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Here's one for any EGI main relay experts.

My car used to have a mildly annoying cold start problem. It would start easily then almost immediately run rough like it was running out of fuel for a second then fix itself and go back to normal cold idle speed. I had read somewhere that this was a symptom of a bad battery, and as my battery was on it's last legs I bought a new one. Problem solved, almost. It still had a small idle dip just after it started. But it did this hot and cold and my NA8 used to do it too so I thought it was normal MX5. A few weeks ago I disconnected the battery and ever since then it has had this rough running at cold start thing again. I cleaned the battery terminals, even though they looked fine and that fixed it for 1 cold start.

Seeing as my car now has over 200,000km for preventative maintenance I have been slowly replacing known problematic parts, hopefully before they fail. Last week I replaced the EGI main relay, the green relay in the engine bay fuse block. Ever since it's started perfectly and the small cold/hot startup idle dip has also gone. I'm quite happy this has fixed the problem but I don't understand how. Surely a relay is either on and working or off and not working. Can a relay only partially work?

Anyone have any thoughts?

Pull the old one apart and you'll find it's an old fashioned copper coil opening and closing a set of points. Like any points they get dirty and pitted and carry less and less current over time. You can file them clean, reset them and extend the life for a while.

Garry wrote:. Surely a relay is either on and working or off and not working. Can a relay only partially work?

Anyone have any thoughts?

Hi Garry,

When the EGI main relay first went on my car (leaving me stranded on the side of the road) I tested and initially discounted the relay because it gave 12V when tested perfectly fine.

Under load thoughm when drawing more current through it, it would break down and not work properly.

You can always try bypassing the relay with a bent piece of wire and see if that makes the car run better.

Mine lasted until 137,000kms. A temp repair was done by an auto elec with a generic version with not very good loose wires. There's now a proper replacement in place and a spare in the car and another in the shed.

Given the age of the car I'm now past the mainly rebuilding and modifying stage and going more towards maintenance and preventative maintenance.

Thanks for the info guys. Hopefully it was the relay and it stays fixed. I also bought a new fuel pump relay. Replacing that will be the next project.

I went and cleaned my EGI relay contacts last night, and combined with my recently serviced injectors, my car is now running super rich. So much so that at low RPM it's killing the spark and missing.

I think my oxygen sensor is buggered.

Is there a trick to removing NB EGI relay? - feels like something will break when pulling straight up.

Cheers

Wiggle

Garry did a guide on removing it years ago - search his posts and you should find it. They are hard to get out.

there is a small plastic clip/tongue on the side closest to the fuses. A really small screw driver can help to press this in while you are pulling the main relay out. It is clipped in, and does not pull straight out.

My mistake. The relay on my SE (aka NB8C with some bastard parts) doesn't have a clip and does just wiggle out.

Mine went and died completely just outside Lithgow on Saturday. Fortunately I had a piece of bent wire in the car, which I used to bypass the relay.

Got home and then remembered the spare relay in the door pocket

Oh well, new relay on the way tomorrow