A new problem has arisen. My 1996 will start right up and drive perfectly and take me where I'm going. The problem occurs when I again drive the car with the engine still warm. It will start right up and I can usually just drive away. When I come to a stop, the car idles fine. However, now when I push the gas petal, the car bogs down and stalls. It so far has always started right back up and I drive away with no more problems. The cars idles and runs smoothly. Any ideas what could be causing this? Is this vapor lock? Could a sensor be the culprit?

 

Assuming no codes.

Do you have an OBD2 reader that can pull the LTFT? (curious to see if a vacuum leak is in play)

When was the last time you:
1. replaced coils and spark plugs
2. replaced fuel filter
3. replaced oxygen sensors
4. cleaned throttle body

an OBD2 reader can also see if the coolant temp sensor is working properly.

 

Vee - Plugs, fuel filter, air filter, oxygen sensors all have about 1000 miles on them. EGR valve is a few months old and and the throttle body was cleaned then. I've never had an indication of a bad coil, but how do you check them? The fuel trim has been a little erratic and the injectors probably need to be cleaned. I'll do a recheck with the OBDII reader. The old oxygen sensors were replaced as routine maintenance and I still have them. Maybe I'll use one of the old ones and do a switch and check.

 

This sounds like a TPS to me. The failure mode for the TPS was exactly that on my 95

 

I'd narrow this down to the TPS or the coils. If Spikepaga says TPS, I would listen to him.

You could do a visual check on the coils, to see if there is any visible signs of cracking, or you can run the engine at night, without the coil cover, and see if you see any sparks. Other than that, there's no good way of testing, other than replacing.

 

Thanks. After all I've read, I really hate to mess with the TPS. I'll go back and read the TPS threads. The engine runs smooth and generally idles fine, so I doubt that a bad coil would cause the stall outs. Is there any maintenance that can be done to the TPS while installed?

 

We all fought that fault at the dealer. I NEVER came up with a permanent solution. The fault was always intermittent so no way to find a definite cause.
Lots of customers just gave up and sold the car.

Sometimes the car would drive fine for weeks and then STALL!
Start right back up and the only fault was the gearbox DTC for ENGINE STALL (duh).

 

No. The TPS is one of those parts that bench tests perfectly fine, and then gets wonky on the car. It happened to me. There is nothing to lube, or resolder.

The coils need a oscillograph, I believe, to properly test them.

I'd hate to recommend parts to throw at the car, however, these two parts should not be crossed off the list of suspects.

 

(Almost) Every AJ16 needs

New quality coils
New TPS
New CTS
New CPS

These parts CAN NOT be tested. They malfunction intermittently . The last XJS rolled of the assembly line when I was in middle school. Unless you have the 12k mile XJS on auction at Hemmings, I would argue these are maintenance parts these AJ16 cars need for reliable use at this point, and unless I knew they had been replaced I would replace all of them...and also pack the ECU with XG-12 to prevent water ingress.

https://www.hemmings.com/classifieds...st_classifieds

but this sounds like a typical TPS failure to me.

EDIT: Also new relays all round IMO.

 

Im gonna disagree on the relays….I’ve not run into trouble with any of mine. Ever.

 

Do you still have the blue ones?

 

Yes, plenty of them. I can see where this is going. Is there a recommended set of relays to buy?

 

lmaoooo ...you know that is involves changing parts, I am on it.

Jaguar themselves recommended these
blue relays be replaced:








HOWEVER, do not buy the relays Jaguar sells for 40 dollars!!

they are quite literally these, in Jaguar boxes :

 

Sorry OP for derailing your topic with Relays

 

I always try to post the CRAPPY BLUE HELLA RELAY TSB whenever I can.
We replaced countless relays when I worked at the dealer.

Glad to see others post it also.

 

I've had a relay fail on me more that once. I no longer use the crappy blue ones and use the later brown relays found in the X300 cars.

As for this issue, I'd try a new MAF. Seems like a MAF problem to me.

 

Agree about the Blue Relays which are above the Fuses that are located behind the Passenger Side 'Knee Panel' as for some reason the Relay Blades didn't seem to be making very good Contact in their holders, which was one of the reasons that my Car wouldn't Start

Though after removing both of them re-seating them and even swapping them around, I'm very pleased to say that my Car Started and that was even after trying almost every trick in the book to get her going

Bad Contact with the Blue Relay Blades under the Passenger Side Knee Fuse Box was one of the reasons why my AJ16 Engine wouldn't Start

 

ICSAmerica, I'm not sure I agree. A MAF problem usually reveals itself when the engine is warm or cold. In this instance, everything starts off fine, the car is driven without issue, and only has an issue after it comes to a stop, then bogs down, gets restarted and the OP in on their way.

What about the IACV? Couldn't that cause this problem?
I also think the EGR Valve could be suspect here.
How about the CTS?

The coils are still on my list, but I wouldn't consider the MAF. MAF issues don't usually show up this specifically. They usually cause problems the entire time.

I would also plug in the OBD2 and check for LTFT, just to make sure you don't have a vacuum leak.

OP, when idling with a warm engine. Is the RPM needle steady...like for an entire minute or two? Helps if the engine is loaded with headlights and air conditioning.

 

Thanks for the replies. I think I'm going to remove the throttle body and soak the TPS in solvent as someone on this forum had previously suggested. I'll also replace the CPS as I have never done that before. I will also check it with the OBD2. If I find the solution I'll let you know.

 

I think thats what you do to destroy the TPS. One of the suspected ways that the TPS is destroyed is when people try to clean the throttle body with the throttle body still on the car. The cleaners then drip down and gather at the bottom of the butterfly and damage the TPS...allegedly.

Let us know how it works out for you.