KidSheleen

Short version:
94 T100 3vze 4wd A/T - 234,000 Miles
At idle, timing showed ~30 degrees BTDC. Engine seems to run okay enough.
Retarded to ~14 BTDC
Engine runs like crapola

Long version:
I thought that my timing was giving me a false indication of fouled injectors. The truck has been sitting 3-4 years with only a very occasional start. After replacing plugs, wires, distributor cap and rotor the engine was missing on #5 cylinder. I bought new gas and Sea Foam and it cleaned up the idle for the most part. I still had an occasional miss and gurgle at idle. I was planning on hooking up a can of Toyota injector cleaner but I thought that I should check my timing.

With E1 and TE1 jumped (CEL and O/D lights blinking), idle set near 800 RPM and a warm engine the timing was about 30 degrees BTDC. I retarded the dizzy as much as I could and ended up around 14 BTDC. I adjusted the idle screw but the best I can get is around 750 RPM. The idle sounded okay but the RPM acceleration response was not as it was before.

The next AM, I started the T100 before I left for work and I had NO cold start high idle. It loped at around 500 RPM until the engine warmed up and it was not quite at 750 RPM. I went home last night to double check that my timing light was actually on the #1 wire. I reset the dizzy near where it was originally and went through the whole process again. This AM I started the engine again and I still have the same symptoms: no cold start high idle, slow throttle response and the exhaust sounded like an old Ford 8N tractor. Plus, I cannot get the idle speed up past 750. I can keep on turning the idle speed screw out but it makes no difference.

One of the other odd (to me) things is when I have the timing light on the timing mark, when I rev the engine the timing very briefly drops to 0 and then advances from there.

I have never touched the timing before. The timing belt has been replaced twice, once at 62,000 when the HG blew and again around 130,000 when the water pump pulley shaft ended up in two pieces. A dealership did the work (Certified pre-owned covered the HG). The TPS has never been touched to my knowledge. It still has the yellow paint marks lined up from the factory settings.

I had pulled the intake plenum and throttle body when I replaced my valve cover gaskets and rear cam seals. I have checked twice for any vacuum leaks, once using an unlit propane torch and the second time with some starting fluid spray. There was no change in idle speed.

Do you think that I might have a plugged vacuum line that would be giving me this odd reading? Any advice would be accepted.

For the time being, I'm going to move the timing back to ~30 BTDC. I was getting no pinging and a more responsive throttle. I still have the occasional miss but hopefully it is just a dirty injector (or more).

TIA - Mark

KidSheleen

^^^
I put the distributor back near to where it has been for several years (approximately 30 degrees BTDC according to my old Sears strobe timing light). I set the crankshaft pulley at TDC and removed the dizzy cap. The rotor is "spot on" on the markings on the dizzy.
Just some additional information.

miket223

The likely issue is your TPS adjustment has drifted over the years. Force your throttle body closed while you have the timing light going and you will most likely see the timing marks jump to where they're supposed to be and not way out in left field like they are now. You should also hear the engine idle way down. This is your indication that you need to loosen the two screws and adjust the TPS.

millball

As soon as I read this I knew it was true.
I have had exactly the same advanced timing situation on my '87 22RE.
Forcing my throttle plate closed wasn't enough to turn the trick though, I had to move the TPS quite a bit to get the timing to drop, and ended up readjusting the TPS as per the FSM.
After I adjusted the TPS, the 30' advanced timing measurement dropped to about 12' at idle and down to a correct 5-6' BTDC with E1 and TE1 jumpered.
The timing still advances up to near 30' BTDC when the engine is revved, as it should, and after readjusting the idle speed, the idle is much smoother with the timing less advanced at idle.
I was already getting 22-23 MPG even with the TPS out of whack, so it will be interesting to see what she will do now.
Thanks for the insight, miket223!!!

miket223

You bring up another point. If it's too far out of whack it won't show up. You can do it in reverse where you look for the timing marks to jump when you crack the throttle open. If that jump doesn't happen then your TPS is out of adjustment or bad.

KidSheleen

Thanks folks. I'm trying to adjust my TPS at the moment (off the vehicle). I'm fighting the multimeter right now. I can get "Open" but when I move the TPS CW the multimeter jumps all around. I wonder where I left the instructions for the meter?

I should be using the top two pins on the TPS? (3VZE)

millball

No, the bottom two for the idle position adjustment on either 3VZE or on 22RE.

KidSheleen

Weird. I tried the bottom two pins but I could never get an Open circuit. I tried the top two pins and I could get an Open circuit. With a .020" feeler gauge I got some resistance and with a .030" feeler I got the Open circuit. (I could never get the 2.3k Ohms exactly. I have waay too many range settings for resistance on my MM)

I put the Throttle Body back on and the timing mark was ~ 15 BTDC. With E1 and TE1 jumped I could retard the timing back with a lot of spare adjustment on the distributor left, not like before where I had no adjustment left. I left the timing at ~ 12 BTDC. When I took the jumper off the timing dropped back ~ 2 degrees like the FSM said it should.

The FSM is very confusing on what the pin outs are on the TPS. Page EG-240 has the E2 and IDL as the top two pins. On pages EG-245 & EG-246 it has the pin outs opposite but I don't have the same TPS orientation that the drawings show. It's kind of hard to describe the drawing orientations on pages 245 and 246 but it would be like the connector is pointing towards the fender not the plenum.

I have only had the truck sitting, I haven't taken it out on the road since I don't have a state safety inspection yet. But the idle seems much smoother and a better throttle response.

The only other thing is that I am about at the limit for adjusting the TPS. Maybe I should look into getting another.

You folks have been a huge help. It also helped when I figured out the difference between mm and inches.

It's still strange about the pin outs. Maybe I have the TPS all FUBAR.

millball

When you are looking at the pins in the TPS and the side of the TPS that mates with the throttle body is on the left, the bottom two pins are the ones to use to adjust closed throttle position.
It may well be that your TPS is shot.

miket223

The TPS connector can face both directions depending on the year and this can be confusing when you probe the pins based on orientation as it's installed on the vehicle. If you do get a TPS, do not buy a piece of ˟˟˟˟ aftermarket one. Get a new or used OEM one or keep your broken factory TPS, it will be better than a brand new aftermarket one.

KidSheleen

Thanks folks.

1994 T100 - 1994 Toyota T100 Repair Manual (Factory hardcopy, not a .pdf)

This looks correct to me and this is what I followed (Page EG-240 next to last drawing):


This is the confusing drawing. Same page but the last drawing on the page. There is no way that I could have that orientation of the TPS unless the connector was facing the fender, not the plenum. This made things confusing:


I set the TPS as shown in the first drawing. The engine seems to be running okay in its typical 3.0 piggy-ness. I took a chance on skirting the law and gave the truck it's first fill-up in about 3-4 years. I also took it on the Interstate for about 2 miles and it actually got up past 70 MPH. Currently my only concerns are: I can't seem to get the warm idle above 750 RPMs and that I am also almost maxed out on the TPS adjustment. I had to turn it almost all the way CCW to get resistance on the circuit with the 0.020" feeler gauge.

BTW, I now also have a good cold start high idle with the timing at 12 BTDC.

Thanks for all of your help - Mark