I'm trying to diagnose an acceleration issue with a 2002 Jaguar S-Type. If you give it mild throttle, like enough to move around a parking lot, it works normal. As soon as you give it any more than like 15%-20% throttle it bogs down. It acts like you arn't pressing the pedal almost. It stays this way until like 90% throttle. As soon as you floor it everything acts normal again. Car accelerates as it should (when floored). No misfires, skipping or jerking and it pulls good as well. Also the car starts just as it should and it idles well. Almost as if there was no issue. The only codes its throwing are a P1000 and P1647. I know the P1647 has to do with the 2nd bank O2 sensor. I feel the codes are unrelated to the problem though. I have pulled the spark plugs and inspected them, they checked out ok. I suspect the TPS sensor is at fault but its not throwing any codes related to the TPS sensor. I Pulled the intake piping off and had a buddy press the accelerator pedal slowly. It opened smoothly as it should so I don't believe its an issue with the pedal assembly or the motor for the electronic throttle. Is there anything else you would recommend checking? Is there a way to test the TPS sensor? Any help would be greatly appreciated. Thank you

 

Forgot to add, Its a 3.0 V6

 

Add a can of BG44K to your fuel thank and fill it up and see if the problem goes away.

 

To have P1000 you've cleared the codes or had the battery off. With luck it will change to P1111.

Fix that O2 and fast. You're destroying the cats. Don't drive more than you must till fixed and don't thrash the car at all. It's ill.

 

I don't think it's a fuel issue. When crushing, if you let off the throttle you can feel the power briefly come back right before you fully let off the throttle. If something was wrong with one of the injectors or the filter was clogged it should have all around crappy performance. Not just on one particular area of the throttle. If it was an injector it should also idle rough.

 

Don't mess with TPS - it's a redundant pair of tuned sensors so they flag codes if faulty. You have no codes so leave well alone!

 

Certainly replace the O2 but do not underestimate the qualities of a clean fuel system on these cars.

 

I'll go through and switch the fuel filter and run some system cleaner through it. Any suggestions for a cleaner? I'll probably go through and clean out the throttle body well too. It's not the worst I've bee seen but it's not exactly spotless either.

 

CRC Throttlebody cleaner. For the fuel system BG44K

 

With my 2002 S-type 3.0, I was having similar issues with acceleration and having to floor the pedal climbing inclines - turned out I needed new coils. I did screw up one of the Catalyst converters driving the car around, ended up replacing the cat and the O2 sensor. Don't recollect what code I got - but it was specific to one Bank.

 

DTCs are P0420 for the RH side (Bank1) and P0430 for the LH side (Bank2).

If the MIL is flashing, catalyst damage is occurring as raw petrol is being burned by the catalyst causing it to overheat.

 

Just curious, are you independently wealthy? Do you have money to burn? Or would you prefer to fix your car with minimal outlay of time and money? The choice is yours.

You see, your car is very smart and is trying to tell you something via the P1647 code. Now this means of communication (OBD II speak) isn't perfect, but is still pretty darn good. Some problems can occasionally set off seemingly unrelated codes, and you have to be aware of that. But as a general rule of thumb, work the OBD II codes first before chasing squirrels elsewhere.

You can read more about the codes here, courtesy of Gus:

JagRepair.com - Jaguar Repair Information Resource

Please keep in mind that O2 sensors are normal wear and tear items. They get old and drift out of calibration relative to the actual contents of the exhaust stream. Remember earlier I said your car is very smart? That's only half true. Your car is also very dumb. It has no foolproof means to know when a sensor is out of calibration. It has a general idea, i.e. if given so much fuel at this RPM, temperature, etc., the output from the O2 sensor should be in a certain range, but that's it. But in your case, the computer does realize something isn't right and is trying to tell you. It doesn't have an audible voice to tell you. It can't use interpretive dance to communicate. It can, however, slip you a note under the table. It's written in a foreign language (OBD II) and you have to translate it.

The O2 sensor is critical to proper engine control. However, they are generally so reliable we don't think much about them. Just keep in mind if the O2 sensor's accuracy has degraded (normal as they age), the computer is now operating with inaccurate input and can only react as programmed. In other words, the computer will send inaccurate outputs based on the inaccurate sensor, totally oblivious to the actual air/fuel mixture.

So in 50 words or less: listen to your car, quit messing around with the throttle and take care of that P1647 code first. You can do it on the cheap by swapping sensors, clearing the codes, and seeing if the code follows. And if that doesn't help, you'll get to rub my nose in it, which has got to be worth something.

Keep us posted.