3.5L Trooper with RPM surge/misfire, or is it?

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3.5L Trooper with RPM surge/misfire, or is it?

Postby spaceghost » Tue Jan 01, 2013 10:54 pm

As of Saturday 12/29/12, I have a new to me 1999 Trooper LS 3.5L with 184k! (viewtopic.php?f=1&t=66974)

Being my logic is already off-kilter by an overmastering desire to purchase the truck, I could use some help with getting back to 100% Isuzu performance. The owner informed me of two issues:
1) RPMs surge up and down or stumble/misfire on occasion, more often when cruising above 50 mph
2) Burns oil, something like 1 quart in 600 miles

On way home from purchase, check engine light came and pulled code P0125 “insufficient coolant temp for closed loop control” which the Auto Zone employee said meant a bad thermostat. Cleared the code and so far hasn't came back after 200 miles I have been able to put on it (didn't touch the t-stat yet).

Twice on coming to a stop the engine has died, but starts up and goes no problem after. When driving, I do notice the surging after the engine warms up and mostly only on the highway. Video here:
In Drive @ 60 http://www.youtube.com/watch?v=8k6-tVtCqsc
In 3rd @ 60 http://www.youtube.com/watch?v=kOBX-CYbkWg

With New Years off, I ran through some simple things today but the issue remains during my test drive tonight. Here is what I did:
*New tank of gas with Lucas injector cleaner
*Seafoam treatment (1/6 in gas, 1/6 sucked up through PCV intake, ½ in crank drove for 30 miles prior to oil change, 1/6 in spark plug holes 3 hour soak)
*oil change 5-w30 high milage Valvoline
*PCV valve
*air filter
*spark plugs
*Cleaned each coil pack spark plug/boot end with carb cleaner and applied dielectric grease (some looked a bit dirty)

Also, I noticed cylinder #5 (rearmost passenger side) spark plug threads seemed oily compares to the others, but the tip seemed grey/whitish same as the others.

I will try the following in this order unless there are better ideas:
*Fuel filter (couldn't hurt!)
*Get used coil and swap one at a time to see if is a failing/weak coil causing misfire and possibly surging if computer is trying to compensate.
*Thermostat - if failing with opening/closing, could possibly cause RPM surge I suppose.
*ERG valve/porting cleaning
*Get injectors rebuilt in case one is tired/failing
*Differentials & TOD oil change
*Change A/T oil and filter (not flushed, just drained and filled)

Send me on the right direction with your powers if I am off course!


Reported recent maintenance by original owner (was a 1 owner truck!):
*starter (8/18/11 178359)
*valve guide kit; air plenum, intake & head gaskets; timing belt, water pump, coolant flush (12/14/11 179250)
*Oil/filter change; compression check #1-192 #2-192 #3-190 #4-193 #5-189 #6-189 (12/14/12)
*IAC idel air control sensor (1/30/12)
*engine coolant temp sensor (2/2/12 181179)
*crank position sensor; oil change (2/10/12)
*crankshaft position sensor; clean mass airflow filter (2/13/12)
*cam position sensor; air plenum & intake gaskets; fuel pressure reading pre start 42psi, running 35psi (2/28/12 181700)

Once I get it going, I'll get some pics posted. Is super clean Performance Gold package setup!
89 Trooper RS 2.6L/5spd
99 VehiCROSS ebony
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby 5 th rodeo » Wed Jan 02, 2013 8:27 am

interesting link about oil useage


viewtopic.php?f=4&t=66621

looks like what the other owner did and what you are doing is good , i would do the coil idea last , i have read that #6 cyl coil is different on the 3.2 engone , i don't know about the 3.5 engine.

one thing that will cause surging is the intake manifold gasket , listen for leaks as they could change when engine temp changes. if its running and missing you could spray around the intake manifold and see if it changes.

i would also make sure the Throttle Position Sensor is ok , another thing is to find every connector to all sensors and make sure they are seated good.
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby sassee » Wed Jan 02, 2013 5:03 pm

#6 coil is the same on the 3.5's. Do you have any current CEL's? Before you throw any parts at it, get a compression reading on all 6 cylinders. That will tell you volumes of info.

Nothing you can do about that amount of oil usage short of pulling the engine and drilling the pistons (been there, done that!) but you can def get it back to running good.

ernie
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2000 Nissan Xterra SE, Daughters new toy.
94 Trooper 3.2 w/ a 5-speed brand new off the showroon floor in 1994, traded 2 years later for a Power Stroke dually
88 Trooper LS GONE
89 Trooper XS (Red) - GONE to a good home in Alabama
89 Trooper SE (Blackie) - Gone to a good home but won't be forgotten anytime soon!
98 Acura SLX. Sadly, it lost the engine and I can't justify putting any more money in it. Parts anyone???
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89 Trooper, 2.6 w/ 5-speed. "BLUE" Runs great since head R&R. Got lots of left over goodies to put on!
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby BigSwede » Wed Jan 02, 2013 5:46 pm

5 th rodeo wrote:one thing that will cause surging is the intake manifold gasket , listen for leaks as they could change when engine temp changes. if its running and missing you could spray around the intake manifold and see if it changes.

IMG is a definite possibility. They went out twice on my old 99. The second time you could hear it hissing, but not the first time.

The spray-carb-cleaner test is worth trying but isn't real reliable from what I have heard.
95 Trooper LS - 4" lift, 35" tires, 5.38 gears, ARB lockers
Indy4x Revolution 3.07:1 low range gears, Indy4x HD tie rods, homemade sway bar disconnects, Calmini HD sway bars, Darlington diff drop, OME 929 coil springs + 1" poly spacers and 1" body lift, Indy4x HD torsion bars, Indy4x HD rear axle links, Indy4x Kevlar brake lines, ARB bullbar, custom rear bumper with swing-out dual jerry can carrier, rock sliders, Sears Platinum Group 31 battery, ARB mini-compressor, Indy4x kevlar air lines, Warn M8000 winch, Blue Sea 6006 winch cutoff switch, Yaesu FT-1900R 2-meter ham radio, Larsen MHW-150C 1/2 wave antenna, Cobra 18WXST CB radio, Firestik II antenna, generic 8" driving lights, even more generic fog lights, two (2) Blue Sea auxiliary fuse panels, and outofrshell Dave's custom 1" shifter extension. (I actually typed this list as a joke but people seem to like it.)

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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby sassee » Wed Jan 02, 2013 9:30 pm

If you think you have an IMG issue, hook up a vacuum gauge. That will tell you right quick.
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2000 Nissan Xterra SE, Daughters new toy.
94 Trooper 3.2 w/ a 5-speed brand new off the showroon floor in 1994, traded 2 years later for a Power Stroke dually
88 Trooper LS GONE
89 Trooper XS (Red) - GONE to a good home in Alabama
89 Trooper SE (Blackie) - Gone to a good home but won't be forgotten anytime soon!
98 Acura SLX. Sadly, it lost the engine and I can't justify putting any more money in it. Parts anyone???
98 Trooper, 3.5 with a 5-speed. My DD
89 Trooper, 2.6 w/ 5-speed. "BLUE" Runs great since head R&R. Got lots of left over goodies to put on!
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby spaceghost » Thu Jan 03, 2013 12:45 am

Thanks for the info/ideas everyone!

Tonight I changed the fuel filter, and did a quick cleaning of the ERG valve and tube. The issue didn't show up in the first 15 miles on my highway trip like it usually does until I shifted from drive to 3rd, then I noticed a little. As I headed home, it was more noticeable but not as bad as before. No miss/stumble, only the RPM dance. Progress!

No CELs yet. I need to get an exhaust leak near the muffler fixed, so I might as well have the shop perform a compression test and give it a look to see if they notice anything else obvious I may have missed. If the shop doesn't find a magical fix, I'll give the coil swap a try since I have a $40 ebay special on the way and that seems easy to try, and failing that I'll order up an intake manifold gasket kit (which does seem a likely target). Is a replacement ERG valve worth a shot too?

I am digging the idea of a vacuum gauge and thinking about a good mount options inside. What is a good place to T off for it's connection, any place on the throttle body or intake manifold? I will likely tackle this one tomorrow to see if it helps tell me anything good while things go dancy on the highway.
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby sassee » Thu Jan 03, 2013 12:30 pm

Well i wasn't really talking about a permanent mount but hey!

I have a pic of it at home but there's a vacuum hose on top of the engine, drivers side. Pull it and connect your gauge there. be sure to plug off the other. that will tell you quickly if you have a vacuum leak.
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2000 Nissan Xterra SE, Daughters new toy.
94 Trooper 3.2 w/ a 5-speed brand new off the showroon floor in 1994, traded 2 years later for a Power Stroke dually
88 Trooper LS GONE
89 Trooper XS (Red) - GONE to a good home in Alabama
89 Trooper SE (Blackie) - Gone to a good home but won't be forgotten anytime soon!
98 Acura SLX. Sadly, it lost the engine and I can't justify putting any more money in it. Parts anyone???
98 Trooper, 3.5 with a 5-speed. My DD
89 Trooper, 2.6 w/ 5-speed. "BLUE" Runs great since head R&R. Got lots of left over goodies to put on!
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Re: 3.5L Trooper with RPM surge/misfire, or is it?

Postby spaceghost » Sat Jan 26, 2013 3:48 am

Was the IMG as so many thought. Replaced and drives like a dream! Thanks for the help.

I finally picked up a felpro intake manifold gasket kit and used the cheater method Amigo-2k posted from www.isuzufaq.com. Only took me about an hour with the helpful notes (not bad for someone like me)! Some one had replaced it previously, but the bolts and nuts weren't much past finger tight. Also found the drivers side gas line to fuel rail was damp around the connection, needing the hose clamp tightened.

I am still digging the idea of a vacuum gauge. Wanna go old school feather footing aiming to keep my manifold vacuum high when driving, monitored with something like an Auto Meter 2337 (http://amzn.com/B00062YVT8). I'm going to save so much environment I can buy another Trooper!
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