Crizzayota

Hello everyone, my first post here!

Let’s get right into it. So I was having issues with my automatic 86 4Runner (just shy of 200k) I rebuilt the top end about 3 weeks ago and I started having more issues. Previous to the rebuild the engine would downshift to 2nd at highway speed (75mph) and would only fix itself if I popped it into neutral and back to drive. This only happened 3 times over the first 6 months of ownership before the rebuild. Now I had it happen about 3 times the past 2 weeks I originally had just a code 3 (no signal from igniter). At the end of last week it downshifted three times In the same drive (30min to a job) so I did some searching and asking and most research pointed me to the TPS so I just replaced it. I should have checked it first but I just went ahead and replaced it. Now the idle is unstable where it will jump up at the start and drop to 750 or so like it should and slow bogs down and shuts off maybe 1-2 minutes on average from start up. Rechecked my codes and now I have a code 3,4,6,12 all have the possibility of a bad ECU but I’d be kinda surprised since. I’m gonna go get a new multimeter and try adjusting my TPS again tonight. Could it be my igniter? The truck fires immediately when I turn it on it just won’t idle evenly and when I apply gas to keep it idle the rpms jump around inconsistently. I’m not very electrically inclined but very mechanically inclined. If I’m missing anything please let me know. I appreciate all the help!

Jimkola

I find trying to set the TPS with a meter frustrating.
Here’s a method our techs used bitd.

1) set you base timing. Short T and E1 and use a timing light make sure your timing mark is correct. I like to put a tab of white paint on the pulley to make it easier to see. Tighten the distributer and then shut the engine off.
2) now do what you need to do to pre-loosen the tps. I find it easiest to pull the throttle body and loosen the two screws, then tighten the top one just enough so the tps doesn’t move around. Then reassemble.
3) restart the vehicle. Your T and E1 are still shorted. With the timing light make sure you still show it’s on base timing. If it’s advanced then retard the tps until it goes to base.
4) now here’s where you actually are dialing in the TPS. With the timing light on the pulley slowly advance the TPS. All of a sudden you should see the timing on the pulley jump several degrees. Ok, STOP moving the TPS. Slowly rotate it back till you see the timing go back to base. At this point you can lock down your TPS.
what you trying to do is dial the TPS in so it’s locked just before it jumps. If what I wrote isn’t worded well lmk and I can clarify.
We loved our factory manuals, and treated them like gold, but the electrical section wasn’t always helpful. Especially anything to do with ohm parameters.

Crizzayota

So I went to check my base timing and besides not being able to get the engine to idle any kind of consistently the timing will be right on where I have the distributor set when the truck first starts and then the timing completely drops off the map, I can’t see my white mark anywhere. But sometimes with slight adjustments to the TPS I can get the mark back pretty close to the right spot for a few seconds and then it will drop off again and the engine will slow down almost to a stop as it misfires more and then die. I have the terminals shorted with the check engine light blinking so I know I’m in timing mode.
Thanks jimkola

Jimkola

When you briefly get the timing right is the distributer pretty well centered at the adjustment bolt? Or is it off to one side?

Crizzayota

No maxed out but it is definitely rotated to the clockwise side of the adjustment hole

Jimkola

You may have the distributer off a tooth. I’d check that first. My other thought is the timing chain off a tooth.

Crizzayota

Hey jimkola my only concern with pulling the whole distributor is that I had the truck running perfect except for my throttle. I had the timing set a little advanced before but just by ear.

Jimkola

No, I got that. And nobody likes undoing progress, but the distributor adjustment bolt should be fairly well centered in the slot. Maybe favoring one side a bit, but definitely not rotated all the way to one side. The distributor and timing chain are the only two things I can think of that may cause this, and both would have been affected during a headgasket replacement. I think you need to look into this before pursuing other possibilities.
It only takes a few minutes to pull a valve cover and check the timing chain mark on the cam, and at the same time pop the distributor cap and see how the rotor is aligned to #1

edit:my apologies I mentioned headgasket. For some reason I thought you had done that. My mistake. Still doesn’t change my thought about distributor being more centered, but my rationale was flawed. My bad.

Crizzayota

Ok so I got the engine back to base timing and I have it idleing the way it should but now when I put the throttle down it will throttle up evenly then the check engine light will come on just above 2000 rpm and when it gets back to idle it will retard and shut down. It also is now throwing a code 7 on top of 3,4,6,12. Could this indicate that I have the the TPS set incorrectly? Or that my new TPS is bad? Thanks

Crizzayota

Upon more adjustments I got the truck to high idle for 2-3 minutes and when it idles down it it hits 7-800 rpm but it’s struggling very rough lots of engine rock. I pushed the throttle and it stops rocking and smooths out as I throttle up. But as the rpms come back down the. Heck engine light comes on and the rpms drop quickly over 30ish seconds and dies. I’m hopefully gonna replace my dist. cap and rotor today and as many vacuum lines as possible. New spark plug wires tomorrow morning. I also am really considering doing all the fuel injectors. I accidentally pushed on one and it started squirting fuel out the fuel rail side like it didn’t have an o-ring seal. I’m not opposed to undoing work when it’s wrong. I just live in vail without a garage or extra transportation and it has been cold and snowing. Thanks

Crizzayota

Ok so I have now replaced most of the vacuum lines, distributor cap and rotor. The truck is pretty good but not great. It will high idle 17-1900rpm just great on start up smooth as silk. But as it slows it get a few seconds of misfire as it comes down to a low idle 800rpm or so. As it gets to the low idle it begins to run really rough giving off a lot of engine vibration.
could that also be a misfire caused by my faulty fuel injector seal on cylinder 1? I have spark plug wires and one fuel injector to replace cylinder 1 and 3 o-ring kits to refit my existing injectors with new seals all coming in the morning. I’ll take it for a test drive tomorrow after I replace the new parts I’m getting!

Jimkola

Good work! What codes are getting logged now?

Crizzayota

Ok so new spark plug wires installed. Fired it up and it ran great until I put some throttle down and it basically did the same it has been check engine light comes on and the idle gets rough as the rpms drop to 6-700 and dies 15-30 seconds after. I’m gonna replace my cylinder 1 fuel injector and fit the remaining 3 with new o-rings. Should take a couple hours or so. It’s about 15 degrees outside so it may take a bit longer if my hands freeze 🥶
I also disconnected the battery and recheck the codes just a code 11 now which points to the TPS. I didn’t run the truck either so there may be more codes when I start it.

Code 11

Short circuit in Check Connector T with A/C switch ON or TPS - IDL point OFF
- Defective A/C switch
- Defective TPS circuit
- Defective TPS
- Defective ECU

Crizzayota

So I got the truck to idle right seemingly no check engine lights light was blinking once for normal operation. Throttle up and it dropped with some backfires it sounded like and then slowed and died but the check engine light never came on. I also tried moving it under its own power and it backed up and drove forward just fine and the idle started to drop quick and died. After I started to replace my injectors and change out o-rings when I open the box with what I thought were complete gasket o-ring sets I just have the o-ring for the top so I have to wait until the morning and my boss can bring me that rest of the parts I need to fix the injectors. I’m rapidly losing my mind and just about ready to unload the truck for $1000 so I can have something to drive as it is my only transportation.

Crizzayota

Upon further inspection of my intake gasket a 1” piece broke off likely making a vacuum leak. I’m praying that cleaning 3 injectors and replacing one fixing the gasket and cleaning the throttle body fix my issues. I’ll rebuild everything in the morning when I get the injector gaskets I need. If I’m still having issues I’ll try adjusting the tps again.

Crizzayota

Update!! So the truck is running but not perfect and I’d say far from. I think I need more TPS adjusting to get it perfect. But I’m driving the truck around so I can get to work and stuff. What I am currently working with is a code 11 and 12 I’m pretty sure the 12 is due to the fact I lost my knock sensor plug and can’t find the plug anymore. But more importantly is the code 11 pointing to the tps. So the fuel regulator vacuum line that goes into the rear port broke at the vacuum switch valve I tried to epoxy it but immediately broke off. I’m very much considering taking a couple days off driving down to toy tech in Colorado Springs 3hr from me and seeing what magic they can produce. But for now it’s all on me. So it idles great cold and when it warms up the low idle is too low and rough maybe a misfire and after the check engine light comes on it almost feels like It’s lost power, exhaust smells rich. High idle is usually 2000 rpm but sometimes drops down to 1500rpm only in park or neutral though. I tested the AFM based on the 4crawler method. Everything checked out except my E2-Vs which should have been between 20-400 ohm but was reading 950 first then 750 ohm range far above spec. It says that reading should be below E2-Vc which read 181ohm which is perfectly in spec. I’m gonna replace my fuel pump and the AFM both expensive unfortunately and see where that gets me. If I’m still ailing I’ll probably have a mechanic friend look at my vacuum lines and my TPS and hopefully fix it. If nothing else i’ll make the run down to toy tech in a couple weeks.
thanks jimkola for the help and guidance.

millball

TPS adjustment is simple. There is ONLY ONE possible adjustment. All the other measurements and tests are to prove a used TPS fit for further service, or not.

TPS adjustment is not some arcane science.

That one and only adjustment is to make the TPS show idle signal with throttle closed, and to insure that signal stops when the throttle is opened ever so slightly.

Jimkolas' (SEE HIS ABOVE POST) method using the ECUs timing advance parameter should work well. The ECU runs ignition timing up as soon as it sees throttle beginning to open.

I would mention that idle speed must be close to spec also, because too high an idle speed will keep ignition timing advanced higher than base.

Jimkola

If you need pictures of vacuum routing lmk.

one item worth checking is the vacuum line running to the bottom of the egr modulator valve didn’t get disconnected at one time, especially during valve cover removal. I did that by accident and it produced a fluctuating stumble at 3,000 rpms.

those vacuum switching valves aren’t too expensive if you order a Aisin one. I’ll see if I can find a part number.

millball

Mistake

Jimkola

I think maybe the VSV that got the port broken off is the one on the rear of the valve cover that has the vacuum line running down to the fuel pressure regulator. On my 4R it’s light blue.