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1992 940 throttle position sensor

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
1983 - 1992 740
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1986 - 1991 780
1990 - 1998 940
1990 - 1998 960
1997 - 1998 V90/S90

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dm635
Posts: 140
Joined: 16 Jan 2008, 21:46
Year and Model: '96 965
Location: Lou. Ky.
Been thanked: 14 times

Re: 1992 940 throttle position sensor

Post by dm635 »

Pic 1&2 appear to be working as it should. It should click at idle if adjusted correctly.

Pic 3&4 it doesn't look like the throttle plate is completely open. It must be fully open to the stop.

It won't click like at idle. But you should get
0 ohms. If not you don't have WOT. Wide Open Throttle.
WOT signal just sends extra fuel when wide open.

Hope this helps
96-964
09-V70

05-325i
86-635CSi



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markthomas1967
Posts: 3
Joined: 06 Aug 2020, 10:37
Year and Model: 1990 740 GL
Location: NY

Post by markthomas1967 »

Hey dm635:

Yes, this was very helpful, thank you. And yet my throttle seems unresponsive. Not because the TPS is not functioning--pressing the gas pedal immediately switches off the IAC motor (a replacement I bought before I discovered that the old IAC motor was fine...the ground wire had come out of the back of the IAC connector, which explained that "No signal to/from IAC" code). It's just that when the IAC switches off, the RPMs disappear and pressing the gas pedal does nothing to rev the engine. What might this mean?

Injectors, IAC, fuel pump and RSR are all receiving signals from the ECU (though I am not sure of the health of either the original IAC or the replacement I bought; the resistance between pin 9 and 33 on the ECU when either IAC is plugged in is around 2 ohms). I have replaced the FPR. Speaking of which, here's something hilarious that happened that I hope may be a clue: Because I’m an idiot trying everything, I swapped the original FPR back in to see what that might do, and apparently its O-ring had deteriorated so much in the meantime that fuel began spraying out everywhere while the engine was idling--but this was the only moment in all my IAC struggles in which I actually achieved a steady idle???

I don't think I have any vacuum leaks. I think my mass air temp gauge is good. I don't know about my MAP sensor (or that hard slender hose running from it, it looks a bit beat up). I also don’t know how to test my coil (if that affects idle?); it's a Rex (of Rex/Regina) and every guide I have found to testing coils seems to presume the Bosch system (Rex/Regina seems to have been relatively rare/esoteric). I have tested the lead from "high" to the distributor cap for continuity.

Like I said, I’m an idiot. Any perspective would be appreciated.

UPDATE: Got it to start (after a few cranks) and idle for 20 minutes straight. Throttle was responsive too. But it was rising and falling somewhat, hovering around 1500RPMs. ECU compensating for something? Then turned it off to check a few things, and when I went back to start it again I could not get it to turn over again after about ten tries. No idea. Thanks for any help.

PS. I have tried swapping out the old battery (which I suspect cannot bear a load anymore, though it's currently reading at 12V) for the one from my daily driver (2004 V70), no change.

PPS. This car has had its starter coil replaced before. I understand Rex coils are considered less robust and are often the source of many problems. Like the old coil, this new(er...? it's salvaged, idk) one has suffered from many low-voltage cranks (the old one because of a crappy alternator belt, which was one of the first things I replaced on this car when I started in on it, this one because I myself left the key in the ON position too many times for too long over the course of my self-education as a mechanic and have killed at least one battery by now, maybe one-and-a-half)...

diego940gl
Posts: 3
Joined: 30 Apr 2022, 13:11
Year and Model: 1992 940 GL Regina
Location: Virginia

Post by diego940gl »

I have the same car! Is the bosch switch tps good? Or better the oem VDO?

markthomas1967
Posts: 3
Joined: 06 Aug 2020, 10:37
Year and Model: 1990 740 GL
Location: NY

Post by markthomas1967 »

Hey guys. It was the fuel pump that began falling apart after getting IAC and throttle sorted. Replaced. So golden. Thanks for everything.

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