Cleaning the TPS?

[James Scott]

Trevor, I made a copy of your TPS adjust post, if you want me to send a copy to you? (I don't know how to scan!?)

Or anyone else (via mail).

[Beav]

Originally posted by CDG
Stevesby? did you check for codes, or are you justcleaning the TPS because?

could it be acting up without posting codes?

please tell me its not so? how can you test? analog ohmmeter and then move it? look for spikes?

You'd be hard pressed to catch a spike or any type of glitch with an analog meter. I use a graphing meter with a 1 mb/sec sampling rate for driveability concerns. Even if the analog meter was fast enough to display a spike your eyes wouldn't be fast enough to see the needle move. That is if it had an average glitch. If a huge portion of it were dead than you would have a better chance...

[Trevor]

Beav you are spot on.

However surely the guys who designed things would have taken into account that a mechanical device, as is the TPS, could/will not provide a perfectly reliable smooth signal and therefore will have incorporated some slight time delay to cover this. No expense involved.

I suggested a simple check based on what the average handy man could have available and am sure this would show up any fault which would be a problem. I did not think it worth while to set up my scope when checking mine. But !! the design of the electronics could be wanting and belt and braces could be called for !!??

I have not experimented with this but one could connect a few volts (dry cells or a limited current supply and NOT a car battery with lots of amps on hand and no fuse protection) across the element of the TPS together with headphones from wiper to one side, move the wiper and listen. A nice smooth rustle should prove all is OK. But anyone not understanding the basics and why I suggest this should not experiment.

OK...So I read this post and decided to jump right in and try this myself (due to the annoyances of an occasional Check Engine Light at start up). I cleaned the throttle cables, throttle body, and MAF with choke/ carb cleaner. The car runs and drives exceptionally well afterwards. However, I never disassembled the TBS due to the accessibility and my ability (patience mostly). I noticed when I held the bodies open there was a lot of black soot (carbon?) deeper in side the unit. Is this common? Should I worry about taking the entire body off and cleaning it? Right now I have my baby in the shop (Suby dealer) getting the "codes" checked........Update..No codes came up, so I guess that's a good thing.

[Beav]

The black dust is from the TPS itself. Just a by-product of normal wear. The more dust, the more wear that has occured. No need to disassemble further if it's running o.k.

Trevor, I wish it were that easy, it would make my life less miserable. My experience has been that spikes and/or small glitches will be counted as actual events and the system will react to them. There is no buffer or lag time allowed. If the computer is fast enough to see the event it will react accordingly.
Newer control units employ fuzzy logic in some areas, such as ABS inputs, but I haven't witnessed any yet that can/will sort out an erratic signal. Too many times I've seen one or two spikes in a TPS or crank signal all but bring an engine to its knees. I agree, it's ridiculous to be that critical, especially considering the harsh enviroment of an automobile. One could easily build a conspiracy theory against the OEMs and back it up, as there is at least one GMM that knows enough about automotive signals that it will take 'snapshots' of a glitch as it occurs, unattended.

[Trevor]

Beav if it is all as you say my heart goes out to you. However I think there is some confusion here between problems involving analogue as opposed to digital signals.

The TPS is a transducer with an analogue output . Or to be exact it varies an input voltage to provide an output voltage directly related to position. No counting of pulses is involved and if the designer has not incorporated at the very least a bypass capacitor in the input circuitry to smooth any slight Ò noise Ò in the signal, something is very wrong with his design. As an example the gas gauge would tend to flicker if the signal from the sender was not absolutely perfect and the read out was an instantly responsive display.

However I have long felt that those involved in designing the electrical systems in cars would not last two seconds in other industries and if you are right you have proven the point.

[sfsvx]

Originally posted by Aredubjay
Dick,
The TPS fits over the little pin sticking out from the side of the Throttle body and is attached on either side (notice screw holes) with screws. I'll see if I can't find a better pic for you, of an actual engine with the TPS attached.

Originally posted by Mr. Pockets
Dick, here's a photo of the TPS. The TPS is the black device in the middle of the photo. This photo is taken from the left side of the car, looking right. On the right you can see the intake duct and the two hose clamps that hold it to the throttle body.

http://www.subaru-svx.net/photos/fi...mmuter/1285.JPG

You can access the throttle body by removing the throttle body cover - it's the big grey and black plastic thing that says 'H6' on it.

It's all clear to me now. Thanks, guys!