c4 with high idle problems
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Pro
Joined: Jul 2006
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c4 with high idle problems
Hi I have a 93 corvette,pretty much stock. When I first start it the idle is allways about 1200 rpm for awhile then the idle drops to about 900 rpm. also it seems slow to drop in rpm when you rev it slightly. Are there any adjustments that can be done to change or check this? On a different car I once read something about taking the mass air flow meter apart,checking it with electrical meter and adjusting it inside so it had exactly the right electrical reading at the right place. Anyone know of tricks like this or ways to look for idle problems? Thanks Tim
Safety Car
Joined: Dec 2006
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From: St Marys GA
I had this same problem with my '96 LT4, and it ended up being a combination of several things. You may want to at least check them all.
Worn TB shaft
FIX: replaced the TB with a rebuilt and 52mm bored one for like $170
Vacuum Leak
FIX: replaced the intake manifold gaskets, TB gaskets, and plugged up a loose vacuum hose (supposed to go to the Opti)
Binding Throttle Cable
FIX: I think I'm still battling this, but I sprayed some WD-40 into every part of the actual cable I could get to, and it helped.
Also, I had the injectors cleaned and rebuilt, as the FSM suggested this as a first precaution. In your case, I would suspect a vacuum leak as the primary culprit. The best way I found to check for a vacuum leak is to make a soapy mixture in a spray bottle, and spray it on suspect gasket surfaces. If there's a leak, it will bubble and fizz.
Worn TB shaft
FIX: replaced the TB with a rebuilt and 52mm bored one for like $170
Vacuum Leak
FIX: replaced the intake manifold gaskets, TB gaskets, and plugged up a loose vacuum hose (supposed to go to the Opti)
Binding Throttle Cable
FIX: I think I'm still battling this, but I sprayed some WD-40 into every part of the actual cable I could get to, and it helped.
Also, I had the injectors cleaned and rebuilt, as the FSM suggested this as a first precaution. In your case, I would suspect a vacuum leak as the primary culprit. The best way I found to check for a vacuum leak is to make a soapy mixture in a spray bottle, and spray it on suspect gasket surfaces. If there's a leak, it will bubble and fizz.
Thread Starter
Pro
Joined: Jul 2006
Posts: 635
Likes: 1
Hi no lope at idle just too high and not very reponsive.I'll check the other things. Wouldn't a vacume gauge show a leak or would it be too smail to show? When a tb shaft gets worn does it leak vacume at shafts or just bind up? when I'm looking for vacume leaks I use a small peice of hose to listen for them but I'll try the soapy water way to. Thanks Tim
