Fouling plugs in 3 and 7 only
Thread Starter
Teching In
Joined: Jul 2013
Posts: 3
Likes: 0
Fouling plugs in 3 and 7 only I installed a Texas Speed cam and springs (Low Lift Stage 2 Camshaft: 212/218, .550"/.550", 112 LSA) in my 2005 Silverado 5.3. Cylinders 3 and 7 are carbon fouling. When running , I can smell the fuel in the exhaust. As the engine warms up it runs worse and will eventually backfire out the exhaust to a stall. Im assuming the base tune from Holley is not the issue as only two cylinders are affected. Is there anything mechanical that can cause this?
Replaced coils, wires and plugs on 3 and 7
Installed (8) new Holley 42lb injectors/seals
Fuel pressure 55lbs
Single 02 sensor (only 1 required)
Installed Holley Terminator LS MPFI
Replaced intake manifold gaskets and knock sensors
Rockers torqued to 22ft/lbs
Checked for vacuum leaks using smoke and spraying starter fluid when running.
Thanks
Replaced coils, wires and plugs on 3 and 7
Installed (8) new Holley 42lb injectors/seals
Fuel pressure 55lbs
Single 02 sensor (only 1 required)
Installed Holley Terminator LS MPFI
Replaced intake manifold gaskets and knock sensors
Rockers torqued to 22ft/lbs
Checked for vacuum leaks using smoke and spraying starter fluid when running.
Thanks
If the only thing you changed is the camshaft, and you already checked the fuel system for leaks (no leaking o-rings or injectors), the only thing left I can think of right away is the cam itself.
I would:
1. do compression test on those cylinders
2. leakdown if possible
3. pull the valve cover on that side, put a dial indicator on the affected cylinders rocker, and check that the valves open and close when they are supposed to.
Might have been a mixup in the tight procedure of the rockers. Did you follow FSM? It tells you put certain ones up or down or whatever- maybe you got it backwards for those two. You should not have just tight all rockers to 22ftlbs, it needs to be turned in certain sequence and you do 2 at a time I think.
I would:
1. do compression test on those cylinders
2. leakdown if possible
3. pull the valve cover on that side, put a dial indicator on the affected cylinders rocker, and check that the valves open and close when they are supposed to.
Might have been a mixup in the tight procedure of the rockers. Did you follow FSM? It tells you put certain ones up or down or whatever- maybe you got it backwards for those two. You should not have just tight all rockers to 22ftlbs, it needs to be turned in certain sequence and you do 2 at a time I think.
TECH Junkie
Joined: Nov 2013
Posts: 3,913
Likes: 366
From: White Bear, Mn
I have tightened rockers both ways. Once just right down the line no matter where they were on the cam lob and once with it on/around base circle of the cam.
When I went right down the line I had a very faint tick.
Removed rockers to switch from comp trunnions to bushing style and had about .030" play in the rocker arm of cylinder 5.
Put the new bushing style trunnions in and this time I torque every rocker down with them on base circle of the cam and my valve train is just as quiet as stock and I'm running a good sized cam. - Ls7 lifters@ .075" preload -
( All within 800 mi. of cam install )
When I went right down the line I had a very faint tick.
Removed rockers to switch from comp trunnions to bushing style and had about .030" play in the rocker arm of cylinder 5.
Put the new bushing style trunnions in and this time I torque every rocker down with them on base circle of the cam and my valve train is just as quiet as stock and I'm running a good sized cam. - Ls7 lifters@ .075" preload -
( All within 800 mi. of cam install )
Thread Starter
Teching In
Joined: Jul 2013
Posts: 3
Likes: 0
Thanks for the feedback:
I did not follow the FSM, Ill retorque using the FSM guidelines
I will try a leakdown, compression checks
The plugs were all good with the previous cam
Ill check the valve seals
I did not follow the FSM, Ill retorque using the FSM guidelines
I will try a leakdown, compression checks
The plugs were all good with the previous cam
Ill check the valve seals
Trending Topics
After one of my cam swaps I was having fits getting it to idle and eventually found the engine kept fouling plug #1 and only that plug.
I replaced coil, harness, plug, plug wire, injector, and checked everything mechanical multiple times. Changed injector o-rings, smoke tested the intake, changed intake gasket anyway, bore scoped the cylinder...and I'm sure other things I don't even remember doing because they were so far in left field.
A forum member and I did countless logs and tunes with the car not responding to the changes in the expected way.
The source of my problem ended up being some sort of corruption in the tune file. We did some adjusting on one of the oldest tune files I had and it ran like a champ afterwards with no other mechanical or electrical changes.
I replaced coil, harness, plug, plug wire, injector, and checked everything mechanical multiple times. Changed injector o-rings, smoke tested the intake, changed intake gasket anyway, bore scoped the cylinder...and I'm sure other things I don't even remember doing because they were so far in left field.
A forum member and I did countless logs and tunes with the car not responding to the changes in the expected way.
The source of my problem ended up being some sort of corruption in the tune file. We did some adjusting on one of the oldest tune files I had and it ran like a champ afterwards with no other mechanical or electrical changes.
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