HELP diagnosing a problem... MX-5

[TREMAiNE]

MX-5 is playing up!

Was running absolutely fine then suddenly started running really lump, massive dip in power (not that it had much in the first place ). Sounds like its not firing on all 4.


Here is a video of it on idle - the sound is more clear from the exhaust than filming the engine directly.

https://www.youtube.com/watch?v=5S3Vcrvskfc


Here is a video of it on idle in the cabin, whenever I filmed it wasn't too bad, whenever I stopped it would dip right down almost at 0 revs!

https://www.youtube.com/watch?v=xdGzOUpHnH4


Here is a video of it accelerating, in 2nd, 3rd and 4th from 2,000rpm.

https://www.youtube.com/watch?v=jheiJHTwSdo



The plugs were changed last year, so I can't see it being them. We (my friend and I) were guessing HT Leads and/or Coil Pack - but in reality don't even know what the problem is so that's a guess really.

Any suggestions?

Cheers.

[eltax91]

Leads are cheap enough to try out. If it's not them, can you bridge the pins in the diag socket and read the fault code?

It'll give you a cylinder problem if you have a misfire? Then you can swap the coil packs over and see if the code moves?

[Jimbo_888]

First step is to try HT Leads and plugs as they use a wasted spark system, so that a break in any lead can mean losing 2 cylinders. Failing that its try a coil pack.

Any error codes showing ?

[Lancerevo]

Coil pack will prob sort all your troubles out. These mx5 s don't really go wrong.

[Buff Mchugelarge]

eltax91 said:

Leads are cheap enough to try out. If it's not them, can you bridge the pins in the diag socket and read the fault code?

It'll give you a cylinder problem if you have a misfire? Then you can swap the coil packs over and see if the code moves?

That.

Cheap HT leads don't last 5 minutes on an Mx5 for one reason or other, Mine had two sets in a year. I'd start there.

[V8RX7]

MX5 are famous for eating leads - buy GOOD ones.

Lift the bonnet in the dark and you'll probably see the sparks - a wipe over with WD40 can buy a few weeks.

[carinaman]

Have you got an old spark plug in the garage?

Put an old spark plug into the end of an unplugged HT lead and leave on metal engine part, possibly cam cover and turn the engine over. Is there a spark and/or cracking, clicking noise? If you do it in the dark the flash of the spark plug may be more visible.

I've not watched the videos.

Does the exhaust gas taste of unburnt petrol?

[poing]

Yup mine did the same, went onto MX5 Parts and bought some of their good leads, I bought the plugs they recommend as well at the same time. It was next day delivery so really easy to do, well sort of easy but it turned out my spark plug tool didn't fit the MX5 of course!

[Superhoop]

If it's a plug lead, the chances are, it's failed at the plastic bit that goes down into the head and onto the spark plug. If you have any electrical tape, take the lead off the plug, and tape the living bejesus out of it from top to bottom, this will, for a short time at least stop the spark jumping to ground.

It normally lasts a few days before the spark finds its way through the tape, so should buy you enough time to get a new set ordered.

[Krikkit]

The Magnecor Electrosport leads that MX5parts sell are excellent.

[TREMAiNE]

Cheers for the replies guys.

I have new Magnecor HT leads and a Coil Pack arriving in the post this afternoon so will give that a try.

I am useless when it comes to this stuff, I can do the leads but that is it. A friend will do the Coil Pack at the weekend for me. Hopefully that solves it.

[KernowSid]

When I found mine ('92 mk1 1.6) doing the same, I found that two plugs werent firing (middle two - cylinder 2 and 3?).

Replaced the coilpack (wasnt too bad to replace) but that didnt fix it.

Turned out that I needed to replace the CAS, was a bit fiddly to replace between the head and the bulkhead.

[TREMAiNE]

UPDATE

It was the HT leads after all. Not only has it fixed the problem but the car is running even smoother now than before.

I'll send the Coil Pack back as that's not needed and I think I'll tread the car to a new soft top now as the old one has a massive tear in it where I stupidly tried to open it at 50mph!