Hi,

I've now had my XKR for just over two years, its a 2007.

I recently had some serious power loss issues, this was down to a blocked cat, so as a temp fix, i had the internals of both cats removed while I sourced some high flow cats or replacement cats.

The car now keeps cutting out under braking, the idle is erratic on start up and when stationary. Drives fine when revs stay above 1K. I'm thinking it cut be a vacuum leak somewhere, is there any common vacuum leak areas on the XKR 4.2? or, could it be caused by the decat - ramp needed?

No codes show up, car starts after the cut out, but idles very rough. Worse when engine warms up.

Any help or advice would be much appreciated,

Here's a vid of when I first got the decat (has aftermarket backboxes). Haven't driven it much since, the car does pop and bang quite a bit:

https://www.youtube.com/watch?v=oCTa3yWsfxc

Thanks

 

An elm327 is enough to let you watch fuel trims.

 

Can see from your video the car is running extremely rich, this was probably the reason for your cats failing and needing replacement/removal.

I don't see how you can pass an MOT with the car like this.

As for why? Probably a big vacuum leak, maybe a failed coolant sensor, maybe an exhaust leak at the manifold, maybe jammed injectors.

Diagnosis without the SDD diagnostic tool will be difficult, but as JagV8 says, at least start with an ELM or similar to look at the fuel trims. But from what I saw in that video, the volume of fuel coming out the exhaust must be beyond the normal fuel trim limits.

Has the car been modified any other way?

Something very wrong there...

 

Or might be such as a dirty MAF.

Hurry to do something or it could get very costly.

 

An idle problem that doesn't throw codes is interesting. It mean either the processor is happy with it's sensor inputs or the processor is borked. We'll hope for sensor input problems.

How does it cold start, normal or similarly messed up?

One dumb trick I learn a long time ago is sometimes the processor's adaptive tune gets so out of whack a hard reset is needed to get it back. Meaning pull the battery cable off for thirty minute or so and see if the car gets better.

Also, if you punched the cats you should be getting codes for no change at the downstream sensors, I am. I'm getting a code for no continuity and found the heating element is dead on one of mine so you should get a code if they were unplugged too.

No exhaust leaks at the manifolds? Found on mine that the flange seats against a step in the stud so it can only get so tight. Possibly your stud could have came out of the manifold allowing air into the exhaust stream which would make it want to run rich. But that's a lot of black smoke. I'd also expect someone would hear the leak there if it's popping out the exhaust.

How rich does it smell? Mine with gutted cats wasn't eye watering standing behind the car but I bet yours is.

 

FYI the reset procedure is to remove one of the battery cables and touch it to the other cable for a second or so. Then reattach and reset everything that is lost. 10 minute job.

 

Thank you for the replies,

The video was from a while ago, doesnt kick out black smoke any more, nor flames. The video was taken immediately after the decat, so seems to have adjusted since then. Was parked up over winter, and the cut out problem only really became noticeable within the last week or so.

I had it scanned with a snap on tool, but will get it scanned again and post fuel readings. Will also get the garage to check for exhaust leaks.

The car does smell like its running rich, could this be a result of a vacuum leak? and common places for vacuum leaks?

Thanks

 

Any chance the fuel went bad over the winter? What's the Ethanol content in the UK? No check engine light makes me think it's just got water in the fuel from sitting over winter.

I'm not well versed in how the processor interprets input on these engine. They seem to be a mix of speed density and mass air. SD looks at RPM, throttle input and manifold vacuum to decide how much fuel to deliver. It used the o2 as a check and balance. Early mass air looked at the lbs of air (mass), RPM and throttle to decide how much fuel to deliver for the weight of air and the throttle setting (+/- mass air). Same with the o2, check and balance. On a SD car, low manifold told the processor that the engine was under load and it would fuel more.

 

By 2007 it's sophisticated and cross-checks all sorts of things but that's kinda irrelevant here I suspect. (Suspect everything except the PCM. Suspect it last.)

The eth content here is well below what the cars can stand. Water (if any) in fuel seems not to be relevant given what occurs.

 

The 'water in ethanol fuel' thing is a myth pretty well everywhere. I've yet to see a bonafide case on a modern (1970s and up) car.

 

Not trying to start a fight or go too far off topic but you should do some more research. It's pretty prevalent here in the mid Atlantic region. We are blessed with 10% corn squeezing's in our 91 octane stuff, the alcohol will absorb moisture and it will settle out out over time. It's really tough on marine fuel systems and small equipment regardless of how sealed the fuel system is. I think a lot of the water is picked up through transport and storage. Most stabilizers are designed to help keep the moisture dissolved in the fuel so it burns with the good stuff. Usually the first sign the fuel is contaminated is how bad it smells. 91 smells like race gas when it comes out of the pump but smells stale when dead. We are also blessed with winter and summer blend gas. The summer stuff is tamed down so the VOC's don't evaporate. Winter gas rocks and I've had it in my '68 Fairlane for the past four years without it going bad, same tank.

 

Not relevant to modern cars- as stated above.

 

Ah, so other than bash another member's idea you're here why? What do you think would cause the OP's problem?

 

Waiting on basic info from the OP. Without that- throwing out red herring guesses serves little purpose.

 

I guess OP's enjoying a weekend - or cleaning MAF and measuring trims

 

** UPDATE **

Apologies about the delay in responding. Unfortunately the car was hit by my neighbor a couple weeks ago and was only returned to me today after repair.

Upon collecting the car from the body-shop, the idle issue had become worse, was really struggling to idle at all without cutting out.

I called the AA, and the patrol was able to locate a vacuum pipe that had come off, this was replaced and the car them idled much better.



I then drove the car, and it responded a lot better, however it was still cutting out under braking. I called the AA again, this time the patrol spotted that there was a leak near the inlet manifold ...... big leak! The connecting hose had completely split and was just sitting on the manifold.






The car will be recovered to the garage tomorrow, and I shall order the replacement hose. Hopefully this should fix the problem.

Thanks again, will report back on how I get on

 

Now, you're going to need a good seat cleaning.....after you replace that hose.

 

That gasket cannot be ordered as an individual spare part for an X150 XKR, Jaguar will only sell you the complete cast intake tee with gaskets, and they want outrageous money for it. Like $900 !!

I believe that the gasket from the earlier 4.0L X308 XJR will fit however. I have one on order at the moment to check the compatibility.

This is the only gasket I could find as a spare part that looks to be close. Jag doesn't sell this gasket separately for the X103 XKR either, but it looks to be the same design.

I expect my delivery to arrive tomorrow, I will take some measurments and photos, you can check the measurements against your throttle body and intake tee, see if they match.

 

Thank you for the reply. I was told this by Jaguar at the weekend, so I did a temporary fix using 90mm silicone hose. Seems to be holding up well.

Can I please get the part number for the gasket you ordered?

Thanks

 

The diameter is about 85mm, inside diameter I mean.

I measured a spare throttle body I have here from a 2003-2005 4.2L S/C engine, the OD of the throttle body is also 85mm, the gasket fits over it nicely.