I've been having a problem with my 96 XJS as of late.

When the A/C is on, the car turns super sluggish at the throttle and the transmission shifts. From a stop light, I could have my foot halfway down on the gas and the car struggles to move more than 2 mph.

Then as it gains a head of steam, the transmission shifts way hard and way early, almost as if it didn't realize the car wasn't at speed yet?

Eventually the problem goes away. It seems to happen only when I first engage the AC and only lasts a few miles.

Any ideas where to look?

No codes were thrown.

 

Are you running premium / high octain fuel? Sounds like the heat and load is causing knock and then the ECM is cutting back the timing and power falls. If this is the case try some top engine type carbon cleaner like BG to treat and blow out carbon which can raise compression and cause combustion chamber hot spots.

 

I will try that. I'll dump in some Techron?

I've always used Premium gas, I usually stick to Shell.

I don't sense any knock. I do have the Andy Stodart bracket installed.

 

icsamerica, any chance there's an air leak after the mass air flow meter? (disregarding some of the symptoms)

 

Ok, new twist.

Car just shut off on me at a stop light. The AC was off and the car had been running for awhile, so it was hot.

I turned the car over and it started but then sputtered and died as if it were starved of fuel or air.

Could this be my fuel pump dying? It is 18 years old even though it only has 72k miles on the clock.

No codes.

On a related subject, I was noticing some hesitation while cruising at 55mph. It seemed to go away at higher and lower speeds, but something about the 50 range seemed to make the car putt a little.

Make sense?

 

Hi Vee,

Maybe CTS?

 

I will take my laptop with me and start recording live data.

The CTS will probably give itself away of the temp readings drop at any point.

The fuel pump will be tougher to diagnose.

I'm hoping the TPS would give itself away with a similar dead, or minimal reading on the throttle position?

What else should I be tracking?