Ok. I have a 1999 suburban 5.7 4wd. This is one of the ones that has all the common problems lucky us. I worked for 12 yrs in automotive at a few of the more technically advanced shops in the area so I have some very knowledgable techs stumped on this one. Three yrs ago the oil lines blew off while the truck was warming up. We put in a used motor. Since then if you drive around town its ok but take on highway at exactly 65 the service engine soon light flashes then just stays on if you just drive around town it will go off after normal drive cycles. codes are always #2 misfire and sometimes #8. Have replaced a lot partly trying to diagnose partly because of other failure in the last three years but here's the list; fuel pump (failed would not start) full tune inc cap rotor wires fuel filter air filter etc, fuel injector (updated one piece switch over from gm with all 8 inj and regulator all one piece), intake manifold gasket. Then last month we redid the cap rotor wires and plugs and found the cap full of green and it was only 1 yr old and only 12000 miles. we later found out there is a screen under the distributor for the vvent that clogs. we didn't clean that yet but cap is ok for now. still runs poor on highway bucks skips and then almost stalls when come to stop and still has 2 and 8 misfire. Runs really poor with ac on or under severe load. Today I unplugged egr valve to drive aand check but not sure if helped or not. I have no idea wat is causing this normally great running truck run like dog feces
Aug 6, 2008 at 4:04 AM