So I had to take off the intake manifold to replace the notoriously hard to reach fuel filter, and along the way I ended up unscrewing and removing the TPS like an idiot instead of simply disconnecting it’s electrical plug. Now that everything is back on, I’ve followed the instructions on lcengineering pretty obsessively regarding the TPS adjustment, and I get get 4 out of the 5 tests performed on the multimeter to pass - except for the VCC - E2 test (the last one).

No matter what I do for that test, it reads as an open loop, in any throttle position. Is it possible I’m doing something wrong, or does the TPS need to be replaced? I appreciate any guidance that anyone can give me on this.

 

Only one TPS adjustment is possible.
That is the throttle closed/ throttle open adjustment.
The other measurements are to determine if the TPS is functioning correctly and is fit for further service.
Jimkolas timing light method of TPS adjustment is the real deal.

 

I’m assuming then that you’re referring to tests 1 and 4 in the attached image since test 1 seems to meet the condition of completely closed and test 4 is wot? The good news is that I can get those tests to pass.

The only measurement I’m having trouble with is test 5, which tests the total resistance of the potentiometer, if I’m not mistaken. That appears to be an open loop. Does that mean the TPS is bad?

Which method is that? I haven’t seen it yet.

 

You can set your TPS with a multimeter five times and have the set screws land in a different spot each time.

This is not a hack trick. It's the method factory Toyota techs used bitd. use this link, then scroll down till you see my post.
setting tps with timing light

 

I'm having SO MUCH trouble getting my brand new from toyota dealer TPS set in test 2 (the important one) I either get Inginity or way above 2300 despite 7 million adjustments and 5 different people trying the test and I've read everything I can find. Here is a portion of a thread about this I'll link.
http://4crawler.com/4x4/CheapTricks/TPS/index.shtml

From what I've read it seems the only measurement that matters is the IDL - E2 so if youre in spec there and everything related to it's operation seems fine then your tps is probably ok.

• "Test #5 just measures the entire resistance of the outer-most current track seen in Figure 2.
  • This reading will be the same regardless of the throttle opening.
  • It can't be adjusted, so is basically a go or no-go reading.
    • If the reading is within the specified range, it is OK, if not, it is not OK.

So, how do you interpret the above test results and decide if your TPS is good or not? , see the section here for some symptoms of a defective TPS - and if you do not have those symptoms, then it is likely OK as the ECU is the ultimate "judge" of goodness or badness."

I also read that when you jump the 2 terminals to do your timing if the idle drops and you get the check engine light to flash youre good to go. I cant independently confirm any of this info because I cant get my tps set, I am having major idle problems and I can't get my timing set because when I jump the terminals nothing happens and there's no sense setting timing with a bad tps.

If anyone has advice let me know.

 

Quote:

there's no sense setting timing with a bad tps

I'd say there's no sense setting TPS if engine timing isn't right.
​​​​​​​How high is your idle speed?

 

Well, it has recently gotten as high as 3000. That's a new phenomenon. Prior to that the highest was 2500. It drops as low as 250 and almost stalls. Another fun thing is it will rise from 800 to about 1200 over the course of a few seconds then drop back down to 800 and just rhythmically cycle like that until I step on gas. This is with AC off, standing still, not breaking or turning.

I've ofcourse checked vacuum leaks and I'd stake my life there isn't one. Ive reset idle w/ adjustment screw per FSM many times. Next time I drive its immediately off again. Ive tested with an ohm meter and cleaned AFM. Inspected throttle linkage and cable. Removed and tested IACV (old style under intake) it tested good on ohm meter. I trie# setting timing but can't get any response from jumping those 2 terminals (no idle drop, no check engine).

I know I cant get the TPS set so I havent explored any further options such as checking VSVs or ignition stuff accept changing all spark plugs and checking air gap on distributor.

I'm only doing things I read in the FSM or read online about idle problems. I have no first hand knowledge of my own about mechanical things..

 

Additional info if it matters: I test the TPS with the TB off the vehicle. It does it in the first 1 mile of driving and after 60 miles of driving and all the miles in between. It starts fine, it doesn't over heat, ive burped coolant.

 

You might wanna pull the IACV and physically clean the inside with brake cleaner. Be careful of the round disc, they are somewhat fragile. You can reset it per the fsm at the same time.
There's also that short return spring going to the dash pot. Does it feel responsive, or is it weak? If it's idling high can you rotate throttle linkage at the throttle body and lower the rpms?
3,000 rpm idle is insanely high

 

I know it's crazy but its true.. i have videos of it.. Dashpot does seem to be working fine but i took it off entirely and it doesn't seem to help (or hurt). If I rotate the linkage forward with my hand with a lot of force I can get a small RPM drop but it takes an unnatural forward rotation to achieve this. i have tried setting the stop screw per fsm. I marked the threads before I made any changes and ended up in the same spot so it was pretty much set correctly to start.

I've taken it to 2 shops including Toyota dealer. Dealer phoned it in and said it was the dashpot (no). Other supposed local car guru claimed to have set TPS correctly and set timing and he's a liar. I didnt even get out of his parking lot before my idle surged to 1500. I immediately checked TPS when I got home and timing and both were still off. Im about a grand into chasing demons at this point between the 2 shops and new TPS.

To spice it up a bit I enrolled in my local community college auto repair program and go full time just to be able to learn how to work on cars and maybe someday have a norma idle.

 

I wasn't big on dash pot either.
The FSM does mention IACV first. Make sure it's not stuck wide open. They are prone to gunking up, so well worth opening up and cleaning. If you don't have the FSM I can post image of how it should be set after cleaning.
If it has AC and/or power steering, air leaks in those systems (vsv) can throw settings way off.

 

I do suspect the IACV to be stuck. It was about 25 to 30 degrees outside when I took it off (the truck is outside not in a heated environment) and it was partially open and seems like it should have been all the way open with it being so cold outside. I put it on a little oil heater for a while and it never closed. So maybe its no good. Ill have to take it apart. I do have the FSM but its for 88 (mine is 87) and I think 88 has the newer TB/IACV so IDK if it will have the right instructions. If you can share them that would be great.

Even if IACV is one culprit I cant get passed this TPS problem. Test 2 will not give me a number below 10,000. Its either >/= 10000 or its infinity. I know Im the common denominator but if I'm doing it wrong then I dont know how else to do it right because I followed the book to a T and watched a lot of different videos. Im doing it how Im supposed to. Im quite certain of that. I even bought a brand new multimeter and it was the same result.

Is there something on the TB that could be making my TPS unable to be set properly? That's the only thing I can think of. But the butterfly is in good shape. It doesnt rub or drag anywhere. Its not loose or wobbly. It closes all the way and doesn't stick. I cleaned all the air passages in the TB.

I feel like im going crazy or missing someone so obvious that I'm not even thinking of it. I cant find anyone else or any thread who has ever had this problem.

 

I just checked. The same IACV went from model year 1984-1988. So I imagine your instructions for setting it up are the same. Toyota did put a sticker on the valve with a part number that is pretty durable. (22230-35010)
But you want to do it when ambient air temp is close to 68 degrees. So if it's cold outside bring the valve indoors for a few hours, then adjust per FSM.
Hopefully this will get your idle RPM under control. You need it under 950 to be able to set timing.

Once you get your base timing set, and have your timing mark move when you jump wire T1 and E, then move on to your TPS.
And in all seriousness, try the method I've mentioned in the past. How that multi-meter method still has traction eludes me.

Once your base timing is set your distributer lock bolt should land ideally somewhere towards the center of the slot. If its way off to one side something isn't right. Same with the TPS. Once you try the timing light method if it goes well you'll should see the TPS lock screws pretty much centered, too. If it's way off to either side that would be a bit concerning.

 

Can I even set my timing correctly if I cant get my idle to drop or the check engine light to come on when I jump the 2 terminals?

 

This is probably dumb but I know you have to do the thing where you make it flash morse code and then translate it to find out what the problem is but will the chek engine light come on by itself to tell me something is wrong in the first place? Or do I have to just know something is wrong and then make it tell me what. Because no check engine light ever comes on.

 

No, you can’t set timing with rpm’s that high.
DTC’s were still in their infancy back then. Typically if the system detected a problem the light come on.

 

I appreciate the info, I didn't know it before. You made my day


 

the CEL needs to be functional; when it is flashing with T & E1 jumped, it lets you know it is in base timing mode. without being lit, you won't be able to determine that. first, verify that there is a bulb in the CEL position in the gauge cluster [the CEL should be lit when the key is turned to "on" prior to starting the engine - if it isn't, you have to determine why it isn't lit].

 

[the CEL should be lit when the key is turned to "on" prior to starting the engine - if it isn't, you have to determine why it isn't lit].[/QUOTE]

It does light up so the bulb is functional but as I mentioned nothing happens when I jump the terminals. No idle drop or CEL flashing. Is it possible that little box with the terminals is bad? It is caked in what I assume is dielectric grease old enough to be my mother and it's gross. Kind of yellowish-brown. I thought about trying to clean it all out but I didnt want to damage anything. What other functions does it perform that I could test to see if they work or if the whole thing is bad?

 

i use a bent paperclip inserted into those two terminals. wiggle it a bit to create better contact - sometimes that will work.

you can test the diagnostic port by jumping B+ and Fp, and turn the key to "on" but not "start". the fuel pump should now be running, and be audible. turn the key back off, then on if you aren't sure that you hear it. once tested, remove the jumper from those pins - you don't want to drive around with them in place.