I have been having some hesitation/slower acceleration than normal/ and rough idling recently, so I decided to do a minor tune up on the 3.4 today.

Plugs (they were Bosch platinum) had white electrods (with a little black on the tips). There was some blowby on one plug and I would expect some ash on it, but looking at the plugs, it looks like the engine is cooking them. Plugs are 1 year old and have approx 5000 miles on them

Anybody else have this problem with platinum? BTW, replaced plugs/changed oil (at the 3 month interval)and filter/changed PCV valve (old one still rattles, but still changed it)/new gatorback belt.

Tomorrow, fuel filter and diff fluid and cleaning the K & N air filter.

Car seems like its old self again.

Car has 111k on it.

Any insite into this?

 

anyone have any ideas? car never has shown over the 210 mark. or am i seeing ash on all 6 cylinders and need to repalce the rings.

Anybody else running platnum pugs out there?

 

Seems to me like you were getting lean condition. maybe a clogged fuel filter, bad oxygen sensors.

 

wouldn't a bad O2 sensor throw a code? When one went bad on my Cherokee, it was extremely noticeable and also threw a SES code.

Or should I replace them anyway to be sure?

 

Just to make sure and I know this might be a dumb question, did you make sure they were correctly gapped .... even the pre gaps I have found to be set wrong more times than not... Even though they say not to gap them I check them and usually have to regap them. Also did you make sure that they were the right plug... sometimes part stores give you the wrong one and you can end up with a too hot or too cold plug.

 

they were gapped correctly @ .045 (I double check that as well), however as per the part number being exactly what I ordered, I did not check that. They were platinum plugs with the correct gap so I assume that they were correct.

One thing that valter mentioned about running lean. The car runs a 160 termostat in it. Would that contribute to lean running? Seems to me, if anything, it would run a bit richer.

Who knows, maybe I'm just overthinking this and need to change plugs every year regardless.

 

Oxygen sensors can be bad without throwing any codes. They can simply report incorrect amount of oxygen in exhaust gases, and PCM will read too lean or too rich. If it reads "too rich" it tries to compensate this fake rich condition taking fuel out through injector pulse. Most frequent things when O2 sensors throwing codes - O2 geater circuit damaged or PCM compensation for current lean or rich condition is maxed out.
160 t-stat will do no harm, coolant temperature sensor reading is in PCM's formula to calculate air/fuel mixture.
1year/5000 miles is not a lot on a set of plugs. I used NGK TR55, after 30k+ when I pulled them they were brownish in color, worked great. Replaced them anyway with TR55-IX together with wires.
Check your fuel pressure, it may be too low.