Chasing #6 Misfire; An Adventure More Difficult Than Twas Foreseen (93 FZJ80) (1 Viewer)

[BakerFJ]

Hey all, been trying to track down an issue on my 1993 Land Cruiser with the 1FZFE. It has no power and is stumbling, sometimes will die if I lightly bumo the throttle at idle. Sounds like a diesel. I've been through the forums to no avail, so here's what I've done to it and what I've checked so far.
Had a code for IAT, so I replaced the AFM, the injectors were just flow matched and cleaned, replaced #6. The intake manifold was hot tanked and gaskets replaced, new spark plugs, wires rotor and cap were replaced about half a year ago with NGK and Denso parts. Distributor tested good. Ignition timing is at 3°, fuel pressure to the rail was within spec, pressure from the regulator was 60 psi which seemed weird to me so I tried a new one, I've done an EGR delete long ago. Compression was good in all cylinders (about 150 psi on all), valve cover gasket was recently replaced. The wiring loom where the EGR used to be looks good, no difference in idle when I wiggle it around.
I'm about to test my TPS, although that is a relatively new unit. Also the only offbrand part on my car .-. So I wouldn't put it past it to be bad. I haven't replaced O2 sensors yet, dunno how old they are but I dont think they would cause this. And my intake boot was cracked and i duct taped the crap out of it over a month ago with no issues, so those are my 3 culprits left. Then ECU. Any thoughts and advice would be appreciated as this is my daily driver

 

[inkpot]

Vacuum Leak would be my first guess. I would replace the intake boot and check all the small lines also.

 

[BILT4ME]

Did you do the Spark Plug Tube Seals and the PCV grommet when you did the VC gasket? If not, the SPTS can leak a lot of air.

 

[BakerFJ]

Most of my vacuum lines are capped off from my EGR delete, except like, 2; The FPR and one under TPS. I did replace my SPTS during the VC. The first vc gasket got pinched weird when installed and I had to do it again, but left the SPTS and just did the VC the second time, but they're new. the PCV grommet was replaced about a year ago with new PCV.

 

[BakerFJ]

I sprayed the throttle body with some carb cleaner and it ran better for like 15 minutes, then back to the way it was. On a side note, I accidentally popped off a vacuum cap while it was running and it kind of ran better with it off heh. Plugged it back up though.

Maybe I'll limp it to work and try the smoke machine to check for a vacuum leak

 

[BILT4ME]

Do you have your O2 sensors fooled?

 

[BakerFJ]

Nope. Mine is the pre OBD2 model so I didn't have to, I just did the jumper wire on one of the electrical connectors that lies under the intake manifold (or was there something I missed?). It ran great after the EGR delete with no issues, but that was over a year ago.

 

[BakerFJ]

The TPS just needed an adjustment will replace soon with Toyota part. Also adjusted timing after TPS. Runs soooo much better. Still a bit shaky at about 1500 rpms, will replace the remaining vacuum lines soon as well. Happy mudding!

 

[BakerFJ]

Ope nevermind. No vacuum leaks.feels like it's misfiring. Pulled the ignition wires one at a time to see if one wouldn't change idle. Cyl #6 has no change when removed, however it has spark which is puzzling to me. When I go to check timing, and jump the diagnostic terminals while running, instead of going into base timing and contantly flashing, it shows codes 24 and 42 for IAT sensor and TPS. The common cause between the two is ECM which i had on hand so I threw it in. Still runs rough, but now while doing base timing it constantly flashes. I'll pull wiring diagrams and dive into this diagnostic .Will post updates as I go

 

[BakerFJ]

Put the new TPS in today, feels the same. Pulled codes as well, 25 (rich), 26 (lean), and 41 (TPS). I hadnt cleared these before i did the TPS... Took a look at my harness, the EGR side looks fine. But a few of the injector wires are exposed, although not touching anything, makes me wonder if I need a new harness.. Would be good to replace since almost all of my connectors have broken at this point lol. BUTut I'd rather be for sure that it's the problem because I don't like throwing parts at my cars, feels like a guessing game ​

 

[inkpot]

Might want to do a compression test on all 6 cylinders before you start throwing money at it. Currently working on a 93 that had goofy idle and poor power on the road. Turns out it had low compression on 2 jugs.

 

[ajax1]

Buddies did this no power, number 6 injector plug was not fully seated. Had no codes from that, is a 93 also

 

[ceylonfj40nut]

^^^ check plugs, wires, and dizzy cap.

 

[BakerFJ]

Plugs and wires are good, compression is good on all 6, checked the injector plugs as well and all are seated. Could having bad O2 sensors cause this? Will pull the cap and rotor tomorrow to inspect, as well as quadruple check #6 injector plug. From there I'll follow the diagnosis procedure for the O2 sensors.

 

[ppc]

Is the handbrake released and not stuck? Will the truck coast?

 

[ceylonfj40nut]

I would also check O2 sensors and MAF sensor. FSM has a diagnostic on this.

 

[thatcabledude]

Look into your engine coolant temp sensor. The one the ECU reads from, not the for the gauge cluster.

Sounds like you could be running very rich from ECU thinking engine is cold. You mentioned it cleared up a bit when you inadvertently introduced more air through a vacuum leak.

 

[shocktower]

Put the new TPS in today, feels the same. Pulled codes as well, 25 (rich), 26 (lean), and 41 (TPS). I hadnt cleared these before i did the TPS... Took a look at my harness, the EGR side looks fine. But a few of the injector wires are exposed, although not touching anything, makes me wonder if I need a new harness.. Would be good to replace since almost all of my connectors have broken at this point lol. BUTut I'd rather be for sure that it's the problem because I don't like throwing parts at my cars, feels like a guessing game ​

I love it when people, keep throwing suggestions for what you nearly have solved L0L

 

[ceylonfj40nut]

Looks like

Put the new TPS in today, feels the same. Pulled codes as well, 25 (rich), 26 (lean), and 41 (TPS). I hadnt cleared these before i did the TPS... Took a look at my harness, the EGR side looks fine. But a few of the injector wires are exposed, although not touching anything, makes me wonder if I need a new harness.. Would be good to replace since almost all of my connectors have broken at this point lol. BUTut I'd rather be for sure that it's the problem because I don't like throwing parts at my cars, feels like a guessing game ​

If you cite above issues, how can you be certain of cause? Broken injector connectors and open wiring are obvious ones. You need to find a way to eliminate these as causes. Not sure how that is going to be done without throwing some parts at it.

 

[BakerFJ]

Good news! I believe I found the problem. I removed the driver side O2 connector, and the HT side pin is broken. Now to figure out how to get it out of the female side :/ ... Ten minutes later I got it out with a pick and needle nose. There is a bit of corrosion when i pulled it apart, I wouldnt doubt it was the pulling apart that broke the pin. Regardless was worn and corroded. Thus ends my lunch break, going to do a resistance test on both when I get a chabce to be sure