Thread: 4.6 idle problems.... Ideas?

Try to get a spare TPS and swap out to see if it fixes it. If it's seeing 17% TPS then it'll raise RPM as it thinks there's a foot on the accelerator. Seems most likely as when it's touched it drops back to idle speeds.

17% is slightly high for throttle closed but only by 1 or 2%. try bringing it back to 16% and checking for air leaks.

thanks heaps. I didn't know you could adjust them. How do you lower the percentage?

The accelerator cable wouldn't be too tight by any chance?
You would have had to remove it to remove the plenum.
Regard sPhilip A

Hi Philip, the throttle cable has just a slight amount of play so it it is ok. I have checked the intake and it is fully closed. Im guessing it is either the idle control valve or TPS. Im just trying to guess which one now i think...

it is possible to adjust the throttle pot on its two mounting screws (above the stepper motor) but you should never normally touch these. usually the problem is something else. check there is some slack in the throttle and cruise cables.
check there are no air leaks into the manifold from, split hoses,
bad gaskets, injector o rings or incorrectly fitted vacuum tappings.
check the throttle blade has at max 2thou top and bottom and
does not jam closed in the body. (if it is slightly out top and bottom, losen the 2 screws on the blade and let it slam shut 2 or 3 times then tighten the screws and recheck. if it is still out repeat the procedure but let it shut on an old 2thou fealer gauge).
check live readings and check throttle position and if possible the learned throttle closed position, 0.6v to 0.85v.
now depending on what model lucas system your car has and what scanner you have you can go further with adaption resetting but it would be easyer if you phone me (0421 509 083)

Thanks Rupert. About to head overseas tomorrow so its a job for when im back in a couple of weeks. Ill be in touch then. The throttle cables have slack and the throttle blade all operates normally. I tried the allen key screw. Whilst this reduced the idle, the problem still exists as when i start it it is excessive until i put in gear then settles back in the same manner, its just the whole process just occurs at lower revs with the screw adjusted. If i order a new TPS, do i have to get the ECM reset??

the adaptions should be reset but you don`t have to do it. also if you reset the adaptions on some early models they will run rich until an open loop tune is done.
if your tps reads ok there is probably nothing wrong with it.
i have a new tps as a test unit if you want to try it.