My 98 XJ8 has 66k miles and rust free, the thermostat housing, tensioners, and water pump have all been replaced with the proper metal fixes. I drive the car home on a 10 hour trip which went flawlessly 90% of the way until I got an engine light for the MAF sensor. The code is p0172, I drove the rest of the way home fine. Next time I start it has low oil pressure. It is full of the right oil. I had an XJ8 before this that also suddenly dropped oil pressure. That one has a lemon when I bought it so it made sense, but I have no idea what could cause this. Any ideas?

 

Oil pressure sensor or harness? It is located at filter housing

 

First, ensure that you actually have low oil pressure.
If so, then....determine the cause.

 

My son's 1999 XJ had that condition but it was the pressure sensor which is located by the oil filter.

 

Hi HunterXRX,

Welcome to the Jaguar Forums! It's great to have you with us.

As already mentioned, the oil pressure sensor is mounted by the oil filter. It's shown in the upper right corner of this diagram:



Sensor failure is not uncommon, but sometimes the problem is just oil contamination of the electrical connector, so it's worth detaching the connector and flushing both the harness connector and sensor connector with zero-residue electronic spray cleaner such as CRC Electronic Cleaner. Allow to dry or use compressed air before reassembling.

Another less common but possible cause of your symptoms is damage to the sensor wiring. Rodents love warm engine bays and love to chew on plastic and rubber wire insulation.

You can connect a physical oil pressure gauge at the oil pressure switch port, although access is limited.

Please visit the New Member Area - Intro a Must and post a required introduction so we can learn something about you and your Jaguar.

Cheers,

Don

 

3 things,

1) If you haven’t done so already, replace ALL the timing chain guides and tensioners. I’m willing to bet that at least some of the plastic guides have broken off due to age.
2) Remove the oil pan and look up inside the oil pickup screen and if there’s any plastic pieces anywhere, this can and will cause low oil pressure. Fix it with step 1.
3) It’s possible that the oil pressure switch is defective but, you need to do a health check on a 27-28 year old engine first.

 

The 'sensor' is a simple switch. Ford has switched from sensor to switch since the late 1990s so Jaguar did also.
A mechanical gauge can be used to determine the ACTUAL pressure.
Addicted2boost has the fault diagnosis in sequence!