Greetings all. I could use some help diagnosing a non-start situation with my 2000 XJR. Here's what I've got:

• Started her up the other night and noticed a rough idle. The car has not been sitting, as I drive it almost daily.
• Drove 1/2 block before she began to stall.
• At first I thought she was headed for "limp mode" based on the behavior (see more below), but the engine light/restricted performance lights never came on.
• I pulled to the curb as she finally stalled completely and refused to crank.
• I ran my scanner, no codes stored.
• I tried several attempts at keeping the pedal to the floor while cranking. Eventually she started but ran as if she were in limp mode. Again, no lights, no codes.
• Got her back home where she stalled and has refused to crank.

Due to not seeing any codes and the way she ran, I first suspected a fuel issue. I verified that I could hear the pump(s) running in the trunk. I renewed the fuel filter and found the old one was pretty blocked. However, she still would not run after replacing the filter. I tested fuel pressure at the rail at this point and it seems fine, around 40psi when cranking.

I then thoroughly cleaned all connections to the throttle body and MAF. Still no start. For some unknown reason I did not check operation of the throttle butterfly at that point, but will do that next.

I do not suspect a timing issue yet, as I rebuilt the top of the motor under 3000 miles ago. New timing chains, all tensioners, guides, O2 sensors, and spark plugs. I have also replaced the MAF since then.

Since the rebuild the car has intermittently shown signs of a faulty TPS. On a ride home from the beach, she suddenly went into limp mode and threw codes for the TPS and gearbox (apologies but I do not recall the exact numbers). After clearing the codes, she ran fine for several weeks. However, I did notice occasional hard shifts, even after replacing the MAF, and occasional lack of response from the throttle. Perhaps unrelated, but she has also twice since thrown codes for "bank A too rich" and once showed the code for both banks. The TPS code came up once more a couple weeks ago but, after clearing, the car ran like new.

So, long history of what I'm looking at. Would a completely dead TPS keep the car from starting? Shouldn't I be seeing some codes if that's the case? And, if I'm headed in the right direction diagnosing this issue, can anyone provide feedback on ASI's rebuild service?

 

There's a thread running on XK8/XKR section which you may find relevant:

https://www.jaguarforums.com/forum/x...acement-77560/

We're investigating what causes TPS failure.

Graham

 

Throttle Position Sensor - works on the same basis as a scalextric controller or potentiometer.
P1121 is the favourite fault code for failure of the tracks in the pot, only thing to do in this case is replace via a rebuild service or new TB..
Based on my experience, the TPS lets you drive then fails but doesn't stall out the car, just failsafe mode every time. Sometimes a restart clears it, sometimes a code erase, and if particularly bad, a hard reset.

The OP's post doesn't sound like a TPS issue, but having the codes along with others indicates an issue. There was an upgrade gold pin kit for the TPS loom because of stall outs. There's also a TB recalibration flash available via Jaguar IDS that could be worth trying before shelling out for refurb.

If your reader gives live data, and throttle position, slowly depress and see if it's a smooth transition from 0-100% or jumps, if it jumps it points towards a rebuild, next is remove the induction tube and run the same test, does the throttle open nice and smooth or does it stop at any point? if it does, it's rebuild time.

Refusing to crank? check the condition of the big black heavy cable running to and links the fuse boxes visible under the hood/bonnet, unbolt them so you can see the condition of the connecting eyes and joints. There's another to also check - it's bolted the the brake servo housing with a post. They both oxidize to the point of no crank. This fault doesn't post a code.