The exhaust on my 5 is now pretty smokey yet it runs just fine and not birning oil. I am wondering if it might be that the fuel filter needs changing or the fuel injection is running a bit rich. When the car warms up the smoke goes and it seems Ok. Is this something common on MX5’s
Hi, get someone to run and rev the engine from cold start to hot whilst you keep watch on the tailpipe. Let it idle at points during the warm up to see if idle is maintained steady as temp increases. Basically, black smoke is usually rich fuel, blue is buring oil, and white is water or condensation.
See if any codes are showing using a led and resistor. The oxygen sensor should keep mixture about right but it may be getting old without tripping a code and that can cause it to run rich and may also hesitate during acceleration.
Thanks Rich I am thinking it might be the crankcase PCV as the exesive air coming out the oil filler cap hole when the cap is removed. I will change this and see if it improves and a proper vaculme is maintaned.
Hi Robbie,
I tried the common check for a pcv of removing the oil filler cap and putting my hand over to see if was sucked down - and it wasn’t. In fact it was blown off the filler quite forcibly. Another member also tried it on his Mk1 with the same result - so I don’t think it is a reliable test on these engines,
secondly, I’d expect blue smoke if any from a failed pcv as it would be oil being burned.
Please let us know what you find if you do change the valve though as it surprised me a bit.
It is positive crankcase ventilation. You should indeed feel an outrush of air…how much is ‘excessive’ is a little hard to judge, but a compression test will tell you if there is a problem to worry about. Probably not though.
Change the air filter you will find that its is blocked and strugglng to get clean air into the engine cheap repair
Alan
When the engine warms up the problem went away, it is only from cold start up the clouds of smoke came out. Therefore I thought it wasn’t the oxygen sensor and had to be the PCV valve. I have changed the PCV valve now and took advantage of disconnecting the oxygen sensor plug and cleaning the contacts. I have also put some Whynns injector cleaner in the fuel tank and taken the car on a longish journey and now it is fine. Which one did the trick I wouldn’t like to say but I feel it was the PCV??
thanks for all your help and advice and now Spring is round the corner we can look forewards to some hood down sunny motoring.