1994 XJS with I6 engine. Check engine light is on. Does not have OBDll for diagnostics. Car running cold. Could these two be related? Any ideas where to start. Temp gauge barely moves.

 

Rchuda,

Start by checking whether the engine seems to be heating up correctly. A stuck open thermostat could cause the symptoms you're describing.

Start the engine an monitor the top hose temp by the thermostat housing. If the 'stat is working correctly, the top hose will barely warm up until the stat opens, and then you'll suddenly get heat buildup in the top hose.

Cheers

Paul

 

I suspect the cheap, and easy to replace coolant temperature sensor. A critical part of your engines fueling.

I would start there, but it also can’t hurt to order a new thermostat either, as I could be wrong. You have the o-ring, I presume with the AJ6 engine? If you find that there’s no o-ring when you pull your thermostat, make sure you don’t add one..:you need the gasket instead. Installing a o-ring where there wasnt one before will end up in a cracked housing. You don’t want that.

For the most part, AJ16 has gasket. AJ6 has o-ring, however, there have been posts of AJ6 with gaskets before, so be careful! Do not rely on parts counters.

The gasket definitely will not come with the thermostat. The o-ring might.

My suggestion is to order the thermostat and coolant temp sensor. Neither is expensive.

 

Rchuda,

The fuelling of the car, per se, will not make your car run significantly colder. If your CTS is causing the car to run a bit lean, then it may run a bit hotter. But if the CTS is causing the car to run rich, it won't stop the car from warming up.

In general, if you're running lean, the car will be difficult to start, but then run better as it warms up. Whereas, if you're running rich, it will probably start ok, but then run worse as it warms up.

Check that the stat is closed at start and then opens up. My money is on a stuck-open stat that is precluding the car from warming up and then staying in the correct heat cycle.

Cheers

PAul

 

While I agree with what Paul is saying... but the fact that there's been a code triggered bothers me. I don't think there's a code for a failed thermostat.

What it could be...which would be just as easy to fix is the Coolant Temp SENDER, not the sensor. The engine has two sensors on the coolant line. One is the SENSOR, and it communicates to the ECU and affects fueling. One that is bad would cause the car to idle erratically upon startup, especially when the engine is cold.

Then there is the SENDER, which only sends a signal to the dashboard. It doesn't affect anything. It is entirely plausible that the SENDER may have died? That could trigger a Check Engine Light.

Without an OBD reader, you most likely don't have the means to see what the ECU is reading for coolant temperature.

Go to Page 81/140
http://jagrepair.com/images/AutoRepa...stem%20S91.pdf

 

Good points, Vee

Paul