dscottp

98 GS300, totally stock, runs smooth for about a minute then begins to misfire. Seems to be consistant with cylinder three as it is steady and pulling the harness off of the Cyl three injector doesen't seem to affect it.
Code reader is pulling up P0303, Cyl three misfire


I replaced the plugs about 300 miles ago with Denso Iridiums and it has run fine since (until now).

I am going to dive into it tomorrow but have a couple of questions for the experts.

If the coil packs each drive two plugs, wouldn't a failure of the coil kill two cylinders?

Is there an on car way to check injectors? I will meter for resistance but am not keen on taking off the fuel rail for fear of leaks when I put it back. (do the old o-rings hold up)?

Anyone ever had a new spark plug fail shortly after install?

If there is no test port on the fuel rail, is there a way to test fuel presure elswhere?

Any thoughts/ideas are very welcome

Thanks to all!

GS4_Fiend

iTrader: (22)

check the number 3: spark plug, injector, the wire and the coil. If all those works, the you got a compression problem for cylinder 3.