So I bought a 94 XJS convertible last year. Early on (in warm weather) I'd be driving and the car began to feel as though it wanted to stall out. Losing power and getting slower. I'd pull over and either it would stall OR I'd shut it off. A moment later, I could start it up and it ran fine.

As with the first posting on this forum, I could start the engine and it runs fine. After that I may take two, three or four tries to get it to start after running a bit.

Through the winter (cold weather) the car ran fine though the starting issue continued.

A few days ago (mid March and the return of warm weather in Albuquerque) I was driving to church. When I got to the exit, I noticed that the car was idling rough as if it wanted to stall. I managed to get to church (only a few miles away at that point). Afterwards I took off the IGR valve and cleaned it. A few days later I replaced it completely.

Yesterday I was driving across town (towards church again) on a warm to hot day and about 15 mile into the trip the are stalled at speed. I coasted to the side of the hiway. It would start, but idled rough and stalled almost right away.

After a few minutes the car started and ran fine. After church last night (slightly cooler weather by then) I drove back home with no issue.

SO my question, does anyone know what the problem is??

Do I have a failing TPS or IAC valve?

I saw someone say to check connections. Since this happens in warm/hot weather could it be that warm weather causes the connections to be just a bit lose then in winter? Silly I know.

Any info you can provide is much appreciated.

Tony in NM

 

Hi Tony

Do you have a V12 or the Six Cylinder?

 

Very similar to a fuel pump

 

Sounds very much like a too rich condition. Not so noticeable in cold weather. Over rich / flooding in warm weather. Air temp sensor? My 92 V12 has both a coolant temp sensor and air temp sensor. And, almost forgot, fuel temp sensor. The air temp sensor could for sure cause these symptoms. Fuel pressure regulator is also a possibility.

 

Assuming you're running the proper spark plugs, gapped, as well as cleaning out the throttle body, I will give you my advice based from an AJ16, not AJ6 (which I suspect you have) engine. They are similar enough.

1. Check the Coolant Temp Sensor. Could be bad. That could cause your problems. Its a cheap $20 part and easy to get to.

2. The TPS does make the car do crazy things. It's an awfully expensive part, so I'd hold off on that.

3. The MAF Sensor can cause similar problems. Also an expensive part.

4. Oxygen Sensors might be failing. If they are original, could be worth replacing in any case.

5. Crankshaft sensor. I've not experienced it, but I think if you do a forum search, it also tends to cause random issues.

6. Last but not least, fuel delivery issues, such as pump, regulator and filter, as mentioned before.

Without the ability to put a multimeter on any parts, it will be difficult to diagnose.

I did not think that a failing IACV would cause stalling at speed. I think you can cross that off the list.

 

It's a 6 cyl.

Tony

 

Glad to know though it is not an expensive part.

Thanks, I will check sensors you mentioned.

Tony

 

HI all,

I placed an order for new oxygen sensors this morning. The online store made mention of UPSTREAM sensor. Was that correct or is that the only oxygen sensor on the XJS???

 

PS: I intended to tinker with the XJS yesterday, but it was cooler and windy, so I opted out of that project. I did, however, drive to an event yesterday and just as I expected, no stalling, but I do occasionally get the smell of gas. I guess running rich, right? Although the car can smell "Hot" there is no indication that it is running hot at all.

 

The fuel smell could be a leaking tank - as they do like to leak. Take a sniff in your trunk.

 

Oddly enough, it's the downstream sensors you want to replace.

The upstream sensors are kinda dummy sensors. All they do is prove that the cats are doing something by showing numbers that are higher than what the downstream sensors show. Doesn't really matter how much higher, they just need to be higher.

That being said, they are far less likely to be causing you any problems.

All four sensors are identical and interchangeable.

 

This is always a great forum to find out stuff. Can you tell me where the downstream sensors are located??? I found the upstream ones.

Tony

 

Just past the cat, after the pipes bend to be parallel with the ground. You'll have to get under the car to put a wrench on them, but you should have plenty of room.

 

I took the car for a spin today in the heat of the day (to recreate the stalling issue from last time). I drove on surface streets with no issue. I got onto the highway and up to 75 MPH and it started to stumble/stall. I coasted off the road. After sitting for a few moments, it started and ran fine, just as the last time.

Any thoughts??

Tony in NM

 

This has to be a fuel supply problem. On a V12 (I think you have a 6?) the main tank to sump tank hose falls apart internally and starves the engine of fuel. You stop and it recovers, the sump tank refills under gravity, and off you go. I would go through this aspect of the car from tank to fuel rail.
Greg

 

I have been looking for the hose you make mention of, but don't see it listed in either the online repair manual or on any part store websites. Do you know the part number or such??

Thanks
Tony

 

I have been looking for the hose you make mention of, but don't see it listed in either the online repair manual or on any part store websites. Do you know the part number or such??

Thanks
Tony

 

Assuming you have a main tank and a sump tank and an external fuel pump, I am talking about the hose that leads from the main tank to the sump tank. no. 14 in this diagram:

But I am also saying that the entire system needs to be checked and blown through with compressed air from the boot to the injector rail inlet. It could also be the pipe FROM the sump tank to the fuel pump (no. 19) or the pipe FROM the pump to the filter, or the pipe FROM the filter to the corner of the boot where it joins the external pipe that runs under the car. I suppose it just COULD be the tank not breathing, so it would also be worth loosening the fuel cap (or somehow else ensuring air can get into the tank) and seeing if that cures it. Even new filters are occasionally faulty, and are often fitted the wrong way round, too.
Greg