Fouled Timing!

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For the past several months I have been dealing with a legitimate loss of power. 1991 FJ80 207K. I have performed all of the regular maintenance items on Jon Held's list and finally caved and brought it to an independent mechanic.

25 year Lexus/Toyota master tech (shop owner) and his head Toyota mechanic can not figure why the truck is retarding the timing and why the exhaust is extremely hot!

He suggested an ECU but didnt want to throw parts at it until he knew why. I decided to source a used one nonetheless but am awaiting delivery.

Here is what I know so far: The injectors are good, the valves are good, the distributor tested good. The exhaust has been removed to see if there was a clog, but no improvement. Compression is good 155-160 range. Fuel flow is impeccable. Fuel filters have all been replaced.

Does anyone have any ideas I can help throw his way? :bang:
 

CycloSteve

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Stuck between a rock and a hard place
Bad knock sensor or related wiring?...not sure if the 3F even has 'em (sorry I'm a 1FZ-FE guy), but that would tell the ECU to retard if it thinks that the rig is pinging. Other than that could any of the de-smog work caused other systems to influence timing? Vacuum lines and system all plumbed correctly, with the one way valves pointing the right direction?

:cheers:

Steve
 
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Since I don’t know bunk about the timing I called him just now and specifically asked him your questions and this is what he said:

After confirming that he was using the FSM specs (which I didint ask him to prove)

"When you hook the timing light up and cross connectors set between 7 and 10 degrees and pull the wire out it adv 12 degrees at base idle and when you bring the rpm up it goes retarded. Pushed to 1500 rpms it comes back to normal but anything over that it comes back retarded."

As for the numbers he’s getting he said that the numbers are so off he cant give a number. Additionally while watching the O2 sensors he can tell that its not a fuel delivery issue, this coupled with the fact that the exhaust is getting so hot tells him its definitely a timing issue.

So after adjusting the timing to FSM specs it continues to come back retarded.
 
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Bad knock sensor or related wiring?...not sure if the 3F even has 'em (sorry I'm a 1FZ-FE guy), but that would tell the ECU to retard if it thinks that the rig is pinging. Other than that could any of the de-smog work caused other systems to influence timing? Vacuum lines and system all plumbed correctly, with the one way valves pointing the right direction?

:cheers:

Steve

Steve:

All the vac lines have been replaced and hard lines blown through. The EGR and additional smog gear all checks/tests good. Not sure about the knock sensor either. I will put it on the list.
 

ToyotaDon

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If the timing retards as the throttle is opened, instead of advancing, then your Throttle Position Sensor should be suspect. It has an Idle Switch built into it that requires proper adjustment when installing. It may just need to be adjusted, or the internal circuit may have failed, requiring replacement of the TPS.
 
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So he can adjust to FSM spec which means the ECU is working properly and auto adjusting timing.

I'm confused at the statement, "the numbers are so off he cant give a number". What does that mean?

So to paraphrase, you can set timing at 650 RPM to FSM spec.
When the motor is reved above 1500 rpm and returns again to 650 the timing is now incorrect. Is this what he's saying?
 
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So he can adjust to FSM spec which means the ECU is working properly and auto adjusting timing.

I'm confused at the statement, "the numbers are so off he cant give a number". What does that mean?

So to paraphrase, you can set timing at 650 RPM to FSM spec.
When the motor is reved above 1500 rpm and returns again to 650 the timing is now incorrect. Is this what he's saying?

Jon that is correct. Each time the timing is set to spec and rpms are raised above 1500 the timing is then incorrect.

On a new note, I sourced a new TPS which helped some but it still runs like junk. He mentioned when he sets the distributor to 1 it wont run at all. He can get it to run if it is advanced. He has tested the distributor and it tested within specs. He now believes it could be a faulty ECU.

Anyone know where I can get a used ECU?
 
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Who installed the TPS?

Proper adjustment on installation is just as important as replacing it.

The owner of the shop with 25 years Toyota/Lexus experience installed the TPS. He is also a master technician. I hope that he would know how to install it properly. If not I'm at the wrong shop. Ha!

The next item on the list is an ECU which I sourced from landcruiserman. I will update more next week after the part arrives.

In the meantime, if anyone would like to add their .02 I'm all ears.
 

TexasJack

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I recently replaced my wiring harness. After I replaced it I stared to have problems with my TPS. My engine check light kept coming on. I'd reset it and it would come back on. I replaced the TPS but the light came on again. I adjusted the TPS with the same result. I unplugged the TPS and replugged it in....same result. I finally unplugged my wiring harness from the onboard computer and the problem was solved.

Keep in mind that every time you disconnect your battery, you reset your onboard computer. Once your turn your vehicle back on, your computer can do some pretty bizarre things to your TPS like causing the idle to rev very high. Disconnect and reconnect your on board computer. Turn the vehicle off and on a couple of times and see if that solved the problem.
 
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Update...still no go

So the latest is that the shop replaced the ECU and the rig runs slightly better but still retards the timing. So far they have replaced the TPS (which was adjusted per factory specs prior to installation) and the ECU, but neither fixed the retarded timing issue.

The timing is adjusted to factory specs then with a light gun it is measured while bringing the rpms above 1500-2000 and the shop says they cannot locate the timing mark again. So they adjust the timing back to specs (7-12 degrees) use the gun, raise the rpms and cannot locate the mark. ARRGH!:bang:

Anyone have any ideas? He did ask if the vehicle had ever been under water. I told him no but the rig had been sprayed down in the engine bay once, but that was 10K miles ago. The rig did lose electrical after that and I ended up having to replace the alternator.

Im stumped. Any help would be appreciated.:meh:
 
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Im sorry if I sound stupid or if I'm just pointing out the abvious, but...

Are you jumping the TE1 and the E1 in the diagnostic port, and are getting the CEL light to come one before using your timming gun?
Once you pull the jumper off, I dont think you will find the timming mark... or I'm I wrong?

And as far as I know the only thing that will retard your ignition would be a knock sensor. or I'm I wrong again?
 
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Im sorry if I sound stupid or if I'm just pointing out the abvious, but...

Are you jumping the TE1 and the E1 in the diagnostic port, and are getting the CEL light to come one before using your timming gun?
Once you pull the jumper off, I dont think you will find the timming mark... or I'm I wrong?

And as far as I know the only thing that will retard your ignition would be a knock sensor. or I'm I wrong again?

No stupid questions here, although some might ridicule you for it, I wont, its how others learn, including myself.

Per the owner of the shop, he is using the proper FSM process to check the timing.

As for the knock sensor...well the 3FE doesnt have one. I asked about that too.

Keep it coming guys! Surely we can beat this beast into submission!
 

ppc

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Have you specifically asked him what he believes to be the FSM procedure?

I'm not familiar with the 3FE but recalling posts from several years back, just checking the timing is difficult and is not like other Toyotas or other vehicles. Land Cruisers are rare vehicles and in the early nineties there were dealerships that would only sell a few if any each year. Compare that with the number of Corollas very few mechanics could ever develop any expertise.

From my experience when someone makes a statement like "I'm doing it by the book" that they have no idea what the procedure may be and have never read the book. I find it hard to believe that an EFI motor built after '85 would not have a knock sensor.

If the timing stability was as bad as described the engine would have a hard time running not just down on power.

Has the intake been checked for restrictions? New air filter?
?
 
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Once you pull the jumper off, I dont think you will find the timming mark... or I'm I wrong?

I just found my own answer base timming with jumper should be set to 7* @ 650 RPM,
When jumper is removed it should advance to 12* @ 650 RPM.

So it does look like that's working for you.

Have you checked the Exhaust System Backpressure for restrictions?
Plugged Catalytic Converter?
 
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I just found my own answer base timming with jumper should be set to 7* @ 650 RPM,
When jumper is removed it should advance to 12* @ 650 RPM.

So it does look like that's working for you.

Have you checked the Exhaust System Backpressure for restrictions?
Plugged Catalytic Converter?

Oh yeah, about that...the exhaust has been removed a week or so ago to eliminate that problem. No restrictions.
 
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Have you specifically asked him what he believes to be the FSM procedure?

I'm not familiar with the 3FE but recalling posts from several years back, just checking the timing is difficult and is not like other Toyotas or other vehicles. Land Cruisers are rare vehicles and in the early nineties there were dealerships that would only sell a few if any each year. Compare that with the number of Corollas very few mechanics could ever develop any expertise.

From my experience when someone makes a statement like "I'm doing it by the book" that they have no idea what the procedure may be and have never read the book. I find it hard to believe that an EFI motor built after '85 would not have a knock sensor.

If the timing stability was as bad as described the engine would have a hard time running not just down on power.

Has the intake been checked for restrictions? New air filter?
?

He is a master tech for Toyota and is very familiar with LC's. There is no knock sensor on this vehicle. Intake has been checked prior to purchasing parts.
 
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Discovery!

Well it turns out the cam shaft is cracked...see evidence below...
FJ80 Cracked Cam Shaft.JPG
 

bpenn1980

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Is that the cam shaft sub gear or the main timing gear? No master tech here, but I imagine that could create some slop in the timing! Any thoughts on how that happened?
 

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