Ok. My brother in law borrowed my truck and while I have transmission slipping its driveable and not a problem if you dont hammer on it. He gets to where he was going and the check engine light comes on and it wont pull above 45mph without shuttering and the CEL flashes fast signaling misfire, I assume. He took it to a shop and they scanned it and shows misfire on 4 and 6. Swaps coils, no change. Puts in plug and wire, no change. Puts a fuel injector and fuel pump with new filter, no change. ECM was programmed about 6 years ago but thinking that it is not sending out anything to the injector maybe????? Any thoughts or similar problems???? Any help is appreciated greatly..... Dustin

 

What motor and how many miles are on it?

 

5.3 with 150k.. THey also put a MAF on it and no help. Threw misfire code on 4 and 6 and also a MAF code but when reset only the misfires came back.

 

Dumb question, but you are sure injector and coil pak harnesses are plugged in completely?

Fuel pressure checks out?

Ground cables checked?

 

Any irregular noises coming from the valve train?

 

Yeah everything is plugged up tight and he said the fuel pressure was just a little above acceptable pressure. Ground cables all good as far as I know. Nothing has been done to it in quite some time except for pulling the maf about 3 weeks ago and cleaning. He took it to a reputable shop in the area and they are stumped. Said everything else checks out except for the 6 injector seemingly not pulsing. It got late so they quit looking at it. I am thinking maybe the ECM. Compression was good and the mechanics never said anything about any strange valvetrain noise. I drove it wednesday and other than the trans issue, ran perfect.

 

1.Does it have spark yes or no
2.Use a noid light on affected injector circuit does it flash while cranking and running.
3.Do injector drop test w tech 2 and fuel pressure gauge does fuel pressure drop when affected injectors are actuated

4 disconnect drivers front 02 pull the exhaust y-pipe flange bolts on driverside to drop it down slightly fire it up and see if misfire is gone. If misfire is gone the cats are melted. Seen this many many times through the years.

If it is none of the above it's a engine mechanical problem

 

A clogged cat can do this. But #4 & 6 are on the passenger side, not driver side.

 

Ok. I have confirmation that everything is firing and pulsing as it should. Guy doesnt think its an ecm problem and once he described it as choking down once you hit the gas it acts like its being choked which leads me to believe it may be a cat. They used a stethoscope to listen around the engine and heard nothing out of the norm.

 

Listen to both of theses guy's and Test the parts correctly. If you're working with a shop that is doing this . Find a new shop!!! There obviously not capable of Diagnosing it correctly. Throwing parts at it is just costing you money.

A flashing CEL is an indication of a Major Misfire. It is telling you to stop the vehicle. If you continue to drive, it will damage the Catalytic Converters. In some cases by the time the light comes on and starts flashing the damage is already been done.


The fact that he said it feels like it's being choked down is a good indication of a bad cat. Instead of wondering he should have been checking for that.