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Kevin Bourcier
Kevin Bourcier, Technician
Category: Chevy
Satisfied Customers: 385
Experience:  35 Years experience specializing in A/C Repairs and Diagnostics exclusively to GM dealerships
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I have a 2003 chevy express van 2500 w a 6 litre. The motor

Customer Question

I have a 2003 chevy express van 2500 w/ a 6 litre. It is a high mileage motor at 191,000. The motor is rough at idle w/ an obvious miss. I ran a scan and came up with a mass air meter code, misfire code, and right and left bank lean condition codes.

Codes are as follows:

P101 MAF or VAF A CKT Range/Perf
P154 O2 Sensor CKT No Activity (Bank 2 Sensor 1)
P171 System too Lean (Bank 1)
P174 System too Lean (Bank 2)
P300 Random/Multiple Cylinder Misfire Detected

After reading, it sounds something to the effect of the fuel pressure regulator...fuel return line...or fuel pump itself. I figured I should ask a professional for the order in which I should address the possibilities...or maybe I am way off the mark in my guess. I am hoping to get a diagnosis for the problem. Thank you in advance for all help.

Submitted: 5 years ago.
Category: Chevy
Expert:  Kevin Bourcier replied 5 years ago.
Hello . The first thing I would suggest you do with you vehicle is start at the beginning by checking " Basics " . Check the ignition system Thoroughly Spark plugs and wires . Check the fuel pressure and fuel volume . Some codes are simply generated or produced as a byproduct of another issue . Also remember to check your air filter and look and make sure that you have no vacuum leaks ( disconnected or broken hoses ) .
Customer: replied 5 years ago.
I know the previous owner replaced the coil packs, wires, did a full tune up. I am slightly concerned about where he was taking it to be worked on,, as they could not get a diagnostic read....and didnt know to replace the cigarette lighter I did a visual on the motor from the front, but have yet tp take the hump off due to lack of time this weekend. I know the owner basically described to me that it was running fine, he brought it in for a tune up, and got it back idling rough, and stalling randomly when turning (off throttle, under load)...I bought the van as a work van, so I need to diagnose this and get it fixed asap...helpppppppppppppppppp...
Expert:  Kevin Bourcier replied 5 years ago.
You really need to get the engine cover off and perform an inspection . Spark plugs are critical . If the engine was running okay prior to a " Tune Up " and you now have these problems there is a very good possibility that something was left disconnected or was installed incorrectly . The wrong spark plugs , wring gap ? Sometimes it can be a very " simple " thing that causes this type of a problem .
Customer: replied 5 years ago.
I am going to go with a hapless type plug a Bosch platinum 4. I have had success in both my 97 Tahoe and 98 2500. this should solve any gaping problem as I would guess they went with a cheaper standard plug. I will retrace both right and left bank harnesses and make sure the go to the correct coil pack, other than that what should I be looking for as far as misrun vaccum lines, as this is my first 6.0 and I am unfamiliar with hose routing. Is there any good reference for vaccum routing I can review on the net?
Expert:  Kevin Bourcier replied 5 years ago.
There is usually a sticker in the engine compartment ( rad support or under hood ) that you can use as reference . Other than that with the way you have described the occurrence of your issue I would be surprised if you do not find something obvious that has been incorrectly installed or omitted >
Customer: replied 5 years ago.
so barring a miss run or omitted vaccum line or mis run coil pack wire, what would be the next place to look as far as the codes I am being given on a read. Fuel filter, fuel return, fuel pressure regulator, fuel pump, etc? starting cheapest to most expensive I would assume? Is there anything that driving the van will actually tell me (havent driven it yet, as I dont want to "hurt" the motor. I am going strictly on what the previous owner has told me, and what I expierienced trying to get the van to sit and idle in my driveway. (I had the van towed to my house and only own it 3 days
Expert:  Kevin Bourcier replied 5 years ago.
You will want to eliminate the misfire . Confirm it is not a plug , coil or wire . Rectify whatever is the cause . Check fuel pressure and confirm that is not an issue . You may want to check engine compression . " Begin with basics "
Customer: replied 5 years ago.
Understood...fuel pressure should read about where?
Expert:  Kevin Bourcier replied 5 years ago.
Fuel pressure range is 55 to 62 PSI .
Customer: replied 5 years ago.
Okay so I took the cover off nd did a visual...all wire and plugs are in the correct place, a plug wire was off, after replacing it the motor seems more apt to idle, but is starving for fuel...idling rough...missing...same fault codes. Ideas?
Expert:  Kevin Bourcier replied 5 years ago.
Do you still have the P0300 code ?
Customer: replied 5 years ago.
Yes still throwing a 300 code along with the rest. Didn't smooth out as much as I figured putting the plug wire back on...
Expert:  Kevin Bourcier replied 5 years ago.
You should check your fuel pressure .
Customer: replied 5 years ago.

i am trying to find someone I know with a gauge, as I dont own one, and would rather not have one in my arsenal when this is all I cant borrow one by the weekend I will purchase one and check the pressure and post my findings. Kevin I just wanted to thank you for your help this far...much appreciated.



Customer: replied 5 years ago.
Borrowed a gauge, fuel pressure is at 60lbs...well within spec. I am going to go and change the fuel filter, and put in new plugs...wondering if they didnt bother to gap them...I will go with the gapless Bosch platinum 4's so it isnt a concern for me.
Customer: replied 5 years ago.
okay changed the fuel filter, plugs, checked fuel pressure (60lbs), changed a vaccum hose that looked suspect, checked all connections to plugs, coil packs, injectors, etc. I cleared the codes, and ran the motor for about 10 minutes...drove it for about 4 miles. It is now throwing a PO300 code for random misfire still...ideas?
Expert:  Kevin Bourcier replied 5 years ago.
You may want to check to see that the correct spark plugs are installed and that they are properly gapped .
Customer: replied 5 years ago.
I installed the correct Bosch platinum 4 plugs for the motor, and there was no change. I spoke to a firends uncle who is a GM tech, he said to replace the canister purge solenoid, and canister. Sound reasonable. They motor will run under load, it just chokes out when I let off the pedal. I am only getting a random misfire code PO300 now.
Expert:  Kevin Bourcier replied 5 years ago.
With the symptoms you are describing now having performed all of the ignition system repairs you are more likely at this point to have a fuel injector problem ( leaky injectors ) .
Customer: replied 5 years ago.
It was suggested to me that the canister purge solenoid and canister could be the problem...he suggested this because when I pulled the plugs, the front 6 were fouled and the rear 2 were perfect...sound correct before I start changing injectors and fuel rails?
Expert:  Kevin Bourcier replied 5 years ago.
The purge solenoid and canister cannot cause this severe of a driveability issue . You would also have " EVAP " DTC's .
Customer: replied 5 years ago.
So new injectors are the next step than...great...should be fun...any injectors you woud suggest?
Expert:  Kevin Bourcier replied 5 years ago.
The aftermarket injectors all seem to be fine . The OEM injectors have come down in price a bit so are also an option .

Edited by Kevin Bourcier on 3/14/2010 at 10:59 PM EST

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