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HT lead order effects idle

When I fired up TheHoff after fitting the exhaust it was very obvious that the engine was not running as it should. It was a relief that it was firing up but being so close and not having a smooth running engine after all the hard work is a little discouraging.

I videod the engine running and sent the clip to Jon Mitchell at JM Garage to get his views. He suggested it was either spark related or at worst cam timing being off.

I spent a lot of time trying to ensure that the timing pulleys were aligned correctly during the rebuild and I'm confident it isn't the issue - but then again...

So I began problem solving with the HT leads and spark plugs.

Each of the plugs were extracted, cleaned (they were dark from all the firing and refiring I guess) and then connected to an inline spark tester to check if they were in fact getting a spark from the distributor. Thankfully they all were.

Next thing to check was the order of the HT leads on the distributor. The 944 has a firing order of 1-3-4-2 with the number one cylinder being at the front of the engine. If the leads are connected in the wrong order then the spark plugs will fire in the wrong order resulting in a rough running order.

Looking around on the internet and in the manual there is no clear reference to which HT lead should connect to which pin on the distributor of the 16v.

I decided to call Jon at JMG and ask for help and he was kind enough to check a car of his to be sure. As it turns out my HT leads were in the wrong order - this is how I had received the distributor and had left it as it was because I assumed it was correct - but it wasn't... with the HT leads rearranged into the correct order (as seen below) the engine fired up immediately and settled into a smooth rhythm - unlike before! Stoked.



Needless to say I am a very happy wrencher now.

During my conversation with Jon he suggested that the petrol in my car may be past it's best too - it's got to be two years old now at least so I'm off to get some fresh 99RON from the local.

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