testing TPS.

[summit]

83 carb/turbo t type
The original TPS sensor had a broken plunger that just fell aprt. I replaced it with a new one. Upon testing it it reads .77 per spec, but the voltage reading actually goes down as the throttle is opened to zero and stays there. Shouldn't it go up? Top wire has 5 volt reference voltage coming through and bottom wire shows continuity to ground. I used middle and bottom wire to check voltage readings using 2 volt scale on DVM. Sounds wrong to me and car stumbles bad upon full throttle from idle.

I ordered another one today, but it came in broken just like the one I removed. it even had "defective" written on the side of the box! hopefully another will arrive tomorrow and I will check it before installing in the carb. I bought the cheap $15 tru-tech Standard brand part the first time, am trying the $50 AC Delco part this time, if I can get one not broken.

 

[usetaboost]

Any possibility you installed it upside down? If you can't track a delco I would ASSume all other feedback carbs use the same tps.

 

[summit]

the way the connector is made it is impossible to install it upside down. it is square on one end and round on the other. I will check the pinouts on the car harness one more time. I don't tink you can even install the actual sensor itself upside down inside the carb.

 

[b4black]

This should help:
Testing the TPS - TurboBuicks.com



(Last time a posted a link to the other board, Jesse fired me as modertor. I tried finding a thread here, but the search function finds nothing for TPS in the before black forum.)

 

[summit]

yes, I saw that one as well. Thanks.
he was basing his info off the SFI cars as far as full throttle settings, which would not be correct for the carb cars. All the factory manuals I have just reference the idle setting with no mention of full throttle readings. I thought it was weird for the new one to read backwards. I have another new one that arrived today that I will test. it would be nice to know what the ECM wants to see as far as an idle range or full throttle power enrichment. Thanks again for the link.

 

[summit]

Well, unbelieveably the first sensor was wired wrong. The newest sensor reads correctly. .77 at idle at 4.5 at full throttle.
I could repin the harness since the wires on the sensor itself can't be switched around, but long term I think having a good/correctly wired sensor is best.

 

[usetaboost]

Glad it's fixed

 

[b4black]

yes, I saw that one as well. Thanks.
he was basing his info off the SFI cars as far as full throttle settings, which would not be correct for the carb cars.

They are similar. It's a 0-5 volt sensor. If you set the idle too low like the manual recommends, you can't up to the high 4.X where power enrichment begins. Also if it's too low, then the ECM tries to disengage the TCC while cruising down the highway (it thinks your foot is off the pedal decelerating/braking).


It's great you determined it was wired wrong. That could have been a nightmare trying firgure out what's wrong with your car if you assumed it was OK.