Dale Lake Guy

My 2003 Suburban (5.3 litre automatic, E85 fuel compatible) has the check engine light on.

The codes my mechanic get are P0171, P0174 and P0300 indicating O2 Sensor's lean, missfire and low fuel pressure. The fuel pump and filterhave been replace as well as the truck been tuned up. The fuel pressure at key turn on is 50 psi, specs require 53-60. Fuel pressure when running is 40-42 psi. The truck has a rough idle in cold weather (below freezing) only. It runs great otherwise. This problem first surfaced in the winter and dissappeared in the summer. It has 130000 km or 80000 miles. We run regular gas, not the E85.

Help!

shawnvw

Sounds like your problem to the tee......




#PIP3232B: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum - (Feb 7, 2007)
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[align=left]Subject:
Cold Engine Idle Misfire or DTCs P0171 P0174[/align][align=left]
Models:
2002-2005 Cadillac Escalade[/align][align=left]1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer[/align][align=left]1999-2005 GMC Savana, Sierra, Yukon[/align][align=left]2003-2005 Hummer H2[/align]
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This PI was superseded to update parts information. Please discard PIP3232A.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:[/align][align=left]
99 through 05 GEN III truck engines may experience any of the following: [/align][align=left]
[ol]A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle. [/ol][/align]
Recommendation/Instructions:

The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.
[ol]If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements. [/ol]
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Dale Lake Guy

Thank you, I will bring this to my mechanic.

KDMcMillin

We have an '03 Suburban 5.3 Z with 133k miles. Cold idle was fine, but gas mileage dropped significantly prior to check engine light. Codes were P0171 and P0174 banks 1 and 2 lean. Based on forum results, instake gaskets were leaking, but I couldn't find a video detailed enough to change the gaskets myself. Dealer changed the intake gaskets and cleaned everything that was removed to access the gaskets. Service fee was $554 + tax for the repair. Runs like new now and mileage back up if you consider 16 mpg average back up!

Still waiting for the fuel gage to stop working like my '00 Silverado.

iskinxs

Hi KD -I have a '02 Suburban 5.3 with 130k miles with the similar situation....dropping gas mileage, check engine light. How did you check or confirm that the intake gaskets were leaking besides replacing? Was there a test you performed? Did you got to the dealer service and tell them to replace your intake gaskets? I have had this problem for the last year, but was thinking it was the Catalytic converters...but my issue sounds more like yours. Any information would be appreciated. Thanks

offrdk5

Yes, what test did you do to verify the leaky intake gasket? I am getting the codes and when the temp drops to around 50 or less has a very rough idle and sometimes even dies, loss of coolant, and very poor fuel mileage.

Please tell us your test!!

Thank you

Mandy Dunlap

I have my 03 Suburban in the shop. When it turned cooler, I noticed a rough idle when I first started and drove the SUV. It would stop after 15 or 20 minutes. But it would hesitate, almost die, the RPM tach would just go crazy from 1500 to 200. The whole vehicle would rock a lil as it tried to idle. No check engine light on or anything. I took it to the mechanic, he changed the MAF sensor. I picked it up and the check engine light came on and it was just as bad as before...dying when put in park. I took it back to him and he put the old MAF back on it. He wants me to take to the dealership. I took the bulletin about leaky intake gaskets. He ran a smoke test on them, and says he sees no leaks. He then found a small leak around the fuel pressure regulator, but isn't sure this is the total problem......ideas/??

kevinkpk

Could be a hole in the diaphram in the regulator. Pull the hose off it, if you get gas out of it, replace it. What is the dtc?

boriqua_man_99

first time here dont even know how to make a new post yet sorry to interrupt.I own a 2003 Chevy Suburban 1500 LT my 4WD service light came on about 3 months ago I just changed the switch on dashboard and disconnected the battery for about 30 minutes hoping this will do the trick.
But with my luck I didnt work the light still comes on does anyone have any info that they can share with me I'm afraid to take it to the dealer cause over here in NJ they will rob you blind

Mandy Dunlap

Well dealership says I need a new intake and new intake gaskets. I asked how they knew, they said their mechanic has seen this before. From reading here, I'm not sure how they would know the intake itself is bad without inspecting it. Thoughts? I am taking it back to my mechanic, but was considering telling him to JUST change the gaskets and see if that worked before the cost of a new intake....???