Random misfire and cel 2001 Trooper

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Random misfire and cel 2001 Trooper

Postby finaldraft » Tue Mar 08, 2005 5:31 pm

I have been fighting this problem for 6 monts with my 2001 TYrooper: truck runs fine then after a long run starts to miss and buck------had a bunch of Isuzu mechanics look at it, last time thay had the truck for three weeks....comes up random misfire codes on the OSBII ....so far this is what replaced:

1-Spark plugs with Denso's
2-Ion sensing module
3-Fuel filter
4-PCVvalve
5-Cleaned the EGR valve and passages
6-O2 sensor
7-Checked and cleaned all connections, ran dianostic for both banks of cyl
7-And last but not Least the ECM/ECU

Also have been adding the Textron to the fuel.

So far nothing has made a difference..and it is costing me a small fortune...all parts are from Isuzu not junk of aftermarket..still having misfire , but only afer a long sustaned run , when cold not a whimper..All the Isuzu folks a re at loss...HELP !!!!!! :x :?:
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Postby BigSwede » Tue Mar 08, 2005 6:10 pm

Hmmm, I was gonna say O2 sensor, because it the computer ignores it until the engine is warmed up, but you already got that...
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Postby tomster » Tue Mar 08, 2005 7:57 pm

Wow, that sure sounds like a ton of money.

For the most help we really need to know which codes it is/has been setting. Autozone will read them for free as will some other part stores. You can even buy a reader to DIY at Harbor Freight for $40 or $50.

Did they replace all 4 oxygen sensors or just one?

Are you sure you have an engine bucking problem or could it be a harsh shifting AT? If the latter you could have a mode switch problem. That can cause harsh shifting. http://forum.planetisuzoo.com/viewtopic ... bd705db5e1

If it is an engine problem, and I had to guess, I would guess fuel delivery. For example, a partially plugged injector. Techron might help dissolve some deposits but not all. You could try gently tapping on the fuel rail by each cylinder when you have the symptoms and see if that has any effect. It worked for my when I had an individual cylinder misfire code. Again I would only gently tap on the rail using something like a pencil. I certainly wouldn't tap on the injector itself. Could maybe be a bad electrical connector to the fuel pump. I don't know why that would get worse with time though. It could also be the pump intake screen is partially plugged overloading the pump and causing to to run erratic.

It could cetainly be something else entirely hence the need for the codes.
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Postby Amigo-2k » Tue Mar 08, 2005 8:54 pm

http://isuzufaq.ibctech.ca/#faq5
Quote from a Rodeo owner:

"I keep getting a check engine light on my 98 and have two codes that keep showing up.

1) Miss in Cylinder 4 - I've replaced the spark plugs, what's next - coil pack or wires or something else? Any ideas before I spend a lot of money?

2) High idle - I replaced the idle air control valve" - The fix was replacing the IMG.
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codes for misfire and ?

Postby finaldraft » Tue Mar 08, 2005 11:24 pm

The original codes were 1311 & 1312, ---changed the plugs and ion sensiong module

Now the dealer is telling me the code is for "random misfire" I do not know the code # but I thought the mechanic said some thing like 040 ?, I will call them tomorrow ...replaced the o2 sensor after the cat. converter , rear I guess., If I can get it to flash the engine light tomorrow I will see what codes it comes up with .

Sometimes it runs fine, after about an hour at highway speeds it acts up, then it does it so bad the if I stop and try to move again it bogs down and almost backfires , bucks, check engine light flashes or stays on, and will hardly move, in fact if I stop and run the idle up in rpms it will still do it, starts to misfire and rpm's drop...almost llike it is running out of fuel.

What really has me aggrivated that the dealer swore that it was the ECM...wrong...good thing I had one shipped from St. Charles Isuzu for 1/2 the price and dropped shipped it to the dealer....hey those guys are ok, Merlin called me today asking if it solved the problem, when I said no, he said he would talk to his service guys and see what they thought, and even offered to send out another Ion sensing module if the one he sent was bad....now that is service ...hats off to him.

Now if I can only get my dealer to find the problem ---- I even called Isuzu and the dam customer service rep. hung up on me when I pushed him to get the factory involved with the problem...he said that only the dealer can do that and was rude and aggrivated that I even called, told me to bring it somewhere else to get fixed, when I asked him to recommend "somewhere else " he hung up.

This 2001 is my thrid Trooper, I sold my 1999 and 1992 with well over 200k on them without an issue, and they are still running...but---I will never deal with Isuzu again for any new vehicle..but I need to admit I do love the Troopers.
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Postby 2000Trooper » Thu Mar 10, 2005 12:53 pm

why not replace the other 3 o2 sensors? the troopers have 4, two before the cats, and two after.
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Postby bigpoppax2 » Thu Mar 10, 2005 1:14 pm

I would question the knowledge of the mechnic that is throwing parts at a truck with the costs going to you when they do nothing to solve the problem. I could see this from a mom and pop type mechanic, but not a dealer. I'd throw a fit over the cost to replace items that have done no good.

See if they know how to check for a leaking Intake manifold gasket. I tried using a propane torch on mine when the IMG was bad. I got no results. When I removed the gaskets, they were cracked. I replaced them and everything is good with the world.

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now it is a P0447 code plus the random misfire P0300

Postby finaldraft » Thu Mar 10, 2005 6:48 pm

I just got back from the dealer, now they are telling me the code is P0447 and P0300,

Now the 0300 I had before it is a random misfire...but now thet are telling me it is the fuel pump......now the good part--they want $475 for the pump and tolld me the wholesale was $359...well as I found out from St Charles Isuzu the $359 is list price and I gcan get it from them for $305 ,,and free shipping. Pressure regulator from the dealer is $99, from St. Charles $35


I tend to believe it is a fuel delivery issue, and am in the process of composing a letter to the owner of the dealership about the ECM replacement and the 25% increase over list price for any components they sell..they may have the right to charge anything they want for the parts --BUT--not very honest at all...the labor is bad enough...and this was a dealer that Isuzu recommended to fix the problem.
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Postby BigSwede » Thu Mar 10, 2005 7:11 pm

By far the two most common problems on late model Troopers are the intake manifold gaskets and the fuel pressure regulator.
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Postby Amigo-2k » Thu Mar 10, 2005 7:43 pm

BigSwede wrote:intake manifold gaskets


10 bucks this is your problem.

I would change this, since this is a known problem. fuel pumps aren't.


If you are the orginal owner the fuel pump should be a free fix.
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Postby tomster » Thu Mar 10, 2005 9:24 pm

I also vote for the FPR as the next check. Like noted above it is a known issue. AFAIK the simplest check is to remove the vacuum line on a cool, stopped vehicle. If you notice any gas the FPR diaphram is bad and you need a new FPR.

Next, a check of the fuel rail pressure might help find the problem. For example, how well does the rail hold pressure when shutdown? What pressure does it have when running? What about when you have symptoms, any change? Do a search here for more info on checking the fuel pressure regulator.

I doubt the IMG is a problem as the excess air tends to cause problems at idle not under load when the computer can easily match fuel flow to the unmetered/"excess" air flow. Also the computer tends to throw lean CEL codes which you are not reporting. Again just my $02.

Other causes of 0300 are bad ground, MAF, vacuum leak, bad injector (usually the computer will flash a code to the specific cylinder with the problem which you are not reporting so I doubt this is your problem), EGR problem, or poor fuel quality. I think you have checked all of these but the MAF. I don't see why that would go bad after driving nor not set a MAF code. Easy to clean though provided you are careful.

Like noted your dealer is not doing you any favors. You might as well find another shop NOW. Even if they too continue to throw parts at the problem you would be no worse off than now. On the otherhand you could find a good shop that fixes the problem. They could also give you the ammo you need to go back to your present dealer and ask for some money back from their shotgun approach. You might have to make this argument in front of a small claims judge. It could be well worth it though given all the money you no doubt have already spent.

Just my $.02 YMMV.
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mine does the same thing

Postby edrhathaway » Sat Apr 09, 2005 2:56 pm

after long driving...OR...let it sit and idle for about 30 minutes (gets hotter faster than driving)...and sure enough, CEL flashing when giving it gas...jump, buck...barely will get going.

AND I KNOW I have an IMG leak...I heard it. As a temporary fix until I could get the time to do it was to smears some high temp goop where the leak is...didn't help much...but was worth a try.
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