Cobra_R

I got an 88 vert and when i turn it on it goes to 2000 to 2500 rpms instead of 3000, and then immediately drops to about 1500 and stays there. When i start driving the rpms will go back up to 2000 and when im idling it'll remain at 2000. After ive been driving for awhile the rpms will go down to about 1100 when idling, and eventually back down to the regular idle. Whats the problem? I searched and found a similar problem and was thinking it was the tps but i dont know. If it is the tps how to i adjust it and what would make the tps change the idle?

gingenhagen

i think i have the same thing. I've never really seen it as a problem. If AWS likes to set my engine at around 2000 instead of 3000, I could care less. In fact, I'm happier. Don't like my engine running at such a high RPM when cold.

Cobra_R

yea but im worried about smog.

Cobra_R

so is this a problem?

Parastie

As for all idle problems you need to start with 2 things.
Look for vacuum leaks and check the TPS.

EDIT: To answer your question specifically. The Throttle Position Sensor (TPS) detects what you have the throttle open to, reports this to the ECU, then the ECU minister fuel accordingly. If the TPS is not adjust correctly it will send an incorrect signal and mess up the idle.

A Vac leak does similarly, unmetered air is either being pulled in or escaping. This will also throw off your idle.

Cobra_R

how do i check for vac leaks and fix the tps?

Parastie

For the vak leaks you're going to have to follow nearly every vacuum line and look for cracked lines. The quick way to determine if you have a vac leek is to buy a can of carb cleaner and spray it around the TB while the engine is running.

The TPS adjustment is outlined in the Factor Service Manual (FSM) and there are links to download it in the FAQ.

Cobra_R

By spraying around the tb, how will i notice the vac leak.

Parastie

LoL, forgot to mention that part.

The idle will change.

BlaCkPlaGUE

You know, I tried that and it didn't work worth ****...

Spray generously

Parastie

The real problem is if the car is running at a high RPM you're not going to notice a difference until you do spray a lot.

Maybe WD-40 would work better....

Cobra_R

seriously?

Madrx7racer

i have the same problem.....my TPS is NOT set right........so I have a lot of work this spring break....check for vac lines, install FMIC, and other random **** I have to do.