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Misfire on SLR can anyone help?


Mark Piper

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Hmm,

Sounds like something fundamental is out of sync or out of balance.

In no particular order and not sure how these tie in with rev counter falling to zero:-

 

1. How open is the butterfly / butterfly's (throttle) at start up / tickover. I have seen exactly this on a K series that tried to start and run on perhaps 1/4" butterfly opening.

They should be almost closed to the naked eye. If too open just adjust to more shut while she is running and hear her come back to normal.

 

2. If throttle bodies ... Are the throttle bodies in balance? I assume it is a twinned pair.

 

3. Can you do live mapping on that ECU? On my MBE I can see what point in the map ignition and fuelling wise you are on at a given throttle position. So if the rev counter says 1000 - 2000 RPM are you on that setting for ign and fuelling.

 

4. Inlet or outlet cam slipped? Either on the sprocket or could the belt have been put back on with a sprocket / sprockets to the wrong timing. Check position / timing. I'm pretty sure how to do this, for a K is on this site.

 

5. Head gasket gone/going between cyls. I had this on a Crossflow - no water loss or pressuring. just weird and worsening running. - Do a compression test on all cyls.

Do a leak down test (search the archive for this).

 

6. If throttle bodies - is air leaking into one of the venturis? This was a classic with weber 40's where a bolt could come loose and the 'o' ring plate could swing down, or the 'o' ring could get ingested or partially ingested.

 

Can't think of anymore right now...

 

Good luck.

 

Don't forget to add lightness :-)

My 2002/2003 racing pics

here

General pics (mostly of 7's and cars).

here

 

 

Edited by - stevefoster on 17 May 2008 23:07:24

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Don't want this to become my standard reply, but I did have a similar fault and it was the throttle position sensor.

 

Try disconnecting it briefly (And start, give small rev) or swapping it for a good one.

 

Willie

 

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