TPS calibration troubles

[nuggets]

I know that there are a ton of TPS threads so I'm sorry for adding yet another one. I'm having TPS adjustment trouble and am wondering if anybody can help. I've followed the TSRM as well as this thread: http://www.supramania.com/forums/showthread.php?t=97689. I really hope that I'm doing something stupid because this is driving me nuts.

I have a relatively new (8k miles on it) TPS sensor but for the life of me, I've never been able to calibrate it. I've probably tried 4-5 times since I rebuilt the engine. I've tried both with the throttle body in the car and out of the car. I've checked to make sure that my throttle stop is in contact with the throttle body. I have no codes.

It always seems that one of the values is off. I think the biggest problem I have is right from the get go. I cannot get the my meter to read 0L infinity when the sensor is completely counterclockwise during the first step of calibration. The sensor starts by reading resistance and not an open. I've tried two different meters (a Fluke digital and an analog). When i turn the sensor clockwise I can get an infinity reading, but per the TSRM this is completely opposite of what should happen - I should start with infinity and then deflect (resistance) as I turn it clockwise, right?

So I was looking up the correct part numbers on the EPC and ran across two questions:

- I have an 89T, built in 02/89. According to the EPC that means that I use TPS model number 89452-20050, which was used until 03/89. This is the new TPS that I have. Note that I never saved my original TPS so I can no longer look at that model number.

- My throttle body model number is 22210-42270 (the top of the throttle body says 42270 9B16 so I assume this is the model number). According to the EPC, this throttle body was produced from 08/88 - 5/93 and is for use with the turbo auto tranny models (I have an auto that I've converted to manual).

So my first question is if I have a throttle body that didn't change from 08/88 - 5/93, what did Toyota change that required the use of a different model TPS sensor in 03/89?

My second question is could it be possible, since my car is right on the cusp of the TPS change, that I should try the 14050 TPS model number?

 

[ben1984j]

It always seems that one of the values is off. I think the biggest problem I have is right from the get go. I cannot get the my meter to read 0L infinity when the sensor is completely counterclockwise during the first step of calibration. The sensor starts by reading resistance and not an open. I've tried two different meters (a Fluke digital and an analog). When i turn the sensor clockwise I can get an infinity reading, but per the TSRM this is completely opposite of what should happen - I should start with infinity and then deflect (resistance) as I turn it clockwise, right

No, deflection is when the meter goes from a reading of resistance (continuity) to infinite resistance (open). On an analog meter, you would see the needle suddenly jump to the end of its range or "deflect" - that's where the term comes from.

So, your TPS is behaving just how it should.

 

[nuggets]

ben1984j, thanks for the clarification. I tried it that way and I'm still not able to get all the measurements within spec. Maybe my TPS is shot. I'll try another one.

 

[ben1984j]

Which measurements can't you get in spec?

 

[nuggets]

The VC-E2 spec of 4.25-8.25. My meter reads no continuity regardless of throttle position. I even took the sensor completely off and I still get a 0L.

 

[ben1984j]

OK, well since that is the only one out of spec (from looking at your other results posted in Scotty's thread), there must be an open between VC and the potentiometer. I couldn't copy the diagram but take a look at the 3rd page of this: http://www.autoshop101.com/forms/h33.pdf...makes more sense with a visual.

As I understand it, this means there will be no VTA (throttle angle) signal supplied to the ECU. This will barely affect drivability as VTA isn't one of the primary signals used for fuel calculations. Though I would think your car would be throwing a code 41...

Anyway, the other part of the TPS, the IDL circuit (which tells the ECU whether or not the throttle is closed), is obviously fine from seeing your measurements (VC is not part of the IDL circuit). So your car will most likely "run fine" with this TPS, though you might try a spare and see if it gives the right measurements...

 

[nuggets]

Thanks for the info, yeah the autoshop article makes sense. I'll try another TPS and see what measurements I get from that. I had another question that is related - do you know what the spec is for the gap between the throttle plate and housing when the throttle is fully closed? I think that there's supposed to be a small gap in order to allow some air in, but I'm not 100%. I've searched the TSRM and can't find any spec.

 

[ben1984j]

Not that I've ever heard of, out of curiosity why do you think there would need to be a gap? There are several systems on the car which allow air to bypass the closed throttle plate and enter the engine...

 

[nuggets]

I thought that it may be slightly open due to two reasons.

#1 was that whoever had my car prior to me messed with the dashpot set screw on the throttle body (the yellow paint was broken) and looking into my throttle body with a light behind it, I could see a small gap all around the throttle plate when it was closed. This got me wondering if the plate should be completely closed or slightly open as it was on mine. I've been experiencing a slight miss at idle as well as a slightly high idle at warm (about 800RPM) and I was thinking that it could be due to the gap on the throttle plate which is allowing some air into the manifold.

#2 was that in the "2 - Air Induction System" pdf at the http://www.autoshop101.com/ site, page 4 states, on the left hand side under "Idle Air By-Pass" "During idle operation, the throttle valve is almost completely closed". Looking at the diagram above it, Toyota is calling the throttle plate the throttle valve. So that got me wondering if the throttle plate should indeed be slightly open at idle.

 

[jetjock]

When set up properly it'll be very nearly closed. It'd have to be open quite a bit to exceed the ISC system's range and even then it wouldn't cause misfire.

 

[nuggets]

Thanks JetJock. I was playing with it today and got it to be 100% closed (no light peeking through the edges). I'll adjust it so there's a little bit of light coming through. Thanks for the info on idle too.

 

[jetjock]

You be welcome. Set it to be closed when on the stop screw but not so closed as to feel any "sticktion" when opening. Just fully closed. And remember: stop screw first, then TPS, then dashpot...in that order.