Eunos Mk1 engine diagnostics near Southampton?

[notax]

My girlfriend has bought a Eunos which has an occasional missfire. The spark plugs and leads have been changed, I guess it could be a coil pack but wonder if the diagnostic port would help identify the issue? My local garage (and even Mazda main dealer!) don't have the necessary equipment. Any ideas? Thanks

[lilwashu]

Necessary equipment = a 12V LED and a bent paperclip. Follow this to see if it reports anything:

http://www.miata.net/garage/Engine_Diagnostics.htm...

[HorneyMX5]

Coolant temp sensor behind the coilpack.

For reference you're in MX5 Nirvana on the southcoast with both AutoLink and Skuzzle Motorsport within striking distance.

[notax]

lilwashu said:

Necessary equipment = a 12V LED and a bent paperclip. Follow this to see if it reports anything:

http://www.miata.net/garage/Engine_Diagnostics.htm...

Thanks, that's a neat idea!

[notax]

HorneyMX5 said:

Coolant temp sensor behind the coilpack.

For reference you're in MX5 Nirvana on the southcoast with both AutoLink and Skuzzle Motorsport within striking distance.

If we get nowhere with the above idea I'll get in touch with them, thanks for the suggestions

[With these feet]

How bad is the missfire? Is it occasional - ie could be fuel pressure, or does it run on 3? - tip is with the engine warm/hot exhaust squirt water on the exhaust headers and if it evaporates - ok, if it rolls off then thats the offending cylinder.

If I remember correctly, there were some issues with hight oil pressure which made the hydraulic followers stay open causing a missfire and in some cases non start. Doubt it is this but came to mind.

Recheck the leads for the pin-dot of white powder that highlights arcing as the leads are always the first port of call...

[notax]

The missfire is occasional. It doesn't happen every day, but is getting more frequent. It can happen when the car is hot or cold but seems to happen every time my girlfriend drives home from Whitely up the sloping slip road, which is odd. It has now got to the stage where the car actually missfires so badly it stalls and can be hard to restart. The leads have just been changed so I doubt it is caused by them. Thanks.

[VladD]

Could it be the alternator starting to fail? It might not be producing enough juice to allow the plugs top spark 100% of the time. Just a thought.

[With these feet]

Sounds like its under load which indicates HT. All the plug ends tight? Sometimes they need a little nip with pliers to get a decent contact. Also check and make sure the leads are fully seated, it will still run if the HT lead is close to the plug but break down if under load.

Did the lead change improve the missfire?

[skinny]

probably coil pack. get one off one of the decent breakers like junk yard dog etc or frazbomb. for the money they cost 2nd hand it's worth giving a go.

[notax]

Thanks for the ideas, Emma has been concentrating on moving house, but the MX5 is getting worse. Think I'll try a secondhand coil pack as suggested, any idea how big a job it is to change?

[HorneyMX5]

notax said:

Thanks for the ideas, Emma has been concentrating on moving house, but the MX5 is getting worse. Think I'll try a secondhand coil pack as suggested, any idea how big a job it is to change?

3 bolts and one plug from memory, not too tricky.

[notax]

Great thanks, just chatted to my friendly mechanic and he is going to knock up the code reader suggested earlier in the thread in the first instance and see where that takes us...

[GarryDK]

If you still have troubles speak with Autolinkuk they are based the other side of upper swanmore

[MX-5 Lazza]

You might well get a fault code from it but an intermittent misfire rarely causes a code on a Mk1. The ECU just isn't very intelligent.
The most likely causes are leads & plugs (which you say you have done), then coil-pack, CAS and engine temp sensor.