TPS- think mine is bad

[SchlockRod]

Thanks guys.
Roger on the Haynes manual being worthless. Last night I found some FSM pages posted; not for my '92 model year (XFi, 5-speed) but still clear that the TPS resistance "specs" given in Haynes are questionable. I'm pretty sure I should have continuity @ 0.012" setting A-to-B and NO continuity @ 0.035".
That said, Roger also to voltage being a better way to test.
I need to know:
(a) voltage specs for my 4-wire TPS, and
(b) how to check the voltages.
I have a DVOM but what is "backprobing"? I don't want to poke holes in wires or corrupt connector seals, and I'd rather not dig around to find the other end of these wires. Is there an easy way to supply 5V reference to TBS terminal B with the connector disconnected, and then check the other three terminals? I have a 6V battery charger. Can I use a wire, test light, or ??? to reduce that to 5V @ terminal B?
Ross:
Coolant passage to Coolant Temp Sensor definitely OK, but I'd like to check the sensor. What are the specs?
Will get fuel pressure gauge this evening to check regulator.
Will get vacuum gauge hooked up or disconnect catalyst pipe to check for plugged catalyst, also this evening.
Compression was OK last time I checked, since installing reman cyl. head within last 12k miles. Don't remember values but readings were even 1-2-3 and above factory spec I got of 155 psi. I think they were 175-185 range.
Will get TPS part no. and post it this evening. But first I would like to adjust/test it a bit better. It is rotated max. CCW now and I think it's too far in the lean direction, going to almost no fuel at light throttle, causing the nosedive effect.
Woodie:
Regarding fuel press./exh. restriction: True my idle has been the main problem, along with heavy rich fuel stinky exhaust - really bad - but the car has also been intermittently way down on power at speed. I checked for leakage at injector with key on and found none.
I checked all the grounds with ohmmeter (manifold, left & right fenders). All good but cleaned up & greased them anyway.
I thought a plugged dryer in the MAP line would cause car to run BETTER with line disconnected. Are you saying no change means plugged dryer or bad sensor? Please explain. Should I have plugged the disconnected hose when I left the MAP sensor port open? I'm thinking maybe I should have done that because I may have created a vacuum leak that cancelled out the results of no MAP vacuum "input". Let me know.
Thanks.
Ted

[SchlockRod]

PS:
Don't forget the fact that my mileage went from 50mpg to about 35.
Also: I'm thinking that bypassing the MAP dryer with a straight vacuum hose to the sensor would be a better test for plugged dryer. Any thoughts?
Thanks again. Gotta get this thing running right. It's getting really cold out there and snow is coming.

[SchlockRod]

Ross,
The TPS (Denso part) has the following numbers on it:
13420-61B00
198500-0450
If you or anyone else have the right replacement laying around I really appreciate you letting me know.
I'm going out after dinner to adjust the TPS according to the FSM page I got last night, which it turns out IS for the '92 Metro. I'll let you know if I can get teh ohm readings correct and how the car runs. If still running poorly I am going to check voltages at the harness connector and at TPS with 5V reference applied to the A terminal.

[SchlockRod]

OK. I went out and did the adjustments the way the FSM says to do, with the ohmmeter. I also did some voltage checks a guy said are smart to do (on some other forum): Verified 5V @ the D terminal of the harness connector, and that the A terminal was within 50mV of battery negative post.
After adjusting the TPS, I checked the resistances according to the FSM. They are all perfectly within the specs.
I then checked two things the smart guy said to do, but I'm not sure if what he was talking about applied to the '92 XFi. Here's why:
He said the TPS (C terminal) should sweep from 0.5 to 4.5V when opening/closing the throttle, with 5V applied to D terminal. But mine stays at 5V. The A terminal also stays at 5V and the B terminal is 5V at idle and goes to zero when throttle slightly open. He says the C should give 1V +/- 0.02V with a 3.5mm (I think he meant 0.035") gap gauge. As I said, it stays at 5V always.
I'm beginning to think that this is not a TPS I'm testing. I see lots of reference to the following in the literature:
Throttle Switch (TS) (M/T Only)
Throttle Position Sensor (TPS) (A/T Only)
My car is a M/T XFi.
Anyway, after all the above adjustments/tests I started the car and it seems to run fine now. I will have to see if my fuel economy is back to normal.
Is it possible my TPS (TS?) just went out of adjustment, and I've fixed it by adjusting properly?

[RossT]

Yes, I have seen many TPS problems solved by just doing the adjustment. Someone posted awhile ago that your more likely to have a tps out of adjusment than having a tps go bad.

I will double check my stash for your #. just in case.

BTW, next time your at the junkyard, always grab a couple of TPS, MAPS, ICS (idle control solinoid), etc... Its great to have a couple extra of each when trying to diagnose a problem.

[Woodie83]

Maybe that's all it was, but I'm still suspicious of the MAP sensor making no difference, it should run like crap without a MAP sensor, but you said it was already running like crap, so maybe that's just shot. The ground that really matters to the engine and computer is under the intake manifold between the throttle body and the alternator. Also, make sure your small coolant hoses feeding the throttle body/intake manifold are getting hot.

[SchlockRod]

Thanks guys
Ross: I've called every junk yard around here. Ain't nobody got Geo Metros or parts for them. Like any other car over ten years old, they are dissolved by Michigan Metal Moss. Hopefully I don't need any parts right now. After I check fuel economy I'll know if everything's OK.
Woodie: It DID run like crap w/o MAP, but yes it was already running like crap. What I probably should have done is plug the vacuum line (I created a big leak so the MAP sensor/dryer test is probably invalid) - maybe then it would have run better. Grounds are all good. Coolant system is perfect - recent cyl. head replacement and complete flush of cooling system & replacement of all hoses - newer radiator.
Car seems to run fine now.
BTW, I think this car does NOT have a throttle switch (TS) even though it is an M/T, but is in fact a TPS. Maybe there was a running change in the '92 model year, or XFi's are different. Here's why: What I did not do when running the voltage tests was ground the A terminal of the TPS. I supplied 5V to the D terminal but without grounding A one would not be able to get the 0.5 to 4.5 volt sweep off the C terminal. Duh. I will run that test again (with ground!) to make sure everything is OK with (what is I think) TPS. I will also check for 1.0V +/- 0.02V @ 0.035" throttle.

[SchlockRod]

Car isn't exactly running fine.
It is down on power (yes, even more down than a normal XFi), and it still sometimes stalls at idle. Other than that it is running smooth and no super stinky exhaust.
I haven't checked the TPS voltages or fuel economy but like I say it is running OK.
I am wondering if a plugged converter might be the cause of the power loss, and also the reason why I had to readjust my TPS (to compensate for the reduced air mass flow with less fuel).
Once we get out of the deep freezer I will get a vacuum gauge to check for exhaust restriction. I saw somewhere that if going from idle to 3,000 rpm produces more than 5" Mercury drop in intake manifold pressure, that is a sign of exhaust restriction.