I've been wanting to get a more appropriate sounding exhaust for my XK8. As you know, these cars, stock. are whisper quiet. However, my car, although still quiet, has had its exhaust become deeper, more muscular, but not any louder. This baffles me because I haven't done any modifications to the exhaust system.

The only other problem I have is an intermittent P0171 or P0174, sometimes both, sometimes only one of them show up, with restricted performance. The RP clears up after a few minutes of driving and there are no palpable symptoms except for the deeper exhaust.

The last job I did involved:
Changing the part load breather hose
Mending the vacuum brake hose (throttle body elbow hose)
Valley hoses
Throttle body gasket
Intake manifold and plenum gaskets
Cleaning of the intake manifold
Cleaning of the part load breather orifice on the valve cover
Changing the intake filter
Changing MAFS oring and cleansing with MAFS cleaner.
Throttle cable adjustment

This fixed numerous problems (Blowby, rough idle, performance los, oil leak, coolant leak) and I'm happy with the results.

Could the change in exhaust sound be a result of Cat damage? I had the car inspected last week (MOT equivalent) and it passed the emissions tests.

Any ideas regarding those two codes? Could it be an O2 sensor or MAF sensor?

'00 XK8 convertible

 

Nothing?

 

I doubt that a damaged cat would cause the exhaust to sound deeper in sound. It is usually the rich codes or misfires that kill them, too much burning fuel clogs up the cat and restricts the exhaust.

Since you fixed your problems have you done a hard reset to clear the old fuel adaptations?

Perhaps what is going on is you have fixed the lean problem and as the car is slowly learning and correcting the mixture, it is running (and sounding) better.

 

No, I didn't think of doing a hard reset. I'll do that and report back with my findings.

It involves disconnecting the battery and touching the negative wire to the positive battery terminal?

 

Yes, and hold them together for 15sec or so.

The other thing that would be helpful for the codes is to know what your short and long term fuel trims are.

 

I've got 2 xk8's parked outside. A 97 and a 01, the 97 is whisper quite. On the 2001, it looks like some of the baffles in the drivers side resonator have disintegrated. It's only obvious when you first turn them on in the morning.

 

On my car, its noticeable between 2 and 4k rpm.

 

I did the hard reset and it seemed like it wasall fixed, but after a few trips, the same two codes reappeared. I'll have to get fuel trim readings.

Edit:
Problem solved. Today in traffic I began smelling fuel. I remembered that when I changed the fuel pressure regulator, the original screw broke. I had used a screw from home window screens as an interim fix, which was woefully inappropriate because it was too short and made of zinc. Sure enough, the regulator was loose. I bought a new screw and tightened the regulator. I got rid of that shady ghetto screw, fixed the fuel smell, got rid of the fuel starvation, and codes P0171 and P0174. They haven't returned since and the Jag now accelerates proper quick.

I guess I was getting a lean reading because of the fuel that was being lost.

I haven't noticed if the exhaust sounds normal or not, but I'll pay attention to that.

 

I may have to do a hard reset myself. And while I know this question may cause a laugh or two, I am going to ask it any way.

Here goes.

Hard reset. Touching negative cable to positive battery terminal. Got that. But with the positive battery cable connected, or disconnected?

 

Disconnected. You don't want to fry the car's electrics do you?

 

I have always left the positive side connected to the car, ever had a problem doing it that way...

 

The goal is to touch the positive and negative cable connectors together, not the battery terminal. Whether the positive cable is still attached to the battery or not is irrelevant.