high revs misfire

[Tomguy]

There are 3 key points on the 4.5's D-Jet throttle position sensor:
1) The idle circuit - at idle these contacts close. This is the easiest way to make sure the switch is set properly.
2) The full throttle circuit - at 100% throttle these contacts close. This gives the engine a 10% fuel enrichment.
3) The contacts as you increase throttle. I believe there are 11 close points, but check the manual for that to be sure.

If any of those aren't working, it could cause your issue.

[Benz Dr.]

Originally Posted by berfinroy

I THOUGHT I put it back in the same place as I found it, give or take a millimeter.
I have a service manual that should tell me how to set it. Hard to believe its that touchy.

A throttle switch either works or it doesn't. Mostly, they give little trouble but they can go bad or be bad right out of the box. The one I had trouble with kept the engine from revving more than 3,000 RPM. We put a skanky old POS switch on it and the car took off like Jack the Bear.

Very confusing symptoms that had us chasing fuel pressure, timing, ignition, vacuum leaks, and a host of other potential problems. I noticed the new switch right away and never gave it a second thought because it was new.

[ejboyd5]

Swap in a known good coil.

[berfinroy]

General service manual doesn't say how to calibrate the TPS, but seat-of-the-pants trial and error works. But it IS really touchy; 1/16" matters.

[Tomguy]

Did it fix the issue?

[berfinroy]

Originally Posted by berfinroy

I THOUGHT I put it back in the same place as I found it, give or take a millimeter.
I have a service manual that should tell me how to set it. Hard to believe its that touchy.

After numerous on the road adjustment experiments with the TPS I can now report: its that touchy. 1/16" matters.