Fast Idle

[tanman722001]

Hi guys, On my wife 93 S10 blazer. It has the vortex 4.3 in it. What would cause it in the last couple weeks idle higher then normal? It idle high enough she can go 40 on flat ground without touching anything. So I need to get it fix. Thanks Tony

[tanman722001]

Any ideas

[68C15]

What is the TPS voltage? How many counts of the IAC?

[Carmen Black]

I had something similar to this. You had to stand on the brake just to hold it at a stop sign. I believe replacing the modulator and knock sensor fixed it. But this was 20 years ago, so I could be fuzzy on that.

[tanman722001]

68C15 I have no idea on voltage. I changed the IAC and TPS. It helped very little. When you use a jumper wire on the plug under dash with the key on it throws 35. Which in my book say its the IAC right? Im lost I don't know what else to do any ideas??

[68c10airstream]

Under the assumption it's a tbi 4.3, lift up the throttle body by removing the 3 bolts and replace the tbi base gasket. It's leaking air in under the base. If you are handy you can still leave the fuel lines and everything else attached. I'm handy because i'm not handsome. That's what i tell my wife! Ever seen a good looking plumber? Mechanic? Maybe on tv, but not in real life.

[68c10airstream]

If this is not a tbi set up, get someone to look at iac counts at idle. Look at target idle speed. As an example; target idle set point is displayed 750 rpm, iac counts 0, actual idle is 825 rpm's you most likely have a vacuum leak bringing unwanted additional air into the engine. Just some idle facts are this; iac counts are a rough means of adjusting idle and fine adjustments are done by advancing or retarding timing to get to the target idle speed. Don't throw your old iac motor away as i can show you how to make the best iac tester by removing the nose and soldering in led's and resistors to be able to plug in and see if the ecm circuitry is complete and the iac drivers are working properly by looking at the led light flashes and color changes. Absolutely no guessing with that tool installed.

[tanman722001]

It is not a TBI.I think I either found out what's wrong or another problem. The upper intake gasket it leaking. Would that cause the problem? Thanks

[68c10airstream]

Absolutely a vacuum leak would cause this issue. Is this the plastic upper half design? Spray carb cleaner near the suspect area and see if idle quality/rpm changes to verify. You can also use the info in post #7 as a guide. GOOD LUCK

[tanman722001]

that's how I found it with carb cleaner. Alum upper half

[tanman722001]

All fixed. Runs good know. I changed the gasket.