I'm guessing this is the oil pressure switch?

88 XJ. I'm underneath it just now, and I notice a blk. plug hanging loose from a wire near the front end. It has two small female slots in the end of it. I notice a spark plug-like object that goes in the bottom of the engine right level with the gasket. It has 2 small male plugs on it, so I figure, what the hell? I plug 'em together...

I'm thinking this is the oil pressure switch, correct? I haven't gotten it started yet, so I'm taking a guess. If that's what it is, I need a new one of them...it barely holds on due to the cap pretty much being dry rotted off...

-greginLA

Not 100% sure without a pic and being renix era i thought that's where the knock sensor is. As I said I'm not 100% sure because it's a renix and mine doesn't have that.

Edit: Just checked auto zone's component location and it says the knock sensor is on the driver's side bottom of block behind manifold and oil switch passenger side above oil filter.

hmmm...sounds like it may be a knock sensor based on the location then.

If only I knew what a knock sensor is/does, then I would be good...


-greg

OP switch or sensor is below the distributor and has a single female spade on a wire.

what you describe matches what looks like the knock sensor to me....

BTW...what is renix? Never heard that one before...

RENIX
REN = Reanult
IX = BENDIX

Try this link

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

All 87-90 4.0L and some 87-90 2.5L were what are called Renix. Closed cooling system, no check engine light, and sometime a pain to diagnose. Some love'm, some hate'm...

BTW

RENIX

Renault programmed the ECM, but Bendix Supplied most of the parts and most of the GM based sensors.

So thats why we get Renix.

The knock sensors function is to detect "pinging" (premature detonation), if "pinging" is detected it will cause the ignition control unit to delay the ignition. If your engine is in ok health and you are running a somewhat decent octane fuel, the konck sensor is not doing anything. If the knock sensor is defect it may cause the engine to run with too late timing, having negative effect on performance and economy. If your knock sensor is disconnected, it may be because it is defective. Disconnecting it is a ok way to "cure" a defetive KS.

Where I live, the lowest octane fuel you can buy is 92, and I have blocked my EGR system. Because of the low compression of the 4.0 this should eliminate any risk of pinging as long as the engine is healthy, and the KS can be safely disconnected. Anyway you can detect pinging "manually" :rof: (submit your engine to high load on low revs, and if you dont hear pinging... well... the you don't have a pinging problem...)