Emissions failure & apology

[mindofitsown]

Firstly my apologies for not contributing to this great forum for some time and only now that I need help.

Problem is my beloved S type (3.0 V6 53 plate) failed MOT solely on emissions.

High Co =1.5%, (limit 0.3%) and low Lambda 0.96, (limit 0.97).Have noticed petrol consumption increase of some 25% in last month but still drives smooth, if that helps.

Note, this time last year (with same MOT firm and 9000 miles back), CO=0.0%, Lambda 1.014

Lots of theories, so took it to Jag Dealer for codes to be read and guess what, car ECU would not communicate with diagnostic software (although other electronics would). Now £100 down just to find that out. I am at a loss and desperately need help to get my baby back on the road. 

Begging for help!

Regards

[Old Peter]

Hi Dennis,

I am no mechanical expert, but working on the principle of what goes in affects what comes out, I would guess that there is a few system issue.  I have a 2.7 diesel and use premium fuel [Shell V power] so I would ask if you have been using the same for the petrol engine.

It could also be worth using an additive that says it keeps the fuel system clean.

Let us know how you get on.

Regards,

Peter.

[Carole Simpson-Hadley]

Hello Dennis

MOH (my other half) says that is a hell of a CO increase and there is clearly a fault in the engine management.     We should suggest an exploratory call to a Jaguar Independent Specialist near enough to you; our experience is that they are usually happy to talk and point the way.    

We wouldn't have thought that simply changing fuel and using an additive would solve a problem like that; more importantly, an Indie should be able to sort out why your ECU isn't talking to the diagnostics

Good luck

[mindofitsown]

Many thanks Peter and Carole. There is another possibility in that I jump started my partner's car last month without having the engine on and I wonder if the sudden drop in battery voltage has caused the ECU to throw a wobbly and I have unknowingly been driving around in 'limp home mode'. Does anyone know what warnings/messages are given if this were the case?

Regards, Dennis

[Guest]

28 minutes ago, mindofitsown said:

There is another possibility in that I jump started my partner's car last month without having the engine on and I wonder if the sudden drop in battery voltage has caused the ECU to throw a wobbly

Hi Dennis,

That's a bit unlikely I think as otherwise simply disconnecting the battery might induce this fault and thats something we all have to do from time to time. To my mind the 25% increase in fuel consumption and the fact that the ECU is not communicating with the dealers Code Reader are the best clues. It could be that the fault lies with the ECU itself, or one or more of its connections to component sensors such as the Throttle Body. I think Carole has the right of it, see if you can find an independent Jaguar mechanic locally - there seem to be all too many main dealers where the quality of knowledge / workmanship is dubious - he/she may be able to provide some help.

As an afterthought, if Carole would care to share the name and telephone number of the indie she, and OH, use you might be able to get some advice over the phone or a recommendation for someone in your neck of the woods. How say you Carole?

Cheers,

Steve

[Carole Simpson-Hadley]

Hi again Dennis, and, of course, not forgetting Cubist; yep, we say fair does and here's some info :

Our main Jag Indie is Elite Performance & Jaguar in Derby (yes, we know it is a fair way from our domicile, but well worth it as several articles in Jaguar World magazine will bear testimony).   Main contact is a chap named John (also the joint proprietor) on 01332 265826.   Always happy to help and don't seem to have the default setting of "bring it in first".

With regard to jump-starting from the S, having the ignition off and engine not running is exactly right.........using the S as the donor car with engine running could cause damage.

In the Wiltshire area, how far are you from Chiltern Jaguar?

Sadly, we quite concur with regard to Jag Main Dealerships; not forgotten that when we collected our XK from one such, we quickly discovered that the tyre pressures were way out, uneven, and clearly hadn't been checked as part of the PDI.

Good luck Dennis

 

[JOE-DOT-COM]

HI

A plug in with diagnostic software will show if there any faults

but a faulty lambda sensor will throw the emissions out, theres usually 2 lambdas, a fault code will tell you which one it is

cheers

Joe

[mindofitsown]

Thanks all who have provided hints and tips thus far,it really is appreciated.

The latest news in this saga is as follows:

Battery disconnection/reconnection didn't  really make much difference but worth a try.

Bought a cheap code reader and got codes P1111 (Intake Air Temperature Sensor Circuit Intermittent High Voltage) and P1646 (O2 Sensor Malfunction Bank 1 Upstream). Note, this is less than a week from taking it to local Jag dealer who charged me nearly £100 simply to say the ECU 'won't communicate'. Grrrr!

After clearing codes, the P1646 re-appeared soon after with MIL light back on again.

Looked into various forums and found contradictory posts about which bank and whether it really was upstream/downstream etc.

Decided to look further in code reader with real time data whilst driving. Found that Fuel Systems 1 and 2 stay in "OL" mode whatever happens. Also found Fuel Trims stay fixed at 0% and both downstream O2 sensors have 'stuck' readings (for current and voltage readings) that occasionally become unstuck and then stuck again.

Checked o2 sensor fuse and relay and they are fine.

Worked out (I think) what some of the cypher language used by the code reader actually means. (had to do this because the instruction manual doesn't cover this and its taken me most of the weekend).

I think what is supposed to happen is that the after start up, the ECU causes the engine to default into "OL" (open loop? control mode i.e. no sensor feedback to make adjustments). After about 15 seconds or so, the sensors have been read and providing there are sensible readings, the ECU goes into "CL" (closed loop? mode i.e. thereafter making adjustments to fuel inputs via the injectors, on a near continuous basis according to feedback from the sensors (MAF, MAP, O2 etc.).The adjustments are called "short/long term fuel trims" and are measured as a percentage from the open loop default value and these adjustments help ensure minimum CO emission and as close to a Lambda (stoichiometric ration index) of 1.0 as reasonable.

The problem in my case is that the CO is too high (1.5%) hence failing the emissions test. Now, 1.5% would have been a good result for my old 245DL Volvo from 1980 which was permitted up to 3.5% but that old skool vehicle was designed as open loop. I thinks what is going on is simply that the ECU does not get sensible values from the O2 sensor(s) at start up and as a result it stays in "OL" mode which causes the fuel trims to stay fixed at 0.0% i.e. the ECU simply ignores the sensors and thus no adjustment are made.

So, with what I can make out to be sensible readings for Mass Air Flow, Manifold Pressure, Throttle Position and non-sensible readings from O2 sensors I have just ordered a whole new set of O2 sensors (simply can't get enough clear information about which sensor is duff).

Will post again with result of replacements.

Regards.

 

[Russ68]

Crikey! You've had to get pretty deep into that Dennis!

On 14/01/2018 at 11:22 PM, mindofitsown said:

(stoichiometric ration index)

Indeed!

Good luck and keep us posted, changing the sensors sounds a good call 

[mindofitsown]

Sorry Russ, that should have read "stoichiometric ratio index" which I have since researched to mean the ratio of mass air flow to mass fuel flow, the result then divided by 14.7. Apparently, the ideal ratio of air to fuel in a petrol engine is 14.7 (when hot) and thus if we achieve the ideal and then divide by the constant 14.7 it will end up as 1.0 as an index which the MOT calls Lambda. Less than 1.0 means too little air for the amount of fuel (i.e. rich mixture) and greater than 1.0 means the opposite (i.e. lean). I guess I am teaching my granny to suck eggs for many of the contributors on this forum but I want to air my thoughts of what's going on and invite correction so that I get it right.

Good news! I have renewed the upstream O2 sensor on Bank 1 (as per code P1646 description) and all is well! The old sensor was easy to remove (luckily)and now I have sensible O2 readings and the fuel systems go to "CL" (closed loop) mode with active fuel trimming. I have cleared the old code and the MIL lamp stays off. Relief! Got MOT re-test later in week so fingers crossed and will let you know the result.

[JOE-DOT-COM]

hi

I'd ignore the p1111 code

its the p1646

these codes are from jaguar jtis attached below

cheers

Joe

[JOE-DOT-COM]

hi

looks like its the upper one item 5, oxygen sensor 1, bank 1 cyl 135 RH

cheers

Joe

 

[mindofitsown]

Thanks Joe, absolutely bang on. That was the sensor indeed. Very useful information supplied, many many thanks.

[mindofitsown]

Forgot to ask.....what is 'JTIS', regards, Dennis

[JOE-DOT-COM]

hi

JTIS is a software, thats like a workshop manual, thats covers all jaguars up to 2005

very handy when you need to do anything

cheers

Joe

[mindofitsown]

Thanks Joe, I will have to see if I can get that at some point.

Good news! Passed MOT with new sensor. CO at 0.00%. HC at 0ppm and Lambda at 1.007 so almost perfect. Should find my mpg get back to normal soon to boot.

Thanks to everyone for your help and I promise to listen in and contribute more to the forum.

P.S. don't think that will be long since one of my key fobs has gone down today and new battery has not solved it.