Well, I put the car in D mode today. With the green jumper connected. I followed the instructions in my shop manual step by step. As far as the ECU is concerned the car is fine. The diagnostic covers the TPS so apparently it's fine. I suspect it may be my knock sensor, the wires are very frayed and that sensor controls ignition timing. Anyone know where i can get a new connector or whole new harness? Otherwise I'm still at a loss. Any other suggestions?

Edited September 27, 20205 yr by SiriusBlack

First up mister , have you identified this as Series One EA82T or Series Two

If Series One you will find a white plastic connector with a female spade terminal with no mating plug, right at the coil.

Think it is black wire with white trace

Get multi meter hooked to this single white female to red lead, connect black to ground.

Turn IGN on without starting should get 5V

Start it, get it to op temperature

All while just idling should be 1.7V,  not a typo

One point seven volts

Now, watch DMM reading as you select D

If it remains at 1.7 it is not your knock circuit causing your problem.

If Series two you can put timing light on flywheel timing marks as an assistant selects D

If knock circuit is causing problems when selecting D you will see timing step back from 20 to about 10 dbtdc

Better publish your location so others near you may be able to help by suggesting local yards, suppliers

Mine must be a series one, as it has the white connector with no mate by the coil.

The engine stalls when the transmission is put into Reverse or Drive could mean the torque converter lockup is not releasing and staying in lockup. When driving and coming to a stop the lockup is supposed to release. If it does not release then the engine will stall. The torque converter uses oil to transfer engine power to the input of the transmission and the lockup clutch makes it a direct connection. Like driving a MT and not pushing in the clutch when you stop.

The Duty Solenoid B controls the valve in the valve body that supplies oil pressure to the lockup clutch in the torque converter and the solenoid is fed a PWM voltage at 50HZ from the TCU. Pulse Width Modulation is an of off signal at varying length of on time. Like, on 10%-off 90%, or on 50%-off 50%, or on 90%-off 10%, all happening 50 times a second. You need a scope to see those pulses.

From the FSM: Engine stalls while shifting to any range.

23 Valve sticking  (controlled by Duty solenoid B)

77 Lock-up clutch seized (in torque converter)

The TCU will not set a code for those problems. It would only set a code if the Duty solenoid B was open or an open or shorted wire.

I did not look to see if there is a way to check that pressure line. It seems like either the valve is stuck or the torque converter is bad.

@Rampage that sort of makes sense. Except that doesn't really explain the wandering idle when not in gear. It wanders in idle and P,N occasionally dipping low enough in the wanders to make the engine die.

Before going too far, I agree the trans or torque converter may be a worth looking at....

Is this a three speed auto or four?

Three speed did not use a TCU or TCM like the four speed

I actually have another discussion I'm part of that discusses just that. I don't know if it has a 3 or 4 speed. My shop and owners manuals disagree. I figured I'd count the shifts once it was running right, but i can't get it to do that.

13 minutes ago, SiriusBlack said:

I actually have another discussion I'm part of that discusses just that. I don't know if it has a 3 or 4 speed. My shop and owners manuals disagree. I figured I'd count the shifts once it was running right, but i can't get it to do that.

Pretty sure all XT's have 4 speed auto or 5 speed manuals.

@Ionstorm66 That's what i thought. I had read an article somewhere that had said that was the case. However several people have said otherwise. I can put a link here to the discussion if you like.

 

 

The 87 will have the 3-speed. But if the car is the 87.5 model it will have the 4 EAT. 

An easy way the tell the difference is the intake manifold.  The spider intake will make it the 87.5 model. 

 

 

 

And the E4AT as the Japanese call the 4EAT had a big fat black round connector and a bundle of wires between box and TCU

The 4 speed auto also had more positions on the selector .

I had both the E4AT and shifter, swapped just the shifter for a whole EA82T spider engine for parts

Is there a make date tag on a strut tower or firewall?

If your talking about the date the car was made, the plate on the door says It was made in late December of 86.

 

I ran more tests today, I replaced the knock sensor plug with one from a donor car. It measured 5 volts with key on engine off. Then when idling at temp, it idled at about 1000 rpm and measured 3 volts at idle, not 1.7.

I also got around to checking the coolant thermosensor plug, it is corroded beyond belief and somewhat damaged. I'm going to see if I can replace that as well.

Good on you for persevering and doing the test on the knock circuit.

You should find the manual describes how to test towards the back of 2.7

If you have 3.0 V instead of ~1.7V I would suggest you have an issue. If that 3.0V is read by the knock control it will retard your timing.

I use an in dash Volt meter to continually monitor activity ( now). Photo shows 0.00 to indicate meter has power from ACC, IGN not on yet

The knock control stuff is in a approx 1" fat black round connector leading to from the dizzy from memory. You can disconnect it and car still runs just does not have knock protection. I accidentally left mine disconnected for three months of daily driving !! No problems, possibly due to my high-octane fuel.

So, to eliminate KCM from your investigation you could disconnect.

Dec 86 make date makes it an 87 MY, not the 87.5 so my bet it is 3 speed auto

Edited September 29, 20205 yr by Step-a-toe

Running, idling used to show bang on 1.7V in its factory application but this is running in the recipient vehicle and it's slightly different electrical

The knock sensor has been disconnected while running before. I did it to test, made no difference. I'd still like to have it working properly, as a knock sensor is good to have on a turbo vehicle. Any idea how I might go about fixing the voltage to it? And of course I still haven't managed to solve the actual running issues, so I'd still like suggestions. Only other thing I really have left to try is replacing the coolant thermosensor connector.

Are you using a factory manual?

If you are, find the diagnostic flow chart to see what it suggests. Someone found these two pin knock sensors on eBay in last year for ten bucks. To buy one here from dealer I think was about $900 ten years ago.

I looked through the auto trans diagnostics for your symptoms of three speed auto - nothing

Following the factory manual troubleshooting we suspect it may be a faulty electrical ground. We tested resistance from one of connectors on the engine side, to body ground and got 0.03 ohms with the key off. Key on that went to 2.00 ohms.

31 minutes ago, SiriusBlack said:

Following the factory manual troubleshooting we suspect it may be a faulty electrical ground. We tested resistance from one of connectors on the engine side, to body ground and got 0.03 ohms with the key off. Key on that went to 2.00 ohms.

oof that isnt good. Pull the ground off the starter from the battery and clean it. Then do the same from the chassis ground from the battery. I also add a ground from the starter point to the alternator.

The way I'm reading the above - Ohm readings are meaningless if there is a power source in the circuit - battery, or running alternator.
If the battery was disconnected, well, the key changing the ground resistance as described make no sense.

Knock circuit earthing goes on at the inlet manifold, centrally, dizzy side, behind the TB.

Maybe scrub it back to new

7 hours ago, DaveT said:

The way I'm reading the above - Ohm readings are meaningless if there is a power source in the circuit - battery, or running alternator.
If the battery was disconnected, well, the key changing the ground resistance as described make no sense.

We were thinking the same thing, why the hell would my resistances go up with the key on? The factory manual troubleshooting guide said to run these tests with the key on, so I assume the battery and everything else needs to be hooked up.

Key on, causes current to flow.   The current interferes with the current from the ohm meter,  throwing the reading off.