97 FZJ80 Stumbling off idle (2 Viewers)

[jjg]

Hi Squash, Thank you for your persistence in trying to help. I did do the definitive test recommended. I removed the connector to the gauge sender located just above and to the left of the oil filter on the motor. The gauge needle dropped to the bottom dead but the ODBII feed to the Tourqe app still read perfectly from the 60 degree ambient temperature at first start of the day right up to 185 degrees which seems to be my steady running temperature.

I am still in need of a trial MAF sensor if anyone happens to have one I can try for a moment local in NJ.

 

[Jhayesvw]

Did you ever solve this?

 

[jjg]

Yes I did but unfortunately, I cannot tell you what worked. As the weather got warmer in the spring, the stumble continued but lightened. I learned at some point in time if I could get the revs up in neutral to about 4k by continuously stabbing the throttle to get the revs up past the fall flat on your face mark then I could keep it running good enough to drive it barely. I would then drive manually shifting through the gears holding each to high than normal rpm to allow the engine to spin higher under a lighter load.

Over time it seemed as though the more I drove the better it got. At some point further in time, it got good enough that if I let it fully warm up it was fine. All the while I was still trying things and improvements were being made. I put a new OEM FPR on. I did the cap rotor and wires. I cleaned plugs and ran a top engine decarb treatment called "Small engine tuneup" by the pb blaster company in the engine. (I use this stuff with great success in outboards all the time). I jumped the FRP resistor to drive it at high voltage all the time.

By the early fall the truck was running pretty good but I kept getting PO171 code. Again, there was no one smoking gun that I can say made the difference. I researched the heck out of solving the PO171 issue and tried a bunch more stuff. I searched repeatedly for air leaks in the vacuum lines and plenum. I replaced vacuum lines and PVC lines. I retourqed my intake. I did pretty much everything thing anyone will tell you for a PO171 with no luck. Finally, I decided to rip into my fuel tank to check the pump. I found some pretty scary chit. See : Scary Chit

I replaced the pump with a cheap amazon knockoff pump. Guess what. The truck was running well but it still did not solve P0171 problem. Since the truck was running well I decided to use it for hunting season. I made a few long highways runs up north through November and early December using the opportunity to clean the fuel system with a half dozen different types of fuel system/injector/ top engine cleaners in the fuel.

The truck got better and better but still, the PO171 persisted. In late December I started looking at the O2 sensors. They were denso and not that old so I really felt they were fine but my wiring harness connectors seemed frail. I rebuilt the connector once reset the codes but no joy. I week later I said freak it and cut the connector off and hand crimped the wires with heat shrink marine grade connectors. Again no joy.
I decided since nothing seemed to matter I might as well remove the jumper bypassing the fuel pump relay and pretty much gave up on clearing my check engine light for PO171 code.

Through some miracle last week after doing nothing to the truck for weeks the check engine light went off on its own. After a few days with no CEL I figured I try NJ Motor vehicles for an inspection as my sticker was long overdue. Thankfully I was rewarded for my efforts with a nice new purple 2021 sticker! As of today I can start it up and take off Ice cold with no issue.

To all that have struggled with problems like this, All I can tell you is don't give up.

Here is another thread that helped me with problems solving ideas:

97 fzj80 strange issue, engine cooling, system lean

Alright guys my name is matt ive had my cruiser for a year now no issues when i got it. 167,000 miles all maintenance maintained. Runs 15w40 cold air intake and high flow exhaust. Dual battery So the issue is a get a system too lean code po171 and she runs around 190°f coolant and 90° to 100°...

forum.ih8mud.com

 

[Jhayesvw]

That is so weird.