ordered a new Throttle switch from 928RUS yesterday. It will be here today, and I will get started on replacing it. Did I mention that I hate doing things over?

 

yeah pulling the manifold AGAIN sucks! Ive pulled the manifold 3 times now. Once on the old engine and twice on the current new engine.

John, When you install the new one, make sure you correctly orient the switch. It can be adjusted a few degrees and a new switch incorrectly adjusted can lead to the same issues. When your holding the throttle body, adjust the switch's position so that you hear the audible click when the throttle is closed, or even slightly before it closes. Its simple to adjust and pretty obvious when you know what your looking for, but I think it can often times be overlooked. I know when i did this the first 2 times on my manifold repairs that i never bothered to check the position of the thing.

 

Thanks Ryan

 

John,

Before youve taken the Intake manifold off, try pulling the ball socket from the throttle body cable OFF the linkage on the manifold. Listen for the click.

If the cable is disconnected and you hear no click then proceed to replace the TPS switch.

If you hear it click when the cable is loose then your cable is too tight and isnt fully closing the TB and isnt engaging the switch. In which case you need to lenghten the cable by either shortening the sleeve that it runs in by screwing the sheath farther into the linkage bracket. Or you can lengthen the cable by adjusting the screw and nut that goes into the ball socket portion of the cable. Both ways will loosen the cable itself so that its not binding.

I replaced my throttle cable through the firewall and finally got my idle to where its supposed to be. My cable was too tight so it was never fully closing the throttle body and never hitting the TPS switch consistantly. Now my car idles PERFECTLY and the revs are flat at idle and it sounds much smoother at idle.

If you want more info see a thread i started on cable adjustments. I just updated it tonight so it should be on page 1.

 

Thanks again Ryan. Roger and I put the Hammer on the car and it did not detect a signal from the Throttle switch. I was hoping it was just not connected, but alas that was not the case. Intake is removed at this point to gain access to the switch. I will swap it tonight and put the intake back on.

 

Just an update: Replaced the throttle switch, and spent about 30 minutes getting it adjusted so that the switch engaged/disengaged when the throttle linkage moved the least amount. Put the intake back on, the injectors, fuel rails, etc. Started the car and voila, it seemed to work for about 1 minute before the car warmed up and then it started hunting for idle.
I said "DAMN"
Drove it anyway to the DFW GTG. On the way to the GTG, I started thinking to myself;" Did you ever hook the electical connection to the throttle switch up?" I honestly could not remember hooking it up after spending all that time adjusting it.
When I got home from the GTG, I pulled the air cleaner and the MAF off, and climbed up on the engine to peer under the intake. SURE ENOUGH, the doggone throttle switch wasn't plugged in. I was able to manuver my hand in under the intake and hook it up.
Finally success! The engine idles perfectly now.

Thanks to all who contributed to this little success: Ryan, Mike, Sean, Jim R. ,MrMerlin and Roger Tyson from 928RUS

 

John,

If you ever have any future idle issues just play with the cable's too, sounds good though!

Its nice having a car that idle's correctly isnt it!

 

I love the low pitch of the idle when it develops into the BWAAAAAAAAAH from a traffic light. Magnificent!!!!
Thanks again Ryan.

 

so, what fixed the idle problem? the switch does little, in fact, as ive posted, i usually run the car at the race track without the idle switch connected. (the idle doesnt fall off as fast, as the engine doesnt get starved for gas on decels.)
during the idle only, without the switch, the only drawback is that the idle speed is higher. the other part of the switch is near WOT , which also doesnt effect idle.

So, what fixed the idle?

mk

 

The TPS switch should engage the ISV, so if the switch doesn't work, then the ISV will never function.

At least thats how i understand it

 

but, if the idle is higher, you dont need the ISV to work. (as what happens to idle when the switch is not engaged at idle)

mk

 

uh ok Mark, but i guess your talking about the race car? How much higher is your idle?

I can keep the car "idling" at 1000 rpm by just holding the throttle pedal open but thats not how the system is supposed to operate.

I also believe there is an emissions law or concern to keep the engine idling as it was intended.

 

Mark, as long as I kept the idle above about 1500, you are absolutely right, I never needed the idle stabliservalve. However, that is not real handy in day to day driving with an AT.

All I know is that when I finally hooked up the circuit to the switch, it idled where it was supposed to. My understanding is that the switch keys the ISV to function. It seems to have worked.

 

with the throttle switch deactivated, the engine idles around 1100 or 1200rpm
when the throttle switch is activated, idle is still 1000 only when cold and even higher with the switch deactivated.

you can test this by slightly pressing the gas pedal, not enough to give the car gas, but to break the contact in the idle switch.

Yes, there are reasons why you would want the idle switch working, emissions are one of them.

I have it on a on off switch to select when it is actually active.

mk

 

Glad your back in business.................. now about those flappy bearings??? are the seals facing away from the intake to keep out dirt from fouling up the bearings? If they arent i dont think it will hurt things too much, but the bearings will be more susceptible to dirt.