Small issue 1994 corvette

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Oct 29, 2013 | 01:51 AM

VirajPatel21

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Small issue 1994 corvette

I recently got my c4 corvette 94' and it runs great. 2 door coupe auto transmission

The only problem is when I come to a stop at a traffic light and wait with my foot on the brake in drive the rpm's dip a little below 1000rpm and the car begins to shake. when I put the car in neutral the rpms go back to normal and there is no more shaking.

what seems to be the problem or is it normal?

Oct 29, 2013 | 08:42 AM

LannyL81

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From: Green Valley Arizona

My suggestion would be to clean the throttle body throat, especially the TPS air passage and the blade edges. Probably best to remove the TPS and give it a good cleaning.

Oct 29, 2013 | 09:17 AM

Joe C

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Quote:

Originally Posted by VirajPatel21

1000 RPM seems a bit high to me. not real experienced on the LT1, but i'm thinking idle should be in the 600 RPM range.

w/ cleaning the throttle body - also check for vacuum leaks. good luck - keep us posted...

Oct 29, 2013 | 10:18 AM

Kmcoldcars

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From: Puyallup Washington

1000 RPM is too high for the idle. 600 - 700 is much better.

Oct 29, 2013 | 11:30 AM

94z07fx3

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IIRC 750 is stock target idle for an AT and 650 for a MT.

In addition to cleaning the TB, clean out the IAC passageway. Check for vacuum leaks too.

Oct 29, 2013 | 11:52 PM

adamzane

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From: Wyle Texas

I am sure what condition and mileage you have on you Corvette. LT1 engine auto transmission should idle in a range of 750 . Sounds like maybe its just an under load issue . You can adjust idle at the throttle body there is an idle screw . First of all make sure your tach is working properly . I good rule of thumb is if your slamming into gear then your a little high on the curb idle speed . If you just acquired this vehicle it might not be a bad idea to have a good mechanic look it over . As far as things you can do assuming you have some basic mechanical skills is change out the spark plugs , change the air filter , clean up what you can clean . RUN THE HELL OUT OF SOME FUEL CLEAR !!!!! B12 is great and would probably cure all that ales you , lol. Erratic idle , running issues , ect . How well do you know the person that you got the car from . More than likely just like my Corvette probably needs some TLC and you will bring it back to life .

Oct 30, 2013 | 12:20 AM

okinawa86vette

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From: Las Cruces NM

If you use the idle screw on the throttle body without using the procedure, you're asking for trouble. What'll happen is that you'll open the idle up, then the IAC will correct it back and you'll keep opening it until you go past what the IAC can correct for.

The idle in drive for an LT1 should be closer to 700 or 750. 1000 is higher than pretty much any factory motor GM ever made apart from some of the hi-po motors from the 60s.

I agree that the throttle body should come off and get a thorough cleaning including the IAC valve. The IAC may even need to be replaced if it's not working properly.

Chris

Oct 30, 2013 | 03:16 AM

Cliff Harris

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From: Anaheim CA

Is there a minimum idle adjustment procedure for LT1s?

I have never seen one, but it is important for L98s. It should be in the FSM, if there is such a procedure.