Choking, misfiring, hesitation, problem resolved

[///Manuel]

I've had weird intermittent problems after changing an 02 sensor.
The car would miss when starting from a stop off idle and then misfire as the rpm's climb. The problem was present both when cold and warm. Gas mileage was not particularly bad.

Afer cleaning my MAF (never got a code anyway), I suspected a bad plug (Autolite platinum fairly new) and it was. Not sure what cylinder number it is, but it was the driver's side towards to the front of the car. The plug looked like it wasn't firing. Changed all of them with Motorcraft copper ones and so far so good.

Not sure what caused the plug to foul yet but its thread was wet, it didn't smell like gas, and definitely looked like oil.

 

[protomind]

How did you come to suspect a bad plug? How did you knw that the plug was the culprit?

 

[///Manuel]

Well because it didn't matter whether the car was warm or not and I had recently checked for vacuum leaks. The MAF had recently been cleaned and I had no codes (also drove with the MAF disconnected and misfires remained). The spark plug wires are new. The car doesn't smoke or anything. I just got a brand new O2 sensor and gas mileage was good so besides the occasional misfire, the car would run fine. Depending on how bad a plug is fouled, it may also ignite at higher rpm's but not lower.

I also didn't hear good things about Autolite's. I fouled plugs on an older carbureted engine and got similar symptoms.
Oh and it wasn't a fuel problem because the car started right up just fine, I changed the fuel filter not so long ago and the previous wasn't bad at all.

 

[Anime]

Motorcraft is usually the way to go. Also, the recommended replacements are the platinum plus plugs, not the basic copper.

 

[///Manuel]

Well since I just bought platinum ones and had bad results after only a few miles (had copper in before with good results), I figured I would try copper again. I can always inspect them and change them as needed.

 

[Eraser]

How big of an issue is it choosing the basic copper over the platinum plus?

 

[///Manuel]

I'm not sure I understand the question, I guess if it is to question my choice of plugs then my answer would be that it's easier to throw away cheaper plugs than more expensive ones especially when troubleshooting.

 

[///Manuel]

Hey guys, here is an update on this, the misfire recently started again. I had leaky valve cover gaskets and thought it was grounding my plugs (misfired more when cold). I cleaned out the area around the plugs and re-tightened gaskets. It's not leaking anyway, however the misfire came back and was also present when warm.

I pulled out all driver's side plugs and found the one that caused me trouble before to be rusted out. It had rust deposit around the ridge and the porcelain was red. The car did smoke slightly in the winter (hard to tell when it's cold out). All other plugs looked very nice and near new (black/brownish) with no rust whatsoever.

I changed the lower intake gasket some time ago and that took care of the coolant disappearing problem but once in a while the coolant level will come down some.

I suspect a bad head gasket or a cracked head.
Other possibilities?

 

[Tony H]

Funny you mention this. I have had this issue for almost 2 years now. About every 10000 miles the Front drivers side plug starts to fail, It smells burnt when removed. Sometimes the Ceramic insulator cracks, sometimes nothing physically different. I change out the one plug and I'm good for another 10K .

 

[///Manuel]

Mine has been 1.5 years and close to 10,000 miles as well.

 

[Tony H]

How big of an issue is it choosing the basic copper over the platinum plus?

Autolites 765's and put them in..no biggy.

There will be no gas mileage difference or performance. The only advantage that I have seen with Plats is they last longer. But since most Heads are aluminum, I choose to Pull them out after a year anyway/ Aluminum Heads and Steel plugs do not play well with each other.