Running Rough

After the last breakfast drive, I noticed the car was running a little rough. It had picked up a minor missfire/stumble at idle. The car was also starting to crackle and pop more than usual on the overrun. Now I like the aural delights of four Webers on overrun as much as the next carburettor addict but now mine are getting a little loud and embarrassing. Finally, and what bothers me the most, is a distinct tick-tick-tick-tick sound that rises and falls with engine speed. Have a listen…

The misfire could be anything in the ignition system. I pulled the plugs and they were all fouled and sooty. Unsurprising since this is a carburetted car.

Fouled spark plugs

On the positive side, none were wet, so at least I had spark on all cylinders but the soot showed the car is running rich and the state of the plugs was clearly sub-optimal. Time for a change. I’ve read that NGK’s iridium plugs are less susceptible to fouling in over rich conditions. I’ve also read that a hotter plug may perform better with the Weber carburetors. So I decided to switch from the standard copper NGK BP6ES recommended for 308s to hotter iridium BPR5EIX plugs. Hopefully the new plugs will fix the misfire/stumble as well as resist fouling.

NGK Iridium plugs for Ferrari 308

The carbs popping so much on overrun probably means they need rebuilding. A job I am not going to do now. I’ll empty some carb cleaner in the next few tanks of gas and see if that helps.

And the tick, tick, tick, tick? It sounds like a leak in the exhaust manifold to me. To be continued…

Disclaimer: describes the restoration work I perform on my car and only my car. I am not a professional mechanic. The website content is presented for entertainment purposes only and should not by seen as any kind of advice, information, instruction or guidance for working on any other car. The opinions stated here are my own and no-one else’s.

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4 Responses

  1. Gohardson says:

    Yes sounds like a exhaust leak check extractors for cracks, if it is the extra air drawn in is most likely the causing the extra pops and crackles on overrun

  2. Hi David

    Great blog, I have enjoyed reading it. My name is David and my wife and I also have a 1978 308. It’s a GTS.
    I wanted to ask about the new NGK Iridiums you put in. Did they resist the fouling like you hoped? We are having a similar issue with fouling.


    • David says:

      Hi David. Thanks for the kind comments. Yes, the new spark plugs have not fouled at all yet although the car has only done around 400 miles on the new plugs. A broken throttle cable has kept the car in the garage this winter. Now I need to find the time to fix that and get back on the road.

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