misfire

Post by **SPUZZZ** » Sat Aug 01, 2009 5:18 pm

when the vehicle is on tick over the engine runs as sweet as a nut, when pulling away from junction or travelling along at a steady speed the engine starts cutting out, the car starts jumping about, also does the same when trying to increase speed, also it does a slight misfire from exhaust but not a loud bang, more a pop of sorts,if this happens and i dump the clutch the engine goes back to normal, the car has had a new fuel pump, a new coil, new plugs, it's also had the head converted before i owned the vehicle though, the diaphragm seems fine...can anybody help or have any suggestions please..

Post by **PSL184** » Sat Aug 01, 2009 5:26 pm

Have you checked the timing is correct - It sounds like it could be retarted too much. Check if the dizzy is tight as it may have come loose....

Post by **SPUZZZ** » Sat Aug 01, 2009 5:35 pm

the dizzy is tight as it should be, i think i may have to have the timing checked, thanks for the suggestions..

Post by **cormorant** » Sat Aug 01, 2009 7:14 pm

Maybe some kind of fuel starvation/partial blockage? Muck in the carb? Might be the reason tickover is ok but not enough fuel getting through for anything more.

Post by **rayofleamington** » Sat Aug 01, 2009 7:39 pm

popping from the exhaust would lead me in the direction of electrics or valve timing and not fuel. A missfire from fuelling problems would not normally cause an exhaust pop.

A faulty condenser/coil/dizzy cap/rotor arm can lead to strange issues - all worth checking. Also for checking if there's a burnt exhaust valve a compression test should give a quick answer.

Post by **alzax3** » Sat Aug 01, 2009 7:54 pm

I'd definitely want to check points/condensor/coil - I've had interesting times with both the Nova (VW aircooled engine) and the Moggy van (in fact both the cars in my sig photo!) and it's been down to those components in both cases......... and it's one of those 'so bad it's the end of the world' sort of problems that you completely forget about once you cure it!

linearaudio · Post by **linearaudio** » Sat Aug 01, 2009 8:00 pm

Your timing will have to be way out to cause that, if in doubt, slacken pinch bolt a bit, mark your present position, and twist the dizzy about ten degrees clockwise. If that cures it then get a bit more finicky! HOWEVER- I would suggest the points have closed up- had that many times myself, will run at a tickover but gets all muddled up when you ask it to do anything! Other thing I would check is that the little braid earth wire in the dizzy hasn't broken- has the same effect!

Post by **SPUZZZ** » Sat Aug 01, 2009 8:14 pm

a compression test has been done..11.5,11.5,11.3,10.5.. so thats ok,points not stuck together and it's also got a new coil fitted..but thanks for all the suggestions..everybody..

Post by **LouiseM** » Sat Aug 01, 2009 8:38 pm

I would check is that the little braid earth wire in the dizzy hasn't broken- has the same effect!

Yes - I had similar problems a couple of months ago. Some of the braid covering the low tension wire had worn away, causing it to short. It only happened intermittently but caused the car to stop on a couple of occasions.

Post by **bmcecosse** » Sat Aug 01, 2009 9:39 pm

Put some 3 in 1 in the carb! You mention 'diaphragm' is ok - what do you mean ?? The vacuum advance unit ?? It sounds like it is running horribly weak - what colour are the plugs ?
The 10.5 is significantly lower compression - something going on there - but not the present problem. Why did you change the coil ? It's almost 'never' the coil! You certainly don't need to 'get the timing checked' - just advance it till it pinks - then retard slightly. Simples !

Post by **autolycus** » Sat Aug 01, 2009 10:39 pm

bmcecosse wrote: It's almost 'never' the coil!

unless it's one of the rubbishy, wrongly-described new ones.

Is it worse when the engine's warmed up? Did it do it with the old coil?

As usual, it's worth listening to Ray and Roy (bmcecosse) on such matters.

Kevin

Post by **SPUZZZ** » Sat Aug 01, 2009 10:50 pm

only had car 3 days, it does get worse when engine warms up, i've not changed the coil, but it does look brand new, have done the 3 in 1 oil no change, in fact a little worse, plugs dry but creamy brown on electrode, sooty black on little bit of the threads about 2 threads deep, no smoke at all through exhaust, blowing through fine just clear

Post by **SPUZZZ** » Sat Aug 01, 2009 10:51 pm

don't know what happened there but posted 3 times my apologies

Post by **bmcecosse** » Sat Aug 01, 2009 10:53 pm

Plugs sound fine - so now look to fuel supply and ignition/timing problems. And the 'diaphragm' thing ?

Post by **SPUZZZ** » Sat Aug 01, 2009 11:00 pm

it has also got a new fuel pump on, the diaphragm i refer to is i've been told, the advance and retard on the side of the dizzy connected via a pipe to the carb, if the head has been converted to run on unleaded in the last year or so ( cannot be specific cos no real info as to when it was done) surely the timing wouldn't need looking at would it, i personnally don't know which is why i pose the question..

Post by **bmcecosse** » Sat Aug 01, 2009 11:09 pm

Ahh - ok - so the vacuum advance is working as it should ? The 'converted' head is not relevant to anything - if in doubt about timing - advance till pinking, then retard slightly.

Post by **SPUZZZ** » Sat Aug 01, 2009 11:23 pm

ok..thanks again for all of advise.. really apreciate it..will try as much as i can tomorrow..again cheers

Post by **autolycus** » Sun Aug 02, 2009 8:06 am

SPUZZZ wrote:only had car 3 days, it does get worse when engine warms up, i've not changed the coil, but it does look brand new

If you can get hold of a digital multimeter, check the resistance of the primary side of the coil (Ignition off, disconnect the two thin wires, measure the resistance between the two screw or spade terminals). Let us know the answer. You can do this with the engine hot or cold.

Kevin

Post by **SPUZZZ** » Sun Aug 02, 2009 1:18 pm

Right, my apologise, all my previous info was based on a friend who said he had checked these items but obviously he hasn't, rotor arm, points and cap look like they could do with replacing, on tickover there has now developed a clicking noise ever 30 sec's or so behind the drivers glovebox, also on tickover the ignition light is on, and all other issues are still there someone else has also recommended cleaning out the float chamber on the side of the carb, do you recommend this... thanks again for help.. sorry for some mis-informartion..

Post by **PSL184** » Sun Aug 02, 2009 1:59 pm

Well start off by changing plugs, points, rotor arm and leads but do the changes one at a time and check if the problems are still there after each change. The clicking noise may only be the fuel pump - tha's normal.... If the ign light is shining brightly just increase tickover slightly - It should be a dim glow at normal tickover speed.