ideas on 4.8 vortec issue please.

99seirra · February 4, 2015

Afternoon everyone. Iv got myself a bit of an issue and I wasblooking for some ideas. Iv got a 99 gmc sierra with the 4.8 in it. Well Monday it snowed like hell and it ended up in the ditch. In the process of getting it out it may have hit the rev limiter a time or two. Well I get in it this morning. And it was missing terribly. Check engine light is constant flashing. But obd port is dead so I cant read the codes. Also it has 307k on original everything. Thanx for any ideas gents.

99seirra · February 4, 2015

I forgot to add the engine makes no unusual noise except at 2500 up it has a ting sound from drivers side.

00Silverado4x4 · February 4, 2015

First check/replace your cigarette lighter fuse, that should get your OBD port working again. Second, provided you get to scan the truck, get the codes and go from there. Third, double check everything, plugs, wires, fuses, battery cables all tight? Also double check your oil level and look for anything possibly leaking. After going into a ditch you may have suffered some damage and will to need to check it all out.

99seirra · February 4, 2015

Cig lighter fuse is good. Port hasnt worked in a long time, havnt been abel to find the issue. As far as anything loose nothing I have checked so far has been. And no leaks as well

99seirra · February 4, 2015

Also the intake gaskets were done about a week ago.

99seirra · February 4, 2015

Well I found the intake tube had gotten knocked off the throttle body. It seems to idle better havnt Driven it yet. Not sure if that would cause a miss or not.

99seirra · February 4, 2015

Well that wasnt it. Pulled valve covers also everything looks good their to

00Silverado4x4 · February 5, 2015

What about the condition of the plugs and wires. Are the plugs still gapped correctly and not burned up or covered in crud? The wires still good, not corroded or anything. You have plenty of miles on the truck so it's going to be tough to figure out especially if you can't get it scanned to get a code.

99seirra · February 5, 2015

Im slowly working my way thru everything. Wires look ok. Coils look pretty old and the metal band around them is rusted. But really dont want to buy eight coils if I dont have to.havnt pulled plugs yet. Thats next on the agenda.is their a way to jump power to that port for diagnosis?

00Silverado4x4 · February 5, 2015

I personally don't know a way to jump power over to your port. What about the fuse for the "Power Outlet"? Is that one good?

99seirra · February 5, 2015

Yes that one is good as well. I didnt gind any that were blown

99seirra · February 9, 2015

Got the port working showed evap can codes and random missfire.

Colossus · February 10, 2015

what did you do to get the port to work? (will help future folks out) If you are on the original evap canister then it's likely a sure thing that's going out, and the missfire would be causing the flashing check engine light. Time to start figuring out what coil(s) are toast. Original engine and tranny?

99seirra · February 10, 2015

To fix the port I spent a whole day tracking wires and found a spot shorting out behind the dash. Iv put new wires on it checked plugs. Still havnt tracked down the miss the coils dont look that bad but I guess that dosnt mean much. I do have a manifold missing three bolts and it ticks, not sure if that would cause a miss or not.