I have been chasing a wandering idle problem for quite some time now. I have bench tested my TPS with the FSM, it itself tested fine. But when jumping the TE1 and E1 connectors with the engine running (at op temp) there is no drop in idle.

So just having tested the TPS itself, im assuming there is some wiring problems to the ECU.

How would I do about testing the connections? Got any hints or tips?

Thanks guys..

 

You would perform the same resistance tests as you did when you bench tested it, only this time test at the pins of the ECU connector:
- http://www.4crawler.com/4x4/CheapTri...roubleshooting

 

So i would unclip the ecu connector and test the pins... What kind of resistance should I look for? Would I test the 3 pins specified on your page you posted? How would I test those?

 

Well yes, how else would you get to the pins in the connector.

And what resistance? Obviously the SAME resistance that you measure at the TPS itself. I.e. the wiring between the TPS and ECU should have essentially 0 resistance, probably be an ohm or two different between the two points, but not enough to throw off the readings.

 

Sorry, just trying to understand what exactly to test.

So, Unplug the plug on the ECU. Then test that plug that runs to the TPS. Im not testing the ECU. Just the wiring. Okay, if thats right then I understand...

Looks like a two person job now. I will post back after I get someone to help me, thanks Roger!

 

Yes, you are testing the wiring between the ECU and the TPS by probing the pins at the ECU connector. No need for two people, you just want to see if the TPS resistances are the same at the ECU connector as at the TPS connector itself. No need to do the feeler gauge tests per se, you just want to see if whatever reading you get at the TPS is reflected back at the ECU. Basically, you just want to check each of the signal wires and verify that they are intact or not.

 

Ahh, okay, that makes sence.

I will give it a go after class today, thanks Roger!

 

OKay, here are some results:

I used the 1993 FSM for the pin locations.

Resistance on TPS between:

VTA- E2 = .72
IDL- E2 = .05
VC- E2 = 5.92

Resistance at ecm clip:

VTA - E2 = .67 ***
IDL - E2 = .05
VC - E2 = .27 ***

So it looks like I have found my problems. The VTA - E2 is about .05 difference and the VC - E2 is about 5.65 difference!

So, how should I go about fixing this problem? The wiring is pretty tough to get to. Think I could just replace the wire, and splice it in near the TPS. Defantly not the best way to do it, but to do it properly would require removal of ALOT of parts....

Also, not quite related but, I am missing a few wires:

I am missing " TE2, TH02, OX-, and VS on the middle connector.
And somebody spliced into the SPo1 connector on the right hand connector. I know the PO had an alarm installed, sound related?

Not sure about the missing wires though, was those connectors not used in 91?

 

You could try adding a wire in parallel for that one signal. I did something similar on my VW once in an attempt to fix a problem. As it turned out there, the actual problem was found after I ran the wire and found no improvement. As it turned out, the problem was in the connector where the relay that was getting the signal inside was plugged into. It was damaged and that led to a poor connection that caused the problem I was seeing. So you might check the connectors closely and see if perhaps the problem might be found there. One way to check is to scrape back a little insulation on the wire(s) you suspect is(are) bad and then check the resistance with the connector plugged in. I ran into a similar problem with the AFM connector/wire on my '85. Found a problem with a pin inside that was not making solid contact and I got different readings when I probed the connector pins vs. probing the wire beyond the connector.

As far as missing pins and splicing, might check that out closely and see if it may be causing the problem. And there are often unused pins on any given year ECU, could be pins for a 2nd O2 sensor or something like that.

 

Hmm, that sounds like a good idea. I will scrape a little of the protective sheild off the VC wire at the connector, and I will test it again. I will also try running a test wire from the connector to the TPS to see if that helps..

Thanks again Roger

 

Okay, so I think I have narrowed the problem down to where the harness goes into the TPS plug in. the TPS connectors....

I scraped some of the protective sheild off the VC wire at the ECU, that yeiled no results.

So I did the same at the TPS connector, nothing. So im not getting anything from the green wire RIGHT after the tps plug in. So I think the connector in the TPS/wiring harness plug is gone.

So are the wires that go into the TPS connector removeable? I have had to do some wiring on other parts and most of the plugs you could remove the wire by using a flathead screwdriver and unclipping it...

If not, how am I gonna add a new connector inside the TPS plug in?

 

Probably worth trying to dig into the connector and see how it is put together. I haven't messed with that one but like you say, most have some way to pop the contacts free. Probably either some corrosion at the wire crimp or the wire itself has broken inside the insulation after the connector crimp.

 

Well I figured out how to get the wire out of the clip. Just needed a 2mm long flathead to get in there.... The connector used is pretty weird lookin, nothing that I have ever seen at the parts store... I wonder how the heck im gonna get one to replace that.

So, the wiring harness that the TPS wiring goes into is pretty darn buried, I wonder how the heck im gonna get a new wire in there without it totally looking like a hack job

This is QUITE the PITA!!!

 

See if you can figure out where the open is, likely the connector itself is OK unless it is mangled up somehow. Or snip off a connector from a junkyard truck and slice that into your wiring.

 

I was going to do the latter, but honestly. Trying to find a toyota in the local junkyards.... aint gonna happen. There is one yard around these parts, they buy up all the toyotas and charge an arm and a leg for parts

I put everything back together, Im gonna try a few different things, see where that gets me. I probibly won't get a chance to touch it again till wednesday or later.. At least the truck runs (pretty darn well too) with this messed up wire.

Thanks for your help Roger

 

What guage wire is used? Incase I need to make something myself....

 

Okay, so the problem is not with the connector like I though. There is a break in the wire somewhere in the harness..

I scraped off some insulation about 2" from each connector on the wire (ECM connector and TPS connector) added my test wire and started it up. Truck idled great, I jumped the TE1 and E1 connectors and the idle dropped accordingly.

So what I want to do is cut the wire near each connector and splice in a new wire.

Now, to do this it, it looks like im gonna have to remove the upper intake manifold as the harness is literally buried under it. Then splice in my new wire.

So, any hints or tips? What guage wire should I use?

 

Use the same gauge wire as what is there, probably 18 or 20 ga. would be my guess. Really not terribly critical on the size.

 

mine is doing the same thing. just built a new motor dropped it in, fired it up and cant set the timing. this thread gives me a direction to go.

 

Yeah, im wondering how much my timing is off right now

This wire has caused so many little problems!! Im really not looking forward to fixing it