I'm sure this is a regular thing but while working in the engine bay I heard what I thought was air being sucked in when I revved and noticed the concertina section of the air intake pipe had some small splits. When I touched that area the whole section was extremely brittle and basically about to fall apart (53k miles). I've ordered a replacement pipe but what kind of symptoms would I experience from this? (I already have poor mpg which this is obviously a part of)

Could any of that brittle plastic have got sucked into the throttle body and injectors?

Also would it have any bearing on the p0305 misfire code I'm getting for cyl 5? I wouldn't think so but I will know as soon as I replace the air intake pipe I guess!

Why no codes regarding incorrect air mix?

Thanks
Alan

 

P0171 and P0174 are the codes that will show up if the air leak is large enough. I wouldn't worry about plastic making it into the engine. You're likely to have poor fuel economy, and loss of power.

P0305 is unrelated to the situation. For that, my first diagnostic step would be to swap the coil with one in another cylinder and see if the code changes accordingly. If the valve cover gasket and spark plug seals are failing, you may find oil in the spark plug well and the boot of the coil when you remove it. If you do find that, then that is probably what is contributing to P0305.

 

You can check the throttle body and inlet manifold for random bits of plastic, but this won't have anything to do with the fuel injectors.

Have you tried swapping the coil units for cylinder 5 with other cylinders to see if the DTC changes to that cylinder?

Quite often misfire(s) in a cylinder doesn't set a DTC or turn on the MIL. Check for oil in the spark plug well, which can cause a misfire for that cylinder. If a substantial amount of oil is present, the cam cover gasket and spark plug boss seals must be replaced.

 

I recall several reports on the forum over the years of this type of failure on the plastic Air Intake at the concertina section. Usually reported as a result of troubleshooting codes. Nowhere near enough reports to make it a regular issue but definitely not unknown.

Graham