PF Guru's...help!! Misfire!!
 

Hi all,

I have a mid-range misfire (worse under heavier load) and just can't seem to get rid... :wall:

Cars a 4x4 saph by the way. It was running standard leads and coil so i replaced with motorsport and grp A items, inc. uprated spark plugs. This seemed to slightly improve the misfire but still really bad under load. What would be the logical sequence by process of elimination??

Thanks guy's :?

Chris

Does the car also misfire when revved without load (parked)?
When yes, I suspect a mixture problem. Measure exhaust gasses with a 4-gas analyzer.

Hey oldford,

It doesn't misfire when revved parked up; it's nice and smooth... :?

CheeRS, Chris

Clean the multiplugs on the bulkhead above the rockercover with some electrical contact cleaner

how longs it bin like this, and have ya bin dring it in heavy rain

Thanks timster, i'll give that a go! :top:

gingerturbo, it's prob been like it for abt a month and never go out in heavy rain if any rain at all :oops:...

CheeRS, Chris

its only what timster mentioned and it reminded me what my m8 2wd saff used to suffer with was water(rain) getting in the vents and making it cof and splutter

Identical problem to mine..:sad: And I don't have the multiplugs on the bulkhead anymore.

Honestly, there are only 3 things that haven't been changed on it...:oops: Must be getting close though..(I hope)
Fuel pump.
Dizzy.
Throttle switch.

wow how strange, what dizzy have ya got on it cos i hade someone come into halfords last year to get a dizzy from us and i went outside when he fitted it and it didnt run right so it might be that, and you say its only when your boosing, i dunno if it could be fuel starvation under load

Have you checked the phase sensor on it?

+ 1 and new plugs too????

this is baffling me, im going to loose sleep over this, what colour are the tips of the spark plugs

not realy sure on cosworths but just an idea does it have an ignition amp i no some do maby ur problem ???

Again, maybe different on escort turbo, but I had exactly same problem - changed plugs, leads, dizzy, rotor arm, injectors, fuel pump, ecu and accumulator.... NO GOOD! It turned out that a valve was not seating properly.... :roll:
Check compression and see how she is. Eliminates any engine faults then.

Phase sensor won't cause this, it's is only needed when starting, how old is the fuel filter, is the CO correct for the chip, have you rewired the fuel pump ?
tabetha

I never knew that Tabs :D

My Sapph had an annoying miss on it very similar to this chaps and after I tried new plugs, leads, cap, arm and coil I got fed up and put in my spare dizzy with new phase sensor in it and at the same time replaced my crank sensor. Incidentally it cured it and about a week later it cut out and wouldnt start again. A bit of investigation discovered a lug had come off the crank pulley, my only guess is that it was possibly hanging off and losing its pickup a bit on the old sensor but the new one was better so made it run ok until the lug flew off???

Might be worth the lad checking his crank sensor out.

uprated plugs ponder what type ? iridium some users have probs with them ??

Hello chris. Sorry to have jumped in on your thread, similar issues that we're havin. Can I just ask, how old is your fuel pump? Just been looking at some other posts. Apparently when some of the focus' suffer with a similar symptom, it's down to the pump and it's common. I know mine isn't new.

Have to say I'm starting to lean towards fuel starvation now. I'm 99% sure all sensors, gaps and supply voltages are good. Plus, hard to explain the sound it makes, but it isn't like a 'normal' misfire. Doesn't pop and bang, more like a kind of harsh buzzing when it does it, and obviously loads of vibration and loss of power. Does anyone recognise the sound I'm badly describing?

i hade same,changed eveything still the same.all it was in the end was plug gaps

That's harsh. Still, at least you know then that everything's mint in all the other area's now. :cry I've got mine,071c's, gapped at 0.7mm with a grpA coil. That sound right to you?

Hi Guy's thanks for all the tips and advice...

I think i'm going to change the crank sensor as it does look a bit worse for wear, even if it isn't that prob worth doing for future safeguarding.

Captain Cotswold - No probs m8, i hope you sort your misfire too!! I'm not sure how old the fuel pump is as was already on when i bought the car. It's got Siemens 55lb injectors, not sure if that makes any difference, i.e. needing more fuel?

CheeRS again chaps,

Chris

Hi tabetha,

What do you mean by rewire the fuel pump m8? Renew? Uprate?

Chris

Captain Cotswold.... Do you have a Halfords trade card or know someone with one? If so go and get NGK BCR8ES plugs and gap them to 0.6mm just to try them. The plugs are less than a fiver on trade ;)

Had bother with 071's in the past and I always use the cheapy NGK's gapped at 0.58 now and get no bother. I run greys and 34psi on a T34.63.

do ya want my trade card number pm me if ya do

i recall having problems on a r5gtt which use to misfire under load and jolt back now and again and that was the fuel filter, i take it your pumps a 044

Hello mate,
Yes, It's gapped at .22 and is new and clean.
Thanks for the tip on the spark plugs too, when I up the power, I'll be getting myself some of those based on your experience.

Slow ass reply mate, sorry about that.:oops:
And, thanks very much for the offer of the use of your trade card. Much appreciated but not needed. Have some good connections for bits and bobs;-)

Chris,
Might be a long shot for you. Hopefully you're a bit more thorough than I.
Check your dizzy cap.
I replaced mine for a new one about a year or so ago (only done about 3000 miles on it) Long story short, stripped my bay out to change throttle sensor. Had a clearer view of cap, noticed full on crack across top. Misfire solved. Funny really, but the noise it was making when it did it was very harsh and buzzy, I don't know like a factory bar coder or something like AN ELECTRICAL DISHARGE of some kind. What an idiot. Still, I had a lumpy idle misfire late last year along with the under load misfire, and that was down to the loom and the bulkhead plugs, therefore making me feel better for the ball ache that was building a loom.:roll:

Hello mate,
Sorry to hear of your valve problem mate. :sad: I really didn't want to even consider this being the problem as a head-off-on-the-drive cossie with this weather isn't my cup of tea, fortunately though, I'm just a bit slow. I had a cracked cap:wall:
Cheers for putting the fear into me though:cry: hehe

Hi guys,

Just thought i would post the solution to my misfire problem i was on about earlier in the year! Turned out to be Turbo Surge!! Something i was aware of but have never experienced!

Thanks for all your help anyways. :top:

Cheers, Chris