my cosworth has a missfire under load, its fine on idle & when driveing it normally but assoon as u give it sum welly & the turbo is about 2 launch you it holds back & misssfires, sounds asif it drops a plug or sumthin

i have cleaned all plugs & cap up but still no good & the car is no fun lol

sum1 mentioned phase sensor??????
any idears?

 

When mine did this, twas the plug leads.

 

i had that prob it was my plugs .what plugs u running

 

mine used to do that also and that was the plug leads too

 

will try a set of leads on it 2morra & maybe plugs/cap & rota arm

just seems like sumthins breaking down under load

 

it could be leaning out

 

Plugs mate, mine does the same and its always plugs every time

 

mine did this and it was ign coil - changed to a grp a and prob solved

 

So basically could be any of the above

As said what plugs and gap u running?! Failing that just try and borrow things to try before going out and buying bits u dont need!

 

it can be so meany things mate iv had a nuth of my car doing this so my car is going in to REYLAND to be sorted . the list of stuff it can be

plugs
plug gap
ht leads
fuel reg
fuel pump
fuel fillter
fuel pressure
fuel pump volts
phaz + gap
map sencer
tps + it setting
to much boost on the turbo for the chip
pipes on amal valve not right
blue tep sencer

Hope some of this might help you mate

 

A mate on mines was doing this and it was the alternator

 

thats a new one on my but it could be right

 

Mine was crank position sensor. But it could also be anything listed above.

Replace plugs, phase sensor and crank sensor in that order, as I'd say they're most likely

 

Had the exact same problem.
Rolling roaded on Friday..........plug leads arking off the inlet under load.
Would never have found the problem if it wasnt on the rollers.

Insulate temporary with something to stop the spark jumping, and take it a short run. If it works, problem found. If it doesnt, back to the drawing board.

Its free, so worth a try.

 

fuel filter ... commonly overlooked ... gets clogged up ... less fuel .. no power ...

 

Start with the cheapest thing to check first...

Close the plug gaps to 0.5mm to see if that improves things....

 

quote=rosie;4807494]my cosworth has a missfire under load, its fine on idle & when driveing it normally but assoon as u give it sum welly & the turbo is about 2 launch you it holds back & misssfires, sounds asif it drops a plug or sumthin

i have cleaned all plugs & cap up but still no good & the car is no fun lol

sum1 mentioned phase sensor??????
any idears?[/quote]
i had this problem took it to MSD it was coil they fitted group A item was a different car after

 

car allready has a grp a coil fitted but will try swapping a few bits over 2day & see what happens

i just didnt want 2 spent £££££££££££ replacing bits that arnt needed but spose its a case of trial & error

 

rosie,
please take my advice above before you waste money on changing things that are not needed.... simple and cheap to check... and the most common cause of cossie missfire problems

Chances are the plugs just need changing !

(they may look clean but the internal resistor still wears out)

 

Spark plugs...everytime i had a misfire plugs always cured it....use 071's avalible from R&B Motorsport...about £15 a set i think

 

Bloody Cosworths. Mine did this when it was hot and we never tracked down the problem. Instead I went for a new loom, new ECU, new fuel system, new shell. Hoping the problem is fixed now

Charlie

 

turned the boost down 2day & its sorted it

i had turned the boost up on the car as it was only running 3psi on stg 3 mods but the car doesnt have a boost gauge fitted so just guessed it. but it didnt feel like it was running too much boost?

will put a gauge in 2morra & try set it as 20psi & then go get fueling set up

will the fuel pressure need turning up?? as my fpr grub screw looks knackerd & dont think it can be adjusted or is this done on the ecu screw?

car doesnt pink but seems really flat & no major kick when the turbo is cutting in as cars still on std 15's so should be abit arse happy, doesnt even lite the wheels up on boost in 2nd & seems flat to rev aswell

 

You just guessed it!?

Lucky you still have an engine mate!

 

Just get the whole car set up on a dyno.

 

u wound ur boost up without a gauge?! jesus u were lucky u didnt melt something lol, who's gonna set the fueling up for u?! Wouldnt bother setting the boost up to 20psi, thats something that needs doing when the rest is being done really!!

The regulator adjustment is done at that grub screw, im guessing if u can see the screw then someone has messed about with it in the past so really u need to fit a pressure gauge onto it so u can see what its currently running and adjust it so its right, if it needs changing oviiously!!! The ecu screw just affects the emissions side of things so dont touch that!!

 

yer i just guessed the boost but dont think it was that high , car didnt pink atall

yer will try free off grub screw & get it set up as said b4 its really flat & no boost spike

 

wouldnt bother touching the grub screw unless u have a fuel pressure gauge to set the pressure properly...............

 

As been said above, get it on a dyno and set up properly by the pro's.
Just guessing and fuckin' about with things has "CARNAGE" written all over it.