What's technically a missfire, and what causes them please??

[Tom]

Ahh... lots of info you failed to mention

nicos car isn't lacking power. Infact I think he has too much now

Peak power on a 155HGT is under 6k, but 80 at the wheels is rather low.

Engines can missfire when cold cos they are cold. Simple as that. The combustion process doesn't work as well when its cold, the compression is usually lower as all the metal parts have not expanded to the right size, spark plugs don't spark as well, valves don't quite seat right, the oil is VERY thick and causes drag, lots of fuel has to be added to make it run and this can foul plugs making them stop sparking for a few revolutions etc etc etc..

Engines like to run at ~85-88degC, not 10degC.

When you add cams with longer duration and longer overlap the problems are compounded at cold idle as the compression will be even lower.

 

[Anonymous]

Mine has never misfired before.

It really misfires. It sound like gun shots coming out of the exhaust.

I know engines dont like cold but an engine should never misfire if running normally.

 

[Tom]

A cold engine is not running normally. Thats why the ECU has a cold start enrichment and proper cars have chokes

If it bangs out the exhaust thats a backfire. Can be an indication the timing is screwed. Also quite an important factor when diagnosing faults.

A missfire is when the engine skips a beat.

 

[Ash]

if it is a 155 and the timing is out u will need a new variator its quite common that they go wrong

Im Driven to Earn, and I Earn to Drive......

 

[Hi Guys]

So what's a MAF sensor do anyhoo?

I do rather doubt it could be at fault in this instance, cos as Tom notes, power shortages at pace arn't really a problem/symptom

My limiter is set at 7 by the way anon.
Listening to that engine rack it up to 7K whilst being stood next to it on the rollers is jurrrst unforgetable I highly recommend it. You'll be walking round in a daze for days!!

I do still have a rattle of sorts that bugs me.
I can't actually hear it unless I've got the hood up, but I do still have a very high frequency rattlenake ticking coming from those air control bits between the inlet manifold and throttle body. I had a problem with idling before the cams and chip and it became chronic when this ticking got loud once (so loud I could hear it inside). The tuning shop said they gave the throttle body a good clean out, but something still dosn't sound like it's quite right. Bit like ....air flow being obstructed perhaps. i might try taking it to bits if I had confidendce I wasn't guna mess anything up. There's some sort of a butterfly valve in there isn't there?

Ash is right about the variator. They don't don't have an infinate lifespan, and again they are crucial for sustaining good power (nico pretends he knows what he's really talking about ). Managed to pretty much eliminate this as a potential suspect with my prob though, cos of noise being localised to air feed area.

 

[Tom]

MAF - Mass Air Flow. Its the airflow sensor. Tells the ECU how much fuel to add.

You will always get noise from the induction system, you're hearing the valves closing!