3FE TPS Install - Not Going Well

[PabloCruise]

I got a Toyota TPS and set about installing it. I need some insight as I think my technique may be the issue/problem.

I have posted on here before, but I will run down the specifics:

Application: 3FE w/ block # 3F 017791x (hard to read the last digit). Based on
this block # I believe the 3F to be an early 1988 engine. It is tucked in my
1974 FJ55 Pig, complete with factory AFM, harness and ECU

Incident: Repeated episodes of loss of ability to idle once engine reaches
operating temperature. Check of the ECU diagnostic codes pulls Code 12 - RPM
signal and Code 41 - Throttle Position Sensor Signal. Clearing codes returns
the same results. I believe ECU is not getting valid signal to determine
throttle position AND RPM signal. I think this would make it difficult to
manage idle. New Car Features 1988 says ECU will manage engine as if throttle
is closed if it gets no TPS signal, but combined with no RPM signal, I don't see
how it could do this.

Resolution (attempted): Tried two prior TPS from Autozone - Duralast brand.
Installed as per FSM, but they would not check out as per page FI-69 in FSM.
Order Toyota TPS and pull Throttle Body to facilitate install w/ feeler gauges and ohmmeter.

So I set up my new, Toyota TPS as per page FI-70 in my FSM, using
-0.93 mm feeler gauge
-ohmmeter on IDL and E2 terminals
-turn sensor clockwise until ohmeter deflects from 0 ohms to some value less
than infinite.
-NOTE: my combo of feeler gauges is closer to 0.94 mm.

Then I check reading at VTA and E2 with no feeler gauge clearance btwn lever and stop screw. I am over the 6.3 k-ohm.

I then open throttle valve fully open with ohmmeter still on VTA and E2, my
reading is well over the specified 10.3 k-ohm. Closer to 40 k-ohm.

I go back to 0 mm clearance and decide to reset the TPS position to get
resistance less than 6.3 k-ohm. I set the TPS with resistance btwn 4 and 5
k-ohm at VTA and E2.

I leave ohmmeter on VTA and E2 and move throttle valve fully open and get
resistance value of about 40 k-ohm. WTF?!?

I decide to reset TPS position with throttle valve fully open to see if I can
get resistance value at VTA and E2 less than 10.3 k-ohm.
FAIL.
I clocked the TPS through the entire range of adjustment and can not get resistance value to move from approx 40 k-ohm.

What gives guys? Everyone says this is easy to do. So what am I doing wrong?

 

[PurpleFJ62]

have to taken the TPS off the throttle body and verifyed that its resistance is within factory spec? I remember from my time on a 3fe thats a real pain in the ass to work on.

Is the wiring harness in good shape, no shorts or open circuits?

 

[dilligaf]

the way i do it is jumper wire to te1 and e1 then press the accel. if it blinks 51 x and then continuous its set if not then move a touch each time till it does.

 

[PabloCruise]

have to taken the TPS off the throttle body and verifyed that its resistance is within factory spec? I remember from my time on a 3fe thats a real pain in the ass to work on.

Is the wiring harness in good shape, no shorts or open circuits?

No, but I like the idea - thanks.

I'll check it out tomorrow...

 

[PabloCruise]

have to taken the TPS off the throttle body and verifyed that its resistance is within factory spec? I remember from my time on a 3fe thats a real pain in the ass to work on.

Is the wiring harness in good shape, no shorts or open circuits?

I want to make sure I understand your question correctly:

Are you asking if I pull the TPS, is it possible to get values that fall within factory specs by manipulating the TPS off the Throttle Body?

I tried this and for the first three checks on the table below (from the FSM), the answers are yes - possible.

For the 4th check - throttle wide open, at terminals VTA and E2 I get an infinite reading. Resistance goes infinite before the TPS is opened all the way, off the throttle body.

Does the 5th line in this table mean you should have throttle wide open and check VC and E2? If so, that fails as well. Reading is infinite resistance.

Does this mean my brand new Toyota TPS is defective?

 

[PabloCruise]

Nice watermark - all over the values...

Try again

 

[Dunbar]

Pablo,

As I mentioned in 3FE land I think you might have eliminated the TPS as the main contributor to your problem.

All I can think of is checking the harness for bent pins or dry cracked sections of wire. Hopefully the pro's will chime in.

 

[PabloCruise]

Pablo,

As I mentioned in 3FE land I think you might have eliminated the TPS as the main contributor to your problem.

All I can think of is checking the harness for bent pins or dry cracked sections of wire. Hopefully the pro's will chime in.

I am confused - shouldn't the TPS pass inspection set forth by the factory?

 

[slcfj62]

Pablo, here is how mine behaves:

EDIT: I just read your post again after taking the measurements on my TPS, and I hate to say it, but if you have 40K ohms you must have the wrong TPS or a measurement error (batteries in the ohmmeter??). Check the VC-E2 and it should be somewhere close to mine. And if the FSM is still valid, it should be less than 8.25 K ohms.

With the throttle closed (measured at the TPS with the connector off)
VTA-E2 is .539 K ohms (which is 539 ohms)
IDL-E2 is 17.3 ohms
VC-E2 is 6.29K ohms (this won't change no matter what the throttle position)

With the throttle cracked open, the IDL-E2 goes to infinity. I actually didn't make that adjustment with the feeler gauge. I just rotated the TPS a bit against the throttle spring and tightened it down. I did it mounted on the engine, and didn't have three hands. I was just going to try it and see what happened, but it has worked out so well, I didn't go back and check it with a feeler gauge.

As the throttle is smoothly opened, the VTA-E2 resistance also smoothly varies between the 539 ohms with the throttle closed to 4.63K with the throttle fully open.

Hope that helps.

EDIT: And I think if it doesn't behave in this manner for what ever reason (bad TPS, out of adjustment, or even bad test meter) you have a problem. If it is behaving in this manner measured at the TPS (connector off), but you still have your idle problem, measure it at the ECU with the TPS plug on and the key off. According to my wiring diagram, the wiring colors at the ECU are as follows:

E2 is the Brown wire with the Black stripe
VTA is the Green wire with the Black stripe
IDL is the Green wire with the White stripe
VC is the Green wire with the Red stripe

There is also some other stuff that connects to the E2 port and the VC port on the ECU that might change the readings a bit, but they should behave the same, even if the resistance values are changed a bit. This will confirm the connectors and wires are OK between the TPS and the ECU.

My fj62 is a 1988 model year, and I have the 1988 FSM.

 

[PabloCruise]

Pablo, here is how mine behaves:

EDIT: I just read your post again after taking the measurements on my TPS, and I hate to say it, but if you have 40K ohms you must have the wrong TPS or a measurement error (batteries in the ohmmeter??). Check the VC-E2 and it should be somewhere close to mine. And if the FSM is still valid, it should be less than 8.25 K ohms.

With the throttle closed (measured at the TPS with the connector off)
VTA-E2 is .539 K ohms (which is 539 ohms)
IDL-E2 is 17.3 ohms
VC-E2 is 6.29K ohms (this won't change no matter what the throttle position)

With the throttle cracked open, the IDL-E2 goes to infinity. I actually didn't make that adjustment with the feeler gauge. I just rotated the TPS a bit against the throttle spring and tightened it down. I did it mounted on the engine, and didn't have three hands. I was just going to try it and see what happened, but it has worked out so well, I didn't go back and check it with a feeler gauge.

As the throttle is smoothly opened, the VTA-E2 resistance also smoothly varies between the 539 ohms with the throttle closed to 4.63K with the throttle fully open.

Hope that helps.

EDIT: And I think if it doesn't behave in this manner for what ever reason (bad TPS, out of adjustment, or even bad test meter) you have a problem. If it is behaving in this manner measured at the TPS (connector off), but you still have your idle problem, measure it at the ECU with the TPS plug on and the key off. According to my wiring diagram, the wiring colors at the ECU are as follows:

E2 is the Brown wire with the Black stripe
VTA is the Green wire with the Black stripe
IDL is the Green wire with the White stripe
VC is the Green wire with the Red stripe

There is also some other stuff that connects to the E2 port and the VC port on the ECU that might change the readings a bit, but they should behave the same, even if the resistance values are changed a bit. This will confirm the connectors and wires are OK between the TPS and the ECU.

My fj62 is a 1988 model year, and I have the 1988 FSM.

This does help a great deal.

My concern is that VTA-E2 goes open (infinite resistance) when I open the throttle, as does VC-E2

 

[slcfj62]

VTA-E2 should never go open, and VC-E2 should never change at all.

 

[PabloCruise]

Ha ha...

I learned some very important lessons today:

1) kilo = 1000, not 100. In other words you need to be smarter than your
mechanical gauge multi-meter. I was mistaking 40x100 to be 40 k-ohms. Not 4
k-ohms. D'oh!

2) You also need to be smarter than a high-tech digital multi-meter if it
requires you to select between high and low resistance ranges! Trying to be
clever, I grabbed an alternate multimeter to double check my work. The meter
would show an open when we got up into the k-ohm values. Switching to high
range (Hey, what does this switch do?) yeilded results on the last 2 tests
listed for TPS. I was decieved when turning on the multimeter showed "0 k-ohm".

3) The Toyota TPS looks to pass all requirements set forth in the FSM off the
Throttle Body. I'll bolt it on tomorrow and see if I am smart enough to dial it
in.

If ECU keeps flashing 12 and 41, I will go after the wire harness.

Thanks for listening to me rant.

 

[PabloCruise]

VTA-E2 should never go open, and VC-E2 should never change at all.

This was so helpful to me!

I kept looking at the test grid and trying to figure out what they meant for clearance on the last test for VC-E2.

Your comment, combined with the schematic made the pieces click!

 

[slcfj62]

Glad to be of help, and glad you are on your way!

 

[PabloCruise]

the way i do it is jumper wire to te1 and e1 then press the accel. if it blinks 51 x and then continuous its set if not then move a touch each time till it does.

Can you elaborate on this?

It sounds like a cool way to set TPS, but I am not sure I understand your process...

 

[PabloCruise]

I have some significant updates about my 3FE Pig since the last time I made a posting.

I hooked up a Check Engine Light (CEL) and checked for diagnostic codes. I got codes 12 (RPM Signal) and 41 (TPS). I replaced the TPS with a Toyota piece and swapped in a used distributor. While I had the throttle body off, I replaced the PCV valve, grommet, hoses, valve cover gasket and the “donuts” that seal the valve cover at the mounting bolts/studs. After this work, I still got codes 12 & 41

I sought the help of a friend who is more skilled in automotive electronics than myself. We started out tackling the Code 41 (TPS) first. Using the troubleshooting protocols outlined in the FSM, we discovered an open in the line between the computer and the VTA terminal on the ECU. We replaced this wire and then discovered no voltage at the VC terminal at the TPS – this means the TPS was not getting any power to issue a signal. We determined the line providing power to the VC terminal at the TPS was disconnected under the dashboard – wow!

I re-checked for codes and found that both code 41 and 12 were gone. I am not sure why code 12 went away now that the TPS was happy, but that is what happened. Now that the TPS was live and I had my timing set with some advance in the dizzy, my Pig had some pep in her step.

Fast forward to re-setting idle speed (golden screw) and re-checking timing… When I had the 3FE nice and warm and tried to set idle to 650, I noticed my idle was “hunting” or wandering up and down again. When I was driving home from work on a nice warm day, I noticed the idle was stumbling while I was sitting at a traffic light. And, I was getting a code 12 again. So, back to the drawing board…

I went back to the friend with the automotive electrical background. He also has a smoke machine which is really cool, because you can use it pressurize a system and see where smoke pops out. Using the smoke machine, we found the gasket around the EGR valve at the intake was leaking. We fixed that and “smoked” the intake again, and found a very slight puff of smoke at the ISC where the plastic meets the metal. I pulled the ISC apart, flipped the o-ring and dabbed a little silicon in there. We buttoned everything up and fired the 3FE up. After it warmed up, the idle was stumbling. Wow…

We broke out the fuel pressure gauge and hooked it up at the cold start injector. Fuel pressure in the rail: 71 PSI!!! We pulled the fuel pressure regulator and tested it with compressed air, it would open to pressure. We then found we were unable to blow any air into the fuel return line. We traced the blockage back to the soft line between the gas tank and the hard line under the floor. After clearing the soft line, we blew out the hard line, blowing from the tank to the engine compartment. When we lowered the Pig (nice to have access to a lift) the engine compartment was nasty with the debris that blew out of the return line. I had it disconnected where the soft line met the return line on the engine, just behind the thermostat.

We fired the Pig up again and checked fuel pressure on the rail – all was good!!! We checked pressure with the vacuum line hooked up to the FPR, as well as with it disconnected. We then set the idle and let it idle for a good 20 minutes and the 3FE purred like a pussy cat!

The bottom line is that I believe my problems were caused by a clogged return fuel line. I think the ECU was doing all it could to manage idle when there was almost double the specified fuel pressure in the rail. I am guessing the ECU had injector pulse width pulled all the way in. But along the way I discovered issues with the fuel tank, and that I needed to pre-filter my external pump. I found my o2 and TPS to be dead. I found timing incorrectly set. I found problems in the wire harness related to the engine swap. I found a leaking EGR gasket that probably made for a good vacuum leak. I am amazed this engine ran at all!!! I am also amazed I drove it from Colorado’s Front Range to Moab, UT (and almost made it back home!) So I am glad I found these issues before finding the obstructed fuel return line.

I had tanked up just before fixing the return fuel line and noted 11 MPG. I cannot wait to see what mileage is now that the system is running 38 PSI vs. 71 PSI!

My only other observation at this point is that I think the 3FE may be missing some of that extra pressure in the fuel rail when I accelerate. I have in excess of 7 degrees advance in the engine (the BB is no longer visible in the window) and it felt nice when accelerating. Now that the fuel pressure is restored to spec, the 3FE idles flawlessly, but I think I am missing a little power. My plan is to drive it for a while and note any issues that may arise. I cleared codes on Saturday, I will check codes again next weekend.

I hope this info is helpful to other 3FE converts. This is truly how I learned to stop worrying and love the 3FE!

 

[cruiser88]

damn I am so happy you fixed this. I know you have been banging your head for months

 

[slcfj62]

Wow. That is a story! I really like my 3FE as well. It really runs smooth once you get the bugs ironed out.

 

[PabloCruise]

Thanks All, I couldn't have done it w/o the support of other 3FE'rs...

 

[bperz]

real time help on TPS

i have read and tried all above and believe my TPS is bad, I get a 1 on my meter, on the truck off the truck, manipulating it off the truck and on the truck. I assume it is a bad one--confirmation?? comments--if so any comments on non yota TPS?? thanks in advance for any comments