I am having a lot of difficulty starting first time for that day. I have recently put a new back box on the exhaust and the trouble started from then, but I think that’s coincidental. I check the plugs before starting and they are light grey which seems OK.When the car eventually starts, (sometimes I have to pump the pedal to do this) I warm it up to normal temperature. If I switch off and leave for even a few hours It still starts 1st time. If I check the plugs after it has warmed up they are very sooty. If I clean the plugs and run the car, even on tickover, the plugs still look fine. It is just when it has been left overnight that I have trouble starting. Any ideas anyone?
What model is it?
Looking at your picture it looks like a mark 2 (pre-facelift), but what engine?
It is a MK2 1998 1.6 Auto Jap import. It seems that it is over-choking.
Early 1.6 NB’s had a issue with burning intake valves out (what is your VIN?). This can give hard to start symptoms. You could be in the early stages of that. If you can, do a compresion check & check the valve clearences as you may find one closed up.
My starting problem only occured after fitting a new s/steel backbox from MX5 Parts.Everyone I talk to about this tells me that the new silencer should make no difference to starting.I have been told about a dozen thing it may be, some of them scarily expensive. I have already changed the battery, the plugs and the plug leads.
This morning I pushed the dogs rubber float in the tailpipe. The car started immediatly.Is this just a flook or is the reduced back pressure affecting the starting?
I’m still struggling with this starting issue. I’m now told it could be the crank angle sensor. Does anyone know where this is on a Mk.2 ? How do I check it or replace it?
Right I’ve given up now[:S] I’ve taken the car to the local Mazda dealer.They say low compression on two cylinders (approx 50% )
Valve clearance on two valves zero. It appears to have been trying to start on one cylinder. They are going to re-shim it to see if they can get the compression up, and see how it runs. Failing that they will recondition the cylinder head cost approx £500-£600+ vat.
Trying not to think about it[*-)]
At least it will be sorted though, which is the main thing now that summer is here.
On a different note, I’m amazed I deduced your car was a MK2 pre-facelift from your avatar - quite how I did that I don’t know
It’ll be the seats on the valves, not in the head that have burned out. Madza produced modified valves part number (B6MC-12-111). Assuming it’s the intakes that have gone and the seats in the head are not damaged due to running it for an extended period with the burned valves you should get away with just replacing the valves. Re-shimming (if it fixes it) is just masking the problem, the seats will continue to wear.
Second hijack thread of the night - I’m doing well 
Robbie, do you think new exhaust valves would be OK in my engine?
I have all of the same symptoms as the OP since taking the head off to lap the valves and finding that mess (I just ended up cleaning it up after lapping two of the exhaust valves and putting it back together)
You’d need to take the valves out and check the seats… you put that head with those valves back on your block [:O] Remind me not to buy a car off you [;)]
Had to, Robbie. No other way to get to work and my wife get the kids to school. It’s been running on those valves for some time now I guess. Car runs fine when up to temps, just a little hesitant at low revs. Backfires and blows blue/grey smoke on startup for a few seconds though. Didn’t do this at startup before the woodruff key was fixed and the head was taken off though.
I suppose the worst that could happen is the engine craps out and I need a replacement. At least I’d have an excuse to swap the clutch then - every cloud etc.
By the time I got your last thread the car was in the [maz]dealers. They have re-shimmed it and it starts first time now. Cost £202.22
How long do you think it will last ? [*-)]