the hamster

iTrader: (7)

Had a replacement engine fitted this weekend and the car drove fine on the way home (MY00 classic, standard engine, vf35, fmic, walbro).

Came home in it and it drove perfect then 30 mins later went out in it again. After a short drive up the road it developed a loud pop/misfire over around 2500rpm so I pulled over.

The car idles fine but if you blip the throttle in neutral it pops after a certain rpm, around 2500. When you're driving, the pop feels like a misfire/twitch so the car will only drive very slowly/short shifting.

Any ideas? It feels ignition based like a plug or lead but nothing looks loose under there. The plugs are the ones from my old engine that we swapped over. No warning lights on the dash.

Any advice/help is appreciated

the hamster

iTrader: (7)

forgot to say, the replacement engine didnt come with an inlet manifold etc so this was swapped over from my original engine.

lazscooby

iTrader: (2)

im no expert but might be worth checking the fuel pressure regulator? I had similar symptoms with my99 a few years back

the hamster

iTrader: (7)

Thanks chap.

Update : it only does it when its hot. Left the car for an hour and went out to it, started and idled fine and revved to 4k without a pop/twitch.

Whats the chances of this being coilpack/plugs/leads and whats the best way to test it?

ukpaisley

iTrader: (4)

Mixture problem, as the car runs rich when cold, normal pop is running lean. MAF , air leak, An electrical problem like plugs coils dont manifest themselves like that unless its causes a complete electrical short.

the hamster

iTrader: (7)

is it something thats likely to be able to be cured by Zen? I have it booked for a remap on Friday but dont want to drive it an hour to get there if its a waste of time.

I'm suprised it would run lean at such low rpms.

I've heard of coilpacks/leads breaking down due to heat, it was a common problem on Mazda's that I used to modify.

ukpaisley

iTrader: (4)

My coils or plugs have gone, mine will pull under part throttle up the fevs, but I I put my foot down the spark blows out, this causes a miss, but the revs still rise as this happens. if it stops dead then you dont have any fuel, or too much, aka boost problem.

the hamster

iTrader: (7)

It doesnt stop dead and it doesnt have boost problems.

Like I said, it drives ok when cold but when it warms up it gets to a certain rpm then misfires/pops loudly and the car twitches. It does it even if i'm not making boost.

Im not sure if I need to physically check things under the bonnet or if its going to be a map fix??

Turbotits

iTrader: (2)

Sounds like a vacum pipe has fallen off or split and its pulling in unmetred air

the hamster

iTrader: (7)

If a vac pipe had come off surely it would run rough all the time, not just when its hot?

Can someone give me an idea of what physical checks to do before I hand my wallet over to the Impreza pixies who'll make the contents magically disappear?