I discovered this problem with my TPS while checking my
dashpot. With the dashpot hose pinched the motor rpm's
can't drop to idle, they stay at 1800 or so which is
correct. But while doing this I noticed that the engine
speed was surging between 1700-1900 rpms. It seemed like
the ECU was getting two mixed signals and couldn't make
up it's mind whether to go to idle or the 1800 rpm. So
I decided to retest my TPS. My VTA-E2 ohms are dead on;
500ohms and 4700 ohms. But the IDL-E2 readings seem way
off. At .57mm I only get 12 ohms and at .85mm about 13
ohms. It does go to infinity, but not until the throttle
is opened about 1/4". No amount of adjusting would get the
readings within spec's. Right now the TPS is adjusted as
far as it will go CCW to get it the VTA-E2 readings where
they are now. I opened the TPS up to look at the printed
circuit surfaces. They were solid black on white plastic;
does this sound right? I cleaned the contact surfaces with
alcohol anyway...no change after. At this point I'm
thinking the TPS is just worn out and needs replaced, but
before spending the hundred bucks I'd like to get some
opinions from here that agree with that assesment. Thanks
for you input.

-Indy

The TPS's made by Toyota are actually some of the best on the market. The black stuff is resistive ink printed on a ceramic substrate. They're baked at a very hight temp. but I'd be carefull what used a cleaning solvent. If you wear any of this ink down, the resistance goes up. The contact springs will usually wear out before any damage to the ink is done. The contact springs should have a little radius to them, if not, flush the whole TPS down the turlet. Hope this helps a bit.

Yeah, the springs still had their radius and the ink
was solid. I should also meantion that the rpm's are
fine at all other speeds except the 1700-1800 range.
The truck drives fine, where I notice it is at low speeds
in first or second when I hit that dead spot the truck
will trip over it's nose.

-Indy

I personally wouldnt worry about it Indy. Ive never been able to set the TPS so that all 4 checks come inline. I always setup where the VTA-E2 is deadnut 500 Ohms with throttle closed and verify the same at WOT to make sure it falls in range...let it snap back to closed throttle to make sure the meter doesnt waver off 500 Ohms. Couldnt tell you what the 2nd and 3rd test results with the feeler gauges were/are because I quit doing them. My gas mileage and performance has never been better and I do this on both 22R-E equipped rigs. Keep in mind also that these rigs are getting up there in years and electronics get tired.

Check it- Toy4ick did a rebuild on his 87' 4Runner, when done the engine just didnt seam any more powerful or faster even with an EB StreetRV head. Swapped my 87' ECU in for his and test drove it. He came back with an ear to ear grin...and promptly went shopping for a used ECU...found a good one and has been golden ever since. ECUs for 87' didnt have any different programming/fuel mapping etc...just over the years things get old and start forgetting chit. WTF were we talking about again??

~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Dammit Darin, you made me pee myself aggin.

I've got no problem on the road since the only time
I operate that low an rpm is parking.
I recently took a trip and with my little utility trailer
full of camping stuff I was at 5900# total combined weight.
Do you think my truck cared? Hell no...she towed the hell
out of that load and was grinning the whole way! But off
road when I'm crawling along in low/low it can be hard to
stay out of that rpm range...just makes for a jerky
ride sometimes.
I think I'll continue tonight and tomorrow to check all
the vacuum lines and other electronics I can think of.
I want to replace the phillips head screws with allen
head screws anyway, so I can play with the TPS some more.
Sometimes it's the littlest sh*t that drives a person
nuts...you know what I mean?!
If anyone else thinks of anything else please chime in.
I plan on having this truck for at least another ten years
so I want to keep her happy.

-Indy

Well, I've got an extra TPS out of my '94 22RE if you're interested. I changed it when I thought there might be a problem, but I don't think the problem ended up being related to the TPS at all. Oh well, always nice to put in new Toyota parts whenever I can <img src="/forums/images/graemlins/wink.gif" alt="" />

<img src="/forums/images/graemlins/confused.gif" alt="" />Could the problem be on his AFM board?You can take an eraser and clean the afm board.Just a thought. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Thief, your steps are exactly what I thought I'd done and
what the FSM says to do. But I'm going to take the throttle
body off the truck tomorrow so I can replace those screws
and more easily check the setup on it one more time.
I also will be checking the AFM and EGR too, just because
I've got all day tomorrow and nothing better to do.
That and I've been doing more experimenting and notice that
the problem seems worse when the motor has warmed up...so
could be an EGR system problem too. Unfortunately the FSM
lists almost everything as a possible cause...talk about
CYA. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I appreciate all the replies. <img src="/forums/images/graemlins/kewl.gif" alt="" /> At least I feel more
confident that I'm on the right track to solving this.

-Indy