Restricted performance , how to remove it - 2004 Jaguar XJ

For the money you spent on another computer, you could have brought your car to a qualified mechanic and had the problem correctly diagnosed and repaired. 'Restricted performance' meant the computer saw something wrong in the engine, and restricted the performance to keep from destroying the engine. You killed the messenger and still have the same problem.

several things can cause restricted performance...anything from low circuit sensors,to malfunctioning modules...you must read the ecu code and pin point nthe issue..

performance restriction popped on, then engine light stayed on. Any solutions?

MODERN CATS HAVE VIRTUALLY NO AFFECT ON PERFORMANCE, THEY ARE NOT RESTRICTIVE LIKE THE OLDER ONES 1ST USED IN THE 1970'S IF U REMOVE IT U CAN CAUSE A CHECK ENGINE LIGHT.

DTC P3400 - Cylinder Deactivation System

It most certainly is not normal for one cylinder to shut off. I would think it would have to be one of the MDS cylinders, which are 1, 4, 6, or 7. Here is what he shop manual says about DTC, P3400. In any case, you're still under waranty, so I'd let the dealer worry about it. If it is a solenoid problem, the intake manifold has to come off. In any case, it shouldn't require a major engine teardown. Let us know what they find.

P3400-MDS RATIONALITY BANK 1
For a complete wiring diagram Refer to Section 8W.
Theory of Operation
When all criteria has been met, power is supplied to each MDS Solenoid when the engine is making a transition
from 8 cylinder mode to 4 cylinder mode. By actuating the solenoid, oil pressure is raised to the pair of lifters that
coincide with each particular solenoid. The oil pressure pushes in the locking pins that allows the lifter to collapse,
decoupling the valves and camshaft.
² When Monitored:
Transition from 4 to 8cylinder mode.
² Set Condition:
O2 sensor readings on Bank 1 side indicate a lean condition while in 4 cylinder mode.
Possible Causes
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1. ACTIVE DTC
NOTE: Diagnose any Deactivation or Oil Pressure DTCs before continuing with this test.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
Yes >> Go To 2
No >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2. MDS SOLENOID 1
Turn the ignition off.
Remove the Intake Manifold per Service Information.
Turn the ignition on.
With the scan tool actuate the MDS Solenoid 1.
Can you feel and hear the Solenoid Actuating?
Yes >> Go To 3
No >> Remove the Solenoid and check for any debris that may be blocking the oil passages to the Solenoid.
If the passages are clogged, clean the passages and replace the MDS Solenoid 1. If the passages are
not clogged with debris, replace the MDS Solenoid 1.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
LX ENGINE ELECTRICAL DIAGNOSTICS 9 - 915
3. MDS SOLENOID 7
With the scan tool actuate the MDS Solenoid 7.
Can you feel and hear the Solenoid Actuating?
Yes >> Go To 4
No >> Remove the Solenoid and check for any debris that may be blocking the oil passages to the Solenoid.
If the passages are restricted, clean the passages and replace the MDS Solenoid 7. If the passages are
not clogged with debris, replace the MDS Solenoid 7.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
4. OIL PASSAGES RESTRICTED
Turn the ignition off.
Remove both Solenoids on Bank 1 of the engine block.
Remove the Bank 1 Cylinder Head per Service Information.
Remove the Lifters from the left engine bank.
Inspect the oil passages to the Solenoids and from the Solenoids to the lifters.
Are the passages blocked?
Yes >> Clean the oil passages as necessary. If the entire engine is restricted disassembly of the entire engine
block may be necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No >> Replace both sets of lifters if no other possible causes remain.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE

Hope helps.

I had the same problem. Restricted performance and running rough at 3000 RPM. I have an OBDII code reader and found that the problem was in the air mass flow sensor, which is just after the air filter. I pulled this out and found it was dirty and had butterfly wings in it. The last shop where I had the oil changed replaced the filter for me but put in the wrong size. Close but no cigar. Bought some *** Flow Sensor cleaner at auto store and fixed the problem. Get an OBDII reader with the ability to erase the codes. Comes in real handy.

Anything can cause the check engine light to go on from a loose gas cap, to a transmission issue. When the onboard computer detects an issue, it will restrict performance so as to not damage the engine any further. An Oil change won't affect this light. The only way to determine the cause of the light is to have the computer scanned with an OBD-II tool (Autozone does this for free) to determine the codes and cause for the light. You can also clear the light with the OBD-II tool, but if the problem is still there, the light will just come back on

you would need fault codes

Go to Auto Zone and ask the to run a diagnostic with their OBD-11 computer. This may still be a free service. Write down the error code/codes displayed. This should help pinpoint the correct sensor.

My mechanic said that the front cxygen sensors needed to be replaced on my 03.