Misfire and hesitancy?

Misfire and hesitancy?

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feef

Original Poster:

5,206 posts

182 months

Sunday 28th June 2015
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Last week my MX5 (supercharged mk2.5) ground to a halt with a blown coilpack. I drove it a couple of miles with it running on only 2 cylinders until I found somewhere safe to stop, and by then the cat was literally glowing red hot.

I've since replaced both coilpacks and all plugs (two coilpacks firing a wasted spark on two cylinders each), and it was running fine for a few days, but now it's started misfiring again once it gets warm to the point that it sounds like an impreza with a loud exhaust :S

It'll intermittently idle okay, and sometimes pulls fine as if she's clearing her throat, but more often than not, it's misfire city.

Would a ruined/clogged cat cause such symptoms?

I've ordered plug leads for the two plugs which aren't directly attached to the coilpacks, but am wondering what else might need looking at.

Mr2Mike

20,143 posts

254 months

Monday 29th June 2015
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Blocked cats usually cause a significant loss of power and a big jump in fuel usage. The engine will feel strangled and not want to rev under load.

A straight forward misfire is probably ignition related so wait until the new HT leads are fitted. However, not that the crank angle sensors can be a weak point on these, and bad ones tends to cause problems when they are hot.

feef

Original Poster:

5,206 posts

182 months

Monday 29th June 2015
quotequote all
Mr2Mike said:
Blocked cats usually cause a significant loss of power and a big jump in fuel usage. The engine will feel strangled and not want to rev under load.

A straight forward misfire is probably ignition related so wait until the new HT leads are fitted. However, not that the crank angle sensors can be a weak point on these, and bad ones tends to cause problems when they are hot.
This has a completely non-standard setup, with a crank sensor and trigger wheel mounted on the crank pulley, so I'm not using the OE crank sensor. I've also recently replaced the crank sensor and the ECU software is showing all is well there.

New plug leads should be here tomorrow. I started taking the cat off this evening, and it's pretty knackered

Can see in the end, but not got it off yet. Whether it's just broken up or if there's a blockage there too, I'm not sure. I may check the mid-section pipe to make sure there's no restrictions there with cat fragments clogging up the middle silencer

feef

Original Poster:

5,206 posts

182 months

Sunday 12th July 2015
quotequote all
Looks like it was an injector problem.

Overhauled them (a run through the ultrasonic cleaner, some new seals and basket filters) and she's running beautifully.

Got a remap booked for the 28th, so hope to have my reduction pulley fitted by then so will be looking for more power! smile