Fails to Idle

[newthings]

OK, so now I've got a problem.
Suddenly, with no tinkering or new mods, the engine will not stay running at idle this morning. You can wing the throttle and she revs smoothly. You can drive away and not feel or hear anything amiss. When you stop it may idle at about 1200 rpm or it may die in or out of gear. If you restart, it dies over and over.
I have codes of P0171 and P0174 which are FUEL TRIM SYSTEM LEAN BANK ONE AND BANK TWO, respectively.
I have had a code P1441 for a long time. It shows EVAP SYSTEM FLOW DURING NON-PURGE. This re-codes in a few miles after clearing. I do not think the 1441 code is related to the current problem.
Last gas fill gave the usual 15.5 mpg.

Thanks for any ideas or advice? Yes, I am supercharged.

[Green Dragon]

Sounds like a Vacumn leak to me. Make a good visual - CK PVC at valve & rear of Plenum also EGR connection at back of Plenum also Vacumn line at throttle body and at fuel regulator (Fuel rails Driver side rear).If all else fails spray Carb cleaner with engine running at intake manifold gasket mating services if RPM rises Try tightening manifold, if that fails new Intake Gaskets req. order
PN 8-97237-538-0 two req at $18 + each - 1-800- 727-8066 ask for Merlin. S&H is free

Torque value is 13 FT LBS on all intake manifold nuts & Cap Screws.

[xdfarrx]

Bob is spot on with the advice.... prolly intake gaskets.

[SGT.BATGUANO]

At some point you'll have to address the evap problem. I seem to recall mention of a purge solenoid problem. That may require a trip to a dealer to confirm.

I'm leaning (no pun intended) toward the intake gaskets for the other problem, but the codes seems to indicate too much air or too little fuel. Start your diagnosing with that in mind.

[MachineVX]

The codes showing banks 1 and 2 lean are the same ones I had. I also had problems with idling, including the engine dying out. After changing my intake manifold gaskets, they went away and everything was perfect.

[newthings]

Todays progress --
Inspection provided no joy. All vac hose connections are soft and well seated. Flexing hoses with engine running made no difference in idle.
Without removing fuel rails, I could only check tightness on three of the eight intake maniforld bolts/nuts.
I used this time to replace the S/C nose and get rid of the damn rattle. Fixed.
I visited the local garage with all of my info and codes. They put on a vac guage and said it was steady, thus no vac leak. I am not sure that is a meaningfull test, but their position is that I must go to Isuzu for a deeper diagnostic. No charge for an hour's work, but problem not solved.
I called and ordered intake gaskets. Merlin at St. Charles, says a new replacement part number is on hold to fill many back orders. 27 are in some warehouse and I had to give the VIN number to get expedited access to the parts. If I am lucky, it will take a week. He mentioned this engine is in the Honda Accura and many other models. All are/will have intake gasket problems and the new gasket part number is aimed a solving a wide problem. So much for Japan quality.
When I get the gaskets in hand I will visit the Isuzu dealer 2 hours away and camp out until fixed. Maybe they can fix the 1441 code at the same time.
Thanks for you help. Roy

[Green Dragon]

Sounds like a Vacumn leak to me. Make a good visual - CK PVC at valve & rear of Plenum also EGR connection at back of Plenum

Well speaking for myself " Even a blind pig picks up a few acorns once in awhile"

[newthings]

After a brief respit from idle problems and codes, the problems returned. Zipping under the hood with wrench in hand I found the EGR bracket bolt tight! Dang. After the vac hose check and spray with carb cleaner drill, I could not find a leak source. 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 inaccessable. Off comes the S/C again and the the bolt is LockTited in place. Problem solved, at last. Two different bolt leaks and two different fuel line leaks in a few months has been a nasty exercise.

As to the 1441 code I have had since the S/C went on. The tech said a vacuum line from the back of the S/ C went to the evap control system, but it should go to the orphan plastic switch mounted on the front of the engine. Alpine just capped it off. The tech said the evap system cycles on and off and should not have continous vac. Hose added and port capped. Problem solved.
Roy