Bizarro intermittent misfire, Poor idle, & Concerning tick

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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Thu May 06, 2021 6:38 am

Yeah, i really need to get me one of those. What's the vacuum supposed to read normally?

So far it seems to run okay for the first minute, It's just when it runs long enough to kick down into low idle everything goes south and the misfire kicks in.

The oil emerging from underneath the crank angle sensor cover is what concerns me. If there's oil interfering with that optical sensor, you'd think it'd cause a misfire.

No idea why i'm not getting a check engine light for that, but this is very early OBD stuff, so perhaps they just aren't checking for that. The service manual shows 4 slots on that rotor, which makes me think all it does is tell the computer what cylinder's about to fire. Miss a step, and all sorts of things could go wrong.
I'll hook it up to my scope, see if there's anything weird in the output waveform. If i see missing 'squares' i'll know what to take apart next. (ESPECIALLY if the erratic waveform lines up with the misfire)

Is it true that this particular EFI system dates back to 1983? I've seen pictures of 1983 impulses with a very similar looking fuel injection system bolted on, so it'd explain why it's all so weird.

Sorry for my earlier attitude, BTW. I got told over the phone today that the job i interviewed for needs somebody more experienced to press buttons on a point of sale machine. Really fouled up my mood, especially with how long it's taken me.
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-Calmini tri-Y Header -2" Exhaust -Glass pack muffler -Extended shackles -Aisin manual locking hubs -5 Tec Serviceability Mod -Bullbar - Jerry cam[Coming soon!]
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby DSUZU » Thu May 06, 2021 4:33 pm

Sorry about the job thing.
It's been a long time since I had a 2.6 dizzy opened up, but I thought I remembered a LOT of slots. I could be wrong on that.
Page 43 of my build thread shows where I was having a vacuum leak problem. Includes injector stuff and before and after vacuum gauge readings. Hope it can be of help or encouragement. Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
1989 LS Spacecab 2.6 5 speed 4x4 manual hubs, Rodeo torsion bars, extended shackles, 2" lift, K&N air filter (drop in), dump bed conversion, burgundy interior change, warn brush bar. Engine is bored .020 oversize and upgraded to 1994 pistons, head and EFI system.
Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
Heavily damaged by engine compartment fire while driving on March 24th 2018, condemned by insurance company and taken on March 30th 2018 :cry:.

https://forum.planetisuzoo.com/viewtopic.php?f=15&t=64060
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Thu May 06, 2021 11:01 pm

Yep, you're right. It's got several. This makes a lot more sense to me. guess the 4 slots are just a sync' signal of sorts?

IMG_20210506_234129[1].jpg

I took it apart last night to have a look, and saw the sensor was covered in oil. Strange, considering all the o ring does is seal the oil from leaking outside the engine, not inside the distributor.

I guess this means i need a new distributor? I haven't tested the sensor waveform yet, But this is concerning.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Fri May 07, 2021 4:17 am

Pulled the distributor and figured out why the oil's coming in. Distributor bearings feel very smooth, no rough spots or anything else suspicious. But..

IMG_20210507_180012[1].jpg

O ring looks to have failed from 'compression set'. the most common failure mode of o-rings. The rubber is so hard and brittle that it split in half when i tried to pick it off.


And the oil is coming in through the crank position sensor's plug socket.
distributorleak.PNG


My hypothesis is that the oil is coming in and skinning over some of the fine little slots on the trigger wheel. It'd explain why the problem comes on after it's run for a minute, or about the time it takes to start kicking down into low idle.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Mon May 10, 2021 4:11 am

Okay, I got a new O ring and replaced a cracked hose which was going from the middle of the intake tube into the valve cover. While i dont think that could cause a vacuum leak, i'm sure it'd definitely lean things out.

Now all that's troubling me is the distributor timing. I have done it exactly as the manual has told me to twice, and both times it simply refused to turn over, occasionally trying to fire on one cylinder only.
I know for a fact that cylinder #4 is at TDC. Both valves closed, Cam timing mark on the cam belt pulley is lined up. (pulley mark isn't but thats because the balancer's slipped 20 or 30 degrees :evil:)

I tried pointing the rotor at the stud that locks the distributor down like JLEMOND recommends, and that did make it fire up, but only for a short while before it dies again. Backfired a bunch, too. (perhaps i was a tooth off? i can't really get a true line of sight.)

manualdistributor.PNG

settingmarks.PNG


Is the workshop manual wrong? :?
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Mon May 10, 2021 10:34 pm

Guess it is wrong. I turned the distributor a tooth clockwise from that mark, and it fired right up. Is it any better? Absolutely not.

It still has a serious misfire at 2500 RPM that stops it from going any higher, even though i have a brand new cap and rotor, and have cleaned all the carbon off the plugs.

I got a vacuum gauge the other day, and it fluctuates around 17-18. DSUZU's truck got around 22, so I'm hoping this is because he's at sea level, and i'm a kilometer above.

if i somehow STILL have a vacuum leak, i have absolutely no idea where it is or how on earth i can have one. I have sprayed oil over EVERY gasket, EVERY seal, EVERY hose, and none of what i did changed a damn thing in the vacuum reading. Looks like i'm due to spend even more money..

I have replaced everything seal related on the intake side except for the injector seals, and i didn't replace them because they didn't look bad.

I am getting so fed up with this. I'm going to take the intake off again, inspect the injectors and the seals especially well, and perhaps even shell out ANOTHER 120 bucks to get the stupid things tested.

EDIT: Went over to the injector shop today and handed them in, they'll be phoning me tomorrow to tell me how it went. Least it'll be 100 bucks. not 120.
1990 SWB Trooper -- The best and worst car i have ever owned
-Calmini tri-Y Header -2" Exhaust -Glass pack muffler -Extended shackles -Aisin manual locking hubs -5 Tec Serviceability Mod -Bullbar - Jerry cam[Coming soon!]
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby itsmehb » Tue May 11, 2021 10:51 pm

I got a vacuum gauge the other day, and it fluctuates around 17-18. DSUZU's truck got around 22, so I'm hoping this is because he's at sea level, and i'm a kilometer above.

I have a vacuum gauge hooked up and mounted in my dash. My engine has the carb conversion but I'm thinking the readings should mean the same. The barametric pressure changes about 1 inch per 1000 feet, so yea, at 3000 feet (1 kilometer) your reading is going to be lower. Shouldn't fluctuate, at least not much. Mine reads 22 to 23 at idle, engine warmed up. And it's steady. Just pulling out the manual choke will cause the reading to drop and the more air I take away the lower the reading goes. I'd be curious to know just how much the vacuum reading would change for every 1000 feet above sea level. I'm at 500 feet so that's basically sea level.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby Enemigo » Tue May 11, 2021 11:28 pm

I really hope you can get this figured out. I can feel your pain reading all your entries. Stay on the path and see if you can get out of the woods with this thing!
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Wed May 12, 2021 3:33 am

Thanks for the words of encouragement, guys. I think the vacuum's just fluctuating due to the misfire.

Now, I wonder.. Since the misfire's at its worst at 2500 RPM, it makes me think this might perhaps be a fuel pressure issue? I've already had a couple of fuel filters get blocked up, one time while i was on the road, and both times it completely killed all my power if i tried to give it any reasonable throttle. My tank might be getting rusty.

The tan tops on the injectors also lead me to believe they are the originals. 30 years and 251,000 miles are LONG past when the automotive grim reaper starts calling, so i'm hoping the fuel injector people come back to me with some bad news! :D
1990 SWB Trooper -- The best and worst car i have ever owned
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Sat May 15, 2021 2:59 am

Just got my fuel injectors back last night. The man told me they were within 10% of eachother, and that he got them within 1. He demagnetized them, ran chemicals through them, replaced the screens, replaced the bottom seals, even cleaned the dirt off the casings, Did a very good job of it.

Did it fix the problem? No. The misfire seems to have moved up to 3000 and seems a little less nasty, but it is still there. I haven't tested the idle yet, but i'm sure it'll be just the same.

132 bucks, and for what? Either there's something strange going on with my fuel system, I have a vacuum leak in some unfathomable place, or i have a burnt valve 20 something thousand kilometers into a rebuilt engine.

I have NO idea how the vacuum hoses are supposed to be routed. I only have one vacuum switching valve on the starboard side of the engine bay for some odd reason. does that mean somebody's been fiddling with it before me and routed everything wrong? I get vacuum at the regulator on a cold start, The line coming from the bottom of the throttle body goes into a T plug. one end goes to the canister line (???), and the other end goes into this mystery VSV.

Anyone have a picture of what the vacuum switching valve's supposed to look like on a 90? This is weird!
1990 SWB Trooper -- The best and worst car i have ever owned
-Calmini tri-Y Header -2" Exhaust -Glass pack muffler -Extended shackles -Aisin manual locking hubs -5 Tec Serviceability Mod -Bullbar - Jerry cam[Coming soon!]
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby Enemigo » Sat May 15, 2021 3:06 am

Is there a vacuum accumulator on the frame like the 2nd gen Troopers?
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Sat May 15, 2021 3:09 am

I don't think so. I'm sure i would've seen it when i was working around the frame a few months ago.

Never seen vacuum lines go down there at all.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby Enemigo » Sat May 15, 2021 3:40 am

Dang, worth a thought I guess.
When I discovered mine, and came here to ask what it was, there was a single hard line running to it.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Sat May 15, 2021 4:00 am

I just went out and tested it out. Good news is the injector cleaning really brought the ticking noise down. it's nice and quiet now, only ticking now is from the valvetrain itself.

Bad news is it still constantly tries to die at idle. The high speed misfire seems to clear up when the engine starts coming up to temp, but no matter how high i turn the idle screw, it'll still misfire a bunch and start to stall.

Still hear popping out the exhaust when it does it. I guess if the vacuum lines are misrouted, that could lean out my idle too much. That's all i have at this point.

I'll be going to my dad's place in a few days, and i'll be staying for quite a while. So if this topic goes dead, i haven't given up on it. I'll update if i find anything wrong.
1990 SWB Trooper -- The best and worst car i have ever owned
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Sat May 15, 2021 10:47 pm

Here's a picture of the valve. None of vacuum hoses line up at all with what i see on the diagram, and i get vacuum at the FPR on a cold start. Clearly something is amiss.

IMG_20210516_123920[1].jpg

I sent JLEMOND himself an email asking about this mystery VSV. Hope to hear back from him soon.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby DSUZU » Sun May 16, 2021 12:44 am

aidan7777 wrote: i get vacuum at the FPR on a cold start.

You SHOULD have vacuum on the FPR on a cold start (or any start). Some have hooked the FPR vacuum hose directly to the plenum chamber, and theirs ran okay that way.
What you DON'T want is vacuum to the EGR valve on a cold start and be sure your EGR transducer is working and plumbed properly. If you suspect you have an EGR issue, just unplug the vacuum hose at the EGR valve, plug the hose, and see if that makes a difference. Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
1989 LS Spacecab 2.6 5 speed 4x4 manual hubs, Rodeo torsion bars, extended shackles, 2" lift, K&N air filter (drop in), dump bed conversion, burgundy interior change, warn brush bar. Engine is bored .020 oversize and upgraded to 1994 pistons, head and EFI system.
Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
Heavily damaged by engine compartment fire while driving on March 24th 2018, condemned by insurance company and taken on March 30th 2018 :cry:.

https://forum.planetisuzoo.com/viewtopic.php?f=15&t=64060
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Sun May 16, 2021 1:12 am

Fair enough. Most cars have constant vacuum to the FPR, anyhow.

Here's the thing, though. I don't HAVE an EGR. Either it wasnt standard equipment here in the first place, or it was removed when the calmini tri-y's went on.

One of my EVAP lines is going straight to the T joint on the end of the throttle body line, though. something's clearly wrong with the way this system is routed, and that single vacuum switching valve only makes me more suspicious.

I'll see if i can find a proper VSV from a wreckers yard up at my dad's place. If not, I have a terminal crimping tool and a wiring diagram, Any pair of valves from any make and model will do.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Mon May 17, 2021 3:20 am

Checked spark plug wires today. I see a little cut on one, and long flat spots on the rest where the cables have been rubbing on things, but when i bend them around with the multimeter hooked up, I dont see the needle fluctuate. around 2 to 2.5 kilo-ohms per wire. None of them show conductors.

Only trouble is they fit sort of loose on the plugs. The wire on #3 is noticably looser than the rest, and has a distinct bend in the spark plug boot, like somebody stepped on it or something.

Just ordered a compression tester and a neat little chinese boroscope. When i get back from dad's place, i'll post compression test results + photographs of the combustion chambers and valves.

If i do find a burnt valve, I don't think i'm going to throw away this head. the rest of it is in really good condition.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Mon May 17, 2021 11:47 am

Oh yeah, one piece of information i forgot to add earlier, if its of any use.

My dipstick keeps popping out, and the PCV valve on the top is wrong. its port is differently sized to the corresponding port on the plenum.

Can that cause problems with the vacuum system, or not? apart from plug wires, i am completely out of ideas.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Tue May 18, 2021 9:01 pm

Sorry for spamming up this board, just want to make a quick update on where i'm at right now.

I made a little homemade smoke machine out of a glass jar, a piece of hose, and an old schrader valve from a dry rotten inner tube. Lit up some shredded cardboard in there, made it smolder, then hooked up a little 12V air compressor and went to town.

That intake had more smoke in it than cheech & chong and i still couldn't find anything. both RUN and ACC gave me pretty much nothing at all.

The only smoke that came out was from the throttle body. Couldn't get that sealed perfect, even with tons of layers of glad wrap AND a nice tight constrictor knot. (i had so much pressure that the elastics kept blowing off). Didnt see smoke coming out of anything else at all.
It was well in the little hoses. pull one off the top of the FPR and it would BILLOW out.

It's got to be either misrouting (as i said before, the hoses do NOT match up with the diagrams), a leak in the PCV line, a result of it having the wrong PCV valve(even though it rattles. i can still suck a fair amount of air through the barb side, though.), or something very very serious. I have a reading of 17-18 in/Hg at 3500 feet, which should be well within the normal range.

EDIT: Just replaced a dodgy homemade cap on the intake with a proper rubber plug. It was an old battery terminal connector over a coil of tape tightly wound over the outlet, sealed off with a screw clamp. I dont think it'll help, but if not, it'll at least rule it out.

EDIT 2: It didn't
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby DSUZU » Wed May 19, 2021 5:05 pm

aidan7777 wrote:Sorry for spamming up this board,

NOT! This is EXACTLY what this forum is about - helping people solve problems. There have been "problem child" problems that were SEVERAL pages long.
Now. First on the PCV - try just removing the valve and plugging the hose. This should give you a lower, rough idle.
Another thing. After re-reading this entire thread, I have to ask (suggest) are you absolutely sure the timing belt timing is right. A tooth either direction and they can run, but have all kinds of symptoms. It really isn't difficult to check, just the top cover and align the mark (if your balancer is still accurate (crank should be at zero). Just sayin. Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
1989 LS Spacecab 2.6 5 speed 4x4 manual hubs, Rodeo torsion bars, extended shackles, 2" lift, K&N air filter (drop in), dump bed conversion, burgundy interior change, warn brush bar. Engine is bored .020 oversize and upgraded to 1994 pistons, head and EFI system.
Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
Heavily damaged by engine compartment fire while driving on March 24th 2018, condemned by insurance company and taken on March 30th 2018 :cry:.

https://forum.planetisuzoo.com/viewtopic.php?f=15&t=64060
City of St Petersburg (Fl) Fleet Maintenance 8/23/83 - 12/4/2018 (Retired). Started new job 6/4/2019. Was retired, now just tired.

If your wife has 5.00, and you have 20.00, your wife has...25.00

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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Wed May 19, 2021 9:27 pm

Thanks, dennis.

I removed the PCV and just capped off the port yesterday, the high speed misfiring seemed to subside, but that could be because the engine wasn't stone cold. the issue is at its worst on a cold start. idle really didn't seem to change, still had an erratic 500rpm dip on high idle.
It's obviously the wrong valve. the barb is a different size to the port on the plenum. god knows how wrong the flowrate might be.

Timing, huh? i never would have thought of that, I'll check the timing today.
My balancer is seriously out of whack, though. will that be a problem, or no?



I remember getting this car to run well by spraying oil down the IAC line a few years ago, can't imagine what might've happened in the meantime. crank angle sensor still dirty? i couldn't get the sensor wheel off because the screw stripped.
I'll run another smoke test, too. this time i'll plug up the throttle body extra tight. Vacuum leaks still aren't ruled out.
Can misrouted hoses do the same thing as a leak? i've been having no end of trouble finding them.
1990 SWB Trooper -- The best and worst car i have ever owned
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby Enemigo » Wed May 19, 2021 11:21 pm

You've Mentone a few times that the vac diagram doesn't match, but have you put any effort into trying to connect them the way the diagram shows? I assume you have, but thought I'd ask.
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby aidan7777 » Thu May 20, 2021 2:05 am

I only had one VSV for some odd reason, so I can't match the diagram in the first place. The EVAP canister line goes straight into the T on the end of the hose coming out under the TB instead of going through a VSV with a 'hat' on one end, but crimping that line doesn't seem to do any good.

The problems only really seem to manifest at high and low idle, and intermittently around 2500 RPM as a misfire. but above that everything runs just fine. I took it to 6000 on a test drive and it didnt complain about that at all.

The single VSV i DO have matches up just fine with the diagram, but the fact that i don't have another one on top is what's bugging me. Everything else seems to match ok.

I broke off the straight part of the "T" while i was taking it off, What looked like a nut holding its bracket onto the wheel well of it was actually a captive one, and i thought it was siezed, so stupidly, I put some muscle into it and broke it. Never work angry..
Can't find the piece anywhere on the floor, so it looks like i'll be buying one anyway. In the meantime, i'll route the fuel pressure reg straight to the intake plenum and run it that way if i need to do work around the property.
Despite that, i put it on my test bench and put power to it, it clicked, so it was working fine before i screwed it up, but the thing that interested me was the way it directed the airflow. powered off, it directed air from the 'bent' section of the T to the line behind the solenoid, and powered on, it directed it from the bent section to the plastic line INFRONT of the solenoid which i broke off.
This would give the ECU the choice of taking vacuum from either the intake manifold itself, or the port underneath the throttle body that goes into the T fitting. (NOT the one that if equipped, would go through a thermal vacuum valve, then through a back pressure transducer. word has it those ports have different characteristics of some kind.)

I don't understand what difference it would make. everything behind that butterfly valve is under the same vacuum, isn't it? is there something special about that particular port?

I also ran another smoke test, still didn't find anything. but there was smoke leaking out the top of the dodgy jar setup i was using, so maybe that could've covered something slight.
And as for timing, i'll have to take a bunch of things off to remove the lower part of the cover. Need to rely on both the timing mark up top and the one on the crankshaft pulley if i want to make sure everything's right.
The belt IS tracking a little to the side facing the engine, though. I don't know if that's bad.

All in all, thanks for the suggestions. each and every one counts, as i really don't know where to go next.
1990 SWB Trooper -- The best and worst car i have ever owned
-Calmini tri-Y Header -2" Exhaust -Glass pack muffler -Extended shackles -Aisin manual locking hubs -5 Tec Serviceability Mod -Bullbar - Jerry cam[Coming soon!]
aidan7777
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Re: Bizarro intermittent misfire, Poor idle, & Concerning ti

Postby DSUZU » Thu May 20, 2021 8:21 pm

Is your truck a NON air conditioned one? Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
1989 LS Spacecab 2.6 5 speed 4x4 manual hubs, Rodeo torsion bars, extended shackles, 2" lift, K&N air filter (drop in), dump bed conversion, burgundy interior change, warn brush bar. Engine is bored .020 oversize and upgraded to 1994 pistons, head and EFI system.
Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
Heavily damaged by engine compartment fire while driving on March 24th 2018, condemned by insurance company and taken on March 30th 2018 :cry:.

https://forum.planetisuzoo.com/viewtopic.php?f=15&t=64060
City of St Petersburg (Fl) Fleet Maintenance 8/23/83 - 12/4/2018 (Retired). Started new job 6/4/2019. Was retired, now just tired.

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