How do I adjust the fuel mix?

[peterch]

HI,
I have a bit of a problem with the car misfiring. It doesn\'t do it when the engine is warmed up and has been running at reasonable revs (3,500+), but if I have been driving at low revs for a while, or when the engine is cold, I get a misfire as I take my foot off to go down the gears. Also if I have had a slow drive, then when I start the car after it has been left for more than a couple of hours then I get a back fire.
 Do you think the fuel mix needs adjusting, and if so how do I do it?

[rx7veilside]

only aftermarket ecus can have the fuel altered as far as i know..with things like this it really is best left to the experts depending on ur location,,re worx portsmouth/carl at hayward rotary reading/wgtnorwich i think.backfiring is normally unburnt fuel being ignited while in the exhaust

[Martiny]

My car is standard and does exactly the same thing.

I thought backfiring was a FEATURE and not a problem!  ( Another reason to drive a Rotary!)

[rx7veilside]

no backfiring is not a feature merely an incorrect fuel mixture..lots of scooby owners with a link ecu would adjust the fuelling to show flames out the back and then correct in when not showing off:)

[peterch]

Thanks,
 Its only done it since the engine rebuild, so I think I better take it back to be checked out..

[Martiny]

Right, so the Le Mans winning Mazda was not running properly?

[peterch]

could it be the fuel i\'m using, can\'t always get optimax, but just filled up on it today and it is 90% better?

[rx7veilside]

the le mans is slightly different kettle of fish as the ecu on that would not have to worry about overfuelling etc but a well set up road car will not backfire unless it is blowing unburnt fuel out the exhaust mine is running 420bhp and does not backfire as it has been mapped well with the apexi.it is easy to get flames and bangs and pops just decat add blow off valve alter ecu to add more fuel and it will pop bang and give 20ft flames but u will only get about 2mpg

[zevans]

Originally posted by Martiny
Right, so the Le Mans winning Mazda was not running properly?

If we define "properly" as "streetable and would pass an MOT" then... no.