jmd

iTrader: (4)

I'm trying to get my car tip-top for emissions. New intake is on (EGR was clogged on stocker.) Next up is to set the TPS, then IABV for dwell. Carb is a 17086003 (86 L69 / auto) on an '88 LG4 in an '87 car.

I tried to set the old TPS to .48 - .52 with the Thexton 2.5mm hex tool.
Signal goes from zero to 4.x to .31 and all over the place when adjusting it or rolling into throttle. Scan tool and volt-meter show the same thing. It's not really repeatable; i.e. I can't full throttle it to 4.8 or adjust it predictably to zero either.

Continuity of the blue and black wires to the ECM plugs is excellent - 0.03 on the lowest ohm reading on the volt meter.
Back to the BIG bundle of ECM wires, the wire is in fine shape.

The grey wire (circ. 416 / pin 21 at ECM, TPS pin A) - 5v ref. output from ECM and splices with vac sensor and baro pressure sensor.
The dk blue wire (circ. 417 / pin 2 at ECM, TPS pin B) - input to ECM
The black wire (circ 452 / pin 22 at ECM, TPS pin C) is also shared with vac sensor and baro pressure sensor.
452 seems further shared as 452 is also referenced for CTS

The ECM has no stored codes but will set a 21 with the TPS unplugged.

Is there a way to test the TPS out of carb? I have two old ones, the new Standard tps in the carb and a new Wells tps loose. The behaviour of both new TPSs is this:
digital volt meter on DC volts
TPS plugged into the harness
poking a couple of the wires of tps wire connector
key-on
Proper (4.8v) voltage shows and dwindles as throttle increases to nearly zero.
So I think the two new ones are okay as potentiometers go.

But I still have crap for signal at the ECM for TPS.
Suggestions before I go check to see if I can adapt a later model TPS to the Q-jet?

jmd

iTrader: (4)

Has anyone purchased a TPS in the recent past?
Brand? PN?
Did it provide proper signal back to the ECM?

scooter500

iTrader: (1)

I recently scored a couple of Delphi "TH-1D" TPS on the web and they worked. The TPS is really sensitive so the wandering you're describing is, at least for me, common. This is what I do: park the car in the garage and let the engine cool over night then take the measurement when the car is stone cold (key turned, A/C and engine off) & look for at least .41 but not more than .44. Then each time I make an adjustment I wait as much as 1 - 2 minutes for the meter to get a reading that doesn't change. I noticed that when the car warms up the TPS voltage will go up too. The GM 1987 Driveability/Emmisions manual says an '87 TPS should read .51 plus or minus .01v . I use a little blue lock tight and this procedure works for me. If the TPS is off by a couple of .01s its really not a problem, especially when starting out cold between .41 and .44v. BTW, the Delphi TPS install sheet called for .41v setting.

jmd

iTrader: (4)

The ECM shows a 510k ohm resistor between pins 2 and 22 in the factory svs. manual.

Between #2 and #22 pins of the ECM, my ECM reads in the 300k ohm range.
A second '87 ECM reads in the 100k range; closer to 200k.

With that second ECM, I'm able to get .00 or .01v.

As part of the service manual diagnostics for one of the TPS codes (21 or 22; I forget), it shows that if pins A & C of the TPS connector have between 4 and 6v (mine reads in the 4.x v range) then circuit 417 (pin B which is the grey wire feeding signal *to* the ECM is shorted somewhere.

I think that means I'm pulling my ECM harness. I'd really like to know where the wires are joined for circuits 416 and 452.

Good thing I'm patient?

DoubleV

Are you sure there's a spring under the TPS? If not I could see it fluctuate around by moving.

You can unplug the wires to your TPS and plug another TPS to em and read the voltage buy pressing the 'button' down by hand.

jmd

iTrader: (4)

The TPS absolutely has the new spring underneath it.

I don't know what changed but tonight I went out to test all the TPSs in my car (and another car for fun)
With ECM #2 and the same TPS I just recently swapped in, I am able to adjust the TPS.
Between the paper that came w/ one of the new TPSs, posts on here, the service manual etc., I ended up setting to .48 or .49v. WOT hits about 4.08v.

The readings are no longer erratic, they just update when the scan tool updates.

Now I get to re-harness-wrap my wiring and put new plastic conduit on.