I bought a replacement the other day because the AC Delco one has a cracked housing on it. The replacement is a 'Standard' brand (I saved $5). I put it on and got a code 22 so I took it off returned it as defective and got another one. It did the same thing so I decided to investigate. I hooked it up to my ongoing test bench project and took some readings. When the lever is against the stop it only will let 2 mV thru. I move the lever to see where .5 V is and it is about 3/8 inch off of the stop. So the conclusion is that the ECM isn't getting the needed .2 V when the ignition is turned on. Anyone else have experience with this mfg on Fiero TPS parts?
TIA

I didn't realize I had my own brand of throttle position sensors...

TPS must be installed then setup. Check the ogre's cave I think there might be some info in there If not 24 bucks gets you a chiltons. Or you could get lucky and someone here will post directly out of the manual (most likely)

Ron;

I have had Standard brand in mine. I think is a POS. First time I hosed the engine for cleaning it died. Get an A/C Delco. Anyway, pass by home or call me and we can hook up the AutoXray and check what's going on.

84Bill, what does Chilton's say. I have the $99 GM manual and it says to just install and reconnect it. By design, I don't think tolerances on that part would be so loose that you couldn't just replace it and go (but I could be wrong). The retailer said I shouldn't have to screw with it. The Cave didn't talk about adjustment that I saw, just connection notes.
TIA

87GTZ

GM engines do not like non-GM sensors. Buy GM sensors whenever possible.

Firestarter

Ron; The TPS is a plug & play sensor. There is nothing to do with it. You may want to disconnect the battery for the computer to re-learn again. The IAC sensor is the one that has an installation sequence.

I replaced mine with a Wells from Autozone 3 years ago, works fine for me. It came with stainless steel new screws too, so they wouldnt seize up and break like the OEM in the housing.

I agree w/ Firestarter about ACD only. Alex, the TPS is the one sensor that is somewhat 'adjustable' by bending the tab. It was not designed to work this way though, and I don't want to rig it. I'm afraid that the (voltage) transistion from idle to WOT won't be linear if I try to make this one work. I have already troubleshot it and it and the resistance is too high at the idle side of the mechanism. I've already called the retailer that I am sending it back. He suggested that I get a ACDelco and has said he has not had problems with the Standards. I put this sensor on another throttle body with the exact same result. I usually get orignial equip when I work on other's cars but was trying to save $5. Looks like I learned that lesson yet again...

Thanks for all your inputs. When I get the ACD part, I will characterize the resistance and voltage and submit to Ogre so the next time he updates he can incorporate the info. That should make trouble shooting somewhat easier when the part is off of the car (as in new part check).

Ron; I remember reading that at startup the computer reads whatever resistance/voltage is there and sets that as the closed level. So it is self-adjusting. So even if you bend the tab it will self adjust again. I read that in a TPI engines book that use the same Fiero system. I'll be at home this afternoon (6:00). Pass by and double check with the AutoxRay.

They are right I stand corrected its PnP

Only the 700 TBI used on 87+ 4 cyl is truely non adjustable.

Bothe the V6 and 300 TBI used on 84-86 4 cyl have an arm the moves the TPS. If that arm is bent then the TPS could read to low/high at startup.

AC Delco is nice if you want to got to a dealler for it. Most parts places I've dealt with carry very little if any of it.

Many Do however cary Borg Warner, which I've always found to be of equal quality or better than AC.

A Wells sensor is a renamed GM sensor.

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i usually get two ply TPs
although i like the quilted kind

Alex - that is correct on how the TPS works on the V6 Fiero. The target voltage at ignition on is .5 volts. I am getting 3 millivolts (from 500 downto 3). The computer must see greater than .2 volts or it will set a code which it is doing (code 22 - TPS low voltage). That is a defective part (and in this case design or lot because 2 in a row did it). For those of you that adjust them, you'd have to bend the hell out of this part. As I said, I'm over a 1/4 inch away with the tang straight. When bending the tang, the contact point changes and the intended arc of the sensor also changes. This will now yield a difference in percentage throttle reading to actual. What are the effects? Well you'd need to test that emperically but I'm sure it would be a coincidence if performance matched the intended design. I have a bud that has a car parts shop and can get most OEM parts. He has this part and I just need to pay $5 more than the mail order Standard part (and shipping)...

When I replaced the tps in my 84, the replacement was an adjustable one. The bottom (i think) screw hole was slotted, so you could rotate the whole tps unit. Had the same effect as bending the tab.

OK OK OK - I got screwed! When I first got my car... well the morning after it refused to start for 15 minutes!! I did not know too much about the Fiero even though I have lots of experiece on other cars. Well once I got it started I took it too a tune up place. They told me the TPS was bad....
They told me it needs adjustment and all that.... well I fell for it and I wanted my car running.... so they charged me $89.00 for the TPS and $100 to install it!!!!!
Now knowing alot more about the car.... and seeing my TPS everytime I open the deck....I feel like an ASS**** !!!!!
What should I do? Can I complain to anyone??? Any lawyers any ideas???

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__|aguiler

Everybody allways say that education is very expensive!!

Update on characterized Standard & ACDelco TPS
Search keywords: tps thottle position sensor resistance voltage WOT idle

I bought and characterized the AC Delco part and my conclusion is that the Standard part is a 1) bad design or 2) defective lot

The ECM reads the TPS when the ignition is turned on as the initial point. Typical value as quoted by GM manual is .5 volts which is the target. If the ECM reads below .2 volts, it will set a code 22. I got a code 22 for both Standard parts and no code for the AC Delco.

For the data below, the part was tested separately for 1 - 4 and was put on the car for #5. Sample size of 2 Standard TPS and 1 AC Delco. The data supports the symptoms.

Definitions

1) resistance w/ lever against the stop
2) Voltage w/ lever against the stop
3) distance from stop to reach .2 volts (200 millivolts)
4) distance from stop to reach .5 volts (500 millivolts)
5) voltage at idle position when mounted on the throttle body

Standard / AC Delco

1) high off the chart / 5.86K ohms

2) 3 mV / 145mV

3) > 1/4 inch / < 1/16 in

4) > 3/8 inch / at 1/8 inch

5) .037 V (37 mV) /.487 V (487 mV)

[This message has been edited by 87GTZ34 (edited 05-12-2001).]

[This message has been edited by 87GTZ34 (edited 05-12-2001).]