surging @ WOT
 

So I hit the first brick wall with my new to me 04 XKR.
Yesterday I was out cruising around with my wife, and for the first time since I have bought it, I opened it up to WOT on an on ramp. Once I got going up in the higher rpm range of 5000-6000 RPM I could feel a miss, or a surge. It was a constant feeling, and I could tell it was not quite right. I scanned codes with my ob2 scanner and it came back with nothing. I am not sure how long if ever the plugs or the fuel filter have been changed, but I was going to do that first. Any other items to look at? She has 92K miles.

In "Sport Mode"???

I do not think sport mode was on. I usually don't turn it on. As I have heard of issues switching it on and off.

I do not think sport mode was on. I usually don't turn it on. As I have heard of issues switching it on and off.

Well this sounds familar to what happened with my XJR, also a forum member with an X150 XKR reported similar. The culprit was choked catalysts.

I would work through the following;

Air filter
Fuel filter
Cats

I don't think it would be the cats, as it just passed tail pipe emissions, also when I was doing the undercarriage inspection, I taped on the cats, and they didn't rattle. I would also suspect a code for cat inefficient If that was the case.
Do you have another way to test the back presure to see if that's the case?

Choked cats don't throw up any DTC's, and they still "work" in so far as cleaning the exhaust gases, the problem is because they are choked they cannot flow the higher volume of exhaust gases at high rpms (bigger revs = bigger volume).

When mine were choked, there were no rattles from the cats, nothing loose, and no problems at low-mid rpm, the problem only showed at WOT and higher revs >5000rpm. Same for the guy with the XKR.

I suppose taking them off, and soaking them in a couple gallons of carb cleaner wouldn't help? I really don't want to chunk down $2k for new cats.

Reattach the OBDII scanner and drive the car at times the code reader will capture a temporary code. Do this first to see if you do get a code. Have you used any fuel additive? If not it might be a good idea to add a can to the fuel and see how it goes. I use BG44K and you can find it at most repair shops.

+1
If that doesn't work check the fuel pressure with a gauge that has a long hose so you can see it while driving. If it drops when you have the miss it could be fuel filter, I'd change it anyway, or maybe secondary fuel pump.

I'd do these simple things before I'd start removing cats.

I did not check your car but I see that it is a 2001 XKR and you have 2 fuel pumps. You need to test both. If one is failed this could cause your surging.

PS Please put your car info in your signature.

Edit Sorry I looked at your profile and not your first post that had a 2004 XKR so 2001 xkr 2 pumps 2004 xkr 1 pump. Do look at your fuel pressure.

My spark plugs came in and the fuel filter should be here by this afternoon. I will get them changed tonight. I love BG products, but I don't know of any sold around here. I have used seafoam with great success. I have a fresh full tank of non ethinal 96. Once I swap the fuel filter, and run that tank out, I'll drop a can of it in. I'll keep you kids posted.

Pay triple attention to the fuel filter. Many parts store come up with a screw-on type, but the reality is that you will need a quick connect type (the fuel lines have a tab on a hard plastic end). Check here:

03-xkr-fuel-filter-84194/

Separately, the fuel pressure (with a reference to the manifold) is available in digital form over OBDII. A cheap ELM327 with Torque Pro can show it, and also record it over time so you can keep your eyes on the road as you test.

Best of luck, keep us posted.

I did order the correct filter. I have been scoring the forms for any possible issues. I have seen other people pay about the top end surging, but no real answers.

So my miss came on with a vengeance. It tripped limp mode. I replaced the spark plugs, changed the fuel filter, cleaned and re-oiled my K&N filter. Only now I was able to pull a couple of codes. The computer was saying that I was running lean on both left and right banks... Hrm... a vacuum leak on a pressurized intake system. I looked it over and found a tube on the passenger side of the motor that when moved stared to suck air. It ran from a diaphragm looking thing to the back side of the motor. A couple wraps of electrical tape seems to have fixed the issue. I now have the tube on order and should get it soon. on a side note she does seem to have picked up quite a bit of oomph.

Personally, I am a big fan of those zero-dollar fixes. Identify an issue, find something in the garage to fix it, and see the issue resolved (at least until the new part arrives). Good for you.

Had very similar issue with wife's 2001 XKR, fuel pumps were the reason. Started to act like a surge then complete failure. I believe one of the pumps had failed prior to when we purchased it and then a few months later the other pump failed. Do the relay tests to confirm both pumps are working.

Mike K

I had a similar issue with an xk8... Mass air flow sensor cured the issue. Maybe just a proper cleaning would help.

How do you properly clean a mass air flow sensor?

once again I got bank 1 and 2 lean codes.
I removed and inspected the cold air kit.. it was some cheap home made crap. I found that the MAF sensor was on a piece of pipe that was smaller than the intake tube. they used some sort of glue and foam to fill the gap to make it work. I will be removing and installing the factory air filter tonight.