LS1 Stripper

Please help! neither me nor my mechanic can't figure this out and I may have to give up my 2006 GTO, 6 speed.

Issue: "Random misfire" flashing code, cylinders 4 and 6, code indicating lean in one bank, rich in the other.

Trouble shooting thus far:

- New Plugs
- New Wires
- Coil Swap
- Injector swap
- Compression test
- Running compression test
- Manifold leak down test
- Remove cats to check for back pressure
- MAF sensor is clean

Mechanic says problem could be worn cam lobe. Quoted me 20 hours labor to change cam. Not sure whether this will solve the problem. There are no codes indicating crank position or cam position sensor issues.

I'm so frustrated. I just spent 600 bucks on a steering rack. I currently have a low catalyst efficiency code and have catted mids. (not installed) and a starter (not installed) Already replaced clutch, rebuilt tranny, water pump, new suspension, brand new tires, rear main seal, radiator hoses, and other stuff and I may have to just walk away from the car. UGH.

Can anyone with any help?

The only mod is vara ram cold air intake

R6cowboy

iTrader: (3)

Ok, my first initial thought is to replace crank position and/or cam position sensors regardless of no codes. Both can be had for about $30-40 each new for AC Delco pieces. I'd highly suggest that before swapping the cam. At least you'd rule out a couple inexpensive parts if nothing else.

My other thought would be checking for faulty lifters, weak valve springs and stuck/hung open valves. Even though the compression tests should rule those things out, it maybe worth taking the valve covers off to check those items after replacing the crank & cam sensors and before swapping the cam. Because you absolutely should at least replace valve springs anytime when replacing the cam anyways, regardless if the existing springs aren't even bad yet. So, if you're thinking about replacing the cam, there's no reason not to check the valvetrain first.
Good luck.

R6cowboy

iTrader: (3)

Couple other very simple things to check easily, if not done already. Very closely inspect the new spark plug wires and O2 sensor wires just to make sure they somehow did not get burnt from the exhaust and manifolds. And make sure they're securely held and positioned away from any part of the exhaust. Just thinking of anything that maybe worth double checking.

Also, 20 hrs for a GTO cam swap is outrageous. I believe book time is around 8 hrs. The heads do not have to be removed. You have to remove the intake tube, water pump, balancer, electric fan assembly, front cover, camshaft timing gear, timing chain, camshaft plate, valve covers, rockers, and pull the pushrods (make sure you put them back where they came, keep them in order!), spin the cam 3-4 times counterclockwise to push the lifters up (lifters should hold in place and not fall back down) and VERY gently remove the cam. This swap can literally be done around 4-5 hrs for an experienced person.

LS1 Stripper

Thank you
Could a burnt O2 sensor wire cause a misfire specifically and only in cylinders 4 and 6? I just had a downstream o2 sensor replaced a week before tis happened, as I thought this was the issue causing the P0420. Rookie mistake, it wasn't the root cause, hense the not yet installed catted mids.

R6cowboy

iTrader: (3)

Burnt O2 sensor wire could cause strange issues. As I mentioned, first I'd at least double check O2 sensor wires and new plugs wires (visually and feel for hard/stiff wires) just in case.
Also, now that I think of it, check fuel injector wiring for any sign of damage. I once was dealing with a misfire issue in a certain cylinder and it ended up being that cylinder's injector wire was damaged. I checked all injectors ohm readings and the one with misfire was off, so I swapped a couple injectors around and the same cylinder remained having the misfire. I inspected that injector's wiring and found it burnt (wiring was stiff as a board). Replaced the damaged section of wiring and misfire gone.

LS1 Stripper

Mechanic wont do the job without replacing lifters and he said the heads have to come off to replace the lifters.
Arrrgh!

cmysix

iTrader: (2)

find another mechanic

R6cowboy

iTrader: (3)

Yes, the heads have to come off to replace lifters, mechanic is right on that part. And if the cam is actually bad (probably one of the most unlikely culprits in your case), then yes, the lifters will also be bad.
BUT, the cam can be pulled for inspection without removing the heads. So, if the cam has no signs of damage or bad wear, then there's no reason not to slide it back in and no reason for the much extra labor to unnecessarily remove the heads. This is what your mechanic should be informing you, not unnecessarily pull the heads for the heck of it. The heads should ONLY be pulled if there's signs of damage to the cam.

Kfxguy

iTrader: (1)

88bruce

I didn't see where you said the upstream O2 sensors were replaced. I thought the downstream
O2 sensors were only used to test the catalytic converters, so a problem of running rich or lean
could be a problem with the upstream O2 sensors. What was the brand of any new O2 sensors?

Was the intake manifold removed when the injectors were replaced? What was the brand of the
new injectors? Were the intake manifold gaskets replaced?

Just because the MAF is clean doesn't mean it's operating correctly. A MAF and/or MAP can
output erroneous data without MAF or MAP codes being thrown.