Here's the X350 DTC Entry for P0442:

P0442 EMS OBD II EVAP system leak detected – small leak (0.040 inch leak) Evaporative system monitor drive cycle – page 7 2 N ECM Default: – Canister purge inhibited – Adaptive fuel metering inhibited — Fuel cap not fitted correctly Fuel cap seal defective EVAP system leak (canister damage, pipework damage) EVAP canister leaking EVAP Canister Close Valve failure, leaking fuel tank

- I'm wondering whether the "Canister purge inhibited – Adaptive fuel metering inhibited" is perhaps causing the LTFT values?
- I'll inspect what I can of the evap system while doing the Valley Hose (awaiting parts from Harper Jag now), but a bit at sea as to what to look for
- I did look at fuel pressure while driving yesterday; steady speed ~ 55psi; varied some under load (assume a vacuum FPR working)
- Also looked at MAF; the (Foxwell NT510) showed "Lbs/sec" (vs grams/sec others have mentioned), but 0.01 - 0.02 idle; 0.02 - 0.04 driving ~50 mph varied terrain

 

Hi hisport,

I'm in a race this morning but a few thoughts to toss into the mix:

Does the hiccup occur while the car is idling in Park after a cold start or while you are moving forward in Drive after a cold start, or both?

You mentioned cleaning your MAFS four years ago. Have you cleaned it again recently? I use about half a can of CRC MAFS cleaner spray on the IATS bulb and the wires up inside the sensor - I turn it upside down and fill the cavities with cleaner and flush it around really well. If cleaning it doesn't make a difference in the responsiveness of your signals, you may want to replace it with a new Denso just to rule it out.

Your EVAP system can be tested for leaks with a smoke machine and/or manometer, both of which you can make yourself (see YouTube).

Regarding your cold start hiccup but no misfire codes, my mind is going to things that happen at cold starts, such as the secondary air system operating, the ECM in open-loop fueling...

I like JagV8's question about the IATS and ECTS. What do their signals read at a cold start? Are they close to ambient air temp or significantly different? How quickly do they seem to respond to rising engine temperature?

Sorry to run. I'll check back in later tonight.

Cheers,

Don

 

Many thanks Don B and jagV8!

Does the hiccup occur while the car is idling in Park after a cold start or while you are moving forward in Drive after a cold start, or both?
This is interesting, because the car "misses" upon cold start in park, but backing out of garage I don't really feel it, ditto moving forward (interesting because I'm used to an actual cylinder miss feeling much worse in drive/reverse than in neutral/park)

Your EVAP system can be tested for leaks

I reviewed the evap system section in the Jag service manual (stickies) and cleaned/lubed gas cap seal/filler neck (both OK), tested purge valve (which is actually on engine; LHS, on the '06 and later cars) for vac and pressure (tested OK). I used a big zip tie to seal the air filter box (a broken latch), and reset the evap code (couldn't figure out how to see PCM evap drive cycle test result on my Foxwell NT510). Performed 5 short drive cycles, and no codes have shown yet. I probably need more thorough drive cycles for real test.

Lazy IAT or ECT? Dunno
I checked IAT, ECT, etc temps vs ambient, cold start plus after drive cycle hot idle. All seem plausible. Fuel pressure and MAP values seem OK. The MAF responds to engine speed, though I'm not sure how responsive it should be (or how much scanner latency might be involved). MAF readings on the Foxwell are in "Lbs/sec", and show 0.02 cold idle; 0.01 hot idle. LFTS cold start Bank 1 6.25% Bank 2 7.13%. These LFTS figures diverge to (B1) 9.38 (B2) 13.28 hot idle after brisk drive. The other parameter which diverges between cylinder banks is VVT angle (of all things). This varies with engine speed, but there seems to be a 6 - 7 degree constant difference between banks. (eg, B1: 39 deg B2: 45 deg ( Is this normal? )

 

Hi hisport,

I don't have a supercharged car with VVT here at the moment to check the angles. Both of the X350s in my garage are 2006s, and the supercharged X350s prior to VIN G49701 do not have VVT. One thing you might do, if your scan tool has the capability, is to watch the camshaft position signals while varying engine rpm to see if the signals seem to vary to the same degree. The other thing that occurs to me is that since the cam and valve orientations are mirror images on each bank, advancing the timing will mean that one cam's angle relative to the crank increases, and the other cam's angle decreases. At least my tired brain thinks that could explain the angle differences you are seeing, so in the absence of any cam-related DTCs, I think you are probably OK.

Which reminds me, it would be helpful if you would edit your signature to add the year, model and engine details of your car so we don't have to go back to your first post to be reminded.

Thinking about your cold start hiccup, another question comes to mind. Does your engine start right up eagerly, or does it have to crank a couple of rotations before it fires up? Just wondering about your crankshaft position sensor, which can have intermittent temperature-dependent failure modes that do not always trigger DTCs.

Which raises another question: can you "see" the hiccup on the tachometer?

Cheers,

Don

 

Thank you all, Don B and JagV8, particularly, for wonderful help and advice

- Just a quick note to say the XJR is apart at the moment, awaiting valley hose bits. I will also inspect/replace all vacuum line related things whilst in there (eg PCV, etc)
- Hope to have another go at the CEL/fuel trims issue when its back together, and will update this thread at that point (finders crossed)