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View Full Version : Idle Surge/Lope-Knocking & White/gray smoke



Brimmy
04-16-2010, 18:17
HELP !!!!

2003 GMC 6.6 Duramax. My truck has been problem free until last two days.
First it started engine surging & loping as I braked for stoplights, etc. Then hesitation on accelleration until I hit 1200rpm; then seemed fine. That was yesterday.

Today; truck starts fine, starts surging before even in gear. Get to work fine. After work; starts fine, drop in gear & starts acting up again until I get over 1000rpm mark. I decide to hit friends shop on way home. He can hear my truck surging; inquires to Engine Service light; No light has come on. Scans for codes; There is nothing. I go to leave shop & truck has hard time starting. I pull out & accelerate & get very loud knocking & tons of thick white/gray smoke from exhaust. I pull into next parking lot. Engine is surging & bucking. I baby it, it hesitates till I get above the 1200 rpm mark; then will run okay as long as I don't push it. If I push it, instant knock & smoke.

What should I look for ???

More Power
04-16-2010, 18:45
The first step is to change the fuel filter no matter when the last change was. This'll allow to to check for possibility of gasoline in the fuel and general fuel quality as well.

Using a Tech II Scan Tool, a tech can exercise the rail pressure to see if the related system is OK. A possibility for your truck's symptoms could be a Fuel Pressure Regulator, injection pump, or excessive fuel return flow (due to one or more bad injectors).

Jim