Engine Missfire

[Tiny78]

Guys,

I've got a 99 Speed Six that's got an engine misfire.

From 3,800 to 4,200 rpm in all gears the misfire is quite obvious.

I've changed the coil pack, ht leads and spark plugs and it hasnt made any difference.

Any advise would be greatly appreciated.

Cheers,

Rich

[LeeT350c]

Tiny78 said:

Guys,

I've got a 99 Speed Six that's got an engine misfire.

From 3,800 to 4,200 rpm in all gears the misfire is quite obvious.

I've changed the coil pack, ht leads and spark plugs and it hasnt made any difference.

Any advise would be greatly appreciated.

Cheers,

Rich

One of the injectors not firing?

[Noisy]

Is it under full load? partial throttle?

Could be a throttle pot or need the throttles balancing.

When you fitted the new leads did you make sure they are as far away from the crank sensor wire as possible?

[Tiny78]

Thanks for the responses guys.

If I accelerate through the rev range shifting through the gears you don't notice it.

But if I'm looking to overtake or if it's cruising down the motorway its obvious.

Austec replaced all the bits when I had it tuned on their rolling road. We thought we'd solved the problem when the coil pack was replaced but as soon as I got on the motorway it was their. Unfortunately Austec are a good three hours away from me and I've not had the opportunity to go back there.

[Noisy]

Its worth checking they have sealed the cam cover properly as you can get water in the cover which then causes a misfire, have seen them left unsealed before by the garage you mention.

[Tiny78]

I did change the original cam cover for a TVR Powers cam cover.

I do know the cam cover is properly sealed, that was one of the areas Austec did check.

I don't think I've seen so much sealant in one place.

[Cockey]

Does it feel a bit stuttery/hesitant as you try to cruise through that rev range?

Mine used to always do that at about 2,200 revs. I managed to cure it by resetting the adaptive maps using the diagnostics software.

[Tiny78]

It feels exactly like that, hesitant and stuttery, but as soon as you squeeze the throttle its gone.

[Sagi Badger]

Hi,

Got the same or similar on the Sag. At idle it misses on 1 every now and then, not a constant miss which would be easy to find. I also have a miss around 2K, 2K2 on cruise. Full chat its not there which makes me think not spark. I have yet to gap check the crank sensor, suspected as I also get a "bleep" from the ECU at times.

Tried adaptive resets and balanced throttle bodies, like really balanced even at 2K5 to try to eliminate the issue at cruise. Checked earths, fuel, injector wiring, new plugs, leads etc. Any news will post, but until then I just drive flat out....

J

[Cockey]

I suffered with the 2k2 stutter for about 18 months before I sorted it out (by complete fluke! )

Not exactly sure what may have fixed it but this is exactly what I did...

1. I increased my idle speed to 1,000rpm when engine is hot (didn't like it ticking over at 6/700rpm with super low oil pressure - also would cut out on very cold mornings until warmed up)
2. With engine off, I reset throttle and deleted adaptive maps.

Been fine ever since

[SteveTusc]

Cockey said:

I suffered with the 2k2 stutter for about 18 months before I sorted it out (by complete fluke! )

Not exactly sure what may have fixed it but this is exactly what I did...

1. I increased my idle speed to 1,000rpm when engine is hot (didn't like it ticking over at 6/700rpm with super low oil pressure - also would cut out on very cold mornings until warmed up)
2. With engine off, I reset throttle and deleted adaptive maps.

Been fine ever since

I'm reading up on how to balance the throttle bodies as I think mine are out and I want to DIY (same symptoms as described here). When you adjusted the idle does that also change the flow on cylinder 3? If so I assume you had to balance the remaining cylinders? Or does that cover all of the cylinders as they slave from each other?

Edited by SteveTusc on Tuesday 23 October 12:06

[Robertjp]

SteveTusc said:

I'm reading up on how to balance the throttle bodies as I think mine are out and I want to DIY (same symptoms as described here). When you adjusted the idle does that also change the flow on cylinder 3? If so I assume you had to balance the remaining cylinders? Or does that cover all of the cylinders as they slave from each other?

Edited by SteveTusc on Tuesday 23 October 12:06

Yes it does, but I think you should start with cyl 3 and move towards the front of the engine, then go backwards thru 4,5,6. Balance is the main thing, set the idle up afterwards.

A number of the symptoms on here can indicate poor afr, but could also indicate valve clearances are incorrect so its worth being a bit cautious.

More help here...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...


http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[SteveTusc]

Robertjp said:

Yes it does, but I think you should start with cyl 3 and move towards the front of the engine, then go backwards thru 4,5,6. Balance is the main thing, set the idle up afterwards.

A number of the symptoms on here can indicate poor afr, but could also indicate valve clearances are incorrect so its worth being a bit cautious.

More help here...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...


http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Thanks for the links! I'm pretty happy with what I need to do now.