I know this has probbably been addressed before but I never found any solutions. Running down the highway cruise set at 75. I look in my mirror and there is a huge black cloud following me,but it is still running fine at this point. I slow down a little and it stops, but any slight increase in throttle and it pours out the smoke. I was in the Virgin River gorge outside of ST.George UT. so I baby it into town, about halfway It starts Intermittenly (sp?) knocking like a really loud injector pump knock and sometimes chugging and missing.

I get it to the Chevy dealer in St. George and they put me in a rental so I can continue my trip. They checked Max fuel command, fuel vaccum,fuel api.,injector balance rates, no codes, drove it for an hour, and found nothing.

Halfway back to vegas it starts up again, whenever i turn the truck off it runs great for a while after restart. The dealer here says bring it in when it is running bad.

Sorry for the long post, but I am stumped. I will be setting up a pit for an off road race next week, and I dont want to be stuck in the middle of the desert. I am at 22k miles and the motor is completly stock. any suggestions would be appreciated

You'r EGR valve might be starting to stick open.

That seems to be about the only thing they didn't check. Wouldn't the egr throw a code. I would have thought it would have at least thrown a misfire code.

That seems to be about the only thing they didn't check. Wouldn't the egr throw a code. I would have thought it would have at least thrown a misfire code.

No codes in some cases. Usually it will throw a code for EGR Flow Insufficient if it gets clogged and sticks closed... not the case if it sticks open.
The knocking and surging are sure symptoms of EGR problems.

Hey are you running any sort of programmer, A buddy of mine had the same problem and it turned out to be the bullydog box he had on the truck. He also went the route of a dealer and they gave him the all clear, the problem happened again on the way home from picking the truck up.

Thanks for the ideas. no I am not running any progammers. Maybe I waited to long to do the blocker plate and finger stick. drove the truck to the airport tonight and it happend again. I will take it back to the local dealer when I get back to town. Just for the record the service dept. in ST George were very reciptive and seemed to truly want to find and repair my truck

I had the same symptom, smoke and the loudest knock I've ever heard from an engine. babied to the dealer and had the fuel/airfilters changed. I had that done as my D.I.C. sudddenly showed 1% fuel filter life, and I dont remember seeing it lower than 18% right before that.

Anyway, after that, it has run perfect even when towing. Truck is 100% stock with about 20K miles. about 3K since filter change.

Cant wait to hear what cures yours!

If the EGR is stuck open, will it also cause blue smoke like bad injectors?

Dealer never could duplicate the problem, so I orderd the blocker and finger stick from J.K. Hopefully end of problem. The worst part of the install was the silly little clips on the wire race

Mine did that shortly after I got it. It would last for about a minute and a half. It would start after running about 20 minutes on the freeway. I changed my fuel filter and where I bought fuel the next time, it hasn't done it again.

Good Luck. I am trading my 07 classic in next week for a LMM because of this same problem . It has done this since I bought the truck new in March. I drive a lot and it has been into the dealer at least 6 times for this. Truck already has 30 K miles , no problem ever found. This is a truck used for work, MUST be dependable, I guess I just don't want to take the chance. I will miss the classic body. Thats why I bought this one, had an 04, never a problem in nearly 200K miles and wanted to keep the old body.
Guess the new style will grow on me!:rolleyes:

Had the same problem but I got mine to code. It was the fuel pressure regulator(FPR). Cleared the code and let it sit overnight and has never done it since. Mine started as I was towing up a grade and I started losing power so I gave it more petal to keep from getting run over. It knocked so loud It sounded like the pistons were slappin the heads. :eek: Thats when it threw the code but I can't remember the #. Good luck!! Hopefully it will cure itself as mine did. :D GB

i had this happen to my new 07. down the interstate i looked in the mirror and couldn't hardly see the car behind me. anyway, it was just off the lot, about 500 miles. it turned out to be that the water seperator was full of water. probably from being empty on the lot. this Bosch fuel system runs at extremely high prssures, especially at the rpms at interstate speed. water is thicker than the fuel and makes it overload some cylinders with fuel, hense the black smoke. hope this helps you.