First, sorry for my bad English. Not my native language.


My car: Jaguar X-Type AWD 2.5 V6 automatic, year 2004. I've had this car for three years and it has been super reliable. This is the first issue I ran into.

I had the infamous 1647 error code (upper 02 sensor). I replaced the sensor with no problem, reset the fault codes and the engine light was gone immediately. Part was the original Denso part.

I just wonder, immediately after the exchange of the sensor the engine got this strange twitching and stuttering when using the kickdown and getting to certain RPM level. When there's no pull, there's no stuttering.
It's like some kind of electrical issue... just like when you have a bad distributor or spark plug. Kickdown is working and it's getting the high RMP... the stuttering happens in the "area" where you're "entering the high RPM zone" if you know what I mean.

Idle is fine, everything is fine, fuel consumption is normal. And no errorcodes.

The potential options that I was thinking:

1) I was driving a week with a broken sensor, and then, of course, the car is getting plenty of gasoline and fuel consuption is high. Maybe the gearbox and all computers got "confused" somehow when the new part was put in.

2) The sensor didn't get tightened enough. The place is tricky but ut should be just snug enough. It's like any spark plug, I've changed them many times. On the other hand, if it would not be snug enough, would it give this kind of issues? I doubt it. It was running and accelerating fine even with the broken sensor.

3) Maybe I've had another issue with fuel injection nozzles and with this new, working sensor the fuel consumption suddenly isn't "rich" enough? Or could it be that the spark plugs are "wet" after driving with the bad sensor. These can be complete nonsense... just thinking loud.

I changed the air filter at the same time, now it's new and clean. I also double chacked that the incoming air filter breather pipe is connected properly, there should be no air leaks, either.

Just now I took out the negative pole of the battery and will let it sit overnight. Maybe it resets mm. gearbox settings and others?

Of course the sensor itself could be bad but I doubt it. Original Denso part, brand new.

Is there any other ideas?

 

Disconnecting the battery erases the system adaptations. Prolonged normal driving will eventually restore them, but the Jaguar way is as follows

To enable the ECM to re-learn fuelling adaptions, this procedure should be performed whenever the vehicle battery has been disconnected. Due to component tolerance and wear during the normal running of a vehicle, fuelling and air requirements for an engine will vary over time. The ECM has the ability to adjust for this variation by 'learning' the level of compensation that is required. (These compensation values are referred to as adaptions) If the vehicle battery is disconnected, all adaptions held within the ECM will be lost (ie, set to Zero) The ECM is then referred to as 'green'. To enable the vehicle to function correctly, the ECM must 'relearn' these adaptions. There are four areas or sites that need to be relearnt. Allow the vehicle to idle until fully warm. (Temperature gauge just below mid-point). Allow to idle for a further three minutes, minimum. Drive the vehicle with the air conditioning OFF on a level road using a constant throttle, or speed control if fitted, for at least one minute in the following gears, at the stated engine speeds. The vehicle speed is for guidance only. DO NOT use the vehicle speed as the target to set adaption

For your 2.5 Auto (Other engine/gearboxes have different speeds/rpm) for one minute each;

3rd gear 1750 rpm 23 mph, then 4th gear 2250 rpm 43 mph, then still in 4th 2750 rpm 54 mph. Come to rest and idle for another minute.

 

Brilliant advice. Thanks.

So you think that could be my stuttering issue then?

 

Well, it might be a free get-out-of-jail card if you're lucky!

 

I'd be more inclined to think that a component was left unplugged or came loose during the work done. Check that everything is plugged in properly and there is not vacuum leak.

 

Thanks Revere. I will try tightening the sensor more. That's the only thing I can think of.

This is the prodecure.

 

If you have code reader check your fuel trims.
Long and short term.

This will tell you whether your sensors are working correctly and if there is any vacuum leak.

 

I drove my x-type for many hundreds of miles with a faulty manifold O2 sensor and had no issues. I got some misfires after my spark plugs were changed but that soon cleared up. Automatic climate control can sometimes cause engine misfire/stutter - as the AC compressor is cutting in repeatedly to try and maintain the cabin temperature you have set (I had this problem) turning climate control off solved it for me & I've had no trouble since, worth a try!

 

Tightened the sensor. No effect. Absolutely no jerkiness when the engine is cold. But when it reaches the normal temperature, it starts. This might indicate that it's getting more fuel when cold and no problems. I will put fuel injection system cleaner to the tank and see if that helps.

I have a code reader and I get error code P1796. But I got this code with before the issue too. I believe it's one of the wheel sensors giving this. Is there a "kickdown switch sensor" somewhere? Could that cause the jerkiness?

Google says about P1796:

"A diagnostic system for watching the sound operation of a kickdown switch in an automotive vehicle equipped with an automatic transmission adapted to be prohibited from operating at the highest speed stage according to the operation of the kickdown switch, the system including a comparator which compares an output signal from a throttle opening sensor corresponding to the depression of the accelerator pedal of the vehicle and an output signal from the kickdown switch, and generates a warning signal when the two output signals are not correlated with one another in a predetermined mutual relation so as to inform the driver of a malfunction of the kickdown switch. "

Whatever that means.

PS: Big thanks for all your suggestions. Much appreciated.

 

Best to use Jaguar documentation for error codes.

Workshop manual available here: http://www.mediafire.com/download/xp...Manual.pdf.zip

Much information here (Thank you Gus): JagRepair.com - Jaguar Repair Information Resource