Good morning,

My apologies if this comes out in Bold type with some spacing issues but I am copying & pasting from a Words doc which sometimes does strange things!

My XJ8 3.2l 2001 model was misfiring with very noisy engine clatter, andwith the benefit of forum advice I replaced both broken/cracked secondary chaintensioners and the (LHS) Bank B chain, which had slipped a cog tooth causing misfiringand damaging chain against casing.

On completing this work the engine started first time, and after aninitial short period burning off oil spillage and the ECU sorting itself outshe ran smoothly throughout the range and I drove her for about 200 milesaveraging my normal 22mpg for a mix of heavy town traffic and highway drivingwith individual stop start journeys no longer than 30 miles.

Taking further forum advice I then bought cheap Autel Maxiscan MS300 OBDll Code Reader to check/resetstored DTC’s and MIL.

14.05.13 (1st Scan), and not surprisingly found a series ofDTC’s, which having checked against Code Lists identify as follows:

PO300, Random/Multiple Cylinder Misfire
PO305, 6, 7 & 8, Cylinder(s) 5, 6 , 7 & 8 Misfiring (Bank B)
P1316 Misfire Excess Emission
PO102, MAF or VAF A Circuit Low Input
PO112, IAT Sensor 1 Circuit Low Input
PO128, Coolant Temp Below Thermostat Regulating Temp
PO332, Knock Sensor 2 Circuit Low Input (Bank 2)
PO101, MAF or VAF A Circuit Range/Performance
and
P1111, drive cycle complete.

Most of these seemed related to secondary chain problem, but wasn’t sureabout PO101, PO102, PO112, and PO128. However, as engine was running nicelydecided to reset and see what if anything repeated, either immediately or afterdrive cycle completed.

Then drove for about 225 miles, again a mix of heavy traffic and highway shortjourneys, still running very smoothly, and MIL came back on.

Plugged in OBDll Code Reader and had following DTC’s.

PO420, Catalyst Efficiency Below Threshold (Bank 1)
PO430, Catalyst Efficiency Below Threshold (Bank 2)
and
P1000, showing drive cycle incomplete

Worried I may have damaged Cat’s with initial bad combustion and subsequentoil burn off, but after a bit of thought wonder if Mass and Volume Air Flow PO101/102 Codes originally pulled could be contributing.

Although these haven’t repeated I don’t know whether they would only showup after drive cycle completed.

Also not sure what impact Intake Air Temp (PO112) could have.

Rechecked codes with same results, but PO1638 added. Tried to check exactmeaning but this gets a little confusing. It seems to be related to informationoutput processing wiring/connectors/modules.

Tried to start engine which caused warning beeps and dashboard readout errormessages for Low Brake Fluid, ASC Not Available, Gearbox Fault, and FailsafeEngine Mode!

After a brief panic I switched everything off, left it for a while andthen retested with same results.

I then reset the codes, left the engine switched off for a while andretested after several minutes. MIL and DTC’s all reset and no apparent problem.

I wonder if I could have confusing the system by trying to scan withengine switched off (which I know I did at this point) and after realisingswitched on and got this code?

If this repeats is it worth trying battery hard reset to discharge any residualcapacitive memory?

In fact on that point is it worth refreshing the whole system by doingthis anyway?

As always all wisdom and advice would be greatly appreciated.

 

It is possible that during your camshaft cover removal you moved some connectors in the throttle body area.
I seen the same messages as you seen last time (low brake fluid, transmission fault, TCM, ABS) and it's an obvious throttle body connectors problem.
Any P0121 ?

 

Hi flay,

Definitely no codes except those previously listed, and all seem to have now reset.

I don't want to start playing with anything unless problem returns, in which case I will progressively check throttle body/MAF/VAF connectors, etc, and monitor which if any corrects problem.

I also understand that battery condition can cause a string of (illogical) error codes, so although it seems to hold a good charge it is several years old and I will check it out.
Thanks,

John

 

Hello Dag,

As you have just ekuded to, the battery can be a cause for many spurious dtc's on these cars.
I would suggest you give the MAF a good clean with dedicated MAF cleaner.
Make sure the TB is clean and well connected.
Check the battery vol,tage and connections.
I would take the car for a good long motorway run pof at least 200 miles return and use a couple of bottles of fuel system cleaner in mid grade fuel.
Then check out your car.
The cat's probably need a good burn off...can you put a bottle of cat cleaner in your fuel before setting off and give it a good flogging....you may be surprised by the results.
Loosely referred to as an 'Italian Tuneup' ;o))
I'm assuming of course that you have no intake air leaks and your plugs are in good order?

 

Thanks Xjay8,

Just my luck, started to reply and lost myinternet connection!

Sounds like good advice all round from a seasoned Jag roadwarrior.

No obvious signs of air leaks anywhere. Replaced air filter as well as plugs(with Iridium tipped NGK 1R IFR5N10) when I had cam covers off, so they should be fine.

I will certainly check out battery voltage levels and cleanThrottle Body and MAF with dedicated cleaner as well as try Fuelsystem and Cat cleaners, before giving it all a good blow through on a longerrun.

Will update on progress and/or developments.

John