Emissions Failure

[TripleSix]

Been a while since I posted up here but have finally decided to put the MX5 back on the road after two years in storage.

Trouble is its failed its emissions test and its hunting when idleing cold. The emissions were off the clock and it appears to be running rich. Lambda Sensor and the Cat arent likely to affect the emissions by quite this much and I believe a 1990 1.6 will pass the NCT Emissions without a cat?

So what could it be? The AFM?

Stainless manifold and exhaust system apart the engine is largely standard apart from a JR CAI and timing set to 14deg. True its over 205k miles on it but hey who's counting.

Any ideas or suggestions?

TripleSix

[Steve]

Howdy
Been a while
I'd change the plugs & oil first, then look for leaks between the AFM and intake manifold (also check the little rubber bungs/nipples on the top and rear of the manifold). If there is leaks, this might also explain the hunting.
Check the PCV valve is working between intake manifold and cam cover (might have stuck open).
Also check the thermo sensor on the back of the head (fairly sure this is the one referenced by the ECU to keep it rich when warming up).

Don't forget the "Italian tuneup".

Oh, you could pull the timing back to 8 degrees too just for the test
Cat won't matter on a 1990.

Steve

[TripleSix]

Thanks for the suggestions Steve. Good to see some of the original faithful still here!

The plugs and oil were changed shortly before the layup and the problem was actually there at that time as well - just never got around to sorting it back then.

Will definitely check around the AFM for leaks etc. The thermo sensor was also suggested by someone else.

Will let you know how it goes.

Joe