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I purchased a new M.A.P senor for my Jag. Unfortunately, I can't find one one it. I called techs from Jag who stated it has to be on the intake, throttle body, or air box duct work. After removing my intake to check, not only was there not one, but no place to mount one either. Same with the air box ducting. Is it possible my 4.0L doesn't have one??? There are no air hoses running off the manifold to connect with one on the body either. Can anybody help me with this ????
Symptoms are multiple cylinders missing when it's cold..runs like crap
when it warms up good, it smooths out like normal. It's naturally aspirated, so as you pointed out, there is no m.a.p sensor
Thank you for that great info
It's does have the air temp sensor instead. Now I've got figure out the cold missing
in the 801s doc around page 78 and 86 are the calibration charts for the IAT and ECT sensors
The instrument gauge is the single wire sensor on the thermostat housing and the ECU looks at the 2 wire sensor next to the single wire as the ECT sensor
The instrument gauge is not accurate
It must reach 88 C to go into close loop full O2 sensor engine regulation
The O2 sensors have heaters to be able to read correctly and a single fuse for all 4 in the right engine bay fuse box # 14 / 10 amp
Last edited by Parker 7; Dec 24, 2022 at 02:11 PM.
For it to go open loop, the engine needs four things:
1. TPS readings within range. (About 12.9% at idle)
2. MAF readings within range
3. Coolant Temp Sensor above a certain temp, maybe 170F?
4. Oxygen sensors at temp (I think 500F)
I wonder if your coolant temp sensor has hit the dust?
The air temp sensor at the elbow shouldn’t be able to cause much of a mess.
Its odd that your car runs poorly when cold, but not when warm. The sensors should not come into play when cold.
When was the last time you took a look at your coils? They may be due for a change. Sometimes they work poorly cold and then when they get hot and things expand, they run better. May be time for new plugs (while you’re there) and coils. Stick with inexpensive Champion copper plugs or NTK copper plugs. People have reported trouble with the fancier iridium plugs.
As Parker mentioned, the instrument gauge uses different sensors than what the ECU uses, so an OBD2 scan could reveal the problem.
Funny you should say that. I have new coils on the way. Someone put on new coils before me, but, I'm sure they are a cheaper set, and consequently don't last
.I've heard arguments about copper, or newer material plugs. Just trying to be logical, I can't imagine the cylinder gives a rip about what is conducting the electricity to spark. Sounds like age old wives tale info passed on between folks. But, Im not saying I know for sure. I'm going to pull off the throttle body today, and give it a good cleaning, just for poops and giggles. Can't imagine a bad side to that maneuver. Also, I need to try to determine the ECT, as opposed to the instrument gauge sensor.
Thanks for all the great help guys
I love these old Jags and am trying to learn-em
Can't wait to get her purring again
P.S. Anybody know where I can buy another electric radiator fan ??? One of my is burnt out
On the radiator fan the higher chance is the fan control relay module located fwd of the front right tire under the car can go bad
If it is mounted upside down water can get in ruining the power contacts
The white module for the X300 is slightly different then the blacl one for the later V8 X308
Your current one and the 2 fans can be tested by removing the 3 wire temp switch on the aft lower left on the radiator ( this switch is only for fan control and no temp indication to the gauge or ECU )
With a paper clip jumpering from one of the white wires to the black grond you will get low fan operation
Remove the clip and jumper the other white wire to the black ground and you will get high fan operation
This is a low current portion of the circuit so no arcing hazard
Editing
You can swap the fan connectors to verify both fans operate
The fan connectors have a plastic clip to hold them on so don't spring out too far as can break
There are a couple of fuses involved
On your cold engine spot of stumble a fuel injector cleaner in the tank may free up a dragging injector as the injector pulse width is smallest at idle and the injectors can be freeing up as they warm up
Last edited by Parker 7; Dec 25, 2022 at 11:44 AM.
Thanks....what I failed to mention on my top fan is the motor is shot
I have it disconnected because it howls and grinds while flopping around
Unfortunately, it needs to be replaced....but, where pray tell do they sell them.
Can anyone point me to the ECT on this 4.0L inline non-turbo 6?
Where, if you know, can 2 new fan assemblies be purchased???
I'm kinda scratching head here on the ECT sensor
.the one on top of the thermostat has one wire only.....and the closest sensor to it (just a little closer to the valve cover) has only one wire from it also ? I see no other sensors around them.
If you pull the connector off of the rectangle shape receptacle you may find this is the one missing a wire , it will have 2 sockets
The 1 wire sensor has a copper crush washer on the thermoset housing if you remove it , the copper washer can be cleaned of tarnish to be more accurate on the instrument gauge
Your wire colors for the 2 needed for the ECU engine coolant sensor are Blue / Yellow stripe and Black / Brown stripe
See post # 28 , my car is Lady Penelope as an earlier poster name
Need help with my 97 4.0L. M.A.P sensor question
