My buddy has a 2009 Cooper S 50,000 miles with misfires on every cylinder, hard knock on cylinder 3 and possibly other codes. I am not sure if this car is the recalled N14. I am unsure how much they have driven the car in this damaged condition. Where should I start to determine if they have destroyed the engine? When we were talking about misfires I was all focused on the intake being all coked up but now I am wondering if I need to look at the timing chain issue. I am guessing that I need to start with a compression test or a leakdown test but I am unsure if those can be done properly if the timing chain or intake may be out of spec. I appreciate anyones help as I am trying to help this couple out and they are on a very limited budget and have been taken advantage of at many shops due to their lack of knowledge.

 

Hello and welcome to the forum. By "they" what do what exactly to you mean, i.e. was a shop/dealer working on it previously? Just about every 50,000 miles the intake valves need to be cleaned to maintain optimum engine performance. Once the build-up reaches the maximum tolerable level, the engine will begin to run rough and misfire. You may have a rough idle, poor acceleration, stalling or single to multiple cylinder misfires. If you have any of these symptoms, check for valve residue build-up. We have a tech article that can help you with the carbon removal process. The image below is what you'll want to look for when inspecting the valves. What are all the P codes in the system?

 

Do not take my experience into consideration; however, take Consumer Reports, which coincides with my experience:



Consumer Reports

Cars you’d be foolish to buy

Reliability, satisfaction, and test scores knock out these contenders

Published: April 01, 2015 10:15 AM
Worst used car: Mini Cooper S
When it comes to choosing a used car, you can put the odds on your side by choosing a model that performed well when new and has a great reliability track record. Of course, reliability hiccups can happen with any used car, but the Mini Cooper S has the worst history among all cars we have tracked over the past decade. Sure, the car is cute and delightfully entertaining, but year after year, the likelihood of having a problem that requires a repair is heartbreaking. And among the 17 trouble spots we track, engine major, engine minor, engine cooling, fuel system, body integrity, and body hardware have issues at an alarming rate. Although Consumer Reports often recommends skipping an extended warranty, the Mini Cooper S is a case where the investment would be a good hedge against potential problems.