Dear All,

My car is running rich (petrol smell at exhaust, occasional smoke and backfire out of R/H exhaust , faintly shaky at tick over - worse when cold).

Please could someone try to help an outmoded old car restorer like me to understand what the attached code reader results actually mean!

(I have cleaned my MAF Sensor and at 160,000 kilometres I think I need to replace all 4 02 Sensors, and all 8 coils and plugs)?

Please save me from myself!

Best Regards,

Ray

 

To start: you have the same engine fitted to a few models so answers for any of them usually are good enough.

Your actual car forum is https://www.jaguarforums.com/forum/x...-x350-x358-28/

It's probably not running rich but instead is seeing misfires as air (it can't see the fuel) and so it adds MORE fuel.

You need to fix the causes of the misfires.

It's hard to see how so many faults all happened at once - did they? Importantly, which happened first? Fix it then try again.

Search the forum for your car and read what the posts say about the codes you have.

You need to find if you have bad O2 sensors, bad coils, an air leak or what. Or start fitting new parts and hope.

 

Thank you Jag V8. I do know which forum is mine, but I have been unable to figure out how to start a post from within my forum?

I have no idea which faults happened first. This is the first time I have ever connected a code reader? I am still trying to understand (I have asked) whether faults can accrue over time? I am also at a loss to figure how I can have so many problems and yet no engine fault light? I really do not know where to start, other than to replace all the coils, plugs and sensors that the fault codes appear to refer to?
I have scoured my forum, but all I have been able to glean is that all too often, multiple codes are as a result of poor earths and I have no idea how or where to check them? I was hoping that my wildly fluctuating fuel trims would give one of you experienced guys a clue as to where I should start?
I'll just have to scour again!

Thank you again.

Regards,

Ray

 

Follow the link then a bit down from the top is a button
Post New Thread

As I said if the MIL is off then you have no current faults.

So those you have must be old.

Some will say to clear them BUT they tend not to mention (or know?) that doing so also clears the OBD monitors used for smog tests and also for detecting future faults. Now, if those monitors run OK it doesn't matter but sometimes they don't. And then you can be really in a nasty place.

Old codes stay stored for a while (for techs to use in diagnosis) but eventually are auto-cleared (without changing the monitors). So I'd leave them well alone.

The only issue is to check that the MIL does its self-test. If it doesn't it's usually because it's blown or gimmicked.

 

So if the MIL behaves OK and you're ignoring the codes (because they're old and thus now irrelevant)... is there anything to do?

Yeah... have a look at any sensors you can understand (ECT, IAT, others?) but especially check fuel trims: hot engine, parked, at idle. If LTFTs are under about 5 then all's good (unless you've got high STFTs but in the above situation that's pretty much impossible).

---

All our (petrol) engines are roughly as per this diagram (in terms of OBD):
OnBoardDiagnostics.com - Engine Basics

(we tend no longer to have an IAC valve because the electronic throttle is so good it is used even for fine control of idle etc)

(oh, and only some of the cars have the "secondary air" pump - it's to get the emissions down)

 

JagV8 Thank you very much!
You have now taught me that codes can be old and that I only really need to concentrate on new codes arising from a MIL. Can I assume that this attachment shows my MIL passing its self-test, please?
To be clearer, there are long periods when my Jaguar runs beautifully (apart from a very slight 'tremble' at tick over - Which is set too high and I need to address). But on three occasions since I bought the car a month or two back it has backfired and thrown smoke out of the right hand exhaust (passenger side - My car is L/H drive). On the last occasion there was also a pungent smell of (what I can only describe as) burning rubber? I shut the engine down immediately, but no belts or anything have slipped and nothing appears to have been harmed? I was thinking have I burnt out my catalytic converters and perhaps this event is why I appear to be overreacting!

However, unless you suggest otherwise, I am simply going to replace all coils, plugs and sensors because with 160,000 kilometres approaching and no real service history, the £400 or so it is going to cost me to get the correct OEM parts here to Dubai I will put down to a much-needed major service on what is an inheritably beautiful car!!

JagV8, if you needed the rear inboard disk calipers rebuilding on your 1960s Jaguar then I am your man. This OBD2 business is all foreign to me and I am very grateful to you for your time and for your help........

Regards,

Ray

 

Should be OK (but I actually meant to watch the dash light).

If the LTFTs are within about 5 then it's running OK.

Sorry, I've never had a 1960s jag

You might try watching a few OBD live data items (STFTs, maybe LTFTs) and see what they do when you get the tremble.

If it's running as well as it looks I'd be reluctant to change parts. Oh, the plugs are costly and are due at 100K miles i.e. now. I expect they're NGK IFR5N10. They already have anti-seize and are pre-gapped. Take the old ones out with engine quite hot or at least warm or they can be really tight. Plan how to get at the rear ones! (extensions/UJs/etc)

NOTE: you probably cannot adjust the idle and should not try!
Well, if there's a fault it may be too high but not otherwise. You'd "adjust" it via a fix.

E.g. if it's too high then the fuel trims will be out. Or the MAF is reading wrong (making it seem there's too much air) but then the trims tend to be wrong again.

 

Sorry to be a pain but when you say 'If the LTFTs are within about 5 then it's running OK' do you mean plus or minus 5 percent above zero or do you mean both banks within 5 percent of each other?
I have

STFT Bank 1 2.34375 percent LTFT Bank 1 10.1562 percent
STFT Bank 2 9.375 percent LTFT Bank 2 (minus) -1.5625 percent