Misfire when accelerating uphill (1 Viewer)

[Dove Shack]

Hey all…I have a 1997 LC with a lot of miles 335XXX. The vehicle has ran fine; some oil leaking, etc, but over all great. The other week I was accelerating uphill at about 50mph and 2100 rpm or so and my check engine light came on and started flashing and the car ran really rough. I pulled over and as soon as I stopped accelerating everything went back to normal; smooth driving and idling, except the check engine light stayed on solid. I drove it to the mechanic and they said P-0304 code came up. They couldn’t replicate the misfire situation and told me it was a fuel filter…they replaced that which probably was needed but annoying cause I could have probably done it myself and saved some $$$. I took the vehicle home and the same thing happened again when I drove up the same hill (it’s on the way home so hard to avoid). I took it back to the mechanic and a few days later they told me it’s a real “head scratcher” and they are not sure what it is. A few days later they said it’s either the valve seals ($5000) or I need an engine swap at $13,000. Has anyone had this situation? Does this seem legitimate? Any recommendations for a LC mechanic in the Reno, NV area? Any recommendations for engine replacements that do not cost $13,000? That seems really high…almost laughable. Thanks for any advice!

Oh, and I have long suspected my catalytic converter needs replacing…it makes whistling noises and it’s just a feeling (not based on any technical knowledge lol) When I brought this idea up to the mechanic they told me that would cause many misfires if it was clogged..I was just trying to help

 

[Kernal]

Find another mechanic.

Lots of options but could be as simple as a poor spark plug wire connection: this happened in one of my vehicles 20+ years ago after a dealer replaced the spark plugs but then didn't get one of the plug wires reconnected properly.


Or, could be a short in the engine harness. Known to occur in the large bundle of wires (in the 1FZFE engine) that runs from the top center rear of the firewall as it runs forward near the EGR valve and the hot pipe that brings hot exhaust gas up to the EGR valve.

That main engine harness is known to droop down and get too close or touch the hot pipe and that can melt the wire insulation inside the bundle causing wires to short out against each other. This can happen even when the outside of the wire bundle looks OK.

To check for that the insulation on the engine harness bundle needs to be carefully cut/peeled away to check for burned wires.

You might also want to check the motor mounts as if the engine is tilting/moving too much from hard acceleration that movement might be what's causing the wires (or wires inside the bundle) to also move.

Read through the thread in the link below and then read the other links in the thread itself:

Do yourself a favor and WRAP YOUR ENGINE HARNESS!!!

Years I’ve been here drinking deep from the well of knowledge and experience, and I don’t know how the heck I failed to learn about this common issue, but after an unfortunate PITA experience that I realize now could have been easily avoided, I’m on a crusade to encourage my fellow eightians to...

forum.ih8mud.com

 

[OffRoadScott]

Find another mechanic.

Lots of options but could be as simple as a poor spark plug wire connection: this happened in one of my vehicles 20+ years ago after a dealer replaced the spark plugs (not requested) but then didn't get one of the plug wires reconnected properly.


Or, could be a short in the engine harness. Known to occur in the large bundle of wires that runs from the top center rear of the firewall as it runs forward near the EGR valve and the hot pipe that brings hot exhaust gas up to the EGR valve. That main engine harness is known to droop down and get too close or touch the hot pipe and that can melt the wire insulation inside the bundle causing wires to short out against each other. To look for that the insulation on the bundle needs to be carefully cut/peeled away to check for burned wires.

You might also want to check the motor mounts as if the engine is tilting/moving too much from hard acceleration that movement might be what's causing wire bundles to also move.

The first thing I would check is your O2 sensors. I was having a misfire and rough idle, my o2 sensors were out of spec once replaced thing were back to normal. Luckily for you the O2 sensors for the later model 80 they are still available and OEM as well.

I would also check your wire harness near the EGR valve, Toyota spent millions on RD but they still ran the wire harness near the EGR. Luckily for you the later model 80 series wire harness is still available from Toyota.

 

[landtank]

2100 rpms is where the fuel pump relay switches to high current. I'd start there.

 

[Dove Shack]

Thanks for all the ideas! I checked the engine wiring harness that is next to the EGR valve. I removed the insulation and looked closely…no damage. I replaced with new insulation and heat shield tape and sleeve, like that would be used for around exhaust pipes. I repositioned it as far from the EGR as possible, which isn’t much.

I changed out the spark plugs, wires, and distributor cap. I didn’t replace the rotor because it looked more solid than the new one and was made in Japan, compared to the new one which looked “fake.” I might get another Japan one at some point. The spark plugs looked bad. And I can’t prove it but it looks like they were never checked by the mechanic. The plastic covers were dirty and I would assume would show some type of smudging if they were removed to access the spark plugs. The plugs were kind of black. They smelled like gas. There was no “fluid” on them. I am attaching a picture. All the plugs looked the same, with #4 looking the same as the rest.

I took it to the same hill and could not get the CE light to come back on. No codes or any issues…I wonder if it’s fixed? Time will tell.

If anyone has any recommendations for a mechanic in the Reno, NV area, I would be eternally grateful!!

 

[Zhowardfzj80]

Did you ever have any more symptoms? Did changing the plugs and wires help or was it something else?

 

[SmokingRocks]

Horrible mechanic don’t even take your lawn mower to him. I’m sure the Nevada cruiser guys can clue you into a good shop.

It’d be a good idea to Replace your fuel pump relay and circuit opening relay, then keep the old ones as these are common issues and should be done as PM anyway. I don’t think that’s your issue though, the step between low flow and high flow mode isn’t as disruptive as a misfire and it won’t throw a code.

I suspect you have a damaged injector wire in your harness as it’s super common and hard to ‘see’ or find. The fasted and best way to identify this is to use a handheld oscilloscope, back probing the injector wires at the ecu then going for a drive to duplicates.

I chased down this issue in this thread. Calling all you electrical gurus - stumbling on acceleration

Solution was found on post 52.

 

[Dove Shack]

Did you ever have any more symptoms? Did changing the plugs and wires help or was it something else?

No more symptoms at all. I have taken it off road and up many hills…it drives great!

 

[SmokingRocks]

Well shucks, looks like you'll have to forego that 13,000 engine swap.... Find a new mechanic, ask your local 4x4 or land cruiser club who they suggest.

 

[Dove Shack]

Horrible mechanic don’t even take your lawn mower to him. I’m sure the Nevada cruiser guys can clue you into a good shop.

It’d be a good idea to Replace your fuel pump relay and circuit opening relay, then keep the old ones as these are common issues and should be done as PM anyway. I don’t think that’s your issue though, the step between low flow and high flow mode isn’t as disruptive as a misfire and it won’t throw a code.

I suspect you have a damaged injector wire in your harness as it’s super common and hard to ‘see’ or find. The fasted and best way to identify this is to use a handheld oscilloscope, back probing the injector wires at the ecu then going for a drive to duplicates.

I chased down this issue in this thread. Calling all you electrical gurus - stumbling on acceleration

Solution was found on post 52.

Thanks for the advice!

Horrible mechanic don’t even take your lawn mower to him. I’m sure the Nevada cruiser guys can clue you into a good shop.

It’d be a good idea to Replace your fuel pump relay and circuit opening relay, then keep the old ones as these are common issues and should be done as PM anyway. I don’t think that’s your issue though, the step between low flow and high flow mode isn’t as disruptive as a misfire and it won’t throw a code.

I suspect you have a damaged injector wire in your harness as it’s super common and hard to ‘see’ or find. The fasted and best way to identify this is to use a handheld oscilloscope, back probing the injector wires at the ecu then going for a drive to duplicates.

I chased down this issue in this thread. Calling all you electrical gurus - stumbling on acceleration

Solution was found on post 52.

Thanks for the advice on this! I’ll get the relays ordered…better to be safe than sorry.

 

[Dove Shack]

Well shucks, looks like you'll have to forego that 13,000 engine swap.... Find a new mechanic, ask your local 4x4 or land cruiser club who they suggest.

Haha yes…I saved a bundle. I’ll definitely be checking with them. Thanks!