Spark Plug Problems

Birmingham Bill · 11-17-2005, 04:37 PM

I have a 1990 911. I had the spark plugs replaced in March and now they are bad again. Any idea on why they are fouled again? I did notice the ones they put in, in March were not set as hot as recommended. I could sure use some advice. Thanks. Bill

Oh Haha · 11-17-2005, 06:28 PM

Rich condition most likely. Any pictures of them? The more experienced guys could probably give more clues. How does the car run now? A well tuned engine will be very kind to plugs. An out of whack A/F mixture will kill them fast. Sounds like you are having some issues with your car. Didn't you just purchase it a few months ago?

EDIT: Check your ignition system too. A weak spark will not ignite the fuel properly regardless of the mixture.

ruf-porsche · ruf-porsche's Garage

Is this the engine with the rubber band timing belt for the dizzy? You could have a broken rubber band.

Birmingham Bill · 11-17-2005, 06:54 PM

You guys have been great to help. Thanks. I know you must hate educated goobers who are auto illiterate. I did buy the car a couple of months ago, and yes I am having some frustrations. I sure hope they end soon so I can enjoy the car I have always wanted.

I know the guy that had the car before me used an octane additive to help it run better. If he added too much, could it have affected the plugs by running a rich mixture? I am now getting it tuned up. Maybe it will help? I was just hoping it wasn't indicating engine trouble.

2.7RACER · 11-17-2005, 07:09 PM

Bill,
In this world of specialists, and highly educated people at that, perhaps some time you can educate us a little about what you do. We car enthusiasts come from all walks of life. You have my admiration for choosing a Porsche.

Oh Haha · 11-18-2005, 04:38 AM

Bill,
I have learned a great deal about Porsches, especially 911's, from the guys on this board so I try to give back, so to speak, when I think I can help someone. I f you lived near, I would be glad to come over and look at the problem in person. I have done this for a few of the Pelicans I have met here. It keeps my auto chops up.

Please don't feel like a goober for asking. This board thrives on that stuff!

Birmingham Bill · 11-18-2005, 05:02 AM

Thanks,

As a principal, professor, and author, I can help you in some areas - not mechnical. I really wished you were closer. Hopefully, I can find someone nearby to lend a helping hand. Maybe I can do the same? Thanks. +

Jesset100 · Jesset100's Garage

Keep the revs up. When I first got my 82Sc I would take it easy and not rev the engine much. By driving like that I would have to clean my plugs every 2 weeks. Now, I hammer down (use common sense) and don't have that problem anymore. My engine has 168,700 miles so it does burn more oil.

Gunter · Gunter's Garage

Birmingham: A 1990 is a 964 type with twin plugs meaning: you have 12 plugs. It is important to get the right plugs because the 3.6 liter is a high compression engine!

The 964 has 2 distributors; the second one is driven by a belt coming from the first one. There were some issues with the second distributor overheating, so, Porsche cam up with an inexpensive kit to solve the problem.
Have the right plugs installed, get the shop to confirm that the cooling kit was installed and let them check the condition of the drive belt between the 2 distributors and that they work synchronized as intended.
If the cooling kit is not there, have them install it, it's cheap!
With the right plugs, and all components working, this engine should hum with whatever octane is recommended for this type.