Backfiring

[Stephie]

Hey all,

I have got a Jap import Toyota Celica GT-R 4WS.

I was wondering if anyone would be able to help with my problem that comes and goes like the wind!

We have just had a stainless exhaust put on the car as the garage told us where there was a whole in the previous one there was no back pressure and the ecu shut the car down. So after picking the car up it ran like a dream for 2 days and then whenever revved between 5000-7000rpm it backfires and the rev guage goes crazy. So fiddled about with the fires changed coils, leads etc and loads of electrics and ran fine again. Drove the car 60 odd miles on motorways with a slight misfire here and there when coming in to roundabouts at low speeds mainly. Then just outside my house again on a roundabout and the car backfires and cuts out twice in space of 5 secs.

When you start the car it runs perfect and at a good speed it runs good but when you have been out for a little while and start to run the car slowly around the city, traffic lights etc it just backfires and you really have to rev it to get it to move anywhere which obviously isn't good for it.

Problem is had AA out twice this weekend, first time they said one of the ignition leads wasn't in properly which wasn't the case as it did it again the following day and the guy was on it for 1 1/2 hours and couldnt come up with any real problem. Been to a garage who have also said nothing is wrong with it.

Now cal me stupid but is it that I'm using 95Ron fuel on an imported car? or what could my problem be??

Help!

[GT4 BOOSTER]

its listed as needing premium fuel - ie - superunleaded. could need a new dizzy cap,rotor,spark plug or lead , get some super in its tank and have it analysed by a tune place.

[samsite999]

i don't think the fual is helping, but i would of thought it would be a lot more consistent than it is. saying that the ecu could be retarding the timing to suck a extent to cause backfiring with bad fual....i think...actually thats more than likely crap. some one check that out for me

[japracer]

fuel isn't the problem as i've got an import ant it dosn't effect it, also if it was the fuel it would pink rarther than missfire, so the problem could lie with the fuel system itself, so the first thing to do is to change the fuel filter, if that doesn't fix it get a pressure guage on the fuel system and check what pressure the fuel system is running at, if its low that would either be the fuel pump or the fuel pressure regulator, as on my honda I had a adjutable reg and was play with the different pressure and low pressure does what you described, hope this helps