High Idle in 1998 Vortec 5.7

[BluC10]

Hey guys this is my first post here, thought i would come here since it is specific to our trucks. My truck is a 1998 RCLB 2wd with the 5.7 vortec. I start it up and it does the "choke" idle for a few seconds and then drops down to the normal 650 which is all good. But recently it started to, after it has reached full operating temperature, as soon as I put it in park it goes up to 1200 rpm really quick but then settles down to 1000 rpm. Still too high and I wanna see if anyone here could help me out with this problem. Motor has 210,000 on it, all original. Out here in michigan it has been single digits with a negative wind chill if that helps anyone out. Truck has a CEL, but the code is P0442, which shouldn't have anything to do with it I would think. If anyone can help it would be much appreciated. Thanks!!!

 

[beardeddummy]

Check for a vacuum leak if no vacuum leak. clean the throttle body especially the iac port take the iac out and check for wear.

 

[BluC10]

Ok, thank you. I will try to fix it this weekend. I'll post up what it was if I find the culprit.

 

[BluC10]

I dont know if this makes sense or not but I woke the truck up this week. Usually don't take it over 2k RPM but I got brave and took it up to 3k this week and ever since then the idle has been staying down. Doesn't make sense but I'm not gonna complain I'm happy it is idling low again.

 

[Ironhead]

I dont know if this makes sense or not but I woke the truck up this week. Usually don't take it over 2k RPM but I got brave and took it up to 3k this week and ever since then the idle has been staying down. Doesn't make sense but I'm not gonna complain I'm happy it is idling low again.

Ha ha! We used to call that an "Italian Tune Up". The idea was to get the engine fully warmed up, then take the car or truck out to the highway, and put it in a lower gear, and floor it to max revs. Even better if you could do this on a long uphill climb.

Allegedly cleared up all your problems, and made the truck run good again.

Glad this worked for you, fingers crossed.

 

[racnredneck]

you probable had a piece of carbon stuck in the liner egr valve, once hard acceleration, blew it loose, and now working again, in time will have to remove egr and clean out ports in the intake.. high mileage carbon build up. normal condition of higher mileage vortec. I usually do this when I do an intake reseal on the famous vortec intakes.

 

[BluC10]

Ha ha! We used to call that an "Italian Tune Up". The idea was to get the engine fully warmed up, then take the car or truck out to the highway, and put it in a lower gear, and floor it to max revs. Even better if you could do this on a long uphill climb.

Allegedly cleared up all your problems, and made the truck run good again.

Glad this worked for you, fingers crossed.

So far it is so good, so hopefully it stays good! I was suprised it worked like that

 

[BluC10]

you probable had a piece of carbon stuck in the liner egr valve, once hard acceleration, blew it loose, and now working again, in time will have to remove egr and clean out ports in the intake.. high mileage carbon build up. normal condition of higher mileage vortec. I usually do this when I do an intake reseal on the famous vortec intakes.

Hopefully it was something that simple, makes sense to me! Thanks for the replies everyone!

 

[Supercharged111]

No, it wasn't that simple. Mine has always done this when the temperature drops down low like that outside. Once it gets up closer to freezing again, the idle is good again. This was prevalent across the blackbox, the 411, and 2 throttle bodies. It's done it with the MAF attached and not.

 

[BluC10]

No, it wasn't that simple. Mine has always done this when the temperature drops down low like that outside. Once it gets up closer to freezing again, the idle is good again. This was prevalent across the blackbox, the 411, and 2 throttle bodies. It's done it with the MAF attached and not.

Yep, Temps dropped back down low again here in michigan and here comes the high idle back. It's more or less just annoying cuz it ruins my gas mileage. The Temps needs to raise again so this stops! Lol. I guess I will just deal with it until it is warmer out again