Temporary high(1500) idle speeds

[Todd Richmond]

My 97 GTS often pauses at 1500 RPM for about 20-30 seconds when decelerating from 2000+ RPM before going back to a normal idle. This gets obnoxious when trying to coast down while waiting for someone to get out of the left lane because it only happens around 20-30% of the time, forcing me to hit the brakes if they decide to take their time (common in Northern CA where the slow lane is often the only one w/o traffic)

The car has modified headers, cats, exhaust, intake and a Hennessey computer. Would a different ECU (or something else) fix this?

 

[Fred(DrivingSchool)Kinder]

First check for a leaky intake gasket. Common 97 problem.

 

[RockyTop]

I have a 97 GTS and mine has done the same (and still does occasiionally). The first time it was intake manifold gaskets. Now, it happens very ocassionally. I have been told by some very informed folk on htis board that it is probably idle control motor. Others (Hennessey) have a fix where they lessen the inner diameter of the hose leading to the idle control motor and that does the trick. Have a tech check the intake manifold gaskets first as the original material was apparently defective.

 

[JonB]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by RockyTop:
Others (Hennessey) have a fix where they lessen the inner diameter of the hose leading to the idle control motor and that does the trick. Have a tech check the intake manifold gaskets first as the original material was apparently defective.
<HR></BLOCKQUOTE>

I have seen the "Hennessey Fix" work perfectly for the problem you describe........

 

[Todd Richmond]

Gracias - I will look into both when I get a chance

Thanks,
Todd

 

[JimDavis MT 97GTS 650R]

Todd, check the battery condition, and idle speed motor and intake gasket as stated before. If you restrict the air line to the idle speed motor (ie: the Hennessey fix), be prepared for extremely low cold engine idle as a result. If all the other things check out, you might try "flashing" the computer.

 

[GTS Dean]

The early '96 GTS's required a reflash to return to idle in two steps. Sometimes this takes a few seconds to complete the cycle. This was done for emissions reasons. I think the evap canister may have been dumping too much vapor into the manifold when the throttle snapped shut. I don't know if the '97s have the same strategy programmed into the JTEC controller or not.