i have an annoying mis-fire/spitting back through intake manifold problem.i have replaced all 6 coil packs,plugs,air flow meter and o2 sensors.i have even checked cam and vanos timing twice.when i purchased this vehicle it had swallowed water bending no4 rod so i put a new (gen) rod and piston in but i cannot get rid of this fault.fuel consumption is pretty poor too,but when driving the car hard and flat out this problem doesnt seem to occur.any advice/help would be greatly appreciated

Have you compression tested it?

compression is fine. wet and dry.even performed a leak down test which checks out fine.it has now even started to idle poorly when it comes off cold start.icv is also working fine too.and yet again no fault codes stored.also noticed today cats have started to rattle so analysed co and that is at nearly 9%.i will change the cats this week.has anyone had a problem with the air temp sensor(in the inlet manifold) causing a problem,i will change it anyway.again any info greatly appreciated

When the engine was reassembled, were the BMW special tools used to time the Vanos and cams? What you are seeing is consistent with mistimed cams and if the special tools weren't used it is very likely that the cam timing is off.

yep all proper tools used even bought a 1/4" drive torque wrench to measure 1.3nm to tension main timing chain.only other theory i have is the DME is at fault.hence why i am getting no stored codes.thanx for reply

i have used the pelican guide to time the cams and install the vanos unit

yep all proper tools used even bought a 1/4" drive torque wrench to measure 1.3nm to tension main timing chain
That doesn't tell me whether you have the set of BMW special tools for the cams and Vanos. The only way to be certain of correctly timing everything is with the use of the special tools and following BMW's procedure (in the TIS or Bentley manual).

camshaft locking blocks,crank locking pin,main chain tensioning tool and vanos engagement wrench.this timing set is made by FRANKLIN which i have used before without a problem.is the BENTLY guide the one to follow.thanks again for reply