3fe Ignition control module problem

[BombFJ]

I have a 1991 Land cruiser with a 3fe, my tachometer stoped working. I recently replaced the coil and ignition control module. With the replacement ICM my tach works, however the engine misfires between 1000 and 1200 RPM. Runs fine above 1200 Rpm. I’ve been through 3 new ICM’s with the same symptoms. I am currently running the old ICM , with no Tach. Toyota doesn’t seem to show it as a part for this engine. I have found several ICMs online. But none have worked, like I said I have tried 3 new ones. Any help preferably with an actual Toyota part #.

 

[jonheld]

What you are looking for is commonly called an "igniter" and it has been discontinued by Toyota for quite some time now.
There are several folks on here who part out trucks regularly that may have the coil/igniter set from a 91/92 available. Since they are bolted together in the same bracket, they usually will come as a pair. You shouldn't use the coil/igniter from an FJ62 3FE as they were different part numbers.
@arcteryx is one.

Igniters do fail over time, but they are usually an "all or nothing" type of failure, with a bit of intermittent ignition before complete death.

 

[dirtsock]

Would a faulty igniter cause a Code 14 - Ignition reference signal/no signal?

 

[jonheld]

Would a faulty igniter cause a Code 14 - Ignition reference signal/no signal?

Possibly.
Does the engine run?
Does the tachometer work?
Have you tried to clear the code and see if it come back?

 

[dirtsock]

Engine runs. It idles a little rough and high (around 900RPM). I am checking and replacing vacuum lines. There are two mystery lines that are not connected.. I'm trying to figure out where they go (thanks PO).
Tachometer works. I might be paranoid but it seems a little shaky on the dash.
Codes recently cleared. This is one of two codes that are back. The other I think is unrelated (Code 43- Starter signal - background: I have a starter button bypassing the NSS/relay/etc as I was in a pinch - so in my uneducated opinion this code makes sense)

Might be worth starting my own thread with all the issues/background. But I am ultimately trying to get this thing CA smogged first and foremost. Earlier this week, my HCs at idle were 2.5x over so trying to figure out why CA would call me such harsh things as gross polluting.

The Code 14 - possible igniter issue caught my eye..

 

[jonheld]

Engine runs. It idles a little rough and high (around 900RPM). I am checking and replacing vacuum lines. There are two mystery lines that are not connected.. I'm trying to figure out where they go (thanks PO).
Tachometer works. I might be paranoid but it seems a little shaky on the dash.
Codes recently cleared. This is one of two codes that are back. The other I think is unrelated (Code 43- Starter signal - background: I have a starter button bypassing the NSS/relay/etc as I was in a pinch - so in my uneducated opinion this code makes sense)

Might be worth starting my own thread with all the issues/background. But I am ultimately trying to get this thing CA smogged first and foremost. Earlier this week, my HCs at idle were 2.5x over so trying to figure out why CA would call me such harsh things as gross polluting.

The Code 14 - possible igniter issue caught my eye..

Your idle is way high. It should be 650 rpm (normal op temp, accessories off). Make sure the throttle cable has some slack at idle and the throttle plate is resting on the idle end stop.
The "golden screw", front facing brass screw on the top of the intake, DOES NOT ADJUST IDLE SPEED. Idle speed is controlled by the ECU which pushes the stepper motor in the ISC valve. It will have a TEMPORARY effect on idle speed, but the ECU will continuously try to push the ISC to make it right. This assumes that the throttle plate is at the idle position and the TPS is adjusted correctly. Otherwise the ECU will not "know" that the throttle is at idle.
Proper adjustment of the golden screw should be 1/4 to 1/2 turn from fully seated.
There's a vacuum diagram under the hood.

 

[dirtsock]

Your idle is way high. It should be 650 rpm (normal op temp, accessories off). Make sure the throttle cable has some slack at idle and the throttle plate is resting on the idle end stop.
The "golden screw", front facing brass screw on the top of the intake, DOES NOT ADJUST IDLE SPEED. Idle speed is controlled by the ECU which pushes the stepper motor in the ISC valve. It will have a TEMPORARY effect on idle speed, but the ECU will continuously try to push the ISC to make it right. This assumes that the throttle plate is at the idle position and the TPS is adjusted correctly. Otherwise the ECU will not "know" that the throttle is at idle.
Proper adjustment of the golden screw should be 1/4 to 1/2 turn from fully seated.
There's a vacuum diagram under the hood.

Appreciate the info. Throttle cable looks to have slack. I will check the golden screw setting later this evening. I saw a video online that suggested checking/cleaning the Idle Air Control valve (?) can help with high idle too. Assuming the cable and screw look okay, that was going to be my next check.

 

[dirtsock]

Appreciate the info. Throttle cable looks to have slack. I will check the golden screw setting later this evening. I saw a video online that suggested checking/cleaning the Idle Air Control valve (?) can help with high idle too. Assuming the cable and screw look okay, that was going to be my next check.

ISC/Idle Speed Valve might be the same as the Idle Air Control valve I am thinking of..

 

[jonheld]

ISC/Idle Speed Valve might be the same as the Idle Air Control valve I am thinking of..

Same thing. Toyota calls it an ISC valve (idle speed control).

 

[dirtsock]

Your idle is way high. It should be 650 rpm (normal op temp, accessories off). Make sure the throttle cable has some slack at idle and the throttle plate is resting on the idle end stop.
The "golden screw", front facing brass screw on the top of the intake, DOES NOT ADJUST IDLE SPEED. Idle speed is controlled by the ECU which pushes the stepper motor in the ISC valve. It will have a TEMPORARY effect on idle speed, but the ECU will continuously try to push the ISC to make it right. This assumes that the throttle plate is at the idle position and the TPS is adjusted correctly. Otherwise the ECU will not "know" that the throttle is at idle.
Proper adjustment of the golden screw should be 1/4 to 1/2 turn from fully seated.
There's a vacuum diagram under the hood.

Cleaned the throttle body today. How do I know the plate is adjusted right? It is ever-so-slightly cracked from completely closed. Near the throttle cable and spring assembly, I see the spring assembly bolt hitting the button/plunger. The bolt on the throttle mechanism is hitting the plunger, though the plunger/button can be pushed down a few more millimeters. Does it need to be fully compressed (the button near the sensor)? I see an adjacent stud/lock nut combo that looks like it can be adjusted to enact the throttle mechanism to press the plunger more and subsequently (seemingly) close the throttle plate more.

 

[dirtsock]

FSM says to check that there is "no clearance between throttle stop screw and throttle lever when throttle valve is fully closed" which seems to answer both questions. Plate should be fully closed, and as long as the screw is engaged with the lever I should be good (it doesn't necessarily need to be pressed all the way down).

 

[jonheld]

FSM says to check that there is "no clearance between throttle stop screw and throttle lever when throttle valve is fully closed" which seems to answer both questions. Plate should be fully closed, and as long as the screw is engaged with the lever I should be good (it doesn't necessarily need to be pressed all the way down).

Is your idle 650 rpm at normal operating temp?

 

[dirtsock]

Still high last time I drove. It seemed that in park it idles higher than when in drive. I noticed it to be around 800rpm in park but closer to 650rpm in drive. After I reinstall the intake/throttle tonight, I'll retest that theory. Curious to see how it runs- the intake and throttle were REAL nasty.

 

[jonheld]

Still high last time I drove. It seemed that in park it idles higher than when in drive. I noticed it to be around 800rpm in park but closer to 650rpm in drive. After I reinstall the intake/throttle tonight, I'll retest that theory. Curious to see how it runs- the intake and throttle were REAL nasty.

Have you tested the appropriate sensors/wiring according to the FSM? Specifically the coolant temp sensor on the stat housing.
Have you tested the ISC according to the FSM?
Is your ignition timing correct according to the FSM?
Have you properly adjusted the "golden screw"?
If the ECU is getting false information, it wont bump the ISC to get the correct idle speed.

Also remember that after you remove a battery terminal or the 15 amp EFI fuse, the ECU will have to relearn all the sensors and your idle speed will be higher than normal until you complete several drive cycles.

 

[dirtsock]

Have you tested the appropriate sensors/wiring according to the FSM? Specifically the coolant temp sensor on the stat housing.
Have you tested the ISC according to the FSM?
Is your ignition timing correct according to the FSM?
Have you properly adjusted the "golden screw"?
If the ECU is getting false information, it wont bump the ISC to get the correct idle speed.

Also remember that after you remove a battery terminal or the 15 amp EFI fuse, the ECU will have to relearn all the sensors and your idle speed will be higher than normal until you complete several drive cycles.

ISC and golden screw I have. The others I have not. Added to the to-do list.
I'll update this thread when once complete. I appreciate the help!

 

[NeilC]

A vacuum leak can cause high idle problems. I would check for that. Clean the ISC, it seems to help my idle stabilize. Also clean the Air flow meter but do not remove the screws! Just remove the 4 nuts and the hose clamp. While you have it out you can check it with a multimeter. There is a process somewhere in the manual. Work the gate through the entire sweep. There should be a gradual change in resistance. Any jumping around or falling to zero might require you to try to clean the sweep surface of the potentiometer under the plastic cover. I can go into that a little further but I repeat, DO NOT REMOVE THE SCREWS!

 

[NeilC]

It is important to understand that you might have several problems simultaneously affecting the engine running in different ways. The idle being high followed by stumbling transitioning to higher rpms seems vacuum leak related but it could also be timing related too. My truck ran horribly when I first got it with no lights. The check engine light has only come on 3 times while I was trying to figure everything out: I unplugged the O2 sensors and the light came on, I ran the engine over 1500 rpms for a certain number of seconds and the light came on. Bought a used Air Flow meter which made the light come on when my old one didnt. I removed the plastic cap and cleaned the sweep surface with alcohol and now I have a perfectly good spare AFM. Changed plugs, wires, cap and rotor (original wires from 91) still ran the same. Changed fuel filter which was horrendous which helped a little bit. Changed fuel injectors which helped a little bit more but still idled rough. I then found every vacuum leak including replacing the intake hoses because of accordion splits. This smoothed the idle up a little bit but it still accelerated like a dog but 90% better than originally.

I was starting to write it off as simply the 3FE being underpowered. Then I cleaned every ground connection I could find and magically it ran perfectly. The low end torque right off of idle is like an old fashion diesel. In hindsight, I should have cleaned all the grounds much earlier in the process. It would have helped be identify the other issues earlier. Plus cleaning the grounds was free. All of this was done in 2018 when I first bought it. Truck has run great ever since. I have cleaned the ISV once when the idle started hunting around. I advanced the timing a little and find the 3FE perfectly acceptable for everything except pulling my boat on the interstate over 70 mph with 295/70/17 Toyo MTs, but that is more of a gearing issue.