2006 QP. Intermittent misfire.

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Elliott653

Member
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1,241
I've just returned from a family trip to Dorset for the weekend. We took my 2006 QP. Fifty miles from our destination, the car developed an intermittent misfire under load. It came and went for the next thirty miles, along with a flashing "engine" light.

With about twenty miles to go, the misfire got harsher, I guessed a second cylinder was playing up. Power also dropped - naturally. However, the problem came and went, although it got worse overall as we went along. Especially accelerating away from a roundabout, or up a hill. Cruising down the other side was smooth.

Anyway, We limped to our destination and I got the AA to check the car the next morning. The AA chap plugged in his machine and diagnosed a misfire in cylinders 7 & 8.

Now, I've had this problem before. About a year ago, a misfire developed when I was on the M1. The AA chap then diagnosed a faulty cylinder number 8 ignition coil. He showed me that it was not "vibrating" when the engine ran. He reset the fault codes and the misfire went away. When I got home that time, I took the car to HR Owen who told me that they could not find the fault, the number 8 ignition coil was good and that because the AA man had reset the fault code, they couldn't trace what the problem was. Nevertheless, they had a spare ignition coil which the fitted - for free, which was nice. :)

This time, because I was 150 miles from home and not wanting to go home on the back of a flatbed, I told the AA guy to reset the codes and, once again, the misfire disappeared. I then drove home, in the pouring rain, without mishap. The car didn't miss a beat.

This week I shall take the car in to HR Owen once more. And, no doubt, they will say the same thing that they said the last time. However, I had to reset the codes as that is the only way to get the cylinders firing again.

My question is: Does anyone have any clue what's going on here? The misfire goes when the car is reset. I know HR OWen are pros. But, some of you guys on here seem to have an amazing grasp on Maserati technical issues.

If I can give the HR Owen guys a lead, it may help them get to the bottom of this.

Thanks.
 
Parisien

Parisien

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A sad day when HR Owen charge you £150 + and hour and don't know all the same, doesn't inspire.

Maybe take it to a good indie instead


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Elliott653

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1,241
Parisien said:
A sad day when HR Owen charge you £150 + and hour and don't know all the same, doesn't inspire.

Maybe take it to a good indie instead


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Click to expand...

To be fair, they didn't charge me anything. Owen's is just up the road from me. So, it's easy for me to drop it in. I usually go to McGrath's.
 
Parisien

Parisien

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I'd expect them to escalate it up Modena then, am sure it can't be unique to your QP Elliot

McGraths version of whats happening?

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c4sman

c4sman

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1,261
If the plugs have been replaced in line with service schedules I would suggest coil packs. When modern cars misfire under load it is almost certainly something simple in the ignition circuit that is on the edge or completely failed.
 
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Elliott653

Member
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1,241
I couldn't tell when the plugs were changed without digging out the service records. The car has a full service history and so, I assume that the plugs were changed when needed.

As for the coils, HR Owen said the last time that they were functioning correctly. Yesterday, the car drove 150 miles without missing a beat. Could it be a sensor that is faulty? It falsely detects a fault and shuts the cylinder down?
 
Contigo

Contigo

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I've had problems like that on other cars when O2 and/or EGT sensors have been bad.
 
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