Multiple misfire on 2litre inline six

[The Wexican]

Hi there , My inline six has developed a multiple misfire problem on cylinders 1,2,and 3. This fault is random. Sometimes it is a rough idle upon start up from cold and sometimes when running. This was confirmed by having the car diagnosed and plugged in for diagnosis. The car year is a 1999 model and was originally sold in Japan. Has anybody any id as to where I might check to solve this problem?
Thanks,
Mike.

 

[Althulas]

You could swap the coils around to 4,5&6 and see if the problem then is produced on those cylinders to rule out the coils. Maybe changing the plugs first if they have not been done. Also check all the rubber hoses have not deteriorated a cheap start. What codes were produced?

 

[The Wexican]

The codes were P0300 Random/Multiple cylinder misfire detected. And
P0173 Fuel Trim Bank 2
P0170. Fuel trim Bank 1

 

[The Wexican]

Also P0301, P0302, P0303 all misfires on the relevant cylinder. What are the hoses that are you talking of? Thanks, Mike.

 

[Althulas]

The vacuum hoses, definitely can cause this problem to much air causing a weak mixture also faulty fuel regulator can cause this and a rich mixture plus on the other hand leaky fuel injectors can cause a rich fuel mixture.

I would start with the cheapest things before throwing parts at it. Do a visual inspection of the all the vacuum hoses and a smoke test. If you look on YouTube how to make one or use a bought one. Hopefully someone more experienced can chip in some advice @Pingu @Lee also handy if you have your own code reader pays for itself in a few uses.

 

[Oddly Godly]

As above but check plugs and visual inspect the coils. Sometimes you can get oil from a leaky gasket in the plug holes