Hi there,

Looking for some advice please if anyone can help. Here's the background:

- 2009 XF, 4.2 supercharged. Bought it for my son at 69k miles, now at 110k miles. Lucky kid, I know, but it's a cheap car I know how to work on. I prefer my 2006 XJR.
- At some point in its past, it had an aftermarket exhaust fitted. Normally I prefer stock, but have to admit this does sound good.
- Had various emissions related codes for the last 20k miles, but never affected performance - put it down to the aftermarket exhaust. Cat is rattling in one bank, pretty obvious.
- Earlier last year, it started misfiring above 5,000rpm then went into restricted performance. I cleaned the MAF sensors, went away.
- Came back a few months ago. Cleaned MAF sensors, went away.
- Has come back again, now occurring at 3-4,000rpm. Cleaned and even replaced the MAF sensors, no improvement.

Took some live data readings today, this is what I recorded (all in park on the driveway):



Before I bite the bullet and accept that all of this points to me needing to replace the cats, I wanted to check with the real experts that I'm barking up the right tree.

Thanks for any advice you can give me.

Chris.

 

OK, so some updates here:

I decided to try cleaning the cats with a mixture of citric acid and oxalic acid first while cleaning the O2 sensors with carb cleaner. While I was taking the exhaust apart, I found that the rattle wasn't the cats, but the center section behind it. Whoever added the aftermarket mufflers modified the center section with poor welding and this had failed. Had to put a new center section in. This eliminated most codes, but didn't fix the problem.

The only sensor with any codes now was an upstream O2 sensor. Replaced it. Still didn't fix the problem.

The only code left was now a misfire on cylinder #1. Replaced the ignition coil. Finally fixed.

So, after eliminating all the noise from other codes, I finally got to the root cause of the problem, an intermittent failure from the ignition coil. That's now 5 of the 8 coils I've had to change since I bought the car - it's a well known weak spot. Been replacing the OEM Ford ones with NGK, much better quality. Car runs better than it has in years.

Well, at least it did until last night when it threw the P2105 code after spluttering and grinding to a halt. Apparently a very common throttle body issue. Going to try Seafoam. If that doesn't work, I'll pull it out and clean it. If that doesn't work, there's a good site in the UK that sells them for $140 (incl. shipping), rather than over $600 for dealer prices.

Will I ever get a break?????????

 

Pull the snorkel of the throttle opening and clean around the plate ,and check if the snorkel has any cracks

 

Thanks Dennis. Appreciate the help. Will let you know what I find.