Gen II Throttle Adjustment Problem

[JimDavis MT 97GTS 650R]

Searching for a solution to a low speed running problem. The car has a tendency to "lope" at low RPM causing a jerky driving condition. Changed all the plugs. Checked all the ignition wires etc and now am out of ideas. Recalling that the Generation "I" had a similar problem that related to throttle syncronization, I thought perhaps this might be the problem seeing as how I had a shop remove and clean and adjust the throttle bodys last fall. Since that time, the Viper tech has left and I am currently up a creek with out a paddle. Any sugetions as to how to proceide? Is it the left (drivers side) throttle body that should slightly lead the right when opening. and is this achieved by adjusting the single screw "out" on top of the linkege shaft, or the individule idle screws at the base of each throttle body?

A little knowledge could be a dangerous thing! Thanks in advance. (JD)

 

[Nexus-6]

I have the low RPM lope/**** as well and have been told it's pretty normal...but I'd be interested in hearing the GenII adjustment procecures as well...

 

[JimDavis MT 97GTS 650R]

Thanks for the reply Nexus-6. My 97 GTS has 51K miles on it. I am familiar with what you discribe, but this is not a "normal" moderate condition. The jerking gets so bad at times, I have to completely back off the throttle, push in the clutch, and wait for the engine to settle out! Granted,I have mods to the car, but I haven't had this problem in the past. Hopefully,there is an answer out there.

 

[Nexus-6]

Yup, same thing here - feels like the car is going to stall if you're idling very slowly down a side street for example in 1st gear under 1200K or so...

I've had this problem from day one myself on my new '02 - but if it just started happening to you then it might in fact be something different.

 

[Gerald]

It's pretty basic, just like the GenI, except you don't have to "rachet" the cable..


This is the step where you are going to need help, unless you are some kind of contortionist. Your assistant will step on the gas, while you make sure the left throttle body moves first. This is easiest if you lightly place a finger on each throttle mechanism. The movement needed is so slight that it is difficult to see one moving before the other. Since, as we all know, the hand is quicker than the eye... Have your assistant press down slowly while you feel for movement. They may have to do this a few times to make sure. The left side doesn't need to lead the right by much. Any movement at all is good enough.
(Thanks to Jon Brobst for the finger trick)
If the left doesn't lead, you will need to create some slack on the right side. To do this, press the release button on the right side, and push that cable towards the front of the car. You don't need to move it too far, just a millimeter or two (1/32") at a time is the recommended amount. Have your partner depress the gas again to verify that the throttles are now properly synchronized.

Next, have them put the pedal all the way to the floor. Verify that both throttle bodies are at WOT. The metal blades on the cable mechanisms should be firmly against the throttle body. If they aren't, you will have to remove some slack from the cables by pulling the cable housing rearward a bit. Recheck the synchronization to make sure that the left throttle body still leads the right.



cut and pasted from the "how to" section. VERY similar, just takes common sense to see the differences and take action.. Good Luck!

Gerald

 

[Janni]

Jim,
My car has been exhibiting the same things. Tom Sessions stopped over a couple of weeks back when the car was so bad it was almost undrivable - unbelievable jerking at light throttle applications. Tom cleared the memory on my PCM and cleaned the AIS motor - (air intake sensor motor) or something like that. Car ran 100% better.

It lasted for a few weeks, and now the car is starting to **** slightly at light throttle. We're ordering a new air intake motor - I suspect that will solve hte problem for good.

I know the cars are not super smooth just creeping around - but, as you said, this is nowhere near the normal behavior.

 

[Mike Adams]

On a Gen 11 car their is an ajuster screw on the passenger throttle body. You need to adjust it so that it works the saem as Gerald said.

Problem with these cars is the IAC is on one side of the intake but it has two intake chambers so not as much air makes it to the left side of the intake if not adjusted will cause this jerking movement. Mine did that originally quite bad then I played with the adjuster screw and it no longer does it

 

[ruckdr]

Another possible problem which might help, is to remove your injectors (10) and take them to Dr. Injector, or what ever injector service is available in your area. I had 2 with 'low' flow, and 'poor' pattern. This made a significant difference in "smooooothness. The throttle bodies must take up as mentioned. Plug wires also.
Later,

 

[JimDavis MT 97GTS 650R]

Thanks to all of you for your input. I will pursue each suggestion as mentioned, and report any success. (JD)

 

[GTSnake]

I think I have a similar problem but it only happens when the engine is cold. After it warms up I don't really notice any jerking or lurching. Could this be related to throttle sync as well?

 

[BlueGTS]

Gerald, when you say left side, are you referring to the passenger side? Thanks,

 

[Larry Macedo]

Hello Jim,

Are you using the stock TB's or the aftermarket? Thanks!

 

[Gerald]

passenger side has the adjuster screw, loosen the lock nut, then screw it in or out as to let the DRIVER side TB open a SPLIT SECOND sooner than the PASSENGER side TB


G

 

[JimDavis MT 97GTS 650R]

To all who have replied, Thank you again. I chose to do as Mike Adams & Gerald mentioned above. The 97 GTS throttle bodies are joined by a common linkage that is actuated by a single throttle cable. On top of the linkage bar next to the passenger side throttle body is a set screw & jamb nut which is usually sealed with a dab of paint. I found this devise allows you to adjust the lead time between the TBs. For refrence, I first determaned via the "finger technique" (thanks Gerald & Jon B) that there was no lead movment on the drivers side TB and proceided to loosen the jamb nut, then backing the set screw out. I then retightened the nut. In my case, one full turn has seemed to do the trick. More or probably less adjustment may apply for someone else. Of course, time and some miles will be the true test. Should the adjustment prove not to be the answer, it will be easily undone if you be sure to make a note of where you started.

To answer your question Larry; no the TB's are not stock. 68 or 70mm I think. I can tell by the housing that they are not the same as the original ones. My 650R was one of the last cars to be modified at [******] before you left. It was one of the non strokers. I have since returned the PCM to stock. Got a suggestion?
Best to all.....Jim D.

 

[JimDavis MT 97GTS 650R]

WOW I never got bleeped before. Thats HHHHHHMMMMMMSSSSS!

 

[Nexus-6]

Cool! Thanks Jim...I'm going to check mine out tonight.

Did you use your finger to feel the butteryflys themselves open or could you feel enough movement through the TB itself?

 

[JimDavis MT 97GTS 650R]

I checked for throttle stop movment. Truthfully, it's darnd hard to detect w/o repeated trys. The butterflys might be a better way if you don't mind removing your tubes. No guarantees, but good luck. (JD)

 

[JimDavis MT 97GTS 650R]

UPDATE....After a several hundred miles, the car is back to "jerking" at low speed. I would presume that the PCM learned the new throttle setting, and has compensated for it. BUMMER!

I would be interested in how you make out with your fix Janni. Suggestions welcome. Thanks (JD)

 

[Nexus-6]

I went out the other night and started to do this...

But I have a question.

Why does the driver side TB need to lead the passenger TB at all?

What purpose would this serve? Why would that bank of the intake manifold getting air a split second sooner make any difference whatsoever? Or is the split second too short enough for the butterfly to even crack open and it's just to compensate for spring tension?

Both of my TBs open at exactly the same moment.

Anyhow, I just wanted to see if anyone actually knew what this was supposed to be - there's nothing in the shop manual about it so I figured someone here could shed some light on it.

 

[JimDavis MT 97GTS 650R]

See Mike Adams (problem explanation) post above: #292514 dated 6/30

 

[Nexus-6]

Duh! Right there in front of me....must have skipped a few days worth of posts.

Thanks - makes sense now.