High NOx at WOT
 

Just found out the XJR failed the BC aircare emissions test. I am yet to see the details, but it blew way high NOx under full throttle. All other parameters were within allowed limits. I have my suspicions as to what might be behind such a result, but wondered what some of you certified guys (not mentally of course) might think is at fault. It got a new cylinder head along with all the accompanying gaskets and seals for the job. The fuel pump pin on the ECM had rusted off, and a jumper was made which works fine AFAICT. I can say that the car sat for a long period (almost two years) with low fuel in the tank, and the fuel that was added prior to initial startup was rather long in the tooth. Also, it is likely the injectors have not been serviced for quite a while, and none of the fuel filters have been replaced. Even the spark plugs are the ones bought with the car! I'm also thinking there is water in the grungy fuel that it has in it. EGR and air blower will be getting checked, and will add a good cleaner like Techroline from Chevron.

All other diagnosis are much appreciated! :icon_snow: It's snowing here!

96 XJR 4 litre supercharged 222'000 Kms.

I think youve answered your own questions. I would pull the injectors and send them out to be cleaned your in BC, so this company might not be an option but
www.injectorrx.com
high cylinder temps are your biggest high NOX contributers, and nothing gives you high cylinder temps like lean air to fuel mixtures(not to mention holes in pistons and torched ring lands) so get fresh fuel in there and verify the second fuel pump is operational thats in the tank

I have two injector shops that I know do good work, but thanks for that link!


I know we checked the function of both pumps a ways back when troubleshooting the corroded ECM pin, but I will pull each pump relay and check function again. I wouldn't have thought of that. Thanks! I figured the "extra" pump was simply in case one failed, but Jag isn't really known for redundant systems are they? It's all power to weight with these beauties, so I guess the extra pump must be needed when that blower is wound up?

As for the pistons they looked good from above when the head came off. Minor carbon deps but no hot spots or pitting. The crown edges looked crisp as well, but short of pulling them out I can't vouch for the ring lands... Cylinder walls were relatively score free for an engine with its mileage. No appreciable 'lipping" at the top of the bore. I didn't have cylinder gauges avail so I couldn't check the bore for out of round, but the bores looked quite good considering. Block was dead flat with zero warping and scratches. I am also going to re-torque the intake manifold bolts and check the whole thing from air filter to manifold for loose/leaky connections etc, including vacuum lines. My experience lies mostly with other makes/models and am quite new to Jag troubleshooting. I sure appreciate your help!

The #2 fuel pump kicks in at 3000 rpm.

Cheers
DD

I shoulda figgerd that out eh? I love these cars! :icon_bike:

My buddy figgers he's going to run some good quality (Chevron premium) gas through it for a spell and see where that leads. I'm leaning on him to service the injectors and/or add the techroline cleaner and change the plugs and filters, but I won't hold my breath! I suppose he deserves to have at least one thing sort itself out with that car... We have spent a lot of hours debugging just about everything. Not to mention a small fortune. It's been a fixture in my front yard for almost two years! Not any more though. I have a complete 4 litre supercharged engine in my garage, a complete steering column, a complete exhaust system, a used but functioning cylinder head and various other parts, bits and pieces including a couple thousand Jag nuts and bolts. Buddy found a 95 XJR down in LA and he went a bit nuts. Bought just about everything that could be unbolted and drove the works back up here. Enough to keep her rolling along nicely for a few weeks anyway. Oh, turns out I may have capped off the EGR a while back a forgot about it. (Hey, who can remember things done a year ago?) I can't see that causing higher NOx though. Usually other way around ain't it? But I could see the exhaust gasses inhibiting combustion a bit. Maybe that's all it takes? I dunno. :icon_shrug: I'll open her up again and see what happens. Aside from a bit of a stumble now and then she's running fairly well. Nuts power when matted. Really have to hang on or she'll bolt on you. Speaking of getting back to work, I really oughta quit playin' with this 'puter and go back out and wrestle with my Jetta now until I freeze to the ground again. Bloody thing eats front bearings! I picked up a parts car a month or so back and am at least enjoying working on my car for a change... Just wish it weren't so derned cold! I'll hit the Jag again when it warms up a bit. Let the children play!

Thanks for the advice!

No one of the main functions of the EGR is to lower cylinder temps by introducing inert gas and this lowers NOX. Like I said High cylinder temps increase NOX, If youve disables the EGR don't do that. You need all emmssion control functioning properly on OBII cars. You could get away with stuff like that years ago with carbs and retuning, but not today without changing timing and fueling