2009 XF, 4.2 engine, non supercharged, 32,000 miles on the clock. For quite some time, whenever our XF is initially started, after sitting overnight or longer, the first 10-15 seconds, after starting, the engine runs really rough. After that time, or if we "blip" the throttle, during that initial time, the idle will smooth out.


Last week, my wife took off with the car, and after returning, she told me that the "check engine light" was illuminated, but the car was running just fine. I had put gas in it a couple of days prior, so my first thought was that I didn't tighten the filler cap enough. Checked that, it was tight. Plugged in my scanner, and pulled several random misfire codes.


I'm not sure if this is part of the cause, but the car is garage kept, and the ambient air is generally a tad warmer than the outside air. When we leave with the car, of course we open the garage door, so especially in the winter, there's an inrush of colder, outside air.


The MAF sensor has been cleaned several times, and the last time I cleaned it, I saw that the o-ring that seals it to the air inlet tube didn't look too good, so I replaced it, and hoped that this was the cause of the problem (unregulated air leakage). No such luck. The throttle body has been cleaned several times, over the years, too, just as general maintenance.


Last year, I removed the spark plugs, A) just to inspect them; and B) to apply a dab of anti-seize, as they had been in place for seven years, and I didn't want them to get "frozen" in place. At that time, I found that the center electrode of one of the plugs was "cocked off" at about a 20* angle. I assume a manufacturing defect. Although the car was running fine, I didn't like the looks of that plug, and didn't want to "cheap out" and replace just one, so I replaced all 8 of them.


Still, this "cold start stumble" is rather annoying. Anybody else have this problem, and if so, how did you fix it?


TIA!

 

Read the codes.

It's not running fine. You just don't yet know if it's minor bad or major bad.

 

Why would you say that? When it's first started, in cold weather, it runs "rough" for about 10 seconds, and then smooths out, and runs "just fine". As I said, the codes were a couple of random misfires.

 

Codes = not running properly. Period.

 

Thank you VERY much, for your extremely helpful input...........

 

Tickover started going in a cycle of 625 to 1000 to 625 to 1000 and so on, sprayed the maf sensors with WD 40 and so far so good

 

WD40!!!!
No way you should use that on MAF sensors!
It might clean the worst of any gunk off the wires, but it will leave a film behind which is bad news.
Instead you should use a dedicated MAF sensor cleaner, which dissolves any build up on the MAF sensor wires then evaporates clean away very quickly.
It comes in a spray can, there are a few brands of it, and pretty much all auto parts stores sell it.
Get a can and re-clean your MAF sensors pronto!

 

Did not remove them just sprayed them

 

So did you spray the actual MAF sensors (fine wires, two sets in each sensor) or did you just spray the electrical connections/plugs? Coz WD40 might have worked to clean crud off the plug(s) and improve the connections, or it could have been nothing more than unplugging then replugging them in that solved the problem.

 

Did not remove or unplug them and just sprayed them as they are

 

It's you to blame: you NEED to read the codes (post #2) to get anywhere. Or don't. It's your car so how much do I care?

 

You seem to be missing my point, entirely. In any other automotive chat website that I've visited/participated in, when someone post a problem that they're having, others will offer suggestions as to what to check, as possible causes of the problem, in this case, a rough idle at cold start.


As I originally stated, I pulled the codes, and they indicated "random misfires". If this car was equipped with a carburetor, I'd be looking at the choke mechanism. Since it's equipped with electronic fuel injection, I can't do that. By posting my question, I was hoping that someone could suggest a thing or two to investigate, as possible causes of the problem, and things I could possible repair myself, rather that simply taking it back to the dealer, and letting them poke around in hopes of finding the issue, then presenting me with a sizeable repair bill.


Understand?

 

Post the actual codes then.

You're stuck in a mindset 30 years out of date.

Currently you don't have much data. Anyone reading the thread has even less.

Of course you could guess what's wrong and parts swap some more but it's not likely to be cheap and may take a while.

 

Spraying WD40 on the outside of the MAF connector does not do anything?

Why did you do that?
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Either the erratic idle cleared itself or the WD 40 did, not bothered which

 

Shortly after my initial post, I was in the neighborhood of my local Jaguar dealer, so I stopped in, and talked to them about this issue. What they told me is this, and you can either believe it or not. According to both the service manager and lead technician that I spoke with, it's their opinion that Jaguar fuel injectors are more sensitive to the build up of deposits, especially if the car is primarily driven on short trips.


They suggested trying a strong dose of fuel system/fuel injector cleaner, before assuming it's something more serious/costly. Following their advice, I've added two doses of 'Red Line' brand of fuel system cleaner, a half bottle before a fill-up of gas, then the remainder of the bottle after consuming a half tank of gas, and refilling the tank. So far, there seems to be a noticeable difference in the way the car is starting.

 

It's a miracle then that all the people with well over 100K miles on that engine have no problems with the injectors.

Guess you're just unlucky.

How injectors would be better hot than cold start is a real puzzle.

 

And it's a miracle that my Jaguar dealer might have a better handle on the situation than you do!!


AND, once again, you have added nothing of value to the thread....

 

I have: others should be VERY reluctant about believing the injectors are problematic.

If I may add you seem to have a touching faith in what you were told as if the dealer actually knows much. Many provably (read the forum) do not.

 

No injector problems but it's possible.
Cycle your key off and on 3 times waiting about 30 seconds each time.
Does the car start any better?
Can you measure the fuel pressure and report back? Might be a weak pump and you have low pressure when starting.
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