ses code, lean banks

[mudboy]

I got a 98 chevy 3/4 ton 4x4 has the 350 vortec engine in it. it has a miss to it when trying to hold the rpm's, like when the cruise is on or just maintaining a steady speed. I have had it into a dealer and said it need a tune up and injector flush, put in new plugs, wires, cap, and rotor and have run 2 fuel tanks of seafoam, 1 tank of lucas injector cleaner and 1 tank of stp injector cleaner through it and I run 91 octane gas. still has a miss and still has the ses light(have cleared it twice) with a lean left and right bank code on it 171 and 173 i think they were. from what i have found it can be anywhere from mass air sensor, timing, fuel pressure(is good), O2 sensors but can't get any specific answer on which or what it might be.... anyone have or heard of this problem???

[ChevLoRay]

Just be patient and someone will jump on here with what you need to know. It doesn't always happen as quickly as we'd like, but it will.

Oh, and to the board!

[95 S_Trucker]

could also be a vacuum leak

i had a similar problem

my 98 had had a p0173 an p0171, but it also had a O2 sensor code

[ERASER5]

I fixed a car with a lean bank code. In this case it was the MAP (manifold absolute pressure) sensor. The case was split and therefore leaking. If you have a MAS, I do not think you have a MAP, but I may be wrong.

[ChevyTech]

If you have lean code on both banks and no other codes you should test the fuel pressure.

[bwood]

You said that you checked the pressure, but what was it? Anything below 60 running is low. You truck does have both MAP and MAF sensors. An air leak could be the answer also. There are only a few vacuum connections on the upper intake, brake booster and EVAP solenoid, but the upper intake plenum can be a source of air leaks itself. It is sealed to the lower plenum with a large Oring type seal and the is another oring around the injector body. If you wouldn't mind post your fuel pressure readings. Also, has there been any recent work done besides what you mentioned (intake gaskets fuel filter).

[mudboy]

when i checked the fuel pressuse it was at 66 psi and the intake gasket has been changed 5 years ago. I have sprayed around on the engine, down both sides where intake connects, all the vacuum connections, and the upper and lower plenum with carb/throttle body cleaner looking for a vacuum leak. I didn't find one...

[ChevyTech]

I could be a central port injection problem. In my opinion this a one of the hardest to service fuel systems GM built.

Someone that is experienced with a scan tool could watch sensor data to eliminate potential other problems and get a better idea what the actual problem is, but don’t just assume because a dealer tech looked at it, that he knew what he was doing.

Many of the dealerships treat there employees very poorly, and the better techs are leaving or have already left.

[mudboy]

central port injection? doesn't that have the one injector with the "spider legs" going to the cylinders? mine has the single injectors for each cylinders

[mudboy]

decided that i would check the compression on my truck and it was averaged between 180 for the lowest and 188 for the highest...