The power lost after fixed air pump. I think will need to look around air pump. What is near? Injector's harness, check connector. Power resistor, check connector. On the air box is marelli's air temperature switch, check it. Check inside air box, maybe duster cloth!

 

I chased a similar problem on my brides Towncar. Drove me nuts the end result was bad cats not a problem until it was under a load. Everything checked good out of shear frustration I pulled the cats replaced them with pipes and O2 bungs now she has a Hot Rod Lincoln problem solved. No smog checks here in the beyond beyond. Good luck let us know how it turns out.

 

UPDATE

I finished installing all of the new parts today. The engine is running perfectly. It is so smooth that while sitting at a stop light I am unable to feel or hear it idling. Its fantastic.

However, I'm still not getting the acceleration I expect. During the test drive I noticed that I would get a surge in power at 4000 RPM. I assume that the ECU is providing more timing or fuel at that RPM. The question is, how can I get it to provide that boost at a lower RPM?

Mark

 

Since you have two XJSs I reckon you are familiar with how they preform but, still.....I have to ask....

Are you expecting too much? Was there a time when the car felt like it had lots more power?

The V12 engine does not produce tons of low RPM power. Add to this 4000+ pound curb weight and a 2.88 final drive and the result isn't great low speed oooomph.


Cheers
DD

 

I have had the same thought but I'm pretty sure that the power is there...it just needs to be found.

The power surge at 4000 RPM has me convinced that I'm not expecting too much. I just need to figure out how to get the power it should have before it gets to 4000 RPM.

I keep thinking that one of the sensors is responsible for the ECU in holding back the timing advance or fuel rail pressure. If so, which sensor is it? How can I fool the ECU to test my theory?

Mark

 

WE'VE GOT POWER!!!

After replacing EVERYTHING, tuning and adjusting and returning all the parts modified by the previous owner back to original specifications the low power problem remained until the very last thing I replaced...the catalytic converters.

The car still had it's original converters and once I removed them it was obvious that they were damaged and partially clogged. A new set of converters (all 4) now allows the engine to breath and the power has been restored.

Over the last few weeks I have replaced or restored the entire cooling system, all fan belts, flushed and serviced the transmission, replaced the fuel pump and filter, and replaced all deteriorated hoses (including AC hoses).

The car now runs perfectly and I have no fear of overheating. Smooth, powerful and quiet...just as it should be.

Next on the agenda, rebuilding the front suspension. Time to start a new thread.

Thanks to everyone for their input during this process.

Mark

 

Congratulations. Great job!
greg

 

Welll done TKD, turns out you were 100% right.
Greg

 

Thanks for the feed back

 

Emissions Test Successful!!

The car just passed its emission test with flying colors. Here are the numbers;



........................Previous test...............New Test ............Allowed Limits

HC GPM ...............3.0118........................ 0.4553................2.0000
CO GPM ...............12.3960......................1.9255.................20.0000
CO2 GPM .............530.4679...................609.0927................No Spec7
NOx GPM ..............2.7973....................... 0.4265.................3.5000


As you can see, the Hydro Carbons and Carbon Monoxide numbers dropped significantly. I'm not sure why the NOx number increased but it's well within spec so I'm happy.

As I said on my previous post, the engine now has the power it should and runs smooth, quiet and clean!

It's a sunny afternoon and I'm going for a drive.

Mark