Throttle Body

RDNONE · 03-26-2003, 10:47 PM

i installed a JG Big Bore 55 mm throttle body and it came with a new butterfly, but now its very hard to give the car gas when i first start it after it has been sitting for a while. its like the butterfly is sticking. how can i fix this problem ?

gdelgrego · 03-27-2003, 02:54 AM

Does it feel like a mechanical binding of the throttle when you step on the gas... like something is sticking and has to break free?

Not sure what model, etc you have but I had a similar problem on my stock TB (92SL2) that drove me nuts for a few years. I kept doing the cleaning routine thinking it was carbon buildup causing it to stick. Finally I took it apart and noticed the throttle plate would actually bind in the bore.

All it took to fix was less than a 1/4 turn of the idle stop screw.... just until it caused the throttle plate to not touch the bore when closed.

Been fine ever since.

RDNONE · 03-27-2003, 03:07 AM

yea. thats what it feels like. ill give that solution, do you think i should give it a try? i have it installed on a 93 SL2

wolfman · 03-27-2003, 04:29 AM

Absolutely DO NOT, I repeat DO NOT, mess around with the throttle stop screw. The idle speed is controlled by the PCM and screwing around with the idle speed screw can ewsult in very strange idle behavior, an SES light and a very unfun proceedure to eventually get it right back to where it was before you messed with it.

gdelgrego · 03-27-2003, 12:02 PM

Wolfman, can you clarify the proper setup of IAC versus the idle stop screw? If my reading of the FSM is correct, setting the stop screw properly results in a setting that wouldn't let the car stall if the IAC failed closed, or in other words, in normal operation the IAC would be almost closed during idle.

If the butterfly in the TB is closing too far, then you won't notice an idle problem (like I didn't) as long as the IAC is doing it's job. But if the IAC failed the car would stall immediately. Is this the way it should be or should the stop screw act as a "backup" to the IAC and the IAC can further increase rpm by adding air when conditions require it?

I didn't want to mess around with mine either but it seemed very wrong to me for the butterfly to be stopped by the TB bore and NOT the idle stop screw. So I just adjusted the screw until the butterfly stopped on the screw.

Thanks.

**Ssicarman** · 03-28-2003, 02:52 AM

Chances are that the throttle plate may not be properly aligned in the bore. If it is not it is likely binding because of that. All it may need is to be properly aligned on the throttle shaft in the bore.

RDNONE · 03-28-2003, 10:38 PM

do i have to take it to a pro shop or am i able to align the shaft myself with simple tools ? thanks for the help guys

**Ssicarman** · 03-29-2003, 01:54 AM

First make sure that is what is binding. Chances are that you'll have to take the TB off and check it. If it is out you should be able to do it your self if you have the right driver for the plate screws.

wolfman · 03-29-2003, 06:33 AM

To properly set the idle stop screw proceed as follows...PLEASE NOTE

DO NOT make up your "own version" of this proceedure.
This proceedure assumes the IAC valve and throtte butterfly are CLEAN, FREE and working properly.

1. Start car and run until the fan comes on and then turns off (fully warmed up)

2. Remove the air intake hose from the throttle body and unplug the electrical connnector for the IAC valve. DO NOT REMOVE THE VALVE

3. Using a rubber plug or your finger encased in a latex glove COMPLETELY SEAL OFF the small IAC passage in the throttle body's throat.

4. Start engine and with the IAC passage STILL SEALED and the IAC VALVE IN PLACE and electrical connector DISCONNECTED, adjust the throttle stop screw until you obtain an idle speed of 500~600 RPM (NO HIGHER, NO LOWER) in NUETRAL (Manual) or PARK (automatic)

5. Turn off the engine, disconnect the NEG battery cable for 30 secs to ASSURE you reset the PCM, reconnect the IAC valve's electrical connector.(Remove rubber plug in the passage, if you used one, or just take out your finger)

6. Restart the engine. Initial restart may be difficult and the idle may "hunt" for a minute or so, but should then settle down to the factory specs.