Hi guys/gals

I have an 89 XJ-S 5.0 V12 that has no cats and is straight piped. Runs really well and sounds awesome. 2.25 inch pipes all the way. My issue is that the A bank appears to running a little richer than the B side. Not a lot but a little darker than the left. Has anyone run into this before? All help is appreciated.

1974 XJ6 L , Chev 355 vortex heads Turbo 350
1989 XJS 5.0 HE V12 82K miles
2005 Jeep grand cherokee 4.7

jack

 

My guess would be injectors, most likely an injector that is leaking. The ECU can not control fuel differently to each bank.

 

I am a 6cylinder driver, but wouldn't oxygen sensors possibly create this kind of situation as well?

 

On a V12 the ECU averages the input from the two oxygen sensors...as I recall


Cheers
DD

 

No, the ECU can not adjust fueling on each bank, Doug is correct the ECU averages the O2 sensors. O2 sensors would cause both banks to run rich.

 

Jack says no cats. Will it have any oxygen sensors at all ?

I'm quite sure my '89 HE engine does not have them, but it's Euro spec, not US...

 

Thanks guys,

I do have 02 sensors but no cats. I suspect that what warrjon is suggesting is correct. Car is an 89 HE with 82000 miles. Runs really well. I am about ready to replace injector hoses so would be a good time for injector overhaul and calibration. I am replacing the rear shocks this weekend. Trying KYBs. I'll let you know how it all goes.

Thanks again.

jack

 

My friend changed the wiring of the injectors and mixed a and b banks. The engine worked very poor . The question is, how is it?

 

Hi 314

When was the last time you changed the Plugs and either Checked and or replaced the Distro Cap and Rotor.

Its not unknown for some third party working on an XJS V12 to not replace the 2 Spark Plugs under the Air Con motor.

Because they are a 'Nightmare' to get to and could easily take up most of a day, to replace them all on their own.

A lack of maintenance like that could be the beginning of a 'Marelli Fire' where the Top of the Distro Cap starts to Burn Through.

The XJS V12 Engine is like Two Six Cylinder Engines joined together (as I know you know) where you have 'A' Bank on one side and 'B' Bank on the other.

So if there is a problem with the Distro Cap or Rotor, one side of the Engine could show signs of running not quite as nice as the other.

Where in a worst Case Scenario, one side of the Engine could shut down and leave the other side running on 6 cylinders.

Where Raw fuel could then continue to be pumped into the Hot Exhaust of the Side of the Engine that Shut down, which could then result in the Car catching Fire.

 

Good morning orangeblossom

I keep the car in good tune, new plugs , wires cap and rotor etc. the V12 runs really well. Revs right on up to 6300 in low where the manual gov in the T400 shifts. Also have replaced the secondary coil. The issue shows up as a slight color difference in the right exhaust as compared to the left. As an aside, getting rid of the cats, mufflers etc , and running 2.25 inch all the way back, made a huge difference in performance and, of course sound. It sounds incredible.

Thank you for your input
jack

 

Hi Jack

So tempting to eliminate the intermediate mufflers but at the moment I love the Sound of her purring.

Any chance of a small Vid so we can hear what your XJS sounds like.

 

I will put a vid together with sound. Of course the loaded sound will be different than the car sitting still. Ill see what I can do.

jack

 

[QUOTE=314jjwalls. My issue is that the A bank appears to running a little richer than the B side. Not a lot but a little darker than the left. /QUOTE]

Maybe little licking the vacuum modulator of the transmission.

 

What is the difference in color of the two exhausts.

Black?

Blue?

White?

Hmmm... I've tried many unusual and non-intuitive fixes, but this is a new one!

 

dang. Double posted.