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View Full Version : computer glitch or something else?


grassy
11-19-2008, 17:11
Have 04' 3500 Silverado Diesel 6.6 dually (83k)with several wierd problems
1. Can drive 40 miles one day and get 16 mpg then drive same 40 miles next day and get 8 mpg ??
2. Start truck sometimes and air conditioner won't work but if I shut off and restart it comes on ??
3. Getting the embarrassing intersection gray smoke out. Have new fuel filter and oil change but no change.

No dash codes have appeared.

Plan to take to dealership for computer diagnostic and road test, $240 for test including injector inspection.

Sympathy or advise appreciated..
Mark Rinker
11-20-2008, 04:59
Welcome!

Mileage varys widely from idling in your driveway (0mpg) to rolling down a mountain on cruise control (88mpg!!!) ... how are you capturing and calculating your data? 'Sampling size' is the key - if you base your calculations on too small of a sample (too few miles and gallons) the data will be skewed. The most meaningful number is based on the largest sample. We track mileage on all trucks and calculate averages over months, tens of thousands of miles, and thousands of gallons...

My C4500 doesn't like idling with the A/C on. I think the A/C condensor needs to be removed or replaced, it may simply be too full of bugs and dirt and road debris to be effective while sitting still. Check the forums here on 'de-bugging' your cooler/condensor stack out front...

Sounds like an injector issue...good luck...read up here first and know what your warranty will cover, and what it won't!
grassy
11-20-2008, 06:30
Mark,
I'm new to forum and appreciate the information and curtious members.
Thank you,
Bryan
madmatt
11-21-2008, 16:15
sounds like you need injectors and a a/c cycling switch. When your A/C is inop, try unplugging and plugging back in or tapping on the switch in the accumulator on the passenger side. If the A/C starts working,,, you've more then likely just found your problem.
grassy
11-22-2008, 06:43
sounds like you need injectors and a a/c cycling switch. When your A/C is inop, try unplugging and plugging back in or tapping on the switch in the accumulator on the passenger side. If the A/C starts working,,, you've more then likely just found your problem.

Great suggestion! It's scheduled at dealership on Tuesday. In defense of mechanic's it's had to locate a problem if it's not immediately happening.. Just hope they're straight with me about the smoky injectors..ugh!
Thanks again,
Bryan
madmatt
11-22-2008, 16:55
problems we can't duplicate are the biggest pain in any tech's azz.