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Emgine Problem with a 1977 Porsche 911

My porsche is back firing & popping when it has heated up while driving. What could this be? I took it to a Porsche repair shop where the guy changed the Perma Tune Box and replaced the coil and charge me over $1400.00 and the car is still doing the same thing. Could this be a tune up problem? Someone please let me know what the problem could be.

You should become a member of a Porsche club and forum for your antique 35 year old car. Lots of dedicated enthusiasts for these.

+1 to Texases post.

Got carbon? Carbon retains heat. Great for bar-b-que briquettes, but not so hot for engines. Old engines like this run rich, and over the years they can develop carbon deposits in the cylinder, on the valves, and in the exhaust. That can cause ignition anytime volatile fuel comes in contact with the hot carbon, especially when it get heated even hotter by compression.

Honestly, I think Texases is right that you’re more likely to find a good answer in an enthusiasts forum. But carbon is a possibioity to consider.

Does your vehicle have carburetors? Does it still use points? No doubt is still has a vacuum advance on it. all of these are potential sources of your problems. A Porsche repair shop should be able to fix this, if not, then they are not much of a shop.

I have to agree with texases on finding a club or an on line forum. A local club where you can get together with other owners is the best, but if there is not one in your area, an online forum can be a huge asset. Finding the forum may be the first step as they can help you find a local club.

Ask that question on www.thesamba.com.
They deal mostly with aircooled engines like those on VWs but also have an aircooled Porsche forum.