1994 Fzj80 severe miss Please Help!!! (1 Viewer)

[culturedredneck]

Yeah, I also checked the ECU for shorted cables and pretty much everything else under the sun. Turns out the 02 sensors can go bad without throwing codes and can even test fine. Sucks to replace since they aren't cheap but if they're original its probably a good bet they need to be changed. I ordered these on Amazon.

 

[claiborne86]

Have you checked to see if the main engine harness hasn't been damaged by the EGR pipe? Very common and can cause all sorts of issues.

I did it looks ok.. i mean the whole harness could look better but I feel like it’s about normal for it’s age. I also disabled the egr to avoid future issues

Yeah, I also checked the ECU for shorted cables and pretty much everything else under the sun. Turns out the 02 sensors can go bad without throwing codes and can even test fine. Sucks to replace since they aren't cheap but if they're original its probably a good bet they need to be changed. I ordered these on Amazon.

View attachment 2276504

So I know I can do a search for this but I’m guessing one is bank 1 and one is bank 2. How does one differentiate? Thanks btw I feel somewhat relieved to hear someone say they have been through what I am going through currently.

 

[culturedredneck]

I'm not sure which one goes forward and which goes behind. I had a shop do it because the bung was so rusted that there was some welding involved. I know the answer is around here somewhere.

Also, its a good idea to check the harness behind the egr even if it looks good from the outside. Its the individual wires on the inside you need to worry about. After years of sitting next to the hot EGR they crack/melt and short out on the inside. I had that problem as well and it left me stuck in the walmart parking lot on a road trip. Would have been really stuck is it weren't for this forum. When that happened it was a full-on stall out for me, not the hesitation that you're talking about. It would only stall in Drive though. Not in neutral or reverse. Turns out when the engine moved under throttle going forward it would put pressure on the harness and short it out.

 

[baldilocks]

I did it looks ok.. i mean the whole harness could look better but I feel like it’s about normal for it’s age. I also disabled the egr to avoid future issues

So I know I can do a search for this but I’m guessing one is bank 1 and one is bank 2. How does one differentiate? Thanks btw I feel somewhat relieved to hear someone say they have been through what I am going through currently.

The O2 sensors on obd1 are identical and both do the same job as they both mount before each cat which are side by side not tandem. It’s a straight forward job to simply replace them unless the hardware is rusted badly. You might want to start soaking the nuts with penetrating oil now.

Don’t discount the possibility of wire harness issues especially any area that appears to have been messed with previously. My last 80 was very clean 1994 but the wire harness had an armature repair job don’t on an injector circuit that acted up on me one day. Luckily I was in town rather than on the trail when this happened.

 

[claiborne86]

The O2 sensors on obd1 are identical and both do the same job as they both mount before each cat which are side by side not tandem. It’s a straight forward job to simply replace them unless the hardware is rusted badly. You might want to start soaking the nuts with penetrating oil now.

Don’t discount the possibility of wire harness issues especially any area that appears to have been messed with previously. My last 80 was very clean 1994 but the wire harness had an armature repair job don’t on an injector circuit that acted up on me one day. Luckily I was in town rather than on the trail when this happened.

So as of this morning I deleted the pair system and am getting ready to order the 02 sensors. According to my service records and by the looks of the bolts on the o2 sensors I believe they haven’t been changed since the recall in the late 90s. I opened the harness up by the egr and it doesn’t appear to have any significant damage. Thanks for the comment.

 

[claiborne86]

I'm not sure which one goes forward and which goes behind. I had a shop do it because the bung was so rusted that there was some welding involved. I know the answer is around here somewhere.

Also, its a good idea to check the harness behind the egr even if it looks good from the outside. Its the individual wires on the inside you need to worry about. After years of sitting next to the hot EGR they crack/melt and short out on the inside. I had that problem as well and it left me stuck in the walmart parking lot on a road trip. Would have been really stuck is it weren't for this forum. When that happened it was a full-on stall out for me, not the hesitation that you're talking about. It would only stall in Drive though. Not in neutral or reverse. Turns out when the engine moved under throttle going forward it would put pressure on the harness and short it out.

What year is your 80?

 

[Irish Reiver]

What year is your 80?

First post...its. '94. OEM O2's for this year are no longer available.

 

[ARFCOM15]

So as of this morning I deleted the pair system and am getting ready to order the 02 sensors. According to my service records and by the looks of the bolts on the o2 sensors I believe they haven’t been changed since the recall in the late 90s. I opened the harness up by the egr and it doesn’t appear to have any significant damage. Thanks for the comment.

I have done the same, O2's relocated to PAIR ports. Still chasing a misfire, lean/rich codes and lack of power. @Irish Reiver will comment on inspecting the cylinder 4-6 O2 sensor harness, I am doing that this weekend. Hope to get a solution. Good luck man!

 

[Irish Reiver]

I did it looks ok.. i mean the whole harness could look better but I feel like it’s about normal for it’s age. I also disabled the egr to avoid future issues

So I know I can do a search for this but I’m guessing one is bank 1 and one is bank 2. How does one differentiate? Thanks btw I feel somewhat relieved to hear someone say they have been through what I am going through currently.

Bank 1 (forward 3 cyliners) is the short run to the outboard O2 sensor. Bank 2 is the long run over the transmission.
@claiborne86 worth checking that each of the connectors on the fuel injectors are properly seated. When i opened my harness i think i broke every one of those clips. I was able to get a quick turn round on replacements but wouldn't be surprised if the PO just pushed them in and left them. If one or 2 of them are making/breaking with engine vibes with will cause your symptoms for sure.

 

[claiborne86]

Bank 1 (forward 3 cyliners) is the short run to the outboard O2 sensor. Bank 2 is the long run over the transmission.
@claiborne86 worth checking that each of the connectors on the fuel injectors are properly seated. When i opened my harness i think i broke every one of those clips. I was able to get a quick turn round on replacements but wouldn't be surprised if the PO just pushed them in and left them. If one or 2 of them are making/breaking with engine vibes with will cause your symptoms for sure.

Thanks for the reply. I hate wiring so much.. I am going to pull the intake and get into the wiring heavy. Thanks again.

 

[baldilocks]

I just replaced my engine harness and installed my intake and injectors today to solved a shorted harness problem that caused an injector to hang open. Not complicated but tedious and challenging from an access standpoint.

 

[culturedredneck]

What year is your 80?

mine is a 97

 

[ajax1]

If you are ordering o2 for 94 you want ntk, you can get them through rock auto. These are oem for that year. Have you checked your timing?

 

[claiborne86]

If you are ordering o2 for 94 you want ntk, you can get them through rock auto. These are oem for that year. Have you checked your timing?

Yes I have it a little advanced, I believe at 6 degrees. I read on here they run better at that. My 80 was bought out of Ontario Canada and on rock auto it says they have ntk with a American flag and ntk with Canadian flag. Is this something I should worry about?

 

[claiborne86]

Update... so the last two weeks have been interesting. We took the 80 up to Va and Jefferson National Forest. She did great the whole trip with the exception of about an hour where she had a miss pretty constantly. The miss went away as fast as it started, and we drove about 800 miles throughout the weekend. So yesterday I picked up my two ntk o2 sensors and installed them in the pair ports. Installation went well and was excited and optimistic about it fixing my problem. While I was working on everything I noticed a couple bad spots on the grounds from coil to intake manifold and body. I made some up out of some 8gauge ofc wire I had laying around. I also replaced the rear ground wire with a heavier wire I had made up for a previous project. Put everything back together fingers crossed and started her up. To my dismay she ran more ragged than ever. Constant miss, lack of power and as I ran around the neighborhood she threw a ce light almost immediately. Light cut off and pulled back in the driveway. Feeling very beaten at this point. Hooked up my scanner to find two stored codes; both #12 distributor ne signal. Cleared them and reset ecu and it threw same code again immediately. I then switched my scanner over to datastream and noticed my rpms were reading 3800-4200 rpms back down to 600 back up to 1000 back to 600, when revving the engine it would drop as low as 50. I also noticed both 02’s were reading lean. I ohmed the signal plug on the dist and the ne read ok with one of the g’s reading a little high cold. I ordered a new plug to solder in as mine is a little beat up. I also found that in its new condition if I remove the oil cap the engine will stall. I opened just to check blow by to see if pressure was building in the case for some odd reason. Please help I am about dried up in the money area. Any advice would be greatly appreciated.

 

[Irish Reiver]

I can't recall if you moved the O2's to the pair port before you got the new ones. If not and the new O2s went into the pair ports for the first time then i would suspect you do have a damaged main harness. Moving the bank 2 sensor requires the cable to be pulled over the transmission and it enters the main harness in the same area that is often damaged by the EGR.

 

[claiborne86]

Yes I moved them to the pair ports during this process.

 

[claiborne86]

I can't recall if you moved the O2's to the pair port before you got the new ones. If not and the new O2s went into the pair ports for the first time then i would suspect you do have a damaged main harness. Moving the bank 2 sensor requires the cable to be pulled over the transmission and it enters the main harness in the same area that is often damaged by the EGR.

Thanks for the reply btw

 

[Irish Reiver]

I definitely think it is time for you to unwrap the harness around the EGR area. The damaged wires are difficult to see and don't necessarily need to show signs of being scorched. Some mudders have reported the insulation being ok but the wire damaged inside. The '94 harness is no long available from Toyota. I went through this recently so know how much of a pain it is but it is worth it in the end and doesn't cost any money.

 

[jtmosca]

I definitely think it is time for you to unwrap the harness around the EGR area. The damaged wires are difficult to see and don't necessarily need to show signs of being scorched. Some mudders have reported the insulation being ok but the wire damaged inside. The '94 harness is no long available from Toyota. I went through this recently so know how much of a pain it is but it is worth it in the end and doesn't cost any money.

I have to chime in and 2nd this same recommendation. My 97 had the same frustrating symptoms happening. It ended up being the wiring behind the EGR even though everything looked just fine from the outside. I actually thought I had fixed “the problem” one day when I was inspecting the Egr and I moved the wiring harness out of the way for the re-install. Just that small amount of movement caused the issue to go away for a month or two. Nevertheless, it eventually came back and I was left perplexed again. As others have mentioned, it seems that the constant heat makes the wires brittle and the changing positions of the motor (e.g. going from D to R, etc.) will cause the wires to either break or rub against the block and ground out.

Trollhole Cruisers eventually found the broken / bare wires when they were doing some other repairs on the motor.

Once they addressed the issue, everything has been running fine since then. Anyhow, I hope you find the issue whatever it ends up being. I just thought I would share my observations. Cheers!