P0300, shop giving up

[Dartboy]

On of our work trucks is having ongoing issues.

2004 Chevy 2500 6.0L ~50K miles mostly idling around our property

It's been throwing P0300 codes for a long time, some overheating issues as well. Getting most of this third hand, it's been to our independent service and local dealer a bunch of times.

New plugs and wires, new waterpump, MAF cleaned back in December

June Dealer receipt shows a failed injector balance test, they did a top end cleaning, code cleared up for a while

July dealer service has another top end cleaning and advice to "drive as much as possible to free up sticky valves"

I think we may have done another cleaning, soaking it over a weekend type thorough job.

I see a whole lot of "dump some stuff in and hope for the best" and not a lot of actual testing and diagnosis. Injector test failed, why are they not replacing injectors? Another guy's buddy suggested a quart of ATF in the oil.

ideas? advice? dealer is pushing to buy a new truck, the grounds crew is eager for a big Diesel that they'll do the same thing to.

 

[txab]

Anyone ever do a compression test

 

[Black02Silverado]

Has it been serviced properly as in regular oil changes? Like stated by txab do a compression test. Where are you getting the fuel for it? Bulk tanks on the property?

 

[Dartboy]

Oil's been changed on a regular basis, usually as requested by the little service light. Fuel is purchased at the Shell station up the road, on a bust street, same place we get fuel for all our fleet (~15 vehicles, no other issues)

AFAIK, there's no mention of a compression test being done that I've seen.

 

[OldCracker29]

Along with a compression test, I'd check for low fuel pressure, a vacuum leak and the EGR system.

 

[Draenor]

Do you have a way to read or log fuel trims? Have you done a crank relearn?

 

[Dartboy]

Back and forth again with misfires, they drove past me leaving to drop it off and I could smell the raw fuel in the exhaust. Probably going to lose the Cat soon...

Picked up today, they found two cracked coils. I don't think they've done a compression test, still. Vacuum test showed 16, sheet says spec is 17-23. It also mentions " pip4138p, indicates possible rings or worn camshaft. Vacuum gauge worn steady which indicates valve train normal. Upon further digging found cracked ignition coils. Replaced the 2 cracked coils. Found no misfires after"

Fuel trim data they printed for me says the following, looks like it's at idle, Vehicle speed 0
Engine run time 00:02:04
Short term FT Bank 1 -1%
Short Term FT Bank 2 0%
Long term ft bank 1 3%
long term ft bank 2 4%
Fuel trim learn Enabled
Fuel trim cell 20
Loop status Closed

They're still pushing the "all carboned up" angle. I asked if they looked inside and saw carbon or just assuming it because of age and mileage, but didn't really get an answer. Too pissed off that they found the bad coils I suggested were the issue last December.

It ran decently on the trip home and passed the emissions test it was over due for
Hydrocarbons at idle are a little high, 211ppm at idle, 6 at cruise CO is 0.01/0.00

$685, including an oil change. Gotta love dealer pricing

 

[OldCracker29]

$685, including an oil change. Gotta love dealer pricing