Hey Y’all

I’m joining the jag community with a trial by fire. Trying to pinpoint if my problem is the ecm or something different.

check engine light is on, sometimes when I start the car it stalls and dies. When I’m idling at a stoplight, occasionally the engine will begin rumbling and the gas pedal almost ceases to function and all I can do is idle forward at 2-3mph. This may go on for 30-60 seconds but then normal function resumes, mostly.

Running down the highway, she feels mostly okay. Slight vibration, perhaps misfiring?

I’ve disconnected and drained the battery a few times. After one battery reset, she actually felt great on the way to work. No rumbling, all purrrrr. And I could feel the horsepower she’d been hiding. Only lasted that one ride. Back to inconsistent rumbling and occasional stalling (most often at startup).

So I removed the ecm and it looks okay. A little residue but no visible defects. Cleaned the residue and reinstalled. CEL still on and the “gentle” rumbling present, but no stalling or extreme struggling… yet. Took it to Autozone and codes are as follows:


Front

Back



I absolutely love this car. So elegant and rides like a cloud. After that brief tease in the highway, I am not giving up on this machine.

I have poured through the forums on both these issues, but I thought it best to consult y’all’s collective wisdom before emptying my savings 🙃

I already have a used replacement ECM I ordered, but the reprogramming bit concerns me. If it’s used it should already be programmed right? I’m just concerned about the issue of the immobilizer. I’ve seen people reprogram their keys using the high beams lever method, but would that work with a replacement ECM installed?

Also my gf works with microelectronics and she said she could replace the capacitors on the original ECM board.
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I’m in the weeds right now and need a little direction

 

Silly question but do the wipers work ok?

 

One quick question - how old is your battery, is it a AGM battery? That many codes, and the intermittent symptoms you described, might indicate battery not supplying enough amps. Also, the possibility of bad ground comes to mind.

 

Wipers are good.

Battery is a duralast platinum with a 10/23 sticker. The reading from AZ showed 11.92V. Where’s the best place to start with a ground test?

 

Decent batteries. Duralast H7 'Gold' of 10/19 was still 'OK' in my L320 at around the 5-year mark. Replaced it on principal.

Even so, FULLY charged, disconnected from any loads, should see a skosh OVER 12 V.

Make sure you have it FULLY charged and not being drained, check it again.

First, print yerself a copy of the ground-point location diagram from the manual.
IIRC, there are 36 of them on a X350?

Seem a good idea to have yerself a check list as you go!!!

 

Much appreciated. I’ll test the battery. I’ve got the ground point diagram and will pick up a multimeter in the morning and begin crossing off. I’m looking for variations of >0.4V at each point?

 

11.92V, way too low!
Either completely discharged battery or dead/defective battery.
Start fully recharging it and check voltage again

 

I tend to agree with paydase; My three year old AGM, with ignition in the "ON" position (all instrument lights on, but engine not running) is 12.4. And when you start it, your voltage should be above 14.2 as it should be in the high charge mode as commanded by ECM.

 

You are 'looking for' the cause and for erratic/intermittent behaviour more than the magnitude of it.

Oxidized Aluminium. Corroded / loosened 'washers' and terminals. Even a few that have a degraded attach to the sheet metal or have even crumbled to bits. Some may neeed nowt but loosing and re-tightening. Others you may need to fab a new post altogether - making sure it has GOOD conductivity to Aluminium and/or a decent bus wire from a better place.

Sort the battery ALSO.. if not also "FIRST", of course. You may not have ANY faulty grounds at all.

Even 'El Cheapo' meters of present-day often have battery cranking LOAD test capability built-in. That will spot a dead cell right quickly. My older gear (Fluke 77..) I just use an external load. Flash the headlights, (high & low beams on together) for example, is usually enough to reveal a problem.

 

Stopped at AZ to rent a code reader and let em juice the battery. Was at 84% as seen below





As I was leaving the parking lot it began to idle very roughly. I crawled it around the AZ parking lot twice before the rough idle ceased. Probably lasted about two minutes, the longest one of these episodes has gone on. Eventually the accelerator regained function and it began to ride smooth, for the most part, the rest of the way home.

Began testing ground points in the engine bay. Picture below of the ones tested so far. NR is for “engine not running” and R for “engine running”




I would note that the ground connections look okay but not great. Nowhere near crumbling, and minimal corrosion, but twenty years old nonetheless. The voltage held at each point so far. Plan to take a metal brush to them for good measure once the rain passes. Hit me outta nowhere 😅

one note about G26: the “NR” number for that was grabbed last, moments after killing the engine. Might have impacted the higher reading

 

If the wipers work properly then the earths behind the headlamps are good

 

Well, the last symptom, "it began to idle very roughly. I crawled it around the AZ parking lot twice before the rough idle ceased. Probably lasted about two minutes, the longest one of these episodes has gone on. Eventually the accelerator regained function and it began to ride smooth":

I had the exact same symptom about a year ago. Drove me nuts, as it would clear up all on its own, as yours did, after two minutes of driving. And it manifested itself usually after a hot start (drive to store, restart to leave, and idle so erratic as to almost stall and shake like a wet dog).

I am 99% positive it was bad tank of gas and/or dirty MAF sensor. I did the following - put in one big bottle of Chevron Techron, and then cleaned MAF sensor with CRC MAF Sensor Cleaner (see other threads for procedure); I will never know if it was dirty MAF or bad gas. Following a fill-up after burning off better part of original tank of gas w/ Techron, problem utterly disappeared and has never happened again. I know this does not explain the original code errors, but, when the engine idles that bad it can throw all sorts of codes cause its so close to stall rpm.

 

Friend, I'm optimistic about this possibility. Cheap, easy to access, addresses multiple symptoms, what's not to like?

Day 3 of ownership, I replaced the fuel filter. Also ran tank to empty and haven't filled her with anything but PREMIUM in the month I've had her. Spent a bit of time researching bad fuel pump symptoms after problem persisted. The codes pointed to ECM... BUT there's an MAF sensor fault hidden among the laundry list of codes. Quick detour after work to get some proper MAF cleaner and cross my finger once more. If this doesn't work, moving on to O2 sensor cleaning and installing new spark plugs because why not...

Fun facts that may or may not be related:
There's no audio output but the radio appears to be functional, the dipped beams still do not work with new 6000K HID bulbs (main beams are good), parking brake fault, and the air suspension fault lights up occasionally. Seller sure managed to hide a lot, but who doesn't love surprises!

 

The radio sound may come back on it's own.
It has happened on my Jag 2/3 times in 16 years of ownership.
The suspension light may be just the compresser needs a new piston ring
Try replacing the light stalk to cure light problem.
Easy to do because it's a cassette and the wires are crammed in there.

 

Just because Premium does not preclude bad gas....about a month ago, local mega-station nearest my house had to do public notice of contaminated gas. Was premium, (generally has slower turn-over in underground storage) lucky me I missed stopping there during the problem period.

Be prepared on the changing spark plugs - there are numerous threads on that one, reaching the back driver's side can be a PITA due to limited clearance. Many have done it (myself included), but I'm pretty sure most agree that having right swivels and knowing how to get through the bulkhead compartment is key. But, 90k is about the time for new plugs.

Cleaning O2 sensor is iffy - if you don't mind cost, I suggest just changing it, as extracting and installing is 90% of the work, and cleaning is not always effective.

Well, I seem to be full of opinions this am . Welcome to the world of X350/358 ownership; most reliable car I ever owned except when its not.

 

ctsemicon, pretty well says it.


Welcome to the world of X350/358 ownership; most reliable car I ever owned except when its not.
Best used car deal out there, when i bought mine.

 

Brand new battery should have about 12.6V,
12.4 is still good,12.2 is still ok but not for a Jag At the end of driving I switch of what is unneccesary. And let the car idle a couple of seconds .
your stalk might be the reason or the ground studs behind the headlight if still no good . Ballast is underneath each headlight . So bumper off. 2 models ballast Valeo Lad5G for the older models with dipping self leveling in the headlights . If you put in new ones they will not support selfleveling anymore and here come the thing... since related to the airsuspension heightsensors you will end up with a airsupsp. Fault on the dash. To eliminate that one you got to switch over Sdd from headlights Hid to halogen.
on later models Ballast is Valeo Lad5gL.
the 3 ground studs in the Front . briddle with age but I did not brea a single one on 5 cars. Undo the nut clean the contact rings and the tread with a brass brush put battrey grease on fit back together do not overthighten.
On one of my cars I exchanged the threads with aluminum screws and bolts works fine for 2 years now
emptying battery when alternator does not work anymore give bad studdering too in that case switched of every electric item so I could make it of the street

 

Pops agreed to come through with the assist. Changing spark plugs and O2 sensor with my old man Saturday morning.

I cleaned the MAF sensor last night. After reinstalling, it idled well into 600/650 range for about 15min with no stalling or shuddering. Definitely helped. Still a steady vibration once I hit the highway this am. Not violent, but enough to induce a headache after 45min on the road 😵‍💫


Tackling these problems one at a time. Hoping to address the lights after this weekend. I might order the 4000K HID bulbs. Saw in a post someone had better luck with those as opposed to the 6000K I tried.

A breakthrough Saturday would be okay 👌 Sanity is teetering 😅

 

Glad to hear MAF cleaning helped.

Regarding vibration...a bit more info? What makes you sure it's engine related? Could it be drive-train and/or wheel-tire? By vibration, is it more steering wheel, or is it "seat of the pants" from body?

Now that MAF and ugly idle induced MIL codes are behind you, I would suggest clear any/all MIL codes, then rerun the diagnostic and see what remains.

Oh , think you will find 4k LED's better - I converted all my front lights to 4k while back and they are excellent

 

I’m not 100% on the engine being the culprit, but I feel like it’s related to the other codes based around fuel and air systems. The tires are new pirellis.

the vibration is felt in the steering wheel and on the floorboard up by the pedals. It has a bit of a rhythm. Like a short drum roll on a snare, a brief pause, and again. My gf’s mazda 6 had a bent rim and felt very different by comparison. When she rode in my XJ8 she didn’t notice the vibration so much, even when I brought attention to it