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Have you tried replacing the intake manifold gaskets? I had to do this to my 00 Trooper (Nat. Asp.). It had problems similar to what you describe until I replaced them myself. No dealer had been able to find the problem; symptoms (since brand new!) included surging, stalling (that's right)! Rough idle, no power when cold. Anyway, the thermostat went out, and since it's under the intake, it was easiest to remove the intake manifold and I replaced the gaskets while I was in there.
The guys at St. Charles Isuzu says the problem is notorious on all 3.2 and 3.5's.
Keep in mind in order to install the supercharger, four of the bolts holding the intake gaskets tight need to be removed and reinstalled. The actual installation of the supercharger may have caused the gaskets to leak.
Nate
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Thabnks for your idea. I thought about that, and may replace it just to rule it out, but heres why I think its not that:
That would be sealing pressurised air. a leak there would cause a loss of air outward, and so a rich mxture. My problem is lean.
John C.
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Hmmm... Codes 1171, 0137, 0157 DO NOT indicate the air flow sensors. They are lean condition, low voltage O2 sensor bank1, and low voltage O2 sensor bank 2. Obviously, a malfuntioning or misfed MAP or MAF sensor could cause a problem, but these codes are specific to a lean condition explicitly. I think 0137 and 0157 are side affects and 1171 is your "real" code.
Okay, so it's lean. That's either not enough fuel or too much air. Can you tell if the condition occurs under boost or under vacuum? Maybe you want to buy a boost gauge for the A-pillar- it will look cool and could help diagnose this issue. This one should work well:
http://www.brandsport.com/trd-00602-83100-002.html
An intake leak could cause lean under vacuum, rich under boost. It is also possible that the gasket leaks under vacuum and seals under pressure, and could explain your lean condition.
However, I would look toward low fuel pressure at this point. Perhaps something went wrong during installation of the S/C kit. Check out the fuel pressure regulator to make sure everything is okay... you can also put a gauge on the fuel line to measure the pressure.
A scan tool that feeds live sensor data could tell you rich or lean in real time; combined with a boost gauge you could determine if the lean condition occurs under vacuum or boost. If it's under boost, it's likely a fuel delivery problem (like low fuel pressure).
One more thing makes me think it's fuel pressure: I'm pretty sure the VX has a MAP sensor in addition to the MAF sensor. If there was a discrepency between the readings, there would likely be a seperate, specific code. To find the MAP sensor, go to step 8 of Tone Monday's install instructions.
http://www.tonemonday.com/Storage/isuzu_sc_install.pdf
IT IS MISLABELED as the MAF sensor. That is the MAP sensor.
Incidentally, the other sensor is also mislabeled, it's the Ion Sensing module.
Anyway, I hope this helps.
Nate
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Damn, I'm looking at the pictures of the fuel reg.
I just checked the stock rail, that little O ring is still down in there, and was not transfered to the new regulator body.
I have the SC fuel rail and reg off the engine and apart now, the new reg body doesn't have a recess for that little O ring like the original one did. Should I just stretch over the bottom nipple on the regulator insert?
Obviously this seals the return line, and is what(should) hold pressure in the rail.
John C.
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John, I wish I could see precisely what you are working on...
Does it look like:
-This is where the seal goes?
-This won't distort the seal severely?
-The seal will stay put?
If these are all correct, I would try it. Be careful, this seal is not available as a part from Isuzu.
If you want, post some pictures of exactly what you are working on.
Nate
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There is a place in the bottom of the new reg housing for the small oring - it is below the screen. Pics are in the install manual for the SC which can be downloaded on my site.
To increase the fuel pressure, turn the security torx screw clockwise.
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Tone: Yes, I see the recess, but its soo small in diameter that to put the ring in it has to be kinked. The ring is not swollen, and fits the stock reg housing perfectly still. there is considerable difference between these holes.
I have a gauge mounted now, Itapped the manjo bolt for 1/8" ips. I am seeing 38 psi at idle vac, and pressure rising with boost applied with mityvac. This suprises me with the seal not in there.
I'm making myself crazy over this. I'm thinking of chopping the reg off the stock rail, ans plaicing it to the new rail to see what happens, or going to a quality aftermatker reg.
John C.
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John, I'm anxious to see a resolution to your problem. Do your O-rings look like the photo in Tone's instructions?
Tone, any insight on what could be wrong?
Nate
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Yes, it looks exactly like his instructions. Those are not the same instructions that came with my SC BTW. I almost remember it saying not to use the small O ring... I wish I could find them.
The code almost only comes up on long pulls at steady throttle position. This makes me think the ECU is doing a lookup, and moving a point on the long term fuel trim. It runs off the table, and sets the CEL.
I ordered intake gaskets today, I guess I have to swap them to eliminate that , since they are known to fail often on our engine.
If that doesn't do it, I'm gonna mount my EGT and wideband, and add fuel pressure till its happy.
John C.
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John:
Okay, here's an easy one:
Did you try taking the belt off of the supercharger?
(Does it still set the codes?)
Also, for the intake gaskets, I recommend a dressing (top and bottom) before you install them; I used this one:
http://www.permatex.com/products/pro...&item_no=80696
Especially since these gaskets are known to fail AND you are now putting boost pressure on the gaskets in addition to vacuum. Also, if you've ever wanted to replace the thermostat, now is the time. The intake has to come off to change it.
Good Luck! Keep us posted.
Nate
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No, no, no - intake gaskets go on dry as they have their own sealing surfaces. The problem with them leaking is related to the plastic cracking below the sealing surfaces.
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ITS FIXED!!!
W'hoo
This weekned, despite the cold I removed the supercharger to replace all the gaskets.. I didn't think it could be the intake gaskets, because I was only getting codes at WOT, and leaks of pressurised metered air should cause pig rich condition. I did it anyway, just to eliminate this failure prone posability.
As it turned out the intake gaskets WERE bad, but for some reason I was reading good vacuum at idle. I guess I don't fully understand the logic of how the fuel and fault tables work. I was unable to find this leak spraying propane and carb cleaner on everything.
Another thing wrong I noticed as I was taking the supercharger off. there were 2 loose bolts that could be causing a leak. The bolt behind the lower manifold that holds the fuel line bracket to the manifold, and the bolt that holds the EGR block bracket to the manifold both were loose. These bolt holes are through holes into the casting of the manifold, so any looseness is a vacuum leak. A much better design would have been to have them be blind holes.
I also shattered the upper fan shroud by leaning on it in the extreme cold.
I replaced all the injector O rings. 3 had a nick on them. St Charles was unable to correctly supply them, mailing me one O ring($18) instead of the whole set. The correct part # is: 8-17113-400-0 I was able to order them online from:
www.thepartsbin.com
The first time I hit the gas it was a changed beast. Its back!! I hope this saga helps anyone else having similar probles.
Thanks to everyone who either helped, or tried to help.
John C.
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John, that is spectacular. I went back and looked at my old ones to see if I could find cracks... maybe I don't know where to look (Tone, is it a hairline crack?) Anyway, when I took out the old ones I didn't show them a lot of respect, so it's hard to say whether they were damaged or bad...
Anyway GLAD it fixed your problem. It's about time for me to get a supercharger...
Nate
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I had the same problem discussed here and scanned the very same codes:
I checked for unmetered air via loose connections, examined EGR for leaks, replaced air temperature sensor grommet, replaced Throttle Body Gasket with new one, and replaced fuel filter. I also reinstalled the factory airbox/filter to eliminate any possible issues with my carbon fiber cold air intake/cone filter.
so I then attacked it by going right for the jugular and pulled off the SC and replaced the intake gaskets myself even though they were replaced earlier (about 1 yr ago) when SC was first installed by my dealer for $720.00
After removing gaskets I saw nothing wrong with them but installed new ones just the same. I did find some cut 'o'-rings on some of the injectors and replaced them with new ones (used plenty of lube and TLC!). I found 1 "cracked" fuel injector where the plastic outer shell or shroud (kind of resembles a spark plug boot) seats against injector hole in intake. I really thought this was the culpret! Replaced with new fuel injector ($125 w/tax)
After resetting ECM and test driving the problem still existed and seemed to be happening more frequently and I began noticing lack of power and it stalled once. Check engine light would come on at either steady highway speed or when going up a hill and putting foot into it. GRRRRRRR.
I finally decided I'd change the MAF Sensor and if that didn't do anything I'd proceed to the O2 sensors next. Well, a few minutes work changing the MAF sensor fixed the problem! I got a rebuilt O.E.M. MAF from Advance Auto for $98 plus $35 core charge. Kind of wish I'd started there first:rolleyes: ;but, the cut o-rings and cracked injector probably would have caused problems down the road!
At any rate....I'm surprised I never got a code referring to the MAF system...just the three codes listed in this thread which is why I didn't swap it out earlier!
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Your experiences sound all too familiar.
Hotsauce observed:
Another thing wrong I noticed as I was taking the supercharger off. There were 2 loose bolts that could be causing a leak. The bolt behind the lower manifold that holds the fuel line bracket to the manifold, and the bolt that holds the EGR block bracket to the manifold both were loose. These bolt holes are through holes into the casting of the manifold, so any looseness is a vacuum leak. A much better design would have been to have them be blind holes.
Newthings observed the same thing:
I have codes of P0171 and P0174, which are FUEL TRIM SYSTEM LEAN BANK ONE AND BANK TWO, respectively.
As to the solution to my idle problem--
The EGR valve sits on an aluminum block which is attached in two places: A metal vacuum tube coming from the back of the intake plenum and a flat metal bracket which bolts to the S/C intake manifold. A 1 1/8" spacer is between the bracket and the manifold. A bolt goes down the center of the spacer.
The bolthole in the intake manifold goes clear through into the air path.
So, if the bolt falls up (!) and out of the bracket you have a 1/8" air leak and everything looks fine. My searching with starter fluid spray produced inconsistent results since I was squirting in the wrong places. I pulled off the EGR and replaced the gasket. When putting the valve back on, the spacer fell over. A search for it's home revealed the hole.
Problem soon returns:
Another 2 hr. trip to the Isuzu shop finely got results. They felt it was the intake gasket in the front area. Hmm, the codes say lean in both banks. Both gasket leaking? So off came the S/C and manifold. New gaskets and the same problem returns. Then the search goes to the back on the S/C chamber in the back next to the firewall. Another drilled through threaded hole holds on a bracket for the fuel line. The bolt is loose and inaccessible. Off comes the S/C again and the bolt is fixed in place with LockTite. Problem solved, at last. Two different bolt leaks and two different fuel line leaks in a few months has been a nasty exercise.
There is nothing like the sense of relief when a chronic problem is fixed.
Roy
