Should this loose plug connect to something? Engine bay, near firewall, passenger side...

[RussMcB]

My car has been stumbling under load lately, so I was looking under the hood for something amiss.

I noticed this plug not connected to anything. Anyone know what it is?

It comes out of a bundle near the firewall on the passenger side. I didn't see anything nearby to connect it to.

TIA - Russ.

IMG_2405.jpg

[iscariot]

I'm not 100% positive, but I think that's the oil pressure sender switch. Should be connected to the oil pressure sender right above the oil filter.

[iscariot]

http://crowz.narmir.com/wp-content/u...il_sensor2.jpg <-- Real oil pressure sensor (90-94)
https://www.miataforumz.com/attachme...orks-op_sw.jpg <-- on/off (95+)

[RussMcB]

Thank you! Looks like a good possibility. I'll report back when I get a chance to check (in a day or two).

[RussMcB]

Well, I thought I determined the loose wire isn't for the oil pressure gauge, because it's working in the dash. I see the needle moving when I start and stop the engine.

Tonight I tried to look, couldn't get a good look, so took a picture with my phone (below). Tough to get two fat hands down there.

Now I'm thinking, maybe that IS where it goes (because I see an unused male blade), and maybe it's for a warning light.

Maybe I'll connect it and see what happens. :-)

Miata OP.jpg

[iscariot]

So that's an aftermarket VDO sender - this is for your 99, right? PO might've tried to make it a not-dummy-gauge. Usually one side is the WL and the other is the sender output, ground going through the body.

In my messing about with the 99 cluster, I can say that the oil pressure gauge is absolute crap. Dampened like hell, won't give you any real response. If the wire is unconnected (floating) it shows pressure. If you turn your key to "on" without cranking the engine, does the oil gauge move?

[RussMcB]

If you turn your key to "on" without cranking the engine, does the oil gauge move?

Great question. Will check later today.

[RussMcB]

Ha! My gauge reports healthy oil pressure with the key on and engine not running!