Hi All,

Apologies if this seems like a newbie question. My car is an 01 XJR.

So the other day, I start my engine and upon start up, my RPM goes up to like 3500 RPM....then a few seconds later, comes back down to a normal 1100 or so. Also there are times when I am driving and although my foot is not on the accelerator, the engine revs up a little bit. It seems to rev on it's own. For the most part, it drives fine otherwise.

Any suggestions on what it could be? Could it be the secondary chain tensioners?

Any insight would be greatly appreciated.

 

possible throttle body issue. There was a recall many moons ago. Have you got an engine warning light on the dash by any chance when this occurs?

 

If the ECM looses its fuel trim information, primarily due to loss of battery power it will rev high, usually only to about 3k, for a couple seconds then drift down to normal RPM. Your second statement does, indeed sound like the throttle body, or rather the Throttle Position Sensor.

 

A quick clean of the throttle position sensor connector might help you, a 5 minute job. Had the same symptoms a year+ ago, cleaning both halves of the connectors' pins with Radio Shack contact cleaner/lubricant took care of the issue - corrosion on the pins due to dissimilar metals (there's a TSB about this).

 

I hate to admit this, but my car did this just last week, and after several starts with high revs, I got a CEL light yesterday. Taking the laptop home today (the one with the autoenginuity program on it) to discover what is amiss. I'll repost up when I have something to diagnose.

 

Thanks everyone for your suggestions. I will check out the the throttle body sensor and keep you posted. Sean B, I do not get the engine warning light. I do have the ASC/ABS not available light, but I don't think they are related.

 

My CEL cleared itself after a few days of the rough starting condition. My code reader observed the multiple misfires on bank 1 only. It also captured the data from the CEL appearing, and it showed my air intake was only 0.99 lb/min...which at normal idle, is around 4 lb/min. So, I removed my air pip and mass air flow sensor, cleaned the inside with the special MAFS product, and then did the connector harness and receiving pins with electronics cleaner...as they were dusty (and never been cleaned). Snugly reinstalled, and the line coming off the elbow of the pipe nearest the TB is very loose, perhaps that o-ring is getting tired. I removed, cleaned it, and snapped it back on. Starts have been much better following this cleaning a few days ago.

let us know what you find mike.

 

To h20boy,

To be completely honest, I am very inexperienced when it comes to working on cars...so even something as simple as cleaning the connectors on the sensors takes a lot of time for me...since i need to research first exactly what it is you guys are talking about...then trying to locate it in my car. I know...pretty pathetic. I haven't had time to look into this yet. Hopefully I can get around to it this weekend.

The high rev at start up is the only issue for now...other than that...the car is running fine. I will keep you posted.

 

A Jaguar is the kind of car where either you need to be mechanically inclined, or have a lot of money. Sometimes both!

 

Mike, call me when you have an hour to work on this, i'll be happy describe to you what product to get, and walk you through the process over the phone. I'll PM you my cell number to keep handy. Tools needed - 10mm socket and a small ratchet or one of those screwdriver/socket drive tools, plus a phillips screwdriver.

 

Mine does this occasionally after I've reconnected battery. Try turning on ignition and let it run through it's whole self-check before starting up.

 

Davoid, this is a 7 year old thread, I'm assuming the original poster has fixed the problem by now.

 

Guess so. Or sold the car. If they did fix, they didn't choose to tell us what the fix was. Which is a pity because the primary or secondary purpose of these forums is to be an information source. To which I contributed. 7 years late.

 

wrong thread

 

Amen

 

panthera999,
my 2007 XK NA has done the un-commanded throttle up orbit insertion sequence with no feet near any pedals after depression of brake pedal after pressing start button method. I’m a helicopter pilot and can confirm that these cars do have an issue and I know where my feet are and what they touched during the start sequence.🐍 The rise in RPMs up to 3000 plus has happened to my ride several times. I am sure I have a vacuum leak somewhere between the intake manifold and throttle body. My water pump and thermostat replacement job done by yours truly may have stripped out one of those bolts and or cross threaded one. Also the Duracell red head in tha trunk is not lasting to the 3 year mark as advertised so I am sure it has logged battery errors by going dead multiple times logged in the ECU. Love this car and hopefully one day can get the updates and fix all the oil leaks. 160K plus miles on it and now thinking my timing cover or something on the front of the engine is leaking a good bit of oil. Stay tuned.🐍

 

It's not Jaguar-specific. An air leak on pretty much every modern petrol (aka gas) car typically causes unwanted high revs (*), so such leaks need fixing just as you'd fix a brake problem, suspension problem or leaking fuel problem. (I hope!)

The car / Jaguar is not to blame for any of those unless they occur within too short a period of manufacture.

(*) or if bad enough a non-start