Mongo

Merlin, I have looked. I know what cable goes to what. There was no slack whatsoever on my kickdown cable before. Similar to Perry's old thread, when the bowden is too tight it causes the throttle to slam shut faster. If the ISV can't compensate for the sudden loss of air, it can and will bog down or stall if the ISV is sticking.

Mrmerlin

try disconnecting the bowden ball and see what happens

Mongo

I'll try that after I get home and drive it to get it up to operating temp and see what happens.

Mrmerlin

are you sure the TPS cable is loose?? this is the one that goes around the wheel, it might take one complete turn of the housing adjuster to loosen it up

Mongo

It's definitely loose. I have never adjusted the TPS cable, only the bowden and cruise control cables. When I checked the cruise control cable this morning, it had some slack in it. That would make the cable not part of the issue.

If all else fails, I'm considering even tightening the throttle body screw. Many on here say that this screw should never be touched if everything else is in working condition, but if the ISV is working but not opening fully (even though it's somewhat new still) causing this very low idle, I don't see any other option but to tighten it more to compensate for the lack of some air keeping it from idling at a healthy 675-700 RPM.

Mongo

After tonight, I've added slack to all the cables. The idle has improved, but after shooting some throttle body cleaner down to the ISV, the idle is VERY erratic. It also is constantly below 600 RPM now. It's acting like I need a brand new ISV! The thing is like new again with only about 7,000 miles on it since I last replaced it. I seriously hope I don't have to sink another 170 bucks+ into a replacement ISV again.


Right now I have no choice but to mess with the idle screw on the throttle body. I don't see a lock nut on mine which leaves me to suspect if someone had actually tampered with this before. How do you get a wrench and a screw driver down there? the screw sits below the intake boot!

Bill Ball

Andy:

Find some time to drive over to my place and we'll check the whole business out together. "Idle screw"? 87+ has no idle screw. The idle control is electronic.

RED SHARK 1990

Hey ANDY did you buy from autozone?if so they have 2years warranty or even longer.Check the source you bought from and go from there.

Mrmerlin

BUT there is an adjustment on the throttle housing,. to adjust the throttle plate
This is factory set and i would not be messing with it.
It should have some paint on it indicating that the screw stop is still in the factory set position.
As Bill stated the idle is controlled with the computer

Bill Ball

Oh, yeah, the throttle stop. Don't mess with that.

Mongo

Someone must have. There is no paint on the thing and the threads are nice and shiny. I know I didn't clean that screw up when I tore the intake apart last year. Maybe someone backed it off before selling the car? I know when I bought the car, the sucker was idling at like 900 RPM at operating temp.


On a side note... idle was about 600 this morning. Guess the PMS-ing had the day off today.

Mrmerlin

Before you try to move the screw open the intake( remove the MAF) and look to see how much clearance there is when the throttle is closed the plate should be almost touching the housing, if the screw is shiny that coul;d be normal after the parts have been cleaned. I would compare what you see on your intake to another intake, The factory setting is done so the injection system knows where is working from, changing it may throw off the rest of the engine managment system

dr bob

^^^ What Stan said. The initial stop setting is there to make sure the throttle plate doesn't stick in the closed position, where the edge of the plate might contact the body. If it touches, the brass plate will change size at different rate than the aluminum housing as it all changes temp during operation. Contact and sticking means cable issues and odd tip-in behavior as you stretch the cable. throttle plate releases, and the plate springs open. The setting point also includes the proper airflow for the ISV to midrange at operating temp, so it doesn't need to move around much and will always have enough range to keep the engine idling properly, hot or cold, as AC and other engine loads like the alternator try to affect engine speed.

Bottom line: If somebody happens to have a throttle body out of the car, please grab a set of feeler gauges and check the clearance between the edge of the throttle plate and the housing. That would be a place to start with verifying if the stop screw has been disturbed.

Rob Edwards

I'm sure I'm doing it wrong (given my feeler gauges are too wide for the curvature of the plate) but the 0.005"/0.127mm feeler is a tight fit under the edge of the plate:

BReyes

What books do you guys use to maintain 928

Regards,