S13 TPS complete opposite resistance than tutorial states

[Schrute Farms]

Car is a 93 S13 manual.I am on a never ending quest to find out why my car gets 18 MPG and loses power above 3K RPM. I have tested and/or confirmed the proper operation of the following things: coolant temp sensor, mass air flow sensor, oxygen sensor, spark plugs, spark plug wires, fuel pump, fuel injectors, fuel filter, air filter, distributor, pulled trouble codes (found none) and ignition coil.

I tested the throttle position sensor. The voltage when back probed is within spec. However the resistance (with the sensor unplugged) is the complete opposite of what vancouverbc's tutorial states. Here is what I found- with the accelerator 100% released my resistance was 9.8 OHMS, partial throttle it started decreasing, at WOT it was 2 OHMS. The tutorial states it should be 2 OHMS when accelerator is released, 2-10 OHMS when partially depressed and 10 OHMS at WOT... Is my TPS shot or am I an idiot that doesn't understand how to read?

At this point I'm thinking the car is running way too rich hence the poor performance and gas mileage or the compression is bad or the timing is off so I've ruled out things dealing with spark (ignition stuff, etc.).

Modified by Schrute Farms at 11:26 AM 1/12/2009
Modified by Schrute Farms at 9:52 AM 1/13/2009

[Vegascorbin]

Are these readings done with a digital meter or an older style analog meter? the analog meters read backwords from how most people think.

Other than that are you sure you are checking the correct two wires?

a poteniomiter (which the TPS is) has 3 trminals "A" (one end) "B" (center) and "C" (other end). With you meter connected to the "B" teminal and the "A" you will read a set value and it will either go up or down depending on hte device. IF you read from the "B" terminal to the "C" you will get the exact oppeset reading, IE it will read low from B to C and high from A to B.

Verify you are reading the correct wires at the corect time and re-test.

[Schrute Farms]

The following pictures are with the key set to RUN engine OFF, accelerator RELEASED.

This was the connector I tested-

With my multimeter jumping these two terminals-

This was the reading I got-

Jumping these two terminals-

This was the reading I got (it went up to 8-9 OHMS at WOT)-

[Vegascorbin]

I don't have the proper information here at work to say if it is right or wrong.

Anybody else?

[onosqv]

Is the car an automatic?

I think mine read resistance backwards as well. The more important thing to check is the voltage - .4-.5 @ idle (most people like close to .45), and about 4v at max. Done by back probing those 2 wires I believe w/ everything connected - don't remember since it's been so long since I've done it that way, I have my tps reading from a gauge.

[Schrute Farms]

Is the car an automatic?

I think mine read resistance backwards as well. The more important thing to check is the voltage - .4-.5 @ idle (most people like close to .45), and about 4v at max. Done by back probing those 2 wires I believe w/ everything connected - don't remember since it's been so long since I've done it that way, I have my tps reading from a gauge.

The car was an automatic converted to a 5spd. The voltage is right around .44v-.45v when back probed.

[onosqv]

I'm 99% sure it's reversed for automatic.

If you didn't change out to the manual tps, that's most likely why you have the ohms backwards. Whatever your issue is, it's not the tps.

There's plenty of other things that can cause poor gas mileage (you'll have to search).

A few things off the top of my head:- bad coolant temp sensor (doesn't show up on the gauge, but if you have never replaced yours, it's worth the $20-30 investment for a new one regardless)- bad o2 sensor- bad iacv- dirty air filter and/or fuel filter- spark plugs, etc- base timing set incorrectly

[Schrute Farms]

I'm 99% sure it's reversed for automatic.

If you didn't change out to the manual tps, that's most likely why you have the ohms backwards. Whatever your issue is, it's not the tps.

There's plenty of other things that can cause poor gas mileage (you'll have to search).

A few things off the top of my head:- bad coolant temp sensor (doesn't show up on the gauge, but if you have never replaced yours, it's worth the $20-30 investment for a new one regardless)- bad o2 sensor- bad iacv- dirty air filter and/or fuel filter- spark plugs, etc- base timing set incorrectly

The thing is, I already tested, replaced or confirmed the proper operation of the following: coolant temp sensor, mass air flow sensor, oxygen sensor, spark plugs, spark plug wires, fuel pump, fuel injectors, fuel filter, air filter, distributor, pulled trouble codes (found none) and ignition coil. Now I can add the TPS to that. I also cleaned the idle valve last weekend due to the idle stumbling to ~300 RPM at stop lights.

Next on the list, I will bust out a timing gun and check that as well as pop the valve cover off and verify the valve timing as well. Probably won't happen until spring but I will report my findings then.

[del82]

If you've backprobed and the voltage was within spec, I'd say there's nothing wrong with it, despite the funky ohms reading.

Checked your EGR and PCV system yet? EGR for function/flow, and PCV for leaks, and if you haven't changed the PCV valve since you've owned it, you may as well, along with the grommet it sits in.

Given the gas mileage you mentioned, and the stumbling I'd have been looking at the EGR first, actually.

Oh, and then there's the question of actual mileage. If your motor's old, you're losing power and thus mileage, too. It's not as pronounced, but just something to keep in mind.

[Schrute Farms]

Checked your EGR and PCV system yet? EGR for function/flow, and PCV for leaks, and if you haven't changed the PCV valve since you've owned it, you may as well, along with the grommet it sits in.

Given the gas mileage you mentioned, and the stumbling I'd have been looking at the EGR first, actually.

Oh, and then there's the question of actual mileage. If your motor's old, you're losing power and thus mileage, too. It's not as pronounced, but just something to keep in mind.

EGR is deleted. Motor has 6000 miles on it.

I'll snatch a new PCV valve and report the findings.

[onosqv]

Well, the removed EGR could have something to do w/ it... did you have poor mileage directly after removing the EGR or were you able to get decent mileage for XXX time w/ the EGR removed?

Motor has 6000 miles -> it's been rebuilt -> something could have gone wrong w/ the rebuild? Or when you reinstalled the engine.

And you rebuilt your engine w/o replacing the pcv valve? Did you also keep the original knock sensor?

Now that you let everyone know you have a rebuilt engine, there could be a zillion things wrong... time to bust out the FSM & walkthrough everything if it bothers you enough.

Good luck.

[Schrute Farms]

Motor was rebuilt by the previous owner who was a Nismo mechanic so I'm not thinking anything went wrong there (I could however be wrong... Compression is one of the things I want to test come spring). He also removed the EGR and all the other emissions stuff. I am going to hook the EGR back up and see if that doesn't help.

[onosqv]

Motor was rebuilt by the previous owner who was a Nismo mechanic so I'm not thinking anything went wrong there (I could however be wrong... Compression is one of the things I want to test come spring). He also removed the EGR and all the other emissions stuff. I am going to hook the EGR back up and see if that doesn't help.

Again (this may help other ppl trying to diagnose your problem online), has the poor mileage problem been there since the rebuild/emissions removal? Or just in the past XXXX miles?

No emissions equipment + stock ecu?