low idle in drive and reverse

ghostryder

Registered User
first let me say I did use the search found some things and I did the checks that were suggested ( used lots of different key words) my 90 SC idles low like it wants to shut off in drive or reverse. it has new plugs and wires( I checked to make sure they are all tight and the wires are seated properly) new coil pack, IAC, TPS. I literally put my hand on every vacuum line and inspected it and made sure they were connected and lines were in great shape. it has a brand new exhaust from the manifolds all the way to and including the mufflers.

I am baffled what else can I check or do to solve this issue? any ideas or suggestions would be greatly appreciated.

thanks
Al.
 
Did the idle become an issue only after all that work or did you do that work to try to correct it?

Did you disconnect the battery so the computer would be encouraged to relearn those sensors?

Besides checking vacuum lines, did you check the intercooler tube connections?

How low? What rpm? What rpm does it idle at in neutral? Does the rpm jump as soon as the engine is started and then drop? Is the air filter & MAF sensor clean? Any codes?
 
you may have the exact opposite issue, you may not be getting enough air past the throttle body blade


warm the engine up to operating temperature, unplug the iac valve, the engine should die

fire it back up, let it sit and idle 3 minutes to stabilize disconnect the tps sensor and open the throttle blade 1 full turn, the engine will rev up while your turning it, unplug the iac valve and see if she stays idling, if she dies then repeat the above, if she stays idling check the tach and see what rpm shes at, you want her to idle at about 600 rpm with the iac valve unplugged

once thats done plug the tps and iac back in and enjoy
 
after battery is unhooked it will take 2 or 3 days and a few miles like 50 to 100 to learn to idle right again .
 
Did the idle become an issue only after all that work or did you do that work to try to correct it?

Did you disconnect the battery so the computer would be encouraged to relearn those sensors?

Besides checking vacuum lines, did you check the intercooler tube connections?

How low? What rpm? What rpm does it idle at in neutral? Does the rpm jump as soon as the engine is started and then drop? Is the air filter & MAF sensor clean? Any codes?
it idled the same before the work. intercooler tubes have new Teflon gaskets
 
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