thoroughly warmed up.

 

hehe that's why I always ask that first question.

 

Sorry guys, Its a 1986 22re.. Thanks for posts! and ideas,

 

5 speed stick, recent tune up idel at 850 rpm warm, timing to spec

 

check the operation and clean the ICV , test and ensure TPS is working properly. Make sure it is set correctly as well.

 

Coolant temprature sensor.
On the front of the motor, More toward the passenger side i believe.

Mine broke off and did the same thing.
I had no idea what it was since i had a brand new motor, But im willing to put money on the Coolant temprature sensor.

 

I think its actually 750

 

i second bojangles... my t4r was running like ˟˟˟˟ forever untill i decided to replace the heater hoses. and discoverd the colant temp sensor connector was broken and would make intermittent contact while i was driving. i ended up breaking it compleately when i did the hoses but to my surprise when i replaced it with a used one on ebay it made a world of difference. check it out there like 14 bucks on ebay.

 

Yeah, they are actually only like 20 bucks at the local auto parts store.
But check it out and see.

 

Thanks guys! plan to mess with it some this weekend, will try all your ideas. and re check corret idel speed? will let you know the fix, when it happens?

 

Seem to have fixed her,,,, noticed only happen when pushing brake pedel,,
thanks to you guys, a little adjustment to idel screw and it cleared up,,,its my nephews truck,, so i only see it on weekends, was the 1st week on road after all that motor work,,still getting bugs out!...thanks again to all posts!

 

Thanks Baha Runner!

 

Mine did the same thing, only when i pressed the brake.

You might still want to check that coolant temprature sensor.