4runrjunkie

Hey guys,

So I am trying to pin down the reason for my 4runner's horrible gas mileage, and am starting to think it has something to do with the TPS, but I am looking for some advice on my situation.

Lately I have been noticing that every once and a while my idle will drop from 800 rpm to around 200 rpm, the lights will dim and the oil pressure will drop off. My throttle response isnt ideal but its also not horrible.

All of that has led me to believe its a TPS issue, but before going in a testing the tps with my multimeter I wanted to just unplug the tps and see if anything changed. The result was a rise in idle and a little better throttle response and low end power (may just be the placebo effect), but the confusing part is that unplugging the TPS did not cause a CEL. Is this something that I should be worried about? I will be checking the resistances of the tps tonight to make sure they are in spec but I was quite surprised when I didnt trigger a CEL.

Any thoughts on this matter would be greatly appreciated.

Thanks

edit: The is for a 1990 V6 4runner

Co_94_PU

iTrader: (-1)

Thats not normal, lights shouldn't dim with engine speed. Oil pressure drop with engine speed is normal. TPS not throwing a code is also not normal.

Are you sure the bulb is good? It should light up when you turn the ignition to ON.

Have you checked the codes? Even if the lights not on there maybe codes.

I'd suspect some kind of short in the TPS wires. With the TPS unpluged inspect the wires for shorts to ground at the ECM.

SPARKS89

iTrader: (1)

Mine is doing the same thing. I've been driving mine around for not quite a year with the TPS unplugged and the CEL is not on. Here's a link to what I've been doing to try and figure it out.

https://www.yotatech.com/forums/f116...switch-256641/

kornhuskerwizard

I have a similar problem with my 88 truck. Its my daily driver. I only make short trips usually however ive taken it on a trip to the black hills sd once after i rebuilt the engine. anyways ive had a problem with dialing in the tps by following the writeup on 4crawler. My meter would jump around alot with the feeler gauge in place. I tried a couple of other tps's (all genuine toyotas, nippendensos?? i think) anyways im pretty sure its still not correct. So ive dealt with it getting poor fuel mileage,lack of power and acceleration, cel light with a rich code i beleive... cant remember.

Have you ever checked your fuel pressure out of curiosity??

4runrjunkie

The head lights dim because when the rpm's drop, the alternator isnt creating as much voltage. As soon as i rev the engine, the headlights go back to being bright. Does this make sense or is this an indicator of a problem in the wiring?

The CEL bulb is definitely good, and I have checked for codes and the CEL flashed constantly so there are no codes stored.

How would go about checking the wires for shorts to ground without tearing everything apart?

4runrjunkie

As of yet no ... I dont have a tester for it and I am trying hard to not take it in to the shop, but I may end having to.

SPARKS89

iTrader: (1)

Unplug the connectors on both ends (make sure you unplug ALL connectors for sensors that share a common ground) and do a continuity check from the terminal points to the body.

4runrjunkie

makes sense ... thanks!!

Co_94_PU

iTrader: (-1)

Learn something new every day!
So it is normal not to trigger the light. No shorts or other wire issues, atleast not for the light not coming on issue.

When you test the TPS I highly recommend using a probe set with clips. You can pick a pair of aligator clips up from napa for under 2$ that will work, radioshack also but it might cost abit more but there you can get a set of aligator jumpers(clips on both ends) which are even better than DIY. I'm an advocet for refurbishing(eg. cleaning) TPS sensors if you feel up to the task, and also ask if you're going to replace it to pop the top off and see/show what went wrong. Sensors are cheap at the local salvage yards, but even if you get one from the dealer it's a good deal(so long as you know thats your problem) +200k miles / ~100$.

For the power dropout/failure. Start by inspecting the battery for loose connections and frayed wires, then check the ground strap on the fender and the ones in the driverside kickpanel(behind the trim next to the interior fuse panel).

Ground wire locations are covered in the thread "22re ground wire locations - the guide!!!", it has handy pictures..

4runrjunkie

Thanks so much for making me feel better about my situation CO_94 ... much appreciated!!

I will let you all know the results of my testing once i get a chance to get out and do it.

SPARKS89

iTrader: (1)

Well that sure is a relief. I thought I had other MAJOR issues going on. That's some good info to have right there.

Co_94_PU

iTrader: (-1)

Inspect the voltage regulator, output voltage should be constant. Auto stores test these for free with thier "fancy" machine, if you want to pull it and by pass some on vehicle testing. A faulty regulator will/can put to much load on the engine and cause it to bog.

have to catch up on the rest of the posts Started typing sometime before kornhuskerwizard's first post. Got a little distracted and side tracked.. And of course the suns out so I need to get outside.

Anyway.. Start with the battery connections and then do the charging system inspection. You'll likely find something there.

Co_94_PU

iTrader: (-1)

Arrgg, wish I could remeber where I got the short version of the tps adjustment would save me having to type it out

Here's the shorter short version. Use clips on the meter, for one handed tweaking. Use a mid point feeler gauge(~0.07) to find the point the circuit opens, tighten it down and verify the 0.05 and 0.08 read as they should.

4runrjunkie

Ok can someone please confirm for me the test values I should be getting from my tps. I am currently looking at three different sites that all state different test values that i should be getting when the throttle plate is closed.

http://personal.utulsa.edu/~nathan-b...93throttle.pdf The service manual says I should get between 470-6100 ohms
http://www.4crawler.com/4x4/CheapTri...ottleStopScrew 4crawler says i should get between 200-800 ohms.
http://www.lcengineering.com/LCTechP...Adjustment.pdf lce says I shouldnt test it fully closed but should test it at .50mm gap and should get between 470-6100 ohms.

My assumption would be to go with the service manual but since everyone always says great things about the 4crawler and lce instructions, i am wondering whats going on. When I tested mine I got around 900 ohms, so according to the service manual that is ok but 4crawler would be out of spec.

Any thoughts?

edit: 1990 V6 4runner

Co_94_PU

iTrader: (-1)

Supprised you made it this far. I didn't miss it right? What engine and model year?

*edit*
I think it's explained in the LC and 4crawlers already..

The important thing is the ratio between the opened and closed readings. It is a resistor based voltage divider. The more accurate test is the voltage at the ECM.
The 88 manual lists this as 0.1-1v closed and 4-5v open, 90's era manual is 0.3-0.8v closed and 3.2-4.9 open.

4runrjunkie

Wow sorry i meant to have that in the initial post, it is a 1990 V6 4runner

And thanks for the tip. I just found the ecm tests in the service manual so i will go through and check that tonight hopefully.

4runrjunkie

Ok, so for those of you that have tested your ecm voltages, how did you do it? I have gotten to the ecm by taking the right hand kick panel off, but i can not imagine how I would get multimeter pins down to those pinouts to check voltages. just not enough room.

Any tips?

Co_94_PU

iTrader: (-1)

Best way is to unmount it from the body. Only other way is with bent probes, which is a kinda of feeling your way around in the dark situation and probably not recommended

Wire/clip a ground between the computer case and the body for ESD protection/piece-of-mind.