Went to get the x300 inspected the other day (MOT)

Flying colors except the o2 sensors gave a zero reading. Scantool shows no voltage

Any ideas?

won't pass otherwise.

It's a euro spec car so I believe it has two fewer o2's than the US spec if that's helpful.

thanks

 

Scan tool configuration as the downstream sensors are used for engine regulation for the 4 sensor setup and the 2 sensor setup uses the upstream ( if that is where positioned )

See page 81

http://www.jagrepair.com/images/Trai...20-%202000.pdf

 

Thanks.

It uses the two sensor configuration.

The test facility got a zero reading on volatgae when testing for emissions. The way they test for O2 functionality is through the exhaust problem. Co2. Box etc are measures as well as the output voltage of 02 sensors.

Come to think of it, they did get a measurement: 1.3 volts consistently and it's not allowed more than 1v.

Does this ring a bell.to what you know of exhaust gas testing?

 

I don't have the practical experience since my software licence key disappeared . One thing to consider is the difference in equipment and data obtained from 2 different things one being the vehicles ECU and the other being the tailpipe probe equipment .

The 1.0 reference may be the Lambda number as 1.0 is the desired target .

The X300 sensors are the different Titanium which take a reference voltage from the ECU and by changing the electrical resistance in relationship to the O2 content returns the reaction signal back to the ECU

 

I used to love the aj16. Now it seems to give nothing but mysterious grief in the last few I've worked on.

Changed sparkplugs for new champions.

All coils are measuring 1.2 ohms warm. Each one identical reading. Is this too high?

I have random misses. No codes. Old plugs looked textbook for good mixture. Nice light brown.

Replaced TPS as was oiled and gunked. Replaced IAC as it had been botched in the past.

All to no avail. Idle is messy, with erratic misses. Under load it pulls well no misses. Maintaining speed it does the erratic missing again causing the vehicle to lurch subtly back and forth.

I've checked a million times top and bottom no vacuum leaks.

I've cleaned the intake and had the throttle body off to do so. Done several spirited drives and gotten it all up to temp.

Sealed.off the brake booster line as it was erratically causing vacuum leaks.

Lambda hangs around 1.228 at lowest. I need 1.04 to pass emissions. All other values like CO CO2 AND NOX are very low. It's just the lambda that's too high. No exhaust leaks.

At idle lambda value is around 1.4 and goes down when holding 2.5k RPM to around 1.28.

When I disconnect the CTS it drops the lambda value to around 1.118 (enrichment helping the lean mixture as high lambda would indicate (?): too much oxygen) though CTS measures within spec as well.

Could the high lambda and subtle misfires be related? Where do I go from here?

I am really frustrated with these engines at the moment as some of you may have followed my several year XJR battle which is still to reach conclusion.

This regular aj16 however I'm posting about is to be sold so it needs to be right. It's very frustrating. Please help. Someone. Anyone (tears streaming down face on keyboard) lol

 

Hi scuby,

This sure sounds like an air leak. At idle, when the throttle plate is closed and engine vacuum is high but very little air is entering the engine, even small amounts of unmetered air can cause rough idle and positive fuel trims as the ECM attempts to correct the problem. Under load, when the throttle plate is open and engine vacuum is low but airflow into the engine is high, small air leaks are inconsequential. Maintaining a steady speed the throttle plate may be more closed than open, so a small air leak once again becomes consequential.

Just off the top of my head, some of the harder-to-find air leaks include the carbon canister valves sticking open (if so equipped), EGR valve not closing completely, exhaust manifold cracks, small cracks in the Y joints of crankcase breather hoses, overtightening of the hose clamp at the joint between the intake elbow and the accordion hose that connects to the throttle body, which can cause the opening of the elbow to collapse on the underside, creating an opening between the elbow and accordion hose, carbon buildup in the IACV port preventing the stepper motor pintle from sealing completely, leaks at any gasket where vacuum exists such as at the intake manifold or exhaust manifold, maybe even a loose oil fill cap or leaking camshaft cover gasket.

What are your SFTFs at idle, under acceleration, and while maintaining a constant speed?

Cheers,

Don

 

I apreceate your input.

I've hunted down vacuum leaks for more than 12 hours on this thing. Seriously. I found none except on the booster hose and this air tight now.

I have changed the IAC and perhaps it needs reprogramming. Here a short video of a cold start. It's actually the second time I started it. The first time it stalled. Once it's up to temp it tends to do the same and stall. Or just not shoot up in RPM, once it start to run it will hit 900rpm and then stall. This is a primary issue to deal with.

If the IAC isn't working correctly that could function as a minor vacuum leak like you said and as a result give me the cruise issues I have as well as high lambda reading around 2 - 3k rpm right?

I'm getting ready to drive this thing into a lake.

youtube vid:

​​​​​​

 

This may be a dumb reply but could it have anything to do with the fact that your gas gauge is on empty and your low fuel light is on?

 

clutching at straws but not dumb

No I just got home last night and need to get gas. I've burned through half a tank yesterday driving around trying to get the o2 sensors hot enough to get the lambda down to pass MOT. was too fed up to stop at the gas station. this cold start behaviour has been going on for weeks. as well as high idle. as well as high lambda. replaced IAC in attempt to fix idle issue. replaced TPS in attempt to resolve poor throttle response (helped some). cleaned out inake and replaced plugs.

Anyone know the Ohm spec for coils?

low gas has nothing to do with it.

 

European model so no EGR. Only 2 o2's.

May have a carbon cannister though and I will investigate that.

I've done extensive vacuum leak investigation. On of the things I did was to use clamps to cut off each vacuum hose one by one... although charcoal will have two a feed and a return if I'm not mistaken, I'll look into it.

At this point I'm leaning towards out of wack IAC. If the ECU thinks it's closed but it's slightly open and all the degrees in between than that could be a culprit.

I'm going to a Jag guy on Thursday. It's like admitting defeat to me as a mechanic but I need to shift this thing. No room in the shop and I'm tired of looking at it. It's poisening my motivation and robbing my time to get on the xjr series 2 conversion.

Anyway going to have him reset the IAC and the TPS.

To answer your quesiton on fuel trims I haven't been able to get my adapter to data log.

All I can say is that LTFT and STFT on both banks are equal in their corrections. see if I can't get a screenshot of those values up. Didn't look like noteworthy to me though.

 

I have had an issue in the past where the oxygen sensors were not flipping, and I found that the ECU was at fault. If you looked at the voltages read by the OBD2 tool, it was just a flat line, no matter what I did.

It took me awhile to find, but I did find someone that actually repaired my ECU. They were out of California.

Please keep this forum posted on your findings. I'm always interested in the final result.

 

I have a hint that you are using a ELM327 device to see live sensor data which is a good thing . That way you can see the numbers to see if your engine regulation is correct . I'm assuming you are looking for the STFT to be as close to zero during all regions of your engine speeds and loads . The lambda values on your O2 sensors is your other number you are gauging your engine regulation correctness . As your engine goes through it's ranges and the devices respond correctly we can look at a few of the . These devices covered are :

coolant temp sensor ,
Inlet air temp .
EGR valve . ( you don't have )
EGR temp sensor . ( you don't have )
IAC valve
and others while I think it through

I will be out running errands for hours and will get back to that .

One thing Dan mentioned was the EVAP system leaks and can be capped off on the vacuum line coming out from under the intake manifold . Can you look under the car on both sides of just Fwd of the rear wheel to see if you have a canister on the left side only or have a canister on both sides as this would identify if you have one type of EVAP system with different components or the other type .

One spot item to look at is the brake booster line coming out of the top of the intake with that termed banjo fitting that can be stuffed and sealed on a testing basic to see if that makes a difference .

I wonder if a internally leaking brake booster is a possible suspect ?

This is a draft of what I want to talk about so it is lacking details or sense of whatever and will refine when I get back later .

AS Vee suggested on the ECU replacement before you where t go in that direction there are many different ECU versions specific to the countries for their pollution regulations and a list can be found here : Also there is a 3.2 / 4.0 liter difference .

https://www.jaguarclassicparts.com/u...control-module

 

it's interesting you should mention this as as Lady P suspected I am using an ELM327 OBD. It IS indeed showing o2 snesor voltage of ZERO. Doesn't move or change a bit.

Lady P: thanks for your draught, I was hoping you would chime in. Thanks to others also. It is always a relief to know that more heads will be scratching than just my own. I will inspect for cannister type, where am I looking exactly? forward of the rear wheels? I can get the car on my lift tomorrow and take pics if that helps.

Also I already dealt with that horrible Ford era plastic clip dealing with brake booster vacuum. It was the primary culprit of an initial very high idle. It used to idle at 3k sometimes. It maxes out now on cold starts like the video around 1500rpm. It is fulled sealed now. To test for internal booster leak I'll cap off that line tomorrow to rule that out.

What is the consensus on IAC replacement and TPS replacement and the subsequent need for reprogramming? I read different things.

look forward to your thoughts on where to look next. Thanks in advance

 

As well as the actual hose from the purge valve (mounted under the air filter) there is also a hose from the AC Rochester valve mounted near the fuel tank. This connection is carried via a steel pipe to the bulkhead and then by hose to the throttle body to supercharger adaptor casting. Have you tried closing off this hose with a hose clamp.

BTW,
"air leaks" via the idle speed control valve if it wasn't shutting are not "leaks" that will affect the fuelling control of the engine, because the air will still have passed through the air meter. They would just result in a high idle speed.

It would be really useful to see a plot of the short term and long term fuel trims. If the engine is actually misfiring, then the signals from the oxygen sensors can be misleading. A misfire means the fuel isn't burned and the oxygen isn't used so remains in the exhaust gas, to be measured by the oxygen sensor.

If there is a large unmetered air leak, then I would expect the short term fuelling corrections to be at +25% trying to add the maximum amount of fuel to get back to lambda=1. If the short term fuelling corrections are not at their limits, then I don't think you have any air leak that is beyond what can be compensated for by the EMS

Any OBD scanner tool should be able to read coolant and air temp sensors to check they are reading sensibly, as well as read the fuel trims.

Have you checked for any signs of corrosion on the engine ECU connectors. This can cause a whole range of starting and driveability problems?

 

Thanks! this is not the XJR. This concerns a 4.0 NA

Engine ecu connectors are clean as a whistle. Have inspected them.car has been stored indoors last few years too.

My OBD reader didn't want to plot real-time but I'll try again tonight and post. O2 is showing 0 volts at idle and when giving gas in P

More later driving kids back from school.

 

just a though;

anyone have a full vacuum hose diagram for this engine? euro spec?

thanks. than i can make sure i haven't overlooked anything. can't get on the lift today. was surprised by wife and kids with a compulsory day off! Will sneak out and see if I have one or two cannisters though...

thanks

 

Ding

 

This port at the rear of the engine is the Evap port I'm assuming?



Pulled it and plugged it on the intake. No difference.

Also jus removed all inlet hoses from MAF sensor to throttle body and inspected for cracks, tears, anything. All in good order.

I have a single EVAP cannisters on the (LHD) driver's side.

What other vacuum systems am I missing. Where does cruise control tell pull vacuum from? There's a line feeding the diaphragm on the throttle but surely it pulls vacuum somewhere? Are there ports on the underside of the manifold? NA 4.0 aj16

Will take it out later for a quick run and get those fuel trim numbers plotted.

 

Let me look at mine for the fitting you point to refresh my mind as mine is the same non supercharged engine . The hose attaches to the bundle of 5 fuel and EVAP lines under the car on the car frame on the second to most aft silid line going back .See page 66 of the Jaguar 801S document

http://www.jagrepair.com/images/Trai...20-%202000.pdf

The cruise control produces it's own varying vacuum pressure to the diaphragm attached to the throttle cable aft of the FPR . The controlling device is the large black box just behind the left headlights . I'll look at mine to verify correctness .

There was some people that found the throttle cable in the wrong point in that fixed point just fwd of your screwdrive r as it is stamped A and M for the transmission installed .

Since you have the single canister EVAP system you have the the called " Rochester valve " and a Delco brand part # X was found by others as a substatution . Hookup lines can be crossed . The rochester valve can stick in the wrong position and commonly fail on many different car manufacturers and are cheap . Located right behind tht left canister off the top of my head . The pic does no seem to be correct . It's for the 2 canister system not like mine and your 1 canister setup .






The EVAP closed valve should be closed during lower engine RPMs and can be tested to hear it click with a small 9 volt battery of a 12 volt source . You won't overpower it as the resistance of the pulling coil like a relay devise will limit the electrical current . Did this test with mine some time back .

The 2 lines just inboard of the TPS under there are engine coolant lines which keep the TB throat area heated as the vacuum of the engine consumption air from icing up during certain atmospheric condition like cold / high humidity days . Old school term " Carburetor Ice " on aircraft

The port for the EVAP system line to the EVAP closed valve is very close by under there and can be crossed with the 2 throttle body coolent lines .

There are the terms EVAP control valve ( below the engine air filter ) and the different canister close valve ( only used on the 2 canister setup ) that confuse things .

Editing / taking a break for lunch and erronds

 

I'll have a look on the lift today at the underside of the manifold ports.

meanwhile I did a run and my best to plot data.

Conclusion:

O2 sensor bank 1 does barely anything.
02 sensor bank 2 only under WOT acceleration

Some screenshots. Maybe those wiser than I can make some sense of them. I'm just learning about stft and Ltft.

O2's on short 0-80km/h run. From 0 to speed and maintaining.

This looks ok: EDIT: just notice the voltage (left) not even getting to 0.1 volts.... Not ok.

02 sensor bank 2



This not so ok:

02 Sensor bank 1



Another run testing bank 2 again yielded no input. Didn't get a screenshot. So it's unreliable. Replace 02 sensors?

Fuel trims:



Boils down to:

STFT Bank 1: 0.00
STFT Bank 2: 0.00

LTFT Bank 1: -1.56%
LTFT Bank 2:-1.56%

What confuses me (what does this refer too?)

Fuel trim bank 1 sensor 1: 24.22%
Fuel trim bank 2 sensor 1: 24.22%

What I find odd is that both readings are identical. That stft is at zero and was during logging.

Is my ELM just not reading the data or are these plausible readings, if so do they mean anything is out.of order?

Can one bench test a O2 sensor with a multimeter?

Lastly and I don't know of this is at all important but the overview the Torque app gives of sensors shows the O2 sensor hearing as "incomplete"