Hello guys,

I have an issue with the car and i’d appreciate your help;

The car has a rough start in the morning and the RPM would be on 1500 steady. After 30 seconds or something, the rpm starts to dance (go all the way down to almost 0 then again up to 700) and the car shakes a lot when its dropping.

This keeps going on when the gear on neutral. Whenever am driving at very low speed i still can feel the shake (like a pulse), however in high speeds its not noticeable.

Now, the car started to shut down completely whenever i hit the break to complete stop (approaching a traffic light) !! I have to put it on P to start again and the RPM keeps on dancing.

spark plugs recently changed, air filters, oil, gas filter. I took it to mechanic and he tried to seaech for air leak but there wasnt any.

Acceleration is not as powerful as it was before but is not bad.

What could be the issue?

I’ve uploaded video here:
https://youtube.com/shorts/EZfbCyQgI-0?feature=share

https://youtube.com/shorts/OS1KFVEbO-M?feature=share

The videos are example, the rpm fluctuations usually harder than in the video.

The car has 111K KM on it.

Thanks for the help.

 

Off the cuff, sounds (i.e.: seems) like a vacuum leak to me.
Maybe do a smoke check of the vacuum lines?

 

Did your mechanic check for stored DTCs? (Diagnostic Trouble Codes). If not, find another mechanic who is competent and knows what he's doing, particularly with Jaguars.

Don't guess; that'll cost you a fortune with no guarantee of success. DTCs will help the mechanic to properly troubleshoot the problem and fix it.

 

The elevated 1500 RPM for rapid warm up is controlled by signal from ECT (Engine Coolant Temperature) sensor to the ECM and a consequential drop to 700 RPM is correct. Dropping almost to zero and shaking is not!

This could be faulty sensor, air leak or both. As Stuart suggests - get a code reader on it.

Graham

 

He did use a code reader and no codes were stored. Thats why he said it needs to be checked manually and his first thought was air leak but he couldnt find any. He asked me to leave the car for a couple of days till he figures it out but i wasn’t comfortable leaving it with him messing around.

i thought maybe some guesses here would direct me where to look at first

 

Maybe i’ll try and do that, he just used some water and soap to check for bubbles in the air system. Do you know which product i can use for that test?

 

No relevant codes were stored on the reader. Could it be oxygen sensors or MAF?

 

perhaps a better quality code reader is necessary. MAFs and O2 sensors throw codes too.
Or do as Stuart suggests and get a competent tech with Jags on the job.

 

 

I second the motion on a jag-compatible DTC.

Note we seem to be using "air system" and "air leak" in the context of vacuum leaks. The problem is too much sucking air into the engine's vacuum envelope, not blowing it out somehow. So, a bubble-producing solution may be ineffective. I suppose we could apply solid pressure into the vacuum envelope, and instead of using smoke, we could look for bubbles by spraying detergent in a lot of places. I prefer smoke becuse it creeps out of places you can't directly see.

Moe, If all your guy has is a non-Jag OBD tester, look for Long Term Fuel Trim value. It should be near 0. If it's over 5% you likely have a vacuum leak. They usually set a code at 20%, though.

My old man used to tell me if a tool saves it's own price in costs, buy it and enjoy the learning experience. If it saves more, buy it and enjoy the savings and the learning experience.

Get something like this, for $100 or so:
The real driver of a good smoke test is pressure. You need to pump it up good, which means a decent source of air pressure. The pancake kind of air tank is fine.

Also, you need to make sure the vacuum envelope is sealed at the throttle body -- has to be better than some glove over it. Get a 3" rubber plumbing cover at home depot, the one with the hose clamp. Then return it if you want.

From experience, you'll miss the small leaks until some solid pressure is built up. Aslo from experience, Jag's develop a pretty long list of vacuum leaks as they age.

 

I believe he has the Autel Maxi scanner, i think this is a decent scanner no? and this guy is working only with Jaguars and land rovers, so he should be a good mechanic i think.

I have another Autel AP2000 bluetooth reader with me, let me try to plug it and see the live data and will upload here to check the fuel trim if its still working (last time i checked it wasnt connecting, piece of junk).

I will order the smoke detection from Amazon, it should arrive in a week or 10 days and will update you. Its a good idea to have one on hand, can be very useful.

Thanks a lot for the feedback. I will keep you updated.

 

This is the live data report. I see a lot of misfires there!

Can you please check and let me know your feedback and observations?


Thanks,

 

Hi guys, I’m a new member of this forum as I’ve recently bought myself a Jaguar XKR 4.2 2008.

I’m having the same exact problem on the video, idle jumping up and down but once I put the car on drive the idle settles to about 700rpm and is stable.

I did drive it and ran a diagnostic.

Mass air flow sensor circuit range/performance came up in the DTC.

I’ve changed Bank 2 and will try and now change the drivers side (right hand drive uk car)

Can anyone please help or advise if this may resolve the issue of the rough idle on neutral?

Many thanks.

 

Congratulations on your sweet new (to you) ride!

While you are fiddling with your MAF sensor, make double sure that your intake duct forms a good seal at the throttle body, as Pantera mentioned above. When I reassembled after the valley hose change, I got MAF codes. I solved the problem by smearing a small amount of dish soap on the foam gasket that slides over the throttle body elbow. That was over a year ago, and still good. Cost: $0.

Also, your car is at an age where your plugs and injectors could be in need of cleaning and/or replacement, but I doubt those would show as a MAF code.

 

Welcome @IvaXKR . Stating "there are DTCs" is not very helpful. We need to know specifically the DTC numbers.

 

I have a similar problem on my 07 XKR. It doesn't drop to 0, it just "hunts" on cold start and vibrates. Put it in gear and it goes away. I smoke tested and fixed one leak, but no difference. I am not sure what to try next.

 

Hi guys, just wondering if anyone has found a solution to the problem.

Any help will be greatly appreciated.

Jaguar XKR 4.2 2008. 132k miles.

The car drives smooth and is responsive.

I did notice that if I brake hard and slow down to a stop the rpm does drop to 500rpm and the car then struggles a little but on idle and on drive the rpm is steady (600rpm)

Took it to specialist which knows the car and the car did apparently throw a bank 2 MAF sensor. It was initially cleared to see if it was an old code that was an old code and see if it would come back on. When I put it through diagnostic, there was so stored fault codes on the DTC.

could that one dodgy MAF cause such a surging rpm? Or could be a dirty throttle body? And that it just needs a light clean?

Thank you for any replies in advance.