What is the part # of the MAF sensor installed ?

There is both a Lucas and Jaguar # marked

There are 2 different MAFs one for the normal aspirated and one for the supercharged

Just covering the base that you have the correct part as it happens from reading

Have you done a smooth transition test of the TPS that you have no open spot on the wiper brush ?

 

"You mentioned you saw 85 F ECT at idle"

I'm sorry, I must have typed 85 instead of 185 F

It's at 185F and the needle isn't directly in the middle when its up to temp.
Also, the maf is Lucas and I'll have to find the part number later.

 

The LTFT represent an average of the STFT taken over a period of time. I would not try to diagnose anything simply by reading those constantly changing numbers.

The bigger concern is the -10.2% LTFT.

I have solved this before with the following solutions:

1a. Replacing TPS with a new one. The old one bench tested well, but I had already replaced most every other sensor on the car.

1b. It also could have been fixed by performing a TPS reset, which was done when the TPS was replaced.

2. The unplug/replug option I stated earlier. Not sure why it worked….but it did. Twice now.

3. Replacing the oxygen sensors. You said you had them all replaced with new, so probably not the issue.


I did have a problem with an ECU where the 02 readings were not flip flopping, they were a flat line. Swapping sensors didn’t do a thing. Replacing ECU did. Car would never go open loop.

 

Unfortunately none of that seems to be the issue.
I could try replacing the Air charge temperature sensor and the MAF.
I'm replacing all Oxygen sensors once more.

However, i have noticed the Bucking and random loss of power seems to go away at freeway speeds when its Around 50-60 Degrees F. And then on the drive home, when it's around 70 Degrees to 80 the bucking comes back.

 

The inlet air temp sensor gets coated on it's tip resirc gas deposits that bias the temp it is seeing as higher then a clean sensor tip

So just a clean-up try first

 

I did that when I completely cleaned the intake system. I'll try that once more when I get the chance.

 

On your reading device there is a EGR_Error PID that has a target of 0 % but it won't be perfect

The EGR also has a temp sensor and a valve position sensor that it has moved to the commanded position

This temp sensor is very near the intake manifold / head junction area on the # 3 cylinder inlet pipe

 

And there is no check engine light? No transmission light?

I’m wondering if this is a transmission issue? When was the last time you had the fluid flushed at a shop?

My experience with the transmission is that it is much more generous with issuing codes when something is not working.

 

It's been narrowed down to a fuel delivery issue
yes there is a CEL
​​​​
no there isn't a transmission fault and the fluid is fresh.

 

Checked the 4 / O2 sensors heater fuse # X

This fuse requires the right engine bay fuse box relay to be closed

You can swap this relay with the left engine bay fuse box relay as in reality it only runs the horn

The relay nay be intermittently opening causing the O2 sensors to go in and out of 500 F operating / correct reading temp

Or the relay power contacts can be comprimized

Inspected the Papa Indy 1 and 61 connectors ?

Your first power of the low power side if the Engine ECU is fuse # Y of the same right engine bay fuse box which requires that corner relay to close for fuse 10 , 12 , 14 , and 16

It's a free try but a stretch

You can also jumper between socket 3 and 5 of the corner relay to totally eliminate a relay issue

Flat blade heavy gauge jumper wire connector ends recommended to ensure current

 

Did I miss the CEL code in an earlier post? What it is showing you?

 

Hi Andy
I recently changed my ECM due to high idle with a rusty unit I found on ebay. I instantly got near similar symptoms like you have after first start up. Did'nt cure with driving. Bought another one and now it works fine.
Best regards chris

 

Chris,

Is one of your scan photos a before and after?

You seem to have a LTFT issue in the second photo. -13.3% on one bank and -3.9% on the other. You have a problem between the injectors to the oxygen sensors….

Maybe a cracked manifold? Maybe a leaking injector. Perhaps a bad O2 sensor. Dying coil(s)?


In the first picture, your TP%, or throttle position seems low at 9.8%. The XJS likes to see 12.9%, or thereabouts.

 

Thanks. I think you was referring to Andyboy1971's post. I posted a pic of my scan with the bad ECM I got on ebay. Fueltrim worked fine on my original ECM and are working fine with the 2nd replacement I put in.

------------------------------------------------------------
1995 X300 3.2 / 1996 X300 XJR / 1995 X300 4.0

 

Thank you everyone for your input, I'll be looking to throw in a new ECM this weekend but it's odd, I pulled my ecu apart and checked all connections and soldier and all the chips looked great, the ecu was in wonderful condition. Maybe its one of those things?

As of now, the car runs exactly the same. Both banks are maxed and flipped flopped (-24 b1 +24 b2) I've changed
-Air charge temp sensor
-both upstream oxygen sensor
-cleaned maf
​​​​-cleaned IACV/EGR/TB
-New TPS
-new injectors
-new ignition coils
-new fuel pressure regulator
no clue codes P0300 and P1313 are constant and flashing. Car runs good in closed loop.

 

It could be you have no problem and just indication

Fuel milage good ?

Code 300 could just be a knock sensor saying you have a miss fire on one cylinder that may not actually exist as you would expect more then one or three for each knock sensor if the sensor is failing as a sensor or dirty connector.

You can swap sensor positions and see if the code changes

Off the top of my head without looking a 301 , 302 , 303 is the first 3 cylenders and the 300 may be a group or aggregate regulation issue as a whole

 

I avg around 19.5 to 20 mpg and I'm seeing around 24 to 25 instant on the freeway. So, okay mileage I guess.
however, there definitely is a problem as the car runs like absolutely *****. Seeing random drops in power that fixes itself after I blip the throttle. It'll act like it "resets" then slowly goes back to pinging and bucking then instant power loss then "reset" then over and over. Monitoring the fuel trims while this happens they reset to base fuel stoichiometry then slowly climb to super rich or super lean on each bank.

 

Ok mileage?

I rarely get to 18 in the city! Your mileage is excellent.

p0300 is a random misfire, and p1313 usually comes with it.

The usual suspects for random misfires here tends to be:
1. Leaky camcover seals, specifically the ones at the plugs.
4. Vacuum leak upstream from the MAF
5. Oxygen sensors failing

Other than that; how do the wires at the coils look? Anything seem crunchy? Any copper wire visible? That harness gets abused, so it could be either the insulation flaking, or maybe a ground shorting inconsistently?

You seemed to have addressed the usual suspects, have you inspected the wires?

Have you replaced the downstream oxygen sensors? The upstream are just there as a check.

I’m assuming you’ve replaced the spark plugs, even though it’s not on your list.

 

I actually smoke tested the engine and in the result found two minor vacuume leaks through the EGR and a vac line that's press fitted into the upper intake plenum. Fixing them resulted in no change in operation. I've also completely inspected the intake hose and spray tested it for leaks.
the valve cover has minor leaks through the bolts holding the cover down (very small) and nothing into the IC plug holes. There is no source of corrosion or bubbling in them so that cant be it, and all of the plugs arc very strongly and most of them are new.
the current mileage is in the 130,000 ballpark. All the wiring to the coils and harness itself is in great condition with no tears or cracking.

 

No the downstream oxygen sensors haven't been replaced yet I don't see a reason why I need too. On these cars do the downstream sensors not monitor the catalyst efficiency?
and yes, I've bought copper plugs gapped to OE spec