6.0 Swap now flashing check engine light

[Partsguy19]

just completed 5.3 to 6.0 swap on my 2001 Tahoe. Starts up and runs and drives great. First time on highway my check engine light started flashing for about 30 seconds and stopped. A few minutes later started doing it again and stopped. It seems to only do it on the highway.

I did put a new computer in it programmed for the 6.0. I haven't read the codes yet. Seems to run just fine. I don't feel any mis-fires. Suggestions??

 

[Tonyrodz]

Run the codes and let us know what you got. Could be anything.

 

[#1taho]

Flashing engine light normally is a emissions code. How are your cats and O2sensors.

 

[sumo]

Flashing engine light normally is a emissions code. How are your cats and O2sensors.

s

Yes it mean damage that is harmful to cats. Usually flashing means misfires

 

[Partsguy19]

Code is P0800 multi-misfire. I can clear the code and it will only come back when I get on the highway above 2000 rpm. Didn't have the problem before engine swap. Of course I put new plugs and wires on. 6.0 ran fine before I did the swap. My scan tool only gives basic info. Anyone recommend a scan tool that will give much better info maybe?

 

[#1taho]

Check conections and grounds. Recheck your work. Could be an over sight. What could did you use ?

 

[bottomline2000]

check all of the plug wires and make sure they are all securely connected. If they are and it doesn't stop the misfire, try unplugging them one at a time to see if the idle changes. the one that doesn't change your idle is your problem wire, plug and/or coil. found a bad coil that way on my son's Honda 6cyl accord..unfortunately the cat was already killed due to the cylinder dumping fuel on the cat. its a little harder on an 8cyl, but its a start and we were getting a random misfire code.

 

[Partsguy19]

Thanks for the help.. I'll keep trouble shooting and hope to figure it out. I had a "tunned" computer shipped to me for the 6.0 set-up. I might toss the old computer in and see what it does also. What gets me is it only comes on 2000 rpm or more (driving 70 on the highway). I don't "feel" a mis but...

Also, what the little black canister looking thing right behind the throttle body sticking up. Its real loose (wiggles around a lot).

 

[bottomline2000]

Vapor purge silenoid. Make sure its got an oring on the bottom where it fitsinto the intake. Mine moves around a little but it's snug.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[sumo]

That could cause it. Unmetered air. Since is not read by the maf, the ecu doesn't know how to compensate