I'm looking at a 92 RS LO3 for purchase. My mechanic checked it out and feels the idle is too fast and too long in duration during warmup. What sensors control this? The guy who owns it says it never gave him any trouble but I would like to get it right after I buy it. Any ideas?

 

How long does it take to warm up? Maybe the thermostat is stuck partially open. Stock ECM?

 

Maybe your mechanic doesn't know squat about EFI cars?

First, if your mechanic had a scan tool, he'd IMMEDIATELY see if any sensor was acting funny/weird. If the T-stat was stuck, then it would show with a scan. The only thing I can say is your mechanic DOES NOT have a scan tool (an absolute must to work on EFI cars) and/or he doesn't know his butt from a hole in the ground.

The "warm up time" and "idle speed" is all controlled in the eprom. Yes, an errant sensor and/or stuck T-stat (which affects the CTS sensor) will delay the warm up and cause a high idle - BUT your mechanic MUST have the tools to diagnos this.

Lastly, a vacuum leak (bad gaskets is very common with TBIs between the TBI and the intake manifold) will cause a high idle speed that NEVER decreases - but you'll notice other driveability problems.

What is your car idleing at? Maybe the mechanic is "finding" a non-existant problem other than lightening your wallet. But when I think of all possibilities I come up with the same conclusion - FIND ANOTHER MECHANIC!

 

Glenn98lt1gta, please don't assume my mechanic doesn't know anything. people hjave come to him from all over the east coast about small blocks. Since my parents staryted going to him in 1969, he has never steered them or me wrong and I've driven plenty of cars that never would have run without him. Thanks for your input. It all turnedout to be the coolant temp sensor. I bought the 92 RS last night and I'm loving it .

 

PS my mechanic and I are old friends and he didn't charge me for "squat".