Idle adjustment with larger TB.

[Embassy]

I installed the ported and polished upper/lower intake combo with 62mm TB. Idle appears to be off.

Looks like some trial and error with the allen wrench, adjusting the screw.

To those of you with FIT or other forced induction Mercs, what are your RPMs at idle?

Thanks.

[Zack]

Dont ever touch the set screw!

You need to measure the TPS voltage and make sure its at .98-.99

Anything higher (which I guarantee it is) will raise the idle.

You are probably gonna have to enlarge the TPS holes for proper adjustment.

[magindat]

Dont ever touch the set screw!

You need to measure the TPS voltage and make sure its at .98-.99

Anything higher (which I guarantee it is) will raise the idle.

You are probably gonna have to enlarge the TPS holes for proper adjustment.

The TPS will SLIGHTY adjust via play in the screws.

Speaking of screws, I have screwed up my own throttle and idle by messing with the set screw and it was a beyotch to get back right!!!!

[Dragcity]

I marked mine and moved it 1/4 turn, which helped my situation. I know exactly where it was, But i'll never move it back.

[Embassy]

Thanks for the replies.

Doing some searching I came across this:


I did not have time to look at that thread, but I will tell you that changing the closed throttle TPS setting will do NOTHING for you. Let me explain. When you key on and the PCM powers up, it looks at the TPS voltage and whatever it is, it baselines this as 'closed throttle'. There are several throttle position breakpoints for various things like part throttle mode, WOT mode, open loop fueling, etc..., but these are calibratable settings that are programmed into your PCM. These breakpoints all use the relative closed throttle baseline setting. So fiddling with your TPS will do nothing. This is a misunderstanding that has been circulating for years now.

Mitch

http://mercurymarauder.net/forums/showthread.php?p=416828&highlight=%22TPS+voltage%22#po st416828 (http://mercurymarauder.net/forums/showthread.php?p=416828&highlight=%22TPS+voltage%22#po st416828)

Comments?

I just want to make sure I do this correctly.

Thanks

[Dragcity]

I don't know about anyone else, but my TB did not close as much as I thought it should. There was quite a gap between the plate and body. I turned the set screw 1/4 and that put the plates where I thought they should be.

No science behind it for me. I do everything seat of the pants......

It has worked for me poor idle and sloppy response.

[Fourth Horseman]

Dont ever touch the set screw!

You need to measure the TPS voltage and make sure its at .98-.99

Anything higher (which I guarantee it is) will raise the idle.

You are probably gonna have to enlarge the TPS holes for proper adjustment.

^^^This is what I had to do when I put my dual 60mm TB on.

[Local Boy]

Most times the TB does not close completely cause the cruise control cable comes up short, and prevents the throttle from closing completely...Make sure to check that...Joe, check to make sure your cruise control cable is not binding...there should be @ 1/8 of play there...

If like mine (Accufab) you may need to drill out the TB holes so you can adjust the TB sensor (voltage), to bring it "in range"...Shoot for .98 volts...

ALOHA

[Embassy]

Is there a way to check the TPS voltage with a Diablo tuner?

Thanks.

[Local Boy]

Sorry, not familiar with Diablo...but you can use a simple volt meter...

ALOHA

[Embassy]

Sorry, not familiar with Diablo...but you can use a simple volt meter...

ALOHA

True. I was just trying to avoid the PITA of sticking needles into the TPS wiring. :cool:

Drove the Beast briefly after a warm up. She's still idling at 1700 to 2000.

[Embassy]

More questions:

Can someone elaborate on enlarging the TPS holes?

How does this adjust the voltage amount.

Pics would be helpful too.

Thanks.

[Local Boy]

Embassy, with such a high idle, are you sure one of the two cables (throttle/cruise control) attached to your TB, is not binding?

Try opening the throttle with your hand (WITH ENGINE OFF) all the way...and let it go...Does it "snap" shut? If not...you have binding...

To answer your question, your TPS sensor operates on a 5 volt signal...the rotation of the armature (in the sensor) varies the voltage signal...

closed should be @ .96 thru .99 volts...WOT should be @ 4.50 thru 4.95 volts...

By enlarging the mounting holes on the sensor, you broaden the adjustment "window" allowing you to rotate the sensor to get it "in range"...

Sorry, no pics, as I'm at work right now...I would be happy to put up some when I get home...

ALOHA

BTW: On a side note...I would not recommend you drive it until you figure this one out...

A binding throttle cable = a disaster

If your ECM thinks you are at part throttle, but are really just idling...you will wreck your motor...due to timming and fuel curves being way off...

[Embassy]

Thanks for all of the replies.

#4# and Colonel came over to help me check on things.

We measured the TPS and it was reading dead on .99, thankfully.

So, the high idle must be due to the adjustment screw, right? It was adjusted and easier to drive. Still, she idles high until the IAC does it thing and brings the idle between 1300 and 1600.

Can a re-tune adjust this or is it all in the adjustment screw?

Thanks.

[TooManyFords]

I bet you still have a vacuum leak. With it idling too high, take a can of starting fluid and spray it around the intake till the motor speeds up. You've found the leak.

If you don't find one, then you have the idle screw out too far. With the engine warmed up, screw it in till it forces the IAC to compensate.

Otherwise, I got nothing.

[MitchB]

Before you do anything, measure with a feeler gauge the clearance between the throttle plate and the throttle bore with the throttle closed. Measure at the 6 and 12 o'clock positions. What is it? Do the same with the stock throttle body. There is a factory spec for this. Ideally, the throttle blades should close fully with enough clearance to prevent sticking in the bore(s). Once you get this straightened out, changing some of the idle air calibrations will probably be needed to give consistent idle performance.

Mitch

[OneBADLsE]

you are nuts to touch that screw. I know SCT's have idle settings. Sounds like a tune issue...but i may not know wtf im talking about either...

[ctrlraven]

Would a BBK Twin 62mm that was on a 03/04 Cobra work on our car?

[Marauderjack]

you are nuts to touch that screw.

What happens if you screw with the screw??:confused: :)

[Embassy]

Would a BBK Twin 62mm that was on a 03/04 Cobra work on our car?

That is the TB I am currently using.

Thank you for the replies. I believe there are no leaks and the TB seems to be closing properly. Therfore, I plan to get the Beast retuned the next month to resolve the idle issues.

Don't worry about me driving her in the meantime. It's winter around here. :cool:

[ctrlraven]

That is the TB I am currently using.

Thank you for the replies. I believe there are no leaks and the TB seems to be closing properly. Therfore, I plan to get the Beast retuned the next month to resolve the idle issues.

Don't worry about me driving her in the meantime. It's winter around here. :cool:
Awesome and thanks for letting me know. Hope you get the idle issues fixed.