454navyss

iTrader: (46)

i put high flow cats on my truck and about a year later i was getting a misfire code, replaced cats with cutouts and the code went away (never thought about cats causing that until now) i was getting an o2 sensor code at the same time though

ihdude

iTrader: (1)

The passenger side O2 sensor has been replaced when I first noticed the misfire. Threw a code for that. The truck idles fine, not rough at all.

fredkj3

iTrader: (1)

so it only does it when you drive it??? does it only do it at a certain rpm??

take them cats loose...

dogger

iTrader: (1)

so when was the last time you changed the fuel filter? I bet you got a dirty injector in the 5 cyclinder and should have it cleaned. dirt has a way of getting into the injectors on these motors.

ihdude

iTrader: (1)

I cut the cats off and still have a misfire.

Dealer computer says P0300 code. Autozone's says P0305 code.

I switched the #5 injector with the #2 injector to check for that.

Engine stumbles worse around 2100 rpm but the miss is felt from idle to 6000.
The miss is intermediate and sometimes is quits the miss above 4000.

Cleaned the MAF and Throttle body today also.

Wilde Racing

iTrader: (26)

Stock converter? this just started happening? If it sounds spark related, have you checked the coil pack harnesses? you dont have a spare set of coils or a friend that has some you can barrow?

ihdude

iTrader: (1)

I change the fuel filter about every 10,000. Changed it a couple of months ago.

Manual transmission so no convertor.

Yeah it just kind of started or at least became noticable.

I'll swap coil pack sides and see what happens then. Good idea.

I'm also thinking I'm going to pull the intake and put a new gasket in. It was last pulled when I replaced the knock sensors which was about 1.5 years ago.

Thanks for all the help!

hirdlej

iTrader: (31)

Things I am thinking are.........

vacuum leak (intake gasket)
cracked porcelin on spark plug
water leak into cylinder

ihdude

iTrader: (1)

I've checked the spark plugs and have moved them around to see if my misfire changes cylinders but it doesn't. I would have thought a compression test would show high pressure if water was in the cylinder.

454SuperSport

bad wiring connection on the coil or the injector.