Problem with partial spark plug replacement?

[aceMueller]

I have a 2008 GS350, 170,000 miles.  The quick question:  If I at least replace the plugs on 1-3-5 on bank 1, will I be doing any particular harm to the engine?  (Put another way, can I go ahead and upgrade one side even if it takes me awhile to find time to tackle the other side?)

More context:  It's engine already has a "death warrant" - the dealership says it really needs a seal somewhere that will cost $6,000; it burns a quart of oil in a week of maybe 70 to 100 miles (burns - nothing significant on the block, nothing at all on the floor).  So I'm reluctant to spend too much to solve my problem since it probably isn't long for the world.  

Specifically, the plugs are very old (possibly original equipment - certainly what was in it when I got it 9 years ago with 50,000 fewer miles.  Bank 1 is very accessible; bank 2 not so much. 

Thanks,

Thomas.

[McBrian]

It's not going to hurt anything. I did the same thing on mine. Replaced the plugs and VCG on the front bank and it took almost 8 mos before I could get the timing belt job done to get everything even. You will definitely get "a little" benefit, but won't be too dramatic.

Even though it is probably the ring issue Toyota/Lexus had, at your next oil change run a can of BG EPR and do a back-to-back oil (and filter) change (with cheap oil) and see if that helps a bit. Also you can step up to a (slightly) higher weight oil while you wait for whatever...

[aceMueller]

Thank you so much for the reply!  It was one of those questions that's a silly question since my imagined concern is apparently not valid:  My concern was that 3 fresh plugs banging on one side of the V against 3 old ones banging not as hard on the other side of the V would be somehow dangerous.  I'll sleep better now!

More context - probably TMI:  I am not even looking for a boost - I'm just trying to head off the next problem.  I had to replace #1 because that cylinder died - the P301 code.  I did the simple coil swap between 3 and 1 and the failure didn't come with the coil - still "misfire cylinder 1".  I pulled the plug and it was all oily and barely snug, let alone tight.  I wasn't sure if the amount of oil meant that the cylinder was simply broken (and if so, of course so was the engine).  So I bought an $8 plug to stick in #1 just to see if the the old oily plug was the problem.  It's running smoothly for the first 100 or so miles, including 30 on the expressway.  So I surmise that #1's very old plug's condition, in conjunction with some excess oil leakage, could no longer fire.  I would guess that the physical condition of the other 5 plugs is similar, though hopefully not oily.  So I'll replace at least the 3 I can easily get to ASAP to at least improve those cylinders' chances - and I'll get to the other side later.  (And yes, I'll replace all 3 - including replacing the $8 plug!)

Thanks again for your words of wisdom!

Thomas.

[McBrian]

It's not optimal but *certainly* not catastrophic.

Upper part of the plug being wet might be due to blowby from not being tight and/or the plug tube seals are leaking into the well. This is a common and overlooked cause of misfires. Solved when you do the valve cover gaskets. Smokes like a MF sometimes when you do this stopgap step 1. Don't worry if that happens either.

Just buy the cheapest OEM NGKs for both the temp fix as well as the complete job later. ZERO need or benefit on these cars to go "premium" or multi-spark whatever... 

[aceMueller]

Thank you for the additional wisdom!  Thomas.