Took my faithful old XJ8 in for service and MOT on Monday. It failed on CO emissions but the fault is causing some head scratching at the dealership.
From the limited info I got over the phone they adjusted the C0 level to within limits but it caused the "other reading" (I'm assuming HC) to exceed spec. Bringing "the other" within spec caused CO to rise again.
Car is running fine - no hesitation, missfire or loss of power etc.
No DTCs logged.
Upstream HO2Ss are working OK - output checked and then substituted with known good ones.
MAF checked - not sure exactly how, but told it was OK.
Fuel rail pressure checked.
TPS checked.
Car isn't burning oil and fuel trim levels OK but were reset just in case.
The output from the downstream HO2Ss appears to be OK but they're going to try substituting with new units tomorrow.
I thought that the downstream HO2Ss are basically used just to check that the CATs are working OK and are not used for closed loop control ie. the output normally sits at ~200mv except during the deliberate rich/lean cycle to make sure they switch OK?
Anyone seen anything similar?
Kevin...
PS. I've got a Subaru Justy as a comp. car. I'll post my impressions later.
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Strong smell of bullshine about this. How, exactly, did they "adjust" the CO?
If the pre-cat sensors are sweeping properly and the short-term fuel trim is in spec [is it?] then cat efficiency comes into the frame.
What are the in and out temps of the cats, what are the post-cat sensor readings and what are the emission figures? [All of them.]
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>Strong smell of bullshine about this. How, exactly, did they "adjust" the CO?
Thanks Screwloose, you've confirmed my suspicions which is sad because this dealer has always been very good. They were taken over about six months ago by a much larger company and there seems to have been a culture change. Now, it's like a game of Chinese whispers with all info being relayed through the service receptionist.
>If the pre-cat sensors are sweeping properly and the short-term fuel trim is in spec [is it?]
I was assured that the pre-cat sensors tested OK (swapped with known good ones) and the short-term fuel trim was within range.
>What are the in and out temps of the cats, what are the post-cat sensor readings and what are the
>emission figures? [All of them.]
Those are questions I'll be asking - thanks!
Kevin...
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Kevin
That's getting even more concerning; if the front oxygen sensors' readings were correct; why did they waste their time - and your money - swapping old ones in? There's an impression of unskilled labour, way out of their depth, at work here.
I'd suggest finding a good, ex-dealer, Jag specialist. This bunch of amateurs are only good at emptying your wallet.
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Find a dealer that know's what he's doing!. Is there a slight rattle from the engine at tickover?. These do wear timing chains causing emission problems. I have had these where a heafty squirt up a very steep hill is needed to really burn the cats off but check the chain first. cats may be getting lazy as screwloose say's.
i Doc
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injection doc,
now fixed (see other post). I think that they were chasing their tails by not testing the upstream sensors properly and then going off at a tangent assuming they were OK.
>Is there a slight rattle from the engine at tickover?
No rattles at all - she's been over-serviced and purrs like a kitten ;-)
One slight worry is the waterpump impellor which hasn't been changed yet and is known to disintegrate - must get it done.
Kevin...
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Well, I got the car back tonight after they replaced an upstream O 2 sensor.
It looks like they made the situation alot more complicated than it actually was by not testing the upstream sensors properly.
First Test.
Fast Idle CO - 0.16%, HC - 100ppm, Lambda - 1.02 (PASS)
Natural Idle CO - 2.11% (FAIL)
Second Test.
Fast Idle CO - 0.01%, HC - 15ppm, Lambda - 1.00 (PASS)
Natural Idle CO - 0.05% (PASS)
They've had it for four days and to give them (some) credit charged me one hour labour plus £262.15 +VAT for the sensor, both discounted because of their loyalty programme and the MOT was free for the same reason.
It does feel a little smoother but that may be due to driving round in a Subaru Justy for a few days ;-)
Got to give them a call tomorrow though, they didn't replace the Service book in the wallet and it has the radio code written inside.
Thanks guys.
Kevin...
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