A few days ago, the check engine light started blinking; I was doing about 60 at the time. I pulled over, shut the truck off and waited a few minutes and it was fine for the rest of the trip. A couple days later it did the same thing. So I ran the scanner and came back with a P0307 pending code (cylinder 7 misfire). I immediately thought ignition coil. So I swapped coil 7 with 3, cleared the codes in the computer and ran the truck down the road. CEL started blinking again, same code.

A couple weeks ago, the plugs and wires are all replaced with brand new AC Delco parts, the fuel rail was just cleaned and the injectors were soaked in Fireball injector cleaner overnight. When the CEL starts blinking, there is no noticeable issue with performance. Engine runs fine! The coolant level hasn't changed since I bought the truck so it probably isn't the intake gasket right?

Any suggestions? Things I could look for?

btw, engine is the 5.3. Truck is an 04.

 

[QUOTE=TheRaptor;283273]A few days ago, the check engine light started blinking; I was doing about 60 at the time. I pulled over, shut the truck off and waited a few minutes and it was fine for the rest of the trip. A couple days later it did the same thing. So I ran the scanner and came back with a P0307 pending code (cylinder 7 misfire). I immediately thought ignition coil. So I swapped coil 7 with 3, cleared the codes in the computer and ran the truck down the road. CEL started blinking again, same code.

A couple weeks ago, the plugs and wires are all replaced with brand new AC Delco parts, the fuel rail was just cleaned and the injectors were soaked in Fireball injector cleaner overnight. When the CEL starts blinking, there is no noticeable issue with performance. Engine runs fine! The coolant level hasn't changed since I bought the truck so it probably isn't the intake gasket right?

Any suggestions? Things I could look for?

btw, engine is the 5.3. Truck is an 04.[/QUOTE

Hello... I am having a similar issue with my 03 GMC Denali. Bought it with code P0302 and I gave it a little gas up to 4k rpm the other night and now its blowing P0307. Recieving help through other forums came to the conclusion it is possibly a lifter issue. Truck is a little noisy on cold starts but quiets right up once its warm. Seems lifters are a problem on these engines and its best to check cylinder compression and go from there.

 

I didn't see how many miles are on the odometer. I don't think "soaking an injector" does anything but provide an exterior cleaning to the things. If you have a partially clogged injector, I don't think soaking them will stop an erratic spray pattern. Since you had them out, did you check the resistance of the injector coil(s)? High resistance will create problems.

Maybe you have a vacuum leak where the manifold bolts to the engine. The engine heats up, and the gap opens up.

You can have a smoke machine hooked up to the evap. system and .maybe it might show a leak somewhere.

 

Yes, soaking a fuel injector is a waste of time I agree, they need to have lots of pressure to clean them inside, and its probably cheaper to throw one
bad one away and buy a new injector, should that be the issue.

 

[QUOTE=Edward Farkas;368670]Might not hurt to use a fuel injector cleaner first, before any major work, both Techron and Seafoam are good choices to use. Lots of types of gasoline are not produced well enough to keep the injectors clean, IME.