When I start the car, my RPM's go up...Like it should because of the warming thing. But about 50% of the time, it goes up, down, up, down, etc. then finally settles to where my idle is. What would cause the RPM's to go up and down when its just supposed to go up to like 3k, then back down to idle? And yesterday I noticed the car kinda doing the same thing while I put the car in natural when cruising down from 40mph or so. Any help?

 

You've probably got a vacuum leak. Its supposed to go to 3k, then slowly drop to 700rpm.

 

Yeah it should pop up to 3k unless I believe you put in the clutch...

It probably isnt supposed to jump.

 

Is a vacuum leak a big problem? I'm taking it in for a tune up in 2 weeks, they can probably fix it then if it is. Or I could if its easy enough.

 

Youll probably want to take off the upper intake manifold to replace the vacuum lines. Its a simple job IMO.

 

Upper intake manifold? And wouldn't I hear the vacuum leak? How could I locate it if not? Hole in the hose?

 

and oh yea, is it the seal maybe or the actual line?

 

Idle hunt can also be indicative of a bad/misadjusted TPS.

Jarrett

 

you can find a vac leak by using carb cleaner and spraying it on hoses and vac lines while the car is idling. If the engine bogs you most likely have found your leak. You can also do this with a garden hose running a small stream over vac lines.

 

I kinda have the same thing, when I start it revs to 2k.. then kinda bounces around at 1.5k, then settles down to a lil under 1k.. this is on a newly rebuilt motor (750 miles) and when im cruising it almost always idles fine at stoplights and such

 

The bouncing (about 1.5 second intervals) happens to me sometimes when I run it hard, then let it sit for about 5 minutes, and start it back up. Once I start driving normally, it goes away.

 

mine had been doing the exact same thing, seemed to start in the winter (very cold... around -15 F)... and now that its the summer it seems to be going away... im not sure what it might have been (tps is set... no vac leaks i can find)... im gonna be tearing apart the entire intake manifold to portmatch / clean it and replace all the gaskets, so maybe that will fix any vac leaks it may have

 

Where is the TPS located at and where is the upper intake manifold? Can i turn off the TPS?

 

the tps is the black sensor sitting in front of the throttle body, depending on your series of car it either has 1 or 2 black boxes with cylinders that move in and out of them... and is wired into the wiring harness, it basicaly tells the ecu when the trottle is closed

the upper intake manifold is part of the cast aluminum intake piping on top of the engine (it is between the plenum (box shaped thing after the throttle) and before the lower intake manifold, which bolts to the engine's intake ports

you cant turn off the tps without ditching the ecu... so no

 

awwww ok... i guuess ill just have em fix it with the tune up