just brought my new impreza 555 sti and drove it back about 230 miles and seemed fine apart from what feels like a slight missfire the car pulls well but as i say very slight but definatly there was going to check the plugs tomoz and see if there bad 1 also maybe coilpacks are there any other ideas people pls. hoping its not a valve so fingers crossed. also what the easiest way to change the plugs any help/advice would be much appriciated and thanks in advance

 

if its multi coil pack type then obviously get them out the way first and then you'll need a 2" extension with the plug socket on and get that positioned on top of the plug inside the head first and then attach your rachet and undo,once loose enough to move by finger take off the rachet and undo the last few threads by hand and remove.
It's abit tight between the chassis legs but it not to bad as long you take your time,its easiest off your back with the under tray off get the car jacked up on the side your working on.

 

thanks for that was gonna try the plugs first as the cheapest option what plugs should i fit ??? as used to run some really cheap plugs on my evo and ran as good as any others also could change them every month for the price????

 

its easy to change the plugs from above, if you've got an induction kit fitted the offside 2 are easy and for the nearside just remove the washer bottle and you'll have enough space to get to them, plug wise pfr6b or pfr7b are the ones to use

 

i just find it easiest from below because you havent the worry of slipping with spanners and catching any wireing and the like,its a nice straight pull with nout in the way from below each to there own though
+1 on the plugs NGK

 

not a cheap plug. that will cost you £45 a month plus fitting. you need serious psychiatric help

 

my plugs i used in my evo were used by some well respected tuners in the evo circle and were run on cars running around 600 bhp so im not convinced about the you get what you pay for story i will look into this befor buying anything personally but welcome opinions/advice

 

as others have said, also if your car has the coil on plug type of coil pack then you must inspect them before you refit, to inspect them take the rubber boot off and inspect the end of the coil packs for cracks, which are obvious, or less obvious very faint hairline cracks which could cause your miss fire.

 

aye-i was wondering if there was a plug to use on the scoobies similar to the ngk cheapies that can be used in the evos-i used them myself at 500bhp on a s205 powered evo without issue...anybody shed light on this?

 

Mine once developed a misfire after a service. It took ages to diagnose and eventually it turned out to be a duff/knackered plug LEAD, probably caused at the service.

 

dropped car of tonight at garage for mot and general birthday just hoping not a valve causing the missfire but car looks well clean underneath so thats good also while under the car noticed that the 3" downpipe narrows quite alot just befor it meets the rear part of exhaust does this need sorting to make it a true 3" or not worth worrying about unless going for massive power ?