strange idle and miss fire problem

[Coxeh]

i brought a prefacelift S13 of ebay a couple of months ago, and ive been having a couple of problems with it. The first problem is its idle. From cold its fine starts first time and the car revs to about 1500rpm which is normal. Once it settles down to about 900ish the car seems to be slightly miss fire firing occasionally causing the car to shake a little bit however that may be normal i don't know. However im confused to why it gets noticeably worse the longer i drive it. It seems to idle really bad after a "spirited run".

My second problem is sometimes it starts on 3 cylinders. but after about 20-30 seconds it then starts to go on 4. I have tracked it down the the no 2 cylinder (counting from the cam belt). I have swapped coil packs and checked the dropping resistor which is fine. I have also done a compression test which show ~150psi on the 3 cylinders but its around ~140ish psi on the forth. would the difference in the compression cause the car to "shake".

does anyone have any ideas??

[shortcut]

do the hot start bypass and change your plugs? My head gasket failed on pot 4 and gave these sort of symptons, also clean the afm

[cs200sx]

****ed up lambda probe?

[shortcut]

lambda not normally fitted on a prefacelift

[Coxeh]

Thanks for your comments,

i will look into the hot start bypass but things seem to be getting worse it now running on 3 all the time now .

i have swapped plugs, coil packs and injectors from a firing cylinder to the one thats not but nothing has cured it. i have also done a compression test again and thats still the same.

how do i check for a spark do i just pull the plug out and stick it into the coil pack ? Also i don't have a lambda sensor

[chrishkm]

are the plugs gapped?

i had a miss fire and the harder i drove the worse it was, took the gap down to .6 and it cured it straight away, prity simple but worth a try

[sxsxsx]

remove the spark plug put it in the coil pack wrap a good lenth of wire around the threads of the spark plug and earth that wire then turn the car over see how strong the spark is...i had a doggy power transistor which made it weak...

[Coxeh]

remove the spark plug put it in the coil pack wrap a good lenth of wire around the threads of the spark plug and earth that wire then turn the car over see how strong the spark is...i had a doggy power transistor which made it weak...

Just tested the spark and its not got a spark on no2 , so does this mean a new power transistor or dropping resistor?

[sxsxsx]

chech the plugs on the power transistor its on the suspension turret accross from the turbo, mine were dry and looked like they had a little corrosion from years of damp...

is it getting fuel or flooding that cylinder

also recheck all wiring