Engine Idle Sticking in 2,000 range

[RockyTop]

I have a 1997 GTS (19,000 miles) with the the typical bolt-on mods of K&Ns, headers, cat-back exhaust, larger throttle bodies, straight tubes etc. Yesterday while driving home in stop and go traffic (engine coolant in its normal operating range), my RPM kept hanging up around 1750-2000 and then in 3-4 seconds would drop down slowly and steadily back to normal (750 rpm). It has done this at other times, though intermittently.

The last time I experienced this was before I had the intake manifold gaskets replaced. That fixed it. Is it likely/possible that they need replacement again ? Any other likely causes you can think of ? I will be taking it to the tech fairly soon to prep it for VIR.

 

[GTS97]

You can also check the idle control motor, if it is not working properly it will cause erratic idle

 

[Marv S]

Check to see if there is a lot of oil in the left air intake tube and left throttle body and the TPS to see if it's covered in oil.

If they are oil free try disconnecting the B+ from the post above the ECU (PCM) (on the driver's side) for about 30 minutes to reset the ECU (PCM).


<FONT COLOR="#ff0000" SIZE="1" FACE="Verdana, Arial">This message has been edited by Marv S on 06-13-2001 at 10:38 AM</font>

 

[Tom Welch]

Rocky,

Your problem is an intake gasket leak. It was very common with the 96, 97 vipers. Take a look at the gasket.....if it looks like a strip of bacon or doesn't lay perfectly flat between each intake runner than it has become deformed and has pulled through one or more cylinders......that is what is giving you an erratic idle as the computer is reading too much air in a given cylinder and has to correct for vacum loss, mixture..etc.

THis should be a n/c repair under warranty or TSB from your dealer and is not affected by any mods done to your car.

One more thing to note....DC upgraded the quality of materials of the gasket over the last few years, make sure you get the right one or you will be doing this procedure again one day. I believe the correct gasket part number ends in the suffix "AB"

Call or email me with any questions.

Tom
Http://btrviper.com

 

[jcaspar1]

Had the exact same problem with my 97 GTS with 13k miles. Took it to the dealer and it was throwing over 20 different codes. They finally figures out it was the battery which was the original. They changed it under warrenty and no troubles since. Voltage was apparently ok at rest but would drop to about 8v when cranking. Hadn't really noticed any trouble with starting.

 

[JonB]

Great Thread!

1) Since you replaced the I/M gasket and assuming the correct gasket (Ton is right) I suspect the Idle Air Speed motor.
(Only $80 from PartsRack!)

2) Thank You jcaspar! Battries are the root of many Viper evils, from fuel pumps to ISMs, Injector voltake errors, and more!The OEM battery is a piece of junk. (see rececnt Janni thread) And it can cause a LOT of problems. At PIR last week, we had an otherwise GREAT looking/running 1999. OEM battery. Owner stated Needed jumpstarting frequently. Died on track. Just DIED. Under Gs, and electrical demands, it just DIED. And it can casue OTHER problems when it dies! CHANGE IT 2.5-3 years.

3) While the 97 had a defective PCV line, and might facilitate leaks and puke, I doubt that is the reason. If the valbe cover boots are slimy-feeling, and the boots/lines are falling apart, you need a new system. (If you have a 96-mid 98, E-me for a CHEAP and improved, pre-clamped complete replacement, under $30)

 

[RockyTop]

Thank you for allof the suggestions. I will check it out and try to post my results (may be a few days though).