Hello,
I’ve got a problem with my X308 and can’t find the cause.
I took it out for a reasonably long drive (about 150km) and it drove like a dream.
I was driving up to 200km/h without any signs of a fault (I’m from Germany).
Afterwards I cleaned it, started it and the idle was really rough. I wanted to drive it in the garage, but it barely moved.
After giving it some revs it slowly started to move.
I noticed that it only idles roughly under 1100rpm.
No warnings were displayed on the dash, however, after reading the codes my reader showed the following:
P1798
P0790
P1202
After deleting all codes and letting it run for a minute and reading again, only P1798 remained.
I don’t know whether those codes relate to the problem I have.
I checked several vacuum hoses but didn’t find anything suspicious.
Any advice is very appreciated, I hope someone can help.

(Jaguar X308, 3.2, 1998)

 

I must admit, I am puzzled by your codes. I have been through the references I have and none of them have a definition of those code numbers or even list them. I would recommend getting them read with a different reader. I don't think you are getting valid results.
As to the poor idle i would recommend starting the engine and warming it up. Then let it idle if it will, next unplug the MAF sensor on the inlet snorkel. Does it make a change in the idle condition? If NO then bad or dirty MAF. Try cleaning before replacing.

 

Thanks for the fast reply!
I haven’t found a clear definition of those codes either, they confused me too.
However, the code reader worked fine in the past, but I’ll try unplugging the MAF sensor tomorrow morning and check whether my second reader shows any other codes.

 

Hi FwIcf,

P1798 and P0790 are transmission codes. Here are the definitions from the 1998 ZF 5HP24 Transmission Diagnostic Trouble Codes manual, which I am linking to below:




Jaguar ZF 5HP24 DTC Summaries 1998

I have seen codes like those when the engine takes a little too long to start, and I have associated them with low battery voltage to the ECM & TCM while cranking.

If by "cleaning" your car you mean that you washed it, it could be that some water got into the ECM / TCM compartment in the firewall/bulkhead corner of the engine bay opposite the steering wheel (right rear corner on LHD cars, left rear corner on RHD cars).

You can also check your Sport Mode switch connection by carefully prying up the trim ring around the J-gate and checking the electrical connection to the Mode switch. I have seen two instances of a bad connection to the Cruise switch triggering codes for the brake switch and Restricted Performance, so I assume the connection at the Mode switch could vibrate loose or be contaminated by a spilled drink.

P1202 is a generic OBDII code that indicates a problem with the cylinder 2 fuel injector and cylinder 2 misfire Perhaps some water got into the electrical connector for the injector but boiled off while the engine was running.

The rough running could very likely be associated with the P1202 code. It could also be possible that while washing the car some water got into the fuel tank. Is the drain clear in the gaiter around the fuel filler neck? I use string trimmer line to run down the drain tube to be sure it hasn't been clogged by seeds, leaves, etc. If the drain becomes clogged, water can pool around the fuel filler neck and make its way past the cap seal and down into the tank.

Cheers,

Don

 

Thanks for the reply Don.
I think you’re right with your proposal that water got into any electrical stuff.

I did the following today:
I checked the fuel cap, which was sitting tight and there was no water left from washing the car (yes, by cleaning I meant washing), but I poured some water next to it and the water was gone quite quickly, hence I think there is no water in the fuel tank.

Then I plugged in another code reader and started the car. It was running a little rough, nothing in comparison to yesterday. The code reader showed no codes.
I unplugged the MAF and the car almost died, so I immediately plugged it in again.
Afterwards I got a code for the MAF, which I deleted.

I let it run for a couple of minutes and in this time the engine shudder completely disappeared and the car idled like it should.
Because it is raining outside I didn’t want to take it out for a drive, but moving 1-2meters forwards and backwards worked as it should.

Intuitively I‘d say some water from washing the car got in any electrical connections, which dried overnight and made no further issues today.
Do you have any suggestions where this could happen?
You mentioned the ECU/TCU, I removed the black cover with the tools inside and it looked bone dry under there. Did I look at the right place?

I think I will read the codes one more time with the reader I used yesterday to see whether those transmission codes are gone.

 

I just read the codes with the other reader and it showed P1798 (which was stored from yesterday), I deleted the code and let the car idle for about 5 minutes.
I did the same yesterday and P1798 returned.
Today, however, no codes were shown after I read again.
The idle was, as it should be, smooth and stable at about 800rpm.

 

Maybe battery now has more charge.

 

I don’t see why the battery should have more charge after sitting one night, than directly after taking it out for a long drive.

 

Weirder things have happened.

Water is similarly weird so it may be that.