Misfire

[robert eckersall]

Recently my 2011 a3 8p lost power and engine shaking when on idle. Rac tested it and said it showed misfire on injector 4 and it was loom damage. When it went to the garage they said nothing wrong with the loom and it was injector 4. They replaced number 4 and misfire changed to cylinder 3. We had all 4 injectors sent off and tested. 1 needed calibrating another had a slight blockage. So they sorted them out and when replaced back in the car it still had the misfire. So now the garage is saying they think it's the conrod or bearings. Is this likely? As they have quoted a silly price for for stripping the engine down. This is at a rac approved garage. (Whatever that's meant to mean)

Anybody had this before??

Edited November 5 by robert eckersall
Missed info

[Steve Q]

I notice on the other post you've had a dpf and egr delete. I wonder if this has anything to do with this work and the remap? 

Apparently the removal of a dpf ect can increase engine temps which can put more strain on pistons, turbo ect. 

[cliffcoggin]

It seems that EGR and DPF removal/blanking is a recognised way to ruin engines. Stevey Y has been warning about this for some time on this forum.

[Hammie1982]

Robert,

I dont know how a bearing issue would be causing a misfire, unless the piston slap was REALLY bad and then you would be loosing oil and it would sound like a bag of spanners in a washing machine.  

What are you using to diagnose the issue? Is it a garage computer or a private VCDS / other ODB plug in unit?

It should be able to pinpoint where the misfire is coming from! I have seen reconditioned / reprogrammed injectors throw up errors in the past. Especially on remapped cars.

It might be worth getting a second opinion on the bottom end, as without hearing the car or knowing the fault codes, anyone could be throwing darts into the air and waiting to see what fault it picks.