Hello All

What are the main causes of missfires??

I have not long had the car setup at MSD and its been absolutely fine but in the last week ive had 2 missfires, 1 big one! in 2nd gear at good boost and a slight one last night in 5th using the torque of the car on the motorway to overtake. The one on Saturday i sensed was coming as for some reason the car felt like it had much more power than normal....the temperature was much much cooler than when it was setup...could it be this??? I have replaced both of the coil packs almost 2 years ago (4500 miles) as i was advised to because not knowing if they had been done before. I removed the plugs last weekend (pp8) and cleaned them all up and checked gaps which were fine (0.7mm) only thing ive not replaced is plug leads. But could it be something else ive missed. Ive checked all the boost hoses which are ok and the amal valve connections and pipes are all ok too.

Its so intermittent that i hope its not going to be to difficult to track down the fault.
Hope you may be able to help me

Mart

 

Its that wanky dump valve mate

Ok, you say "the temperature was much much cooler than when it was setup.." ... outside ambient temps or car water temp?

Water temp sensor breakdown can cause misfires, but tends to be rough start up and crap warming up cycle.

did the rev counter jump around with the misfires, any flames out the back etc? Was it a "fuzzy" misfire, as in still firing on 2 or 3 cyls, or was it a hard "bang" with popping flames/ like hitting a brickwall miss?

Worth checking your quick disconnect multiplugs on the right side of the engine bay just behind the headlight. They corrode and get full of water and cause big misfires as the engine moves and wiggles the cables.

Any unusual smell of fuel?

 

Follow me up to MSD on Saturday mucker, see if they will take a quick look

 

could be as simple as a bad plug, whip em out and give them aonce over martin, try not to drive through them,

or ka bang, teeth missing in your gearbox

 

The outside temperature was very cool mate. Rev counter didnt jump at all, no flames either it was going along really well with the front end lifting under acceleration and then dipping back down again really really quick as if id hit a limiter ,it hurt my chest as i went forward thats how big it was . Ive checked the multiplugs and have a nice shiny cover over them keeping them dry. No smell of fuel whatsoever

AJC: did that last weekend mate and they were all fine, i backed off immediately mate as it fuckin scared me TBH.

 

Did you have much fuel in the car?

Its a problem with them when under 1/4 full that you will get misfires.

 

you need a quaife mate

 

No mate, wednesday nights was a full tank

AJC: funds deprive me of one of them mate

 

i had nothing but small problems on ST thats why i went balls out autronic now i just have a sodding driveshaft issue which noone has any idea why its doing it bloody cars...

so basically go get some hardcore manangement you know it makes sense!

 

Ok then mate, Outside air temp makes a big difference to performance, If it was cold you will have felt the car being "faster", as the air is much more dense and will give slightly better power. What boost is it running? As On my small turbo, I had problems last year as in the daytime it was fine (remember the heatwave?!) , but at night it would overboost slightly, and do exactly what you said, like hitting a brick wall. Does the car stop boosting fully after that? I used to have to turn my car off and on again to clear the overboost from the ECU.

I know it has just been set up, but was it a hot day when it was?

Another thing to check is the security of the Chip module into the back of the ECU, ( passenger side footwell behind the fuel cut off Kick panel, again, I had an MSD chip module that had been in the car for some time, and over time had worn the ECU contacts away a bit, and would cause misfires as it made and broke contacts.... Way to sort that is to re-solder the ECU contacts on the board to make them a bit thicker, as Stu checked the module and replaced my chip contacts for free (even though the chip was two owners old ,) , but the problem seemed to be the ECU contacts as it did it again afterwards

 

Its running about 20-22psi it goes off the centre pod anyway since MSD set it up and put a new one of their chips in a month ago. The car boosted fine after that and many times too it was 14 degrees when it missed as i checked the temp out of curiosity as i left my house. When set up it was 20 odd easily during our summer so far

Anyway spoke to Kenny today who has suggested going to the AGPP12R plugs and possibly changing the coil packs. Will start with the cheaper of the 2 and see how it goes for a while. Weird though as the PP8 that are in are fine.

By the way............whats a heat wave,cant remember one in the last 4 weeks

 

when you start to change eveything i have a brand new AFM you can buy

 

Remember the heatwave LAST year? , thats what I am talking about