Misfire - advice please

[petercoll]

Got my Striker out for the first time in several months today.

Had a great blast with my son, but during the last mile the car was misfiring, and sometimes dying on me when idling. The misfire is fairly obvious above 3,000 rpm, but is subtle and persistant. The car struggles to start when hot aswell.

I will have another check tomorrow if the weather holds, but anyone got any ideas ?

It is a tuned crossflow, with twin Webers and electronic ignition, and I put fresh fuel in today. I whipped the tops off the carbs and the levels look fine and the chambers look clean.

Pete

[adithorp]

Miss-fires are rearly fuel related.
Check simple stuff like HT leads for security and dizzy cap and spark plugs for cracks. Check for inlet side air leaks. Good trick for this (if you can't hear it) is a piece of hose on a blowtorch instead of the nozel, then poke it around the manifold with it running; Any leak will show as a pick up in revs when the gas is sucked in. It makes no mess unlike spraying WD40 or the like around.

[philfingers]

blocked airfilters can cause it. I know from bitter experience years back when an all singing and dancing 1700XF with 45's went it for a tune and we got a £330 bill, turn out the pipercross trumpet socks were to blame, tuner couldn't figure out what it was, thought there was a rev limiter as at 3000rpm it just misfired and wouldn't go past about 3200. once the (newly fitted) trumpet socks were removed it rev'd cleanly through to 7500 and 119 at the wheels (XR2 Mk1)

[petercoll]

Thanks Phil. At first I thought that couldn't be the problem, as the trumpet socks have been on the car for years, but I removed them and ran the car this evening without them (I know, I know) and it seems fine again. Perhaps they are deteriorating with age, or are blocked - I have never cleaned them in 9 years of owning the car !

Pete

blocked airfilters can cause it. I know from bitter experience years back when an all singing and dancing 1700XF with 45's went it for a tune and we got a £30 bill, turn out the pipercross trumpet socks were to blame, tuner couldn't figure out what it was, thought there was a rev limiter as at 3000rpm it just misfired and wouldn't go past about 3200. once the (newly fitted) trumpet socks were removed it rev'd cleanly through to 7500 and 119 at the wheels (XR2 Mk1)

[petercoll]

Going to treat the car to a new set of everything electrical Adrian.

Pete

Miss-fires are rearly fuel related.
Check simple stuff like HT leads for security and dizzy cap and spark plugs for cracks. Check for inlet side air leaks. Good trick for this (if you can't hear it) is a piece of hose on a blowtorch instead of the nozel, then poke it around the manifold with it running; Any leak will show as a pick up in revs when the gas is sucked in. It makes no mess unlike spraying WD40 or the like around.

[adithorp]

What happened to treating it to a new engine?

[petercoll]

Ran out of money, and I haven't completely beaten this one into submission yet

Pete

What happened to treating it to a new engine?

[jeffw]

Have you checked the crank sensor and the gap ? I've seen this before when the plug to the crank sensor is loose or the sensor has moved away from the toothed wheel. I'm assuming you have a toothed wheel of course.

[petercoll]

Old fashioned clockwork ignition Jeff.

Pete

[jeffw]

OK...I guess you've checked that then.