1000000to1

I just put an LQ9 in my 58 GMC. My #5 & #7 cylinder are running colder than the others (120f at idle as compared to 300f in the others) and if you unplug the injectors or plugs it makes no difference with the engine. My injectors are firing and I've pulled the rails while turning it over and they all spray good. Also has lots of spark and plugs are new and has good compression. Valves seem to be opening all the way, I've swapped coils, plugs and injectors around with no change. Anyone have any ideas what could be causing this? Motor has about 20000 miles on it.

slogo

You know it has good compression now?

evolocomotive

I suspect bad plugs, just had a similar thing happen in my sons TBI 350. Bad connection inside the porcelain on the plugs.

1000000to1

Yeah I just did a compression test.

1000000to1

I swapped the plugs around and nothing changed.

1000000to1

Turned out the guy who did the harness had the two coil wires swapped.

truckdoug

iTrader: (25)

how did you figure that out? would be very hard to detect.

1000000to1

I have the little lights you put between the plugs and the wires. I then ran the truck while video taping the lights and then played it back in slow motion. It was supposed to fire 7,5,3 but was firing 5,7,3.