2000 LS Misfire Clue, maybe solution?

frank_1

Hi,
My 2000 V6 LS is having the misfire issue again. Already replaced leaky valve cover gaskets, coil packs and spark plugs. Car was running well, until now. Misfire at idle and under load (random misfire). Sometimes it sets the MIL, other times it does not.

Solution: the expensive solution is to use Techron fuel additive with every other gas tank fill up. The engine purrs like a kitten with NO misfire. However, this is too expensive and a temporary fix.

So does anyone have any insight into this? The coil packs cannot be bad again, or else Techron would not be effective. I am thinking that either water in the gas tank, or EGR issues? I think that by Techron increasing the octane in the fuel, it might be compensating for a stuck EGR maybe. I also doubt dirty fuel injectors since they would be faulty even with Techron use.

Any ideas please? Thanks!
Frank

Brian_Lincoln

I wonder if the cause could be carbon buildup in the combustion chamber? I haven't talked to anyone whos done a head gasket, this is just a guess.
The EGR is a more likely candidate: the transfer passages can clog with cabon. I've seen this on newer german cars, so it's definitly a possibility. It happens on every car but is more noticable on engines where the performance has been pushed a bit over normal. (like the 3.0 found in the LS)
I too have an 00 LS6 with a slight, random misfire. It hasn't troubled me much yet (the first misfire I solved was a cross threaded spark plug by the previous owner...that sucked. I think I only have about 2 threads engaged on my drivers side rear plug after re-tapping it.

akirby

Have you replaced the PCV valve?

toomanyfumes

My '95 Thunderbird had a random miss that quickly got bad....it ended up being plug wires. Another possibility might be fuel pump or filter? I replaced those items another time the car had a miss. I think that was only under load, though.

akirby

LS doesn't use traditional plug wires, it uses COPs (coil on plugs) and those were already changed.

toomanyfumes

So if you replace the COP's the wire and coil is one piece? I've heard enough about them but have never seen one.

akirby

It's a very tiny (by comparison) low voltage wire from the controller to the COP. The COP sits right on top of the spark plug, eliminating the traditional plug wire that used to go between the coil and the plug. It is possible for the low voltage wires to go bad but only if they're physically damaged. They don't wear out like regular plug wires. That's one of the big advantages to COPs. The disadvantage is - they're expensive to replace and the ones in the LS tend to fail around 70k-100k miles - sooner if you have a leaky valve cover gasket.

toomanyfumes

Thanks, that makes sense. Mine's an '05, I know the earlier ones have the leaky valve covers.

leadfoot4

That's true about the earlier cars having valve cover gaskets, bit it was also primarily with the V-8 cars.

akirby

That's true about the earlier cars having valve cover gaskets

Don't all cars have valve cover gaskets? :shades:

leadfoot4

I'm SORRY, Allen, I meant valve cover gasket problems.....

akirby

I know - just having a little fun! :P

leadfoot4

Yes, I know you are!!

:P back at you!