My check engine light is on and I've had issues with power acceleration. The truck runs fine around town, but if It is under load (uphill / over 45 mph) there is a severe lack of power and the check engine light starts flashing. I teacher HS, and have been talking to our auto teacher. When he hooks up the code reader it won't connect. I've also had O'Reilly's try with the same results.

I've changed the spark plugs, wires, and fuel injector.

If anyone has any suggestions I would appreciate them.

 

Flashing check engine light indicates a misfire. See if you are getting power to the OBD2 port

 

Are you aware of the plenum gasket issue?
http://www.hughesengines.com/Index/p...p?partid=27091

 

Mine is a V6, but I'll look into it.

 

Forget the plenum gasket for now, given that these PCMs are notoriously lenient with misfires (we had that topic just a week or two ago) I doubt that could trigger a flashing CEL. The OBD reader not connecting would point to an electrical issue and I'd try to solve that first. Most readers draw power from the DLC so I assume "not connecting" means the reader has power but can't talk to the PCM ?

 

"not connecting" could also be as simple as poor (dirty) contacts on the OBD connector.

I’ve had this issue several times in the past, when it’s been a long time since I use the OBD port.
In and out with the plug a few times to scuff up the contacts and it came good.

 

Update

As I said our auto teacher and O'Reilly's couldn't pull a code. I borrowed a reader, and was able to pull the code this weekend (P0304). This seems to be the same code as every other time the light came on.

I have an idea. I realized that about the same time the power issues started, the left turn signal started working on and off. I'm going to check the wireing on that and see if it could be the electrical issue.

 

The plenum gasket will give you multiple misfire codes, I have seen it happen before i knew of the issue. I put a timing light on the coil wire(along with #1 cylinder) and under a slight load timing will jump causing the misfire. Plenum gaksket replaced and haven't had a misfire ever since(this was about 10 years ago). The V6 is the same as the V8 less two cylinders.