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misfire issue
beaver34 - 21/4/13 at 01:57 PM

hi all,

i have a misfire issue on my engine, car has just been mapped with no issues afr are good.

went out yesterday dropped onto 3 i nipped back home changed the plugs over and it cleared it.

back out fine for 15miles then dropped onto 3 again

its fouling no.4 cylinder ever time,

what do i need to be looking into further? all leads sparking fine

its a 1.6 for sigma engine that ive turbo charged running ngk bcr8es plugs

thanks

britishtrident - 21/4/13 at 02:05 PM

Any differences in the appearance of the plugs ?

beaver34 - 21/4/13 at 02:25 PM

yes the misfire plug is black and fuel covered,

if an injector fails does it operate at full power al shutdown and supply no fuel?

dave_424 - 21/4/13 at 02:37 PM

It can do either, but the more common is it to stick wide open. Check your fuel pressure as soon as the ignition is switched off, if fuel pressure drops like a rock and you have a check valve in the fuel system then an injector is sticking open.

Also get a multimeter on the injector terminals and see what ohms it reads.

beaver34 - 21/4/13 at 03:55 PM

Don't have anyway of checking fuel pressure at moment

Am I looked to check the ohms on each plug when engine is running presume them should be the same

perksy - 21/4/13 at 05:38 PM

Disconnect the electrical plugs from the injectors
Compare the resistance values on the injectors that are ok to the one that your having trouble with.
You don't need the the ignition on or the engine running to do this as you are only measuring the resistance of the individual injectors. (probe the injector terminals, NOT the connectors)
*If* the resistance values are ok for the injectors then noid lights plugged into the injector connector/s from the ECU will help show if its an injector firing issue caused by the connector/s or wiring from the ECU or even possibly the ECU itself.

beaver34 - 21/4/13 at 06:32 PM

quote:
Originally posted by perksy
Disconnect the electrical plugs from the injectors
Compare the resistance values on the injectors that are ok to the one that your having trouble with.
You don't need the the ignition on or the engine running to do this as you are only measuring the resistance of the individual injectors. (probe the injector terminals, NOT the connectors)
*If* the resistance values are ok for the injectors then noid lights plugged into the injector connector/s from the ECU will help show if its an injector firing issue caused by the connector/s or wiring from the ECU or even possibly the ECU itself.


thanks,

just tested and the cylinder with the flooding resistance is not stable its bouncing all over the place from high to low high to low the other 3 stay stable

going to try another tester on there as the end of that is broken and its hard to make sure it not my hand shaking effecting the connection

beaver34 - 21/4/13 at 07:39 PM

Tested again there all the same resistance

Is it worth buying a noid light kit?

Paul Turner - 22/4/13 at 10:30 AM

Why not swap a couple of the injectors over. If the problem moves with the injector it proves its a faulty injector.

beaver34 - 11/5/13 at 05:15 PM

still need some thoughts regarding this

swapped out injectors, its not fuel its oil ive further found out

compression test hot and cold all good

stripped engine today so i could see inlet and exhaust valves

its exhaust valve related

here is no.3 and no.4





if compression is good, what can further be at fault valve stem seals?

thanks

rusty nuts - 11/5/13 at 05:42 PM

Compressions can be good with valves that don't fully seat, the best way to check is a cylinder leakage check. I once had an escort that failed MOT due to high HC , compressions had been checked several times but a leakdown test showed an exhaust valve fault

beaver34 - 11/5/13 at 06:35 PM

Ok will look into that,

Although its a new engine build everthing rods pistons valves etc....