You said "took it out", do you mean you measured while driving? If so, we need to do it again. Those figures are all measured at a stop, loading the engine with the brakes held. Maybe I should have stated that, my apologies.

Cheers,

 

For some reason I can't edit the last post. I also need to add that it needs to be done in an open parking lot or similar and NOT in your garage.

That's my disclaimer!!

Cheers,

 

I'll redo the measurement. My test driver (girlfriend) has it out now and reports it's fine. She'll go into the store and when she comes out it will be in RP mode I bet.

I had to drive it home last night in RP mode after it started with a rough idle. It ran rough and flashed the CEL several times in the 10 mile trip. Codes were P0304, P0354, P1313, P1316 and P1000.

JTIS says they all point to A bank, misfire and excess emmissions. Injectors? O2? Plugs? Converter? Jives with the too-rich both banks codes I was getting earlier.

Oddly, while backing it in the parking spot the RP changed to Failsafe Mode and it idle cleared up and CEL went off.

I'll sort out the MAF readings correctly. One thing at a time...

By the way, Rock Auto lets you return Coils.

 

I'm an idiot.

The original code is/was P0354. That's the A4 cylinder, not the A1! I've been working the wrong spot. A4 must be the cylinder closest to the firewall...

Arrrgh.

 

So you do have a corresponding misfire fault. Cool, then putting your new coil in spot #4 will probably take care of those two codes.
Then check your MAF [and fuel trims] and see it there is anything else going on.

Cheers,

 

For my education, what's the difference in terms of engine load between driving it at 1500 RPM and "brake loading" it to 1500 RPM?

 

i thought i told you in the other thread is was the back cylinder passenger side(US)? of course now that you have a p0304 you know that

 

You correctly answered the question I asked, but I asked the wrong question. Anyway the A-4-coil problem (Codes P0354, P1313) seems to be solved for now.

Now on to the MAF...and the Failsafe Mode

 

Steve -

I took several readings (gm/s) this afternoon after driving the car around for an hour or so.

MAFS:

Park at Idle = 4.1 to 5.05
Park at 2500 RPM = 16.3 to 17.3

Drive at Idle = 3.7 to 5.8
Drive at 1500 RPM = 32.09/34.7/30.5/30.8

I would seem to me that the Drive at 1500 RPM readings are low - the target is 39.3 (+/- 3 to 4 gm/s)


FUEL TRIM:

Bank 1 Short Term Fuel Trim readings are -2 to +1.5 at idle and the same at 2000 RPM (Park).
Bank 1 Long Term Fuel Trim readings are in the 5.0 range at idle and in the 2-3 range at 2000 RPM

Bank 2 STFT are -1 to +1 at idle and the same at 2000 RPM
Bank 2 LTFT are in the 6.0 range at idle and 3 at 2000 RPM.

I've forgotten the proper relationship between ST and LT...I can collect better readings with my test driver present.

 

Here is a another thread where we discussed fuel trims and I posted a little primer. That might help you. I see I may have to work on a part two, when I have time.

https://www.jaguarforums.com/forum/s...60&postcount=3

Does look as though you might be a little low at higher loads. After you are sure the misfire issue is corrected, give the MAF readings another try.

Cheers,

 

I failed the quiz. I would have expected the O2 sensors to see the excess unburned fuel in Bank 2 and subtract fuel from the programed amount, causing Bank 2 to go Negative.

Instead, it goes positive, adding fuel while Bank 1 yields no reading at all.

What am I not getting?

 

I found the full post and understand now. Measuring unburned O2, of course.

Let's see if I get this right in practice for my situation:

If my MAF is under reporting the actual volume of air entering the mix and the ECU is balancing to that under reported figure, the O2 sensors will "see" excess amounts of unburned O2 and call for the ECU enrich the fuel count. I would see this as positive LTFT, which I do.

Similarly, if my coil was failing (which I saw in codes P0304, P0354, P1316 and P1313) it would create unburned O2 in the A bank side and I should see Positive LTFT values there. (I might have, but didn't look when it was happening, only after.)

Over time, positive LTFT levels set Lean codes P0171 and P0174.

But I was seeing Rich codes P0172 and P0175, meaning too little O2 in the mix sensed by the O2 sensors. Rich codes and Positive LTFT values don't jive.

I've diagnosed myself into a box! I need to simply let the car settle out for a while and take new measures.

 

I'm sorry, I linked to my post only instead of the full thread. Dumb!!

Now you've got it. That's why I said get the misfire settled, then clear and reassess. Then tackle the MAF.

Cheers,

 

I can really see the value of Fuel Trim diagnosis - I'm surprised you don't hear more people talking about it.

Codes are cleared, nothing in pending. It passed all the diagnostic tests that I can trigger from my scanner.

I'm going to study up on Failsafe Mode which the car drops into repeatedly. I see that it can be triggered from a host of ignition related faults (P1516, 1517, 1571, 1696, 1697, 0566, 0568, 0570, 0567, 0569) I susepct it is triggered from other operating areas as well.

Failsafe seems like a weak cousin to RP, it doesn't seem to do much other than cut out the Cruise Control. And why that of all things. Much to learn.

 

I tried to make that same point in my paper on fuel trims; in my mind they should be the first thing on everyones lips when talking about running issues.

If you are getting Eng Failsafe Mode often, and don't notice anything else but Cruise not operating, zero in on the P1571 fault [Brake Switch]. This is a corporate fault code that not all code scanners can read. Cruise is inop because the system may not be able to recognize the brake activation to cancel cruise, so it won't let it operate. Failsafe shows up because the ABS and Traction Control needs brake sw. input. The brake sw. has two seperate switches, so you may not be able to readily detect its failure or intermittant operation.

Baby steps, one thing at a time. You decide, do you go after the Eng. Failsafe or the MAF sensor function first.

Cheers,

 

Steve -

I impressed my gearhead friend this morning with my exhaustive knowledge of fuel trim and diagnostics!

Thanks for the additional info. I am aware of the Brake Switch issue and even explored it recently on the forum:

https://www.jaguarforums.com/forum/s...ad.php?t=48738

Indeed, In Failsafe mode all I experience is the cancellation of Cruise Control, no RPM restriction or anything else. Also, I occasionally get an "ABS TRAC Inoperative" message, but not in conjunction with Failsafe.

This new information changes things a bit:

If Failsafe is not triggered from the elevated LTFT readings, thus not related to the MAF, it is then coming from some other, unknown cause - perhaps P1571 (which I can't see with my unit...). I can get the switch for $60.

The new coil in the correct place may have cleared the rough idle problem and P304 and 354, etc. Only time will tell.

The MAF is marginal, perhaps, but not clearly defective. A bit more clean running time is needed, then a remeasure. If it's under reporting volume at high RPM I should receive Lean Codes which I am just not seeing. I haven't received Rich codes P0172 and P0175 for a long time, so I'll put that issue on the back burner for a while.

So....If the misfire issue is fixed, and the MAF is not tripping codes I think I'll go after the Failsafe.

Thoughts?

 

<Chuckle> Always happy to help impress a gearhead!

Yep, I'd go after the Failsafe issue next. Sit tight on the MAF, and maybe see if the ABS has stored a C1095 motor fault. That could be your ABS/Tracs message. The ABS module can be repaired if you are gutsy enough to cut the cover off, resolder the terminals and seal the cover back on.

Cheers,

 

I can't pick off ABS codes with my Junior Grade equipment! (My Corvette easily dumps ALL codes right to the dashboard) Anyway, the ABS Trac issue has become pretty intermittant, almost nonexistant, really, after I replaced the right front sensor-to-engine compartment harness wire. A dealer scan told me that was an issue, though I have my doubts.

I've looked over the great tutorial here on resoldering the ABS module, looks like a snap. Seems like I could cut and remove just the corner of the cover and hit the 2 points...I've resoldered some electronics on my Corvette with great results. It's on my radar anyway.

It's Failsafe next. I'll research triggers for the message and maybe roll the dice on a Brake Switch ($60). Again, I don't think I can see that series of codes to know for sure if it's been tripped.

Had I known the Jaguar was so communicative I would have bought a better scanner

More to follow...

 

I ordered the brake switch, it should be here Thursday. I can "defeat" the Failsafe message by simply turning off the cruise control.

Otherwise it runs strong and all systems are fine.

 

An hour spent replacing the Brake Switch ($59 plus $9 shipping) cured the Failsafe issue.

In less than a minute I took the old switch apart, it's a very simple arrangement of 2 micro switches soldered to a small board. A clever person could buy replacements at an electronics store and fix the thing for less than $10.

I'll keep my old "core" if someone wants to try.