TT_Vert

iTrader: (12)

Due to ease of access, I started with cylinder 7. I swapped in a new plug on cylinder 7 from one from my vette and also swapped a plug wire and coil from 5 ( no misfires) with plug 7 and the problem remained w/ cyl 7 regardless so I now know it is not the coil, plug or wire. The odd thing is it is the back two cylinders. I am logging current misfire count in HPT and cyl 7 and 8 get up to 70 at some times, however 1-6 are always 0 to 2. I find it odd that the back two cylinders have problems at the same time, especially after sitting all winter. I'm not an fbody guy can anyone offer any input here? This is a friends car.

Thanks
Dave

TT_Vert

iTrader: (12)

any opinions?

Dav

jay_99z

iTrader: (5)

M6 car? Bent pushrods? Injectors (doubtful)?

Maybe do a compression test?

01redws6ta

Water in fuel rail possibly from condensation in gas tank...settling to the back of the rail. Try the easy way first and dump a can or two of drygas in the tank and run it.

TT_Vert

iTrader: (12)

m6 yes, it ran fine all winter just started up. TOok it out for a run around the block ran fine for a block then sputtered and then this all the sudden. I can do a compression test on #7 since I can at least get to it. I dunno how you guys do it w/ that plug 8 access



Dave

jay_99z

iTrader: (5)

Pull the coil packs on passenger side. Makes life much easier.

FU_I_AM_UltraZ

iTrader: (20)

If not the coils, check the wires.

TT_Vert

iTrader: (12)

i replace cyl 5 w/ cy 7 wires and still misfires on 7. problem follows cylinder, not wire, plug or coil

Dave

jimmyblue

iTrader: (11)

I'd begin with injectors, the rear two cylinders are notorious for
being leaner than the rest and I think it has to do with sediment
accumulation fouling dead-end injectors worst.

I guess these two cylinders can also see highest local head temp
because of the blocked-off rear crossovers (at least my '02 had
plugs from the factory on the rear crossover points) and distance
from the main cooling loop. If it's not plugs/wires and it's not fuel
injectors then it might be wanting some better coolant distribution.
But I don't know what you'd do about it offhand.

TT_Vert

iTrader: (12)

ill try injectors. I thought maybe a vacuum leak but i doubt that w/ the lsx intake sealing design. regardless i checked all intake bolts. The car is 100% stock w/ 13k miles on it. It isnt driven a great deal.

Dave

Irocss85

iTrader: (1)

yeah I think the fuel rail/condensation is a really good thought. Id pull the rail, empty it completly, dry gas into tank, then swap inj.s 1 and 2 with 7 and 8. also, havent experienced this with LS' yet, but sometimes I'll get a car with a dead cyl. , say 3, and the next cyl. 4 will also misfire (or atleast show current misfire on the tech 2) try pulling the wires out of the coils 7 and 8 and just barely install the wires into the coils. while the cars running, pull #7 plug wire out of coil and make sure the eng. doesnt miss harder. if it miss' harder, then it was not a dead cyl.. do the same thing wit cyl. 8 and make sure both are really current misfires. that might save you from chasing the wrong cyl. for the mis.

FU_I_AM_UltraZ

iTrader: (20)

check the wires going to the coils.

Irocss85

iTrader: (1)

yeah I fixed a guys car that had bent over the terminals inside the conn. at the coil. unplug the conn.s and lookinside at the terminals.

TT_Vert

iTrader: (12)

the car hadnt been touched that is the thing. SO no way anything is bent etc. I checked to ensure the injector plugs were seated well though. Kinda hard to get back in there

Dave