jcorenman

I think you should replace the plugs with Bosch WR7DC+ (see post #4) and see if that fixes the problem. The NGK's are probably fine (although you did not specify the part#), and I know the air-cooled guys love them.

But if things are behaving strangely then WHAT POSSIBLE reason is there to not use plugs that you KNOW are correct? Just to see if you are on the right track...

What would also be immensely useful would be some good close-up pic's of the smooshed plugs, and an un-smooshed plug for reference (straight-on, and profile, just like a mugshot); and a picture straight down the spark-plug hole showing the top of the piston at TDC. If the plug got hit by the piston (which seems very unlikely) then there will be some sort of witness mark.

Did you ever find out what the original (smooshed) plugs were??

Ducman82

have him take pictures of the offending plugs. in this case, a picture is worth a thousand dollars...

flyrade

I'm not sure what plugs were originally installed, but they worked fine for 1,500 miles.

I am not close to the shop, but when I do get there I'll ask to see the offending plugs and take a pic of them to send you.

You would think with the piston at TDC you could just direct a light to the piston to see what the top looks like. As I posted before, I can't believe there could be carbon build up, but anything is possible.

Also, is this engine any different than any other V-8? What about a Ford or Chevy - what would we do to one of those engines with the same problem I have here?

Ducman82

carbon build up can come from bad timing, bad fuel, bad rings (to much oil blow by), bad spark plugs (to cold).

that would have to be EPIC carbon build up to cause a plug to be eaten.

V8, 4 banger, W12, all are 4 strokes. wont matter.

Kevin in Atlanta

Is there any chance one of the ignition monitor relay sensors is marginally connected?

FredR

Paul,

You really are "**** out of luck"- did you offend the Petrol Gods or something? With this one the only advice I can offer is to purchase a ouja board and see what that says.

Obviously there is a reason for everything but what? Were all 3 cylinders of the affected plugs fired from the same distributor/coil? Even if they are I still have no clue. At the moment I like the carbon build up causing detonation theory. Carbon build up can happen and can cause detonation but the anti knock system pulling back chuncks of timing usually prevents that. Do you hear any pronounced rattling when pulling away under heavy load/low revs or in the 3500 rpm range? Is there any history of rubbishy gasoline in your region? Are you a responsible driver proceeding legally with consideration of other roads users or are you like most of us on this list?

Good luck with the hunt

Regards

Fred

siscogts

Looks like you're running with 3 wrong plugs, not the correct ones or 3 faulty plugs from factory.
8 new spark plugs are a good starting point. A good mechanic then... It is just great.here in Italy a wr7dc+ is 3,75 euro, can't see the big deal Keeping and re-gapping old ones...
Francesco

OBehave

Many years ago I had a customer come back after a tune up on a Caddy. After about a week the car would missfire and drop 1 cylinder. Pulled the plug in said cylinder and the gap was closed. Reset the gap and sent the car on its way running fine,thinking that I must have dropped the plug during install or just made a bad gap adjustment. One week later same thing. Pulled the plug and gap closed again. Turns out AC Delco had an issue with their plug manufacturer and the porcelean /center electrode assembly loosened from its crimp connection causing it to slide down and touch the ground tip.
Never heard of it happening before or ever again after but this sure brings back a bad memory.
Ed

IcemanG17

this is really scary................ I would change ALL plugs to the correct Bosch version....IF it continues, then the options become really bad..... First thing I think of is glyco rod bearings were installed far too tight and have pounded themselves to death on those cylinders causing the impacts

I would take a look at the oil ASAP.....don't be surprised when there is lots of metal in it

flyrade

Here is the latest. I got a call from the mechanic and his borescope is on the fritz, so he ordered a new one and it will be here in a few days. I also suggested, as you all mentioned, that he change the plugs to those mentioned here and give the car another try. Let's see if he does that, or waits for the new borescope.

GregBBRD

I think Ed is going to end up being the one closest to identifying the problem. Nothing else makes much sense (except for the little guys with hammers inside the combustion chambers.)

I've seen this happen, also.

flyrade

Wouldn't that be nice - such a simple fix. Keep your fingers crossed for me and I'll let you all know what happens.

And, as always, thanks for sharing all your thoughts, ideas and experiences.

flyrade

I e-mailed your suggestions to my mechanic. He replied that he will take your suggestions and first change the spark plugs to the ones you recommend. He has a couple other cars to work on, but hopes to get this accomplished prior to the weekend. I sure hope this works and I'll keep you posted as soon as I hear anything.

flyrade

Here is the latest update, and things are no better.
After getting the borescope tool earlier this week, they found nothing on top of the pistons. They then installed the new plugs and no help.
Then, without talking to me, they decided to give the engine a compression test. I asked them if there is any way compression could be making the problem we are having with this engine. They said no, but there could be other things with the engine that need to be addressed.
I told them to prepare my bill and I'm taking the car. So, after more time and over $700, they wound up doing nothing to fix the problem. So yesterday I had no other choice than to bring the car back to Eric, since he last worked on the wiring and engine. But the last time he had the car for over 9 weeks. How long will he keep it now? Since this is an electrical issue, and he last worked on the wiring, will he find it's something he didn't fix correctly and there will be no charge, or will he claim the computer needed to be replaced and I have another major bill?
Looking back on this I think my big mistake was to fix something when the car was running great. I had the car for about 8 months, running great, when Eric told me the wiring needs to be fixed. I wish I told him to forget it - as long as the car is running great we'll leave it alone. When there is problem with how the car is running, then we'll fix that one problem. Maybe it would have run another 8 months, or 8 years, with the wiring just the way it was. But no - I had to try to do the right thing and make the car perfect. What a jerk I was.

Mrmerlin

Paul your last update post needs more info included,
did they install the Bosch plugs?
is the engine still running poorly?

what were the compression results?

Bosch plug part number is 7900 at autozone get 8 and put them in.


If the plug wires are old replace them
same for the caps and rotors
and coil wires