TPS Experts 86 635 auto

[Jim Con]

My 86 635 auto NA has been running rich and failing smog.100k miles.
For the last 18 mos I have been trying all the usual suspects but I have a specific TPS question.
I have the 86-88 TPS under the rubber boot.
My car per backprobe is running .9 lambda should be about .5 lambda.
I am checking not the idle switch ( clicking properly ) , there are two on the 86-88 autos, but the full throttle switch.

I checked the terrific website http://www.hiperformancestore.com/Motronic.htm ( step 11 ) which says and another website confirms this:

------- Now measure voltage between the yellow wire (terminal 2) and the brown wire. Voltage should be about .7 volts with the throttle closed and increase as the throttle opens to about 4.78 when it's fully open. -----

I am NOT getting these voltages with the key on as directed.
I am getting 4.37v at idle and it decreases to .68v wide open.
Adjusting the two screws in their elongated slots completely the other direction gives me:
3.59v at idle and .75v wide open.

What I'm worried about is that the TPS is stuck in the full throttle position which enriches the entire system to about .9 lambda.

Anybody have an idea what's happening here?
Thanks,
Jim

[tschultz]

Jim,

Have you checked what the lamba reading is when you disconnect the TPS at idle? Does it change to about stoich reading?

Also, any idea if you are failing at idle or normal driving during the e-test?

Have you verified that FPR hasn't failed and leaking internally? I can't recall...

[86 shark]

Tom,
Might try disconnecting TPS at idle see what happens.
Failing at idle and all speeds.I can tell it's running reach even at idle.
FPR has been swapped with known good one, no change.
Did smoke test with bee smoker, great idea, no vacuum leaks, smoke poured out of cylinder where I had removed the plug.

[Kenneth1948]

Some of your symptoms are similar to mine except my car is almost un-driveable.
Your description: "What I'm worried about is that the TPS is stuck in the full throttle position which enriches the entire system" certainly describes my problem.
I realize my '84 has a different TPS but there are similarities.

Also, my problem occurred after a short full-throttle burst followed by an abrupt lift off.
Please keep us informed with your progress towards resolving this and I will do the same.
John Kenneth (see post on this page)

[Kenneth1948]

Also, when you say "per backprobe" do you have a gauge reading an added 02 sensor?

[86 shark]

It's been reported by a computer probe and I can tell by how it runs.
The TPS at full throttle orders a 12 to 1 A/F ratio, very rich (.9 Lambda ) so I'm exploring this.
Today I pulled and cleaned the plugs, discoed the battery and grounded the batt cables together, clean slate tomorrow

[86 shark]

Reinstalled plugs,battery, etc.
Played around with screw in AFM that controls where the pointer sits on the carbon track ( not recommended ).
I changed it to where it is giving less voltage to ECU when flap is moved, idle now is steady, exhaust sounds much better but idle is still high, about 1000.