POP, SMOKE, AND STALL the story of an unhappy FZJ80 :(

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LongDuck said:
Revving with no load will have much less exhause pressure and volume than running on the road with the vehicle load. Could still be clogged cats, but sounding like it could also be vacuum related, or some other gasket. Curious that it would spit a few vacuum tubes,... Worth looking for others at the intake manifod that may have seen overpressure due to that backfire.

Speculation here, but that initial POP! Was probably the last spark which ignited from the coil when the connector came off. I would pull the distributor cap and look at the rotor closely for any carbon burns or tracing. Wipe it down thoroughly afterward, inside and out. You're getting spark, or it wouldnt rev, but just throwing out ideas.

Have you pulled plugs and taken a look for wet/burned?
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Revving, no I wasn't revving the engine. I did bring it up to a sustained RPM test 1 @ ~2.5K and test 2 @ ~3K for 3 to 5 minutes. During that time my neighbor observed the exhaust and it was moving a normal amount of airflow. However, point taken I'll check the cats.

Good idea on checking the distributor cap, the entire distributor is new (<2 years) but I will check it and the plugs just the same. Being the timing is dead on I'd be a bit surprised it there is an issue, but still it's an easy and good check.
 
Simple things first - especially in relation to what you have changed recently.

Let's assume the backfire and stall on the hill was the ignition coil wire coming loose. That will kill an engine pretty quick.

Sluggish after a few changes/fixes. The one thing you did that affects the engine - a lot - is the EGR valve hose you reattached.

Let's also assume the EGR hose has been disconnected for a while (months, even years?). The EGR can clog up when unused. Plugging in the hose causes the EGR to open... good enough... but all that gunk from months of not opening causes it to not close when it is supposed to.

Hence, poor performance due to lean mix and a whizzing noise that wasn't there before.

So my bet is the EGR valve needs cleaning or replacement.

Good luck.

ps: My theory is the two things, coil wire and EGR, are independent and unrelated events.
-- Luck has it the coil came loose on the hill - bang, you are being towed home; but the EGR hose was already loose before that happened... and when you reattached it you started a new issue unrelated to the stall event.
 
Oh, and the loud pop when it stalled on the hill? When the coil wire came off, the engine kept spinning, pumping copious amounts of properly mixed air/fuel mix into the exhaust pipe... and since the exhaust pipe is generally pretty warm and the missing spark was likely intermittent and hit and missed for a few moments before separating completely -- you will ge a BANG!

I have lots of experience with that on the motorcycle, be running down the road and accidentally hit the kill switch ...
 
Unfortunately no, I ran out of time while in Phoenix and now won't be able to look at it till mid-month.
 
Not yet, I'll be able to start looking at this weekend, and will post up an update :) Its not a daily driver so its got a low priority.
 
Hey folks.... I got a chance to look at my FZJ80 this past weekend.

This has nothing to do with the fix I just found it interesting -- Last time I worked on it I drained out all the oil to check for any water etc in the oil, it came out clean. I completely drained out the oil and put the plug back in. A few weeks later I pulled the oil plug and to my surprise out came about another quart of oil. Just interesting that I drained it, it sat for 2 weeks, and then the engine still released another quart of oil.

Attempted fix --
After several weeks of waiting for me to get back to fix it. I put oil back in and started it up, it has the same issue.
I replaced the ERG Modulator, same issue
I noticed a vapor sound coming from the exhaust manifold, so I'm pretty sure the cats are plugged

Ran out of time this weekend, called AAA and had it towed to my mechcanic.
I'll know more next week and will post up.
 
Okay, I got it working.... Yep, it was the CATS... they were pretty new but plugged up from the backfire. Replaced them with a generic cat and I must say there was a bit of a performance boost.

Thanks for all the suggestions...
 
mattman555 said:
Okay, I got it working.... Yep, it was the CATS... they were pretty new but plugged up from the backfire. Replaced them with a generic cat and I must say there was a bit of a performance boost.

Thanks for all the suggestions...
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Out of curiosity what brand were the old cats?
 
Magnaflow was the brand. In 2015 I had the entire header back exhaust replaced including both cats, which now are expensive door stops
 
I bet you could've cleaned the cats as they got clogged up from improper A/F ratio. However, this is something folks don't want to do deal with. Glad you're back on the road.
 
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