Hey all. Latest problem on my car (do I get to shout 'bingo' when I get to the bottom of the common issues list?!):
Thought I'd have a check of my fuel trims (as you do!) and discovered that bank 1 stft isn't quite right! Apart from when it's going open loop, it's reading +24.2 all of the time - after ramping up anyway. Bank 2 is as normal.
Reading the codes brings up 1193, which I believe is o2 sensor related...?

Any thoughts? Lambda? Or could eg a dodgy coil give similar symptoms?
The one thing I don't really suspect is anything to do with a duff injector - a benefit of an LPG conversion is that I have an alternative fuelling system at the touch of a button, and it behaves the same way!
Cheers in advance for any ideas!
Jon

 

Cleared the fault code this morning and it hasn't popped back up after ~30 miles and one stop for fuel... but the fuel trims are still playing up! Bank 1 still sits at 24.2, and whilst bank 2 behaves most of the time, it seems to exhibit the same behavior as bank 1 intermittantly.

So what's my short list?! Lambdas (are there just 2 - post cat on a UK car?), something ignition related (not sure that would exhibit these symptoms?), exhaust manifold...? Guessing not MAF or a vacuum leak as that would presumably affect both banks simultaneously?

Ta!

 

P1193 is related to a fault with the O2 heater circuit. You may have a wiring issue to one or both sensors or one of the sensors may be failing and it's resistance gone high.

Also you might have a fuel burn issue. If ignition is retarded too much on one bank, that would cause exhaust gases to increase in temp and you could get the same fault code.

Just one other thought, make sure no-one has swapped the O2 connectors around. When I bought my XJ6 the PO was having drivability issues and when I plugged in my scan tool, the STFTs were pegged at 24.2, one positive and one negative. I guessed that the sensor plugs had been switched and when I switched them around the car ran perfectly

 

The 1193 code indicates a fault with the the oxy sensor heating circuit, "Sensor 2, Banks 1 & 2 "


That's a bit vague. I would be nice if the system would segregate with bank as it does on the 4-sensor cars.

The service manual recommends checking the sensors heater resistance (5.3 - 6.7 ohm) and replacing the sensors if out of range. After that it's a slew a wiring/circuit tests.

I'm not positive if the 1193 code is directly related to your fuel trim problem. Are the oxygen sensor readings for Bank 1 similar to Bank 2? If they look about the same I'm inclined to say the 1193 code isn't causing a fuel trim problem.

Cracked exhaust manifolds can cause fuel trim problems, yes. Remove the cover and take a peek. If cracked you gotta replace it.

Coil failures are common but my gut tells me that you'd probably be feeling a misfire if a coil was to blame.

Sorting cause and effect can be tricky, especially since these early OBDII systems on the Jags were not....um....'fully matured'.

Cheers
DD

 

Thanks guys - & thanks again as usual Doug!

I guess I need to keep an eye out for that 1193 returning - if it doesn't, it seems likely that it was just a red herring...

Allan, I doubt my lambdas are the wrong way round - I'm not seeing the reverse happening on the other bank, and they seemed to be working fine a couple of months ago when I last looked.

Doug, now that you mention it(!) I have been experiencing an intermittant misfire at idle! Not sure how I failed to mention that - other than having not driven the car for a few weeks over Christmas... I've been meaning to have another check for any 'light show's from the coils - I'll do so tonight.

 

Today's update:

• No arcing is visible on any of the coils (checked last night) - what's the likelyhood of faults there still, given a bit of roughness at idle sometimes, but no funny lights on the dash / fault codes etc. either?
• The 1193 fault code hasn't reappeared after another couple of ~30 mile drives.
• Looking at the o2 sensor voltages directly, bank 2 looks as (I think) it should - fluctuating between about 0 and 1.2v. Bank 1 however, sits at 0, with an occasional blip to 0.1v. I need to remember how to get a graph out of my diag tool, as looking at the voltage directly (and at too low a sample rate) isn't going to tell me much. However, does this look like a faulty lambda? AFAIK, if it was functioning properly, I'd still see a voltage out of it - ie it wouldn't just read zero if it was really running lean on that bank, would it?

Still need to check the exhaust manifolds - is it simple enough to get the heat shields off?

Thanks all!

 

An arcing coil is obviously faulty. Lack of arcing/flashing from the coils doesn't prove they are good, unfortunately.

The only testing specification for coils in the ROM is .75 phm primary resistance. I've had coils with nearly double that amount work perfectly well, so .....

If your idle misfire is fairly pronounced and constant you can unplug one coil at a time and listen/feel for worsened running. If unplugging a coil doesn't make the the engine run worse then it isn't working.

If the misfire is subtle and/or intermittant you may have to buy one new coil and try it in all 6 positions...hoping for the best.

Do check coil wiring and do pull the coils and inspect for charred boots.

At this point I'll add that I've have misfire problems a few times in my XJR ownership. Usually coils but most recently an especially hair-pulling problem was totally solved by installing a new set of plugs. This was done on whimsy (desperation?), as the existing plugs were only a few months old and 'looked' perfect.






Good!

Remember, though, that before a code is set the fault has to fall into a specified window before the OBDII system recognizes it. Each fault code has a different window. It might be [something like] "xx-number of failures within yy-number of drive cycles which include zz-number of miles and include aa-miles driven at speed under 40 mph"

That's completely ficticious example, of course, in an attempt to illustrate what I mean.

Jaguar doesn't tell us what the 'windows' are.




Sounds to me like the sensor is dead. I'd replace it.




Easy. Just a few bolts and wriggle it off. If you have air injection you'll have to undo the pipes but that's no big deal.

Cheers
DD

 

Thanks once again Doug!

It does seem slightly strange to me that the fault code hasn't come back while the other symptoms suggest that it should... Like you say though, it may just be taking its time.

I'll get a lambda sensor ordered, so the next question - is it obvious which one I need to replace?? That's probably a question for someone with a UK (2 sensor?) car, but anyone else is more than welcome to help too!

Plugs aren't exactly old but are coming up for when I'd swap them anyway so that might as well get done. Coils I'm less sure about - they're far too pricey to just replace them all as a maintenance item, and the doubt over quality of new ones is annoying too. I'm tempted to pick up a complete set of used ones so I can resort to trial and error, but that's not the most satisfying option!

& as for the exhaust manifolds, my previous luck with this car dictates that they'll almost certainly be cracked so I'll start looking for replacements now... or maybe I should scrap it and find myself an XJR to do all the work on.

 

The early OBDII system on these cars is quirky. It's very reluctant to set codes for some problems an absolutely over-willing to set codes for others





You mentioned "Bank 1".

Bank 1 is the forward three cylinders. The exhaust pipe just below the exhaust manifolds has two branches, so to speak. You'll easily see which branch goes to the forward three cylinders. The Bank 1 sensor will be in that branch





SNG Barratt is selling the good quality coils. See the "Head's up on X300 coils" thread.





Here in the 'States, at least, good used ones don't come up very often. You'll probably spend a lot of time searching.

New ones are a bit pricey.

It only takes a few minutes to pull the manifold heat shield to verify in you have cracks. Maybe you'll get lucky!

Cheers
DD

 

& apparently never sets a CEL! Ah well, better than not being able to see any of it - I'd have been one of those people who got caught at emissions test time otherwise I expect...


Complicated stuff - I'd never have worked it out on my own!
I was imagining them being fitted into the cat assembly & not necessarily obvious which branch they were into, but that was just me being daft...


Finally! Guess at least one of those should be added to my next order - I'll inevitably need one at some point.

No chance - but I'll count myself lucky that more of our cars must get broken in this country; there are a few manifolds on eBay currently if/when I need one...

 

Got a decent look at the suspect lambda sensor output... zilch. Could be wiring to the sensor still, but I'll get a new one ordered I think!

 

Or, the bank really could be running extremely rich... A titanium sensor lowers its resistance when rich, so it's voltage to ground decreases when too low O2.
That said, I am betting on a shorted lambda sensor.

 

That's odd - you'd expect the STFT on that bank to go the other way then; it currently 'thinks' it's running lean... I guess it's good that it doesn't though - I'm sure someone thought through what would happen when one failed!
It points away from a cracked exhaust mani too (I've not yet checked), other than as an unhappy coincidence.

I'm not sure that the other bank's lambda sensor is quite right either, having had the graph of that sat in front of me, but I guess when I get the other one sorted I'll be able to compare & contrast.

Still no fault code!

 

Ziggy- You are right. That leads me to wonder if the circuit on the X-300 is not using the titania sensor in a sourcing circuit rather than a shunt to ground as I assumed. I really can't remember and I don't currently have a running X-300 to test!

 

Just a quick update - lambda swapped (plus gas and a decent flare spanner came in handy!), trims back to normal.

The fault code never came back btw!

 

May I just add though - what the **** were they thinking when they routed the cables / plugs for the lambdas like that?! My hands are shredded!