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VQ35HR - Intermittent misfire, no errors


Commander

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Any tips on curing an intermittent misfire on my 350 HR?

 

It seems to happen randomly, but always at low speeds and often when the car is cold. From the noise it's making, it deffo only runs on 5 cylinders and after about 15 - 20 seconds it clears up.

 

No errors on the dash and no changes made to the car. Wires / connectors all seem solid. Cleaned the MAFs.

 

I was thinking about just changing the coil packs and plugs, but at £35 each for the packs and about £100 for the plugs, that's a lot of money to throw on a whim. Are there any diagnostics I can do? Any other possible causes?

 

Cheers,

 

Rich

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Just like Kraziekatz1 & yourself Commander I had a very similar issue with my Zed before (DE version though) ~ it was also a coil pack causing the issue but in my case it was a faulty one so needed replacing.

 

The best way or possibly the easiest way to find the faulty plug is to have the engine running and remove a coil pack one at a time. If you pull off a coil pack that is working then you should hear the car "drop" a cylinder. If you pull a pack and there is no change then that's your faulty coil pack.

 

The only problem though with the above method is that it'll only work if the coil packs playing up/faulty at the time you do the test otherwise you could pull or six & still not find the faulty pack. Worth a try though. :thumbs:

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If you have a smart phone then you could always record what the CEL is doing. When I've done the pedal dance before I was too busy counting the timings between each step to count an accurate number of flashes. I'm not implying that this is true in your case but at least you'll have an accurate record of exactly what is happening.

Just a thought.

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