p0300 and p0302 when gas light come on...

i only start getting these codes shortly after my low gas light comes on. after i add gas stumbling goes away.
i own a 2000 chevy suburban with a 5.3 liter engine. any ideas

i know these days its hard to keep gas in cars but you should never run any car untill the gas light comes on because the pump is lubed by fuel and if ran low all the time it can over heat and can give problems..anyway i would guess that the gauge is inaccurate and the fuel level is lower than the guage shows.

unless it's misfiring still when the level is up higher but the scan tool isn't logging the stored misifres just the dtcs!

Could it be that u got some dirt or obstructions in ur tank ? Since they cant go away they mostly cause problems once ur fuel level is low and the pump sucks the last few drops ? Thats my idea, hope it helps

I got a similar problem with my 2000 Tahoe w/ 5,3 Liter. Initially the MIL light came on and soon after it started to idle rough. Got a reading P0300 and most misfires on cylinder 1 & 8. This is what I've done so Far
- New Spark Plugs
- New Plug wires
- 2 New coils on cyl 1 & 8
- Cleaned the MAF with electronics cleaner (wasn't that dirty)
- Cleaned the throttle body
- Cleaned EGR
- Ran through couple of bottles of injector cleaner
- Changed the air filter
- changed engine oil & filter
- changed fuel filter

This is the situation today. The MIL light goes off when the gas tank is full and it will reappear as soon as gas gets lower. The car is getting worse. Idle is rough, it hesitates when driving 45 mph and slightly pressing the accelerator i.e. needing low end torque. The hesitation is gone after kick down, though I can sense a loss of power.

Any suggestions what to do next and how does one go about doing them? I would really appreciate the help.

Nvenezia- Asecmt is right. By running your truck low on fuel you are causing your fuel pump to take in air, creating bubbles in your fuel system. Fill your tank up more often, you really won't spend any more money as your putting somewhat less fuel in each time than if you wait until the light comes on.

Hey Borealis, does it still misfire on cyl 1 and 8 ? Also, when u say " The MIL light goes off when the gas tank is full and it will reappear as soon as gas gets lower. , waht do u mean by lower, as in half way or near being empty ? And when the Mil comes on is it always a misfire code ? For now I would suggest running the truck either always full or at least more than 1/2 the tank full. Perhaps it might give u another clue to ur delema......

Hello, and thanks for replying. The MIL light usually comes back on, when the gas tank is slightly below half full. The only code i Get is the P0300. It's a nightmare! Strangely though, the MIL light and the rough idle does not seem to be connected. I mean that even when the MIL is off, the truck runs poorly.

I don't if it is of any consequence, but usually after driving around for a while and I drive to get more gas, the fuel tank seems to be under a lot of pressure. I am not fully certain, but it seems to be under vacuum.

Also another thing I tried is that I disconnected the temperature sending unit and the truck seem to idle better, but that is propably because the choke was constantly on.

When you disconnect the temperature sender, the circuit opens and the computer interprets the temperature as -40 degrees, or something rediculous like that and richens the fuel mixture. If the truck runs better, maybe you have a faulty coolant temp sender? If you have a scan tool, you can watch the data line for coolant temp and see what it is reading.

Choke? I think you should hook up a fuel pressure gauge and road test this!

Ok guys. I did some research and this is my last thought ! Really hope this helps.

Document ID# 1899786
2004 Chevrolet Chevy K Silverado - 4WD
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Subject: 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 #PIP3232B - (02/07/2007)

Models: 2002-2005 Cadillac Escalade
1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer
1999-2005 GMC Savana, Sierra, Yukon
2003-2005 Hummer H2
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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:
99 through 05 GEN III truck engines may experience any of the following:

A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle.
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.

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.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Here is the link i found it on:
http://www.ssrfanatic.com/forum/f6/taho ... ght-26596/

Let us know if it helped !

Thank you for the tips, I will definitely investigate this. Hopefully this solves the issue. On another note. Keeping the fuel tank above half a tank of gas prevents the MIL light illuminating. Does nothing on the rough idle or hesitation, but at least the light is not on. Maybe a separate problem? I'll keep you posted on the developments.