I have a slightly modified 2004 XJR. The modifications include cold air filter, cat bypass (custom), Mina mufflers, and the smaller blower pulley. I recently did a service including new coils and plugs, new mass air & map sensors, had the supercharger off to also replace the heater hose(basically complete cooling system). It was a tedious job (no doubt) took a few weeks to figure it all out. I recently moved across country and no longer have a shop or tools to do the work myself. I'm currently having problems with the restricted performance light coming on once in a while and the check engine light is on. The car runs rich at a cold start but then runs fine. The cars also is running like a beast when the restricted performance light is off (which is 85% of the time). My brother has a S65 Renntech that's over 700hp at the wheels and on the freeway he only pulls away from me slowly. The only thing I have yet to replace since I bought the car in 2006 with 16k miles on it is the oxygen sensors. Does anyone have any ideas for me?

 

It's pretty hard to guess what happening w/o a codes. Get a generic ODB-II reader (ELM-327 will be fine) and pull a codes. If a check engine light is lit - there's a code(s), which are generic OBD-II codes.

 

+1

Scanning for DTC's is always the first step in powertrain troubleshooting. Without that the possible causes of the CEL illuminated is nothing but speculation or guesswork.

Graham

 

When I scanned it I get all types of misfire codes and fuel pressure codes and electronic throttle monitor data

 

I'm wondering if it could be a fuel pressure sensor

 

Well, it's better to write an exect codes, but, in this situation i'd check all grounding points and electrical connectors in the engine bay(esp. a ECM connector).
But it's not an exect scenario, since a wrong fuel pressure may cause misfires, while a throttle monitor data code (P1582) is present almost all the time and P1582 is not triggering a CEL.

 

did the faults start to happen right after you performed all the work? I would start to go over and check all the work that was performed. Make sure there's no vacuum leaks, Make sure all the sparkplugs are plugged in correctly and properly gapped. Maybe the new MAF or MAP sensors are bad. Do you have the old one to put back in and try?

 

Hi sheerant,

The ECM bases start-up fuel enrichment on the signal from the Engine Coolant Temperature Sensor (ECT, known as the CTS on previous models), so you might check to ensure the sensor resistance/voltage is adjusting properly and within spec and that its electrical connector and harness are okay. I can't remember if you can see the ECT/CTS signal using common OBDII live data scanners but that would be worth a try.

As others have mentioned, looseness or corrosion of ground points can cause hard-to-diagnose gremlins so it would be worth cleaning all the grounds in the engine bay, especially the one on the LH side rearward of the suspension tower, where the ECM is grounded (according to the X350 Electrical Guide available in the download area of this forum). On our LHD '04 car, that ground point is under the plastic cover for the brake fluid reservoir. I do not know if the ground point is on the opposite side for RHD cars.

As others have already requested, please let us know the specific fault codes.

Cheers,

Don

 

Hi Sheerant,
What kind of cold air intake did you install? Is it the "open air cone" filter? The problems you are describing are similar to what I had on my XJ8. I had the Mina Gallery intake (open air cone) installed and later down the line I was getting "Restricted Performance" MAFs code and the engine light would turn on. The car still ran strong though, but it was annoying that those codes would pop up once in awhile. I found out the codes happened mostly in heavy traffic or on hot days. The intake is sucking in hot air plus all the dust particles in the engine compartment so the MAF sensor gets dirty too. I went back to the stock intake, got an OEM MAF sensor from the dealer (don't buy remanufactured Toyota ones from your local auto store), and put the K&N air filter. Problem solved! The stock intake box protects the filter from all the dust particles flying around in your engine compartment plus the heat. Also, the less likely the MAF sensor will get dirty (unless the K&N air filter is too oily). This would be a first step to try to solve your problems and hopefully this helps.


PS: The best way to get a real cold air intake with the open cone filter is to have it going from the bottom of the car to the top (throttle body). This setting will allow the car to capture cold air from underneath without sucking in hot air produced from the engine at the top. Unfortunately, there is no modification available to have that setup for this car.

 

How's your battery, poor ones can cause things to go bonkers..

 

I've read a long time ago that gutting or bypassing the cats on the jag can cause the computer to act up. Don't remember exactly why though.