TPS- think mine is bad

quest4mpg · #1 10-04-2009, 03:40 PM

I am trying to adjust my TPS and with the 0.012 feeler gauge installed in the throttle stop, the lowest resistance I get is 27 ohms I can't get continuity or 1 ohm. I pulled the sensor off the motor and it appears to be the lowest resistance between pins A and B is 27 ohms. I have read here it should be around 1 ohm or continuity. Can anyone help here. Do these go bad?

Airjer_ · #2 10-04-2009, 04:53 PM

year and engine?

i've always set TPS's by voltage?

Airjer_ · #3 10-04-2009, 05:00 PM

quest4mpg · #4 10-04-2009, 08:15 PM

The advice I saw on here was to measure the resistance between Terminal A and B not voltage. Hm This is one of the threads I was going off of.

http://geometroforum.com/topic/1341780/1/

Anyone weigh in??

Johnny Mullet · #5 10-05-2009, 10:32 PM

If you cannot zero the TPS, then it's bad. What problems does the car have? Loping idle?

quest4mpg · #6 10-06-2009, 11:40 AM

The lowest resistance I could get was 27 ohms. A little bit of idle surge(unsteadyness) when you first put in neutral and take your foot off the gas. When your in 1st or 2nd gear and take your foot off the gas, like if your in stop/go traffic and then you want to accelerate all of the sudden the car surges/jerks forward. I thought I fixed it last week by advancing the TPS in one direction but then my gas mileage went to 25 mpg. At the time I didn't take a meter and check the resistance but ultimately what it was doing was raising the Idle resistance. After pulling the sensor and looking at the resistance as it is moved (clockwise/counterclockwise) (cant remember which direction.) It's lowest is 27 ohms and then it moves to about 100 ohms then it suddenly makes a jump to much higher resistance, in other words its not linear. I think that explains the sudden jerky acceleration. Anyone have a good/cheap source for a new one. I've looked online they want about $180.00 for one. Wow there sure isn't $180.00 worth of parts and technology there. Ebay has a few throttle bodys with them installed might take a chance that way can pick one up for around $40.

leonbentz · #7 10-23-2009, 10:58 PM

What year is your Metro? I have a good used one here that I know works. I installed a new one, but found out my old one was fine.

quest4mpg · #8 10-29-2009, 04:25 PM

Mine is a 92, do you still have it thanks

RossT · #9 10-29-2009, 05:32 PM

Quote:

Originally Posted by quest4mpg

Mine is a 92, do you still have it thanks

auto or manual? and number of wires going to your tps?

quest4mpg · #10 11-02-2009, 04:29 PM

mine is a manual, I don't think there is a difference in TPS between the manual and auto tranny's

RossT · #11 11-03-2009, 03:58 AM

Quote:

Originally Posted by quest4mpg

mine is a manual, I don't think there is a difference in TPS between the manual and auto tranny's

prior to 92 there was a difference, but in 92 they changed them so that the auto and manual tps were the same.

quest4mpg · #12 11-03-2009, 04:14 PM

They have a huge impact on mileage. I bought one on Ebay which btw had the same resistance readings as the other one. I installed it to see if there was an improvement and my mileage went from 44 mpg to 38 mpg. Needless to say I switched back to the original one. I'm going to contact the seller and see if I can return it as it does me no good. I also went to several wrecking yards and found 2-3 and they all measured resistance levels around 25-40 ohms at the lowest so I haven't seen one yet that was less than 1 ohm.

SchlockRod · #13 12-07-2010, 11:09 PM

I have exactly the same problem.
The car ran more & more poorly the last month or so, until today it would hardly idle. It stank really bad of raw fuel and my mileage had dropped from 50mpg to 35.
I checked for kinks in fuel return line (negative).
I visually checked injector spray with flashlight and timing light. Either way it's hard to judge, but it looks like it is hitting the sides of the TB bore (like Haynes says it should) and mist looks pretty fine, cone-shaped. No drip with key on engine off.
I disconnected vacuum line at MAP - no change.
I adjusted timing - was about 3 deg. BTDC; made it about 7 now. Still pretty bad running.
Air cleaner OK. No change with it removed.
So I looked at TPS. Going by the Haynes manual (I know. I know. It's all I have plus this forum.). It says to adjust TPS in CCW direction with 0.012" feeler at idle stop, until resistance goes to zero between A & B (the two closest to firewall).
Before adjustment I got the following readings (ohms):
A-B @ 0.012": Infinite (Spec is zero)
A-B @ 0.035": Infinite (Spec is "Continuity")
A-D @ idle: 6.25k (Spec is 4.37k-8.13k)
A-C @ idle: 1.18k (Spec is 0.24k-1.14k)
A-C @ WOT: 5.1k (Spec is 3.17k-6.6k)
After adjustment to 28 ohms A-B @ 0.012" (Haynes says go to zero - couldn't - maxed it in the CCW direction), I got the following:
A-B @ 0.012": 28 (Spec is zero)
A-B @ 0.035": 23 (Spec is "Continuity")
A-D @ idle: Infinite (Spec is 4.37k-8.13k)
A-C @ idle: Infinite (Spec is 0.24k-1.14k)
A-C @ WOT: Infinite (Spec is 3.17k-6.6k)
Seems to run better, but still wants to die sometimes at idle, and has a very "on or off" feel to the throttle - more noticeable when you lift your foot slightly (wants to nosedive).
Need new TPS? Where to buy? Or will I get the same result as our friend here (no improvement).
I haven't gotten to testing fuel pressure or exhaust restriction yet. Maybe I need to check those first?

RossT · #14 12-08-2010, 12:17 AM

Need to know what year and trans type?

Does it run good at start up when cold, then poorly when warm/hot?

My thoughts.

1. Bad ecm coolant temp sensor. Sometimes the sensor goes bad, or the coolant passage way to the sensor get pluged with gunk. Resulting in improper reading to the ecm, causing to much gas to enter the TB. If it runs good when cold, check this.

2. Bad fuel regulator?

3. Plugged cat?

4. Do a compression check and report the numbers back here. You can buy a tester at
china-mart for about $20. I can post a link on how to do it if you want.

5, Maybe TPS. This item you would want to get from a junkyard. Gm will want $200 for it. I have several extra. write down the part# that is on the side and post it here.

Woodie83 · #15 12-08-2010, 05:18 AM

The Haynes book is trying to cover a range of cars spanning three generations, built in two different factories with five different engines and three different engine control schemes. there were five different TPS's, some drastically different from others. Your car nosediving when you let off the gas tells me that the TPS is NOW out of adjustment.

I doubt it would be fuel pressure or exhaust restriction, they usually idle fine but choke off the power when you ask for a lot. Unless the fuel pressure is too high, but that's a rare thing. Turn on the dey without starting the car and look down the throttle body just as you did before. If you see any fuel you've got a leaky injector.

Low compression usually shows up at this time of year, heavily influenced by the cold temperature, but that usually will cause the car not to start. Check compression anyway, if your engine needs rebuilt, there's not much point worrying about a bad idle. Engine warm, all plugs out, wide open throttle, should be 150 to 200.

The MAP sensor worries me, pulling off that vacuum line should make a huge difference in how it runs, maybe the line is clogged or the MAP sensor is bad. Also, all of your sensors work off a single ground connection beneath the throttle body, there's about five green wires that all bolt to the intake manifold there. Those are famous for just giving a bad ground and causing no end of misery, just loosen and tighten back up.

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