hi,my friend had a small misfire on his cosworth,he was told it was the idle control valve(which was disconnected when he bought the car)that was causing the problem,so he changed the distributor cap,rotor arm,washed out the icv with brake cleaner.he also fitted a full samco hose set at the same time.now the problem is ten times worse,as soon as the boost gauge reaches 0.5 psi the engine cuts out and coughs violently,off boost it drives perfect,when it ticks over it does skip a beat occasionally.it doesnt crack a flame out of the exhaust when it cuts out like when a car overboosts.any help would be much appreciated,ta,lee

 

What plugs and gap m8 ? Has he checked the phase sensor ?

 

phase sensor or maybe coil?

 

i have the 2 ford workshop manuals for referance,i also have a spare coil so i can check that,the car ran ok but with a slight misfire before and the plugs have not been out.i dont know what to look for with the phase sensor so any guidance on what to check and what im looking for would be a help,cheers,lee

 

phase sensor is in the dizzy take the cap off pull f
rotor arm off and lift off the dust cap you will see the phase sensor money is on the wires are corroded,make sure the wire insulation is all ok etc

 

ok,im going over to his now so ill check that,is there a gap that has to be set for the sensor to work properly?

 

0.2-0.3 mm

 

checked the wiring at the rear of the engine,it looks in really good condition,sprayed wd40 into the multiplugs,tried it but no difference.it does it even when you rev it up sitting still.the rev counter does not rise whenb the misfire happens,it just reacts with what is going on with the engine.there is no black smoke.i didnt check the phase sensor yet but i will be going back to his tonight and he was going to take the cambelt cover and the boost hose off so we can see in better!

 

Idle speed control valves do not cause misfires period.
They only admit air to allow the engine to idle.
It sounds as though the fuelling is out, but check all the basic free stuff first, ie as said the phase aligment must be 100% correct.
Check to see that the cams/bottom pulley/phase are aligned perfectly, the TDC mark is the NOTCH nearest the "V" groove but NOT the groove itself, both cams pointing towards each other, and in line with the join between head and rocker/cam cover, phase sensor must be EXACTLY IN LINE, ie the scribe mark on the dizzy body and the notch where the rotor arm sits must be perfectly aligned, so the scribe mark sits in the middle of the notch.
Does it induce a misfire when reversing slowly ?
To rule out the rev counter, (as this can cause a misfire or non running engine) you could cut the wire to the rev counter from the coil, then repair afterwards by soldering together again.
Check also for PLAY in the dizzy on the shaft by applying sideways pressure, on some the top bush picks up as it is crap(good old ford!!), and the shaft spins the bush inside the housing, mine did and the gap ranged from touching of the lobe/sensor to 1.3mm, but even went on rollers like this where it was perfect, AFR perfect, power 280+(stage 1), so worth a look.
I can get the dizzies repaired if this for £35, with an OILITE bush a self lubing bush.
tabetha

 

ok,tonight i gapped the phase sensor which was touching the cams,that made it better,it can now take 0.9 psi of boost(thats what it peaks at in 4th gear floored from 30 mph)but it still loses power and clunks and bangs.i changed the coil,map sensor and 3 of the leads.all of which made no differance.all boost hoses are nice and tight so i dont think thees a massive air leak.all timing marks are bang on.what is the problem caused by the rev counter?can that make it misfire?

 

what plugs you got fitted?what gap are they set too??

 

no idea yet,they are the plugs that have been in it since he got it 4 weeks ago,when it happens it feels like a total loss of spark to the engine,its not like it loses 1 cylinder .