Spark Plug Pictures 4 years old.

So my 88 as of last year was pulling down at or near 30mpg, however with me working from home over the last year I really did not notice the extreme decline in fuel mileage until this years Arlington run.  I am working at a new job that requires me to drive 50km round trip each day in stop and go traffic, after the 1st week I knew something was up, so on the 2nd week, I started checking things.  Running the scan tool on the drive to work and such, documenting fuel usage and found the car was getting 15mpg.  OUCH.  I found the TPS (Throttle Position Sensor) which is suppose to read .5 volts at closed throttle was reading nearly triple that, at 1.68 volts.  Which meant stuck in traffic the engine was getting way too much fuel. 

Next thing I noticed a tiny bit of off idle stumble. Not severe but enough to make me wonder when I had changed the plugs last.  After a few days I realized it was 60,000kms ago, WAY too long for my driving habits.

I pulled them all out and the normal new gap for me is about .050 the plugs had worn all the way down to nearly .070 gap.   The really nice thing is that they all had worn the same, all had pretty much the same colour and No Oil spatter on any of the plugs.  So I bought a new set of plugs. Of special side note, when did plugs jump in price, they use to be about $1.75 per plug, now they are near 4 bucks a plug for NGK UR5's.  25 bucks later I stuck in the new plugs and we shall see how much the fuel economy improves over the next 2 weeks of driving.  Well here are the pics of the old plugs.

Hey, be thankful there's six electrodes in that picture.

With the MSD system, I'm surprised they were hesitating at .070"

Your plugs have so little run time on them, they should still be like new, but pulling say plug #3 just to see how it is, couldn't hurt.

(For the record plug #3 is trunk side, middle plug.)

Capt Fiero wrote: So I bought a new set of plugs. Of special side note, when did plugs jump in price, they use to be about $1.75 per plug, now they are near 4 bucks a plug for NGK UR5's.

Is that with our club "discount" at Lordco?

At Canadian Tire they're $3.50, and at my local VAP they're $3 each.

Romeo wrote: I know with the lower resistance Iridiums I could gap those bastards all to hell (0.060"+)...

Were those the ones the side electrode fell off of?

Romeo wrote: One and the same. Can't imagine gapping being responsible for a clean cut along the threads though.

Not sure what you mean by "along the threads"? 

Didn't the side electrode break off right where it connects to the base of ther plug? I'm not saying creating the wide gap should've wrecked anything (I've gapped UR5s to .060" on my GT with an MSD coil with no problems), but I wonder if there was a flaw with your plug and the extra "tweak" was just enough to fracture the electrode mount and allow it to eventually fall off?