Hi All!!

My 2004 R50 started running on 3 cylinders so I:

Kept the motor running and started unplugging the spark plug wires until I found that it was the #4 cylinder that wasn't firing.

I swapped the #3 and #4 wires at the spark plug and and coil pack end and it was still the #4 cylinder so i know my wire is good.

I swapped the #3 Spark plug with the #4 spark plug and still #4 not firing so I know its not the spark plug.

If the Coil pack was the issue then I believe that the #1 cylinder should be failing as well as both #1 and #4 cylinders are fed from the same bank of the Coil pack ( feel free to correct me if im wrong in assuming that )

So the only other part I can think is the injector.

I have not worked on injectors before, so is there any way I can confirm that the #4 is bad? I was thinking of swapping #3 and #4 injectors but it seems like the whole intake and fuel rail needs to be dissembled for that, and im worried I might be getting in over my head doing that work. Unless one of you have done it before and can provide instructions.

Any suggestions you may have???

I appreciate any input that you provide.

Have a great day!

 

I don't have any insight on changing the fuel injectors around but I do think that it's not too hard to check the pressure at the fuel rail. might save you some irritation.

Also I would pull the fourth plug out of the cylinder and plug it into the wire, ground it against motor, and crank the motor to see for sure that you're getting a spark. Then you'll know for sure that it's not a spark problem and you can go down the fuel problem road.

 

Before you dissemble everything...do a compression check...as easy as doing a sparkplug change...
Fuel injectors corrode...the o-ring get hard...getting it apart will be a pain, and you might need to replace them, even if good cause you break them getting them out...
Compression check will rule in/out a valve and or ring issue...
If compression is low...then you usually have a burnt valve from low octane fuel.....actually pretty common since the gen1 cars REQUIRE 90+(might be 91 I forget) octane and many run 87....

 

P.S.
YANKING the whole fuel rail on the r53 was pretty easy...a few bolts...bet the r53 is very similar...
Think I did the injector swap when I did it in under an hour on a cold motor...
But if you do it, buy new o-ring BEFORE you start...

 

thanks for the info guys! ill look into it all.

Any other comments will be appreciated.

 

Nice to see someone actually doing a diagnosis instead of just throwing parts at the car. Zippy is totally right, for sure check compression and try swapping the injectors. A dead cylinder will definitely give you misfires.