Hi, I'm still trying to source the problem of stalling on my XJ300. Car will run fine one day and stall out within a couple of miles of leaving home the next - check engine light showing.
All the induction side has been cleaned and checked including the throttle body - it really needed a good clean. Fuel lines have been blown out and filter replaced but problem persists. My mechanic felt the problem comes from the motor running out of fuel. I wasn't sure about this as the plugs I had just removed were very black and sooty suggesting an over rich mixture especially when motor could be re started when throttle was held as far open as it would go.

The car had sat in a garage unused for three years up until my purchase of it two months ago and he felt we should remove the tank and check it out. This has just been completed without coming across any real problem but while doing this job I took the opportunity of replacing the fuel pump and all flexible fuel lines. I also ordered the Innova 31420 diagnostic code scanner to have at the ready.

Yesterday we completed the tank replacement but still had the 'check engine' light showing. Luckily my scanner arrived in this mornings post and I've been able to plugs it in and get some readings - six in fact. I have no idea when these codes were last cleared so some may not be of concern now but three are of interest - maybe?

First up came,

P1193 02 sensor heated circuit open

P1775 Transmission system MIL fault - could this be giving me the 'check engine' light?

P1138 Lack of HO2S12 switches - sensor indicates rich mixture. See (P2271).

The last one fits in with the sooty plugs I removed a couple of weeks ago.

If anyone can shed any light on what this information is trying to tell me and possibly how to fix it I'd be very please to have their input.

Thanks for listening and any help/suggestions offered.

Cheers, RogerB
1994 XJ300 4 litre
NZ

 

Hi Roger may be try the fuel pressure regulator at the front on inlet manifold side may be faulty. Or the thermo time switch on top of the thermostat housing; this tells the ECU when engine is at wright temp for fueling .worth a try .
Cheers Ray

 

Maybe your fuel injectors are hanging open. Try some fuel injector cleaner in that case. If it gets better, then it's either more cleaner or an out of car cleaning.

You can clear the codes and see which ones come back.

 

If you have a duff O2 sensor your car will run in open loop - taking a guess at fuelling mix.
I think you need to check and, if need be, replace the O2 sensor before doing anything else.

 

Thanks guys for your suggestions. Firstly I found the plug to the thermo switch was not seated so thanks for this suggestion Ray. Will check the fuel regulator when time permits - better safe than sorry.

Have put around 40 litres of 98 in the tank along with some injector cleaner so will see how this goes - hopefully in the next few days.

As for the 02 sensor Steve, not sure just where it is but I'm sure with a little time I'll find it and get it checked out.

Once again, thanks guys.

Cheers, Roger
NZ

 

O2 sensors: one on each exhaust pipe, four wires each. Two on each pipe if you have catalytic convertors (don't think you do in NZ???). Code P1193 could mean a connector plug is loose or disconnected. Trace the wires from the O2 sensors and check any connectors you find. There are two connectors mounted on the right side inner fender. P1138 could be related to an open circuit as well.

Any or all of your codes could probably set the MIL (check engine) light, especially over time.

 

Hi Richard, thanks for your detailed reply. As the car is new to me I'm going to book it in for a transmission service so while it's up in the air I'll have a look for the 02 sensors and if necessary get them checked out. Like you say, only 2 for me to worry about.
After I had made notes of the fault codes from the scanner I erased them and have just given the car a good run around the country roads (without a problem). Have run the scanner again and get the all clear ( I think some of the codes must have been old ones) but the Check Engine light still stays on which possibly gets us back to the 02 sensors.

Cheers, RogerB
1994 XJ300 4 litre
NZ