These cars have coil packs, not wires, but the principal is the same. It is hard to detect, the easiest way is to swap in a known good coil and see if there is a misfire. That being said, the ECU's on these cars are very reluctant to set a misfire code.

 

Hi all,

I have been working and the car recently and it now runs correctly ! Great success !

I have changed the injector N°1 that was faulty. While I was at it, I checked the injector wiring loom that was OK.

I purchased a good second hand injector from ebay. But when fitting it, I noticed that it had a red stripe instead of a white one on mine. I checked for that and it revealed that the red one is for a supercharged engine, while the ones with the white stripe are for normally aspirated 4.0 and 3.2 engines....

By the way, just to see if my diagnostic was right, I fitted that injector and now the engine runs great at high range and even at low range. The idling is still not perfect but I suppose it is because of the "bigger" injector on cylinder 1.

So I have ordered an OEM new one (with correct specs) for 60€, which seems good to me. I should receive it between June 11 and June 15th !

 

Yep, and if you check the TSBs, I think Jaguar changed the stripe colors later. Not sure, but that's what I recall.

.

 

Hello Julien, good to hear your car is now working good, the red strip/band on your injector is different (volume discharge) from the white one, get the white strip/band for non aspirated engine, I tried to tell you over a month ago on the issue of injector which most non jaguar workshop usually fail to see the reason for idling and power lost issue (besides the other obvious preventive maintenance,ex: sparkplugs) on your old injector you may want to try reviving it by cleaning and adopting two separate wire for testing, let me know if you need details on how to clean and check your fuel injector (e mail me I'll be glad to share with you) also make sure all the other injectors are working correctly, while your at it clean the fuel railing and the fuel pressure valve.

 

Yep, and there are several injector rebuilding services that are low cost. Rebuilding the injectors probably just ought to be done every so often/mileage like maybe 5-10 years.

I plan to use "Mr Injector" which is well regarded in the GM 3800 crowd. It is $16 per injector.

.

 

Yes that would be great ! I have purchased a brand new one and hope it will work fine this time. By the way, the cleaning procedure would be greatly appreciated !

I think mine is dead, since the resistance between the two conectors is infinite. It seems to have an internal short circuit or something like that

 

check out Don B 's site for instruction of how to clean
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

 

Hi all !!

I have finally received my brand new injector and I have fitted it.

Now, the engine runs great at high range, but there are still some concerns :

First issue: The idle is still not perfect: most of times, the idle is perfect at 700RPM but randomly, it decreases or increases... I have no idea of the origin...

Second issue: a new fault code as appeared ! it is P1178 Macimum positive amfr correction fault. To me it is chinese... Do you have any idea of the signification ?

Third issue: cooling fans are not running ... I have checked the fuse that is OK. There is a 22v power between the fuse slots. But there is no power reaching the fans... I guess the "Fan conrol relay module" might be at fault but I could not find it... Do you know its location and how to test it ?

Thank in advance for the help ! I feel a bit disapointed since I hoped the new injector was the issue...

Best regards
Julien

 

Dear all,

Long time no update, so time for a new one !

I have been cleaning all 6 injectors with a good method. All of them worked great (same pressure, same flow, same spray form). So they are out of cause.

I have been checking again the fuel pressure:
- With contact on, but engine not running : 3 bars, with small increases or decreases (+/- 0,2 bars)
- With engine running, 2.8 bars, with small decrease (0.2 to 0,4 bars) when accelerating
- When I stop the engine, the fuel pressure rapidly decreases to 0.

Given the symptoms and the fault code the OBD sent me (P1178), I hava read that the fuel pressure regulator may be at fault. I have also found the dedicated Jaguar Technical Bulletin concerning Adaptive Fuelling System –Diagnostic Procedure and it seems to incriminate the fuel pressure regulator.

So a new one is in order (second hand but out of a perfectly running car) and I will try it as soon as I receive it.

So more to come in the next days...

Thanks for reading, any coments are welcome !

Best regards
Julien

 

Hi Julien,

You have had quite a journey!

It sounds as though you have looked up a generic definition of the P1178 code. You can find the official Jaguar Diagnostic Trouble Code definitions in the DTC Summaries manual which I am attaching.

P1178 indicates "Adaptive Fuel Metering Trim Too Lean (air flow rate)"

This indicates that the ECM has used its entire range of adaptive fuel enrichment but the fuel mixture is still too lean (as measured by the O2 sensors).

Possible causes are:

Air intake leak (which could also cause your variable idle)
Low fuel pressure at idle
Blocked injector
MAFS signal fault (low voltage)

You have confirmed all your injectors are working so you can rule out a blocked injector.

Regarding possible low fuel pressure, you have a used FPR on order, but given that they gradually lose their ability to hold pressure over time, and given the work involved to replace it, I would highly recommend that you invest in a new one. The original was made by Bosch, and I found one on Amazon for $80.00, but more affordable brands are available in the U.S. on eBay and at Rock Auto for less than $60.00. I would think similar sources exist in the EU.

The FPR works in conjunction with the fuel check valve to maintain pressure in the rail. Like the FPRs, the check valves fail over time. Unfortunately, the check valve is part of the fuel pump assembly in the fuel tank, so it is difficult to replace (even if you could find a good replacement canister assembly). If installing the new FPR doesn't completely solve your fuel pressure issue, consider adding a check valve in your fuel line. Below is a link to photos showing how I did it using an inexpensive valve from McMaster-Carr. The easiest location for the valve is in the inlet side rubber fuel line in the engine compartment. I started with my valve there, then moved it to under the fuel tank while I had the rear suspension out:

Welcome to Jag-lovers - Members Photo Viewing Page

Regarding a possible air leak, carefully examine all of your air intake plumbing for cracks, loose joints, or overtightened clamps that have caused a plastic pipe to deform and open up a leak. Check your crankcase breather hoses. Check that your throttle body mounting screws and intake manifold screws/nuts are properly torqued.

Regarding the MAFS, it would be a good idea to flush it with special zero-residue MAFS cleaner spray and also clean its electrical connector and harness connector, either with the MAFS spray or with zero-residue electronic contact cleaner spray (MAFS spray and contact cleaner spray may be the same product just labelled differently - the important thing is that they leave no residue of oil, silicone, etc. that could alter the resistance of the connection).


The fan control relay module is mounted in the front left corner of the engine bay (as viewed from the driver's seat) and it looks like a long or tall relay mounted sideways. The 1996 XJ Electrical Guide has a diagram showing its location and appearance on page 21 of the pdf, and you can download it here:

http://www.jagrepair.com/images/Auto.../jagxj1996.pdf

There is also a radiator thermostatic switch mounted on the lower left hand side of the radiator that tells the fan control relay module when to operate the fans. You can view the schematic on page 79 of the 1996 XJ Electrical Guide pdf.

Please keep us informed.

Cheers,

Don

 

Dear Don,

Thanks a lot for the answer and the explainations.

As you said, the fuel injectors are now out of cause.

Considering the FPR, I didn't know they were prone to fail. That is why I ordered a second hand one. I will order a ew one soon, with 3 bars pressure regulation. Just to be sure.

Adding a fuel check valve seems to be a good option. I will try this, since the issue with my car seems to be fuel related.

Considering air leaks, I don't think this is the cause. When I got the car, I tryed to diagnosed the fault by dismently and carrefully cleaning the throttle body and air pipes. I did not notice any air leaks. But I will check again to be sure.

But that let me think to one think. When I cleaned the injectors, they were hard to remove from the intake manifold. But now they are very easy to remove. Do you always change the gaskets when removing the injectors ? They look in a good shape.

I have alreadt cleaned the MAFS with appropriate products. But it may be out of order ! Do you know a simple way to test it ?

Finally, the positive bit, I have change the fans. One of them was out of order and so, none of them was running. Strange design.

Thanks a lot for the help

Julien

 

Hi all,

Just to keep you updated and because your advices are percious, I have changed the fuel pressure regulator and .... Nothing !!!

The symptoms are exactly the same !

So, I have tried testing the MAFS according to tutorials I saw on youtube. The results might be a bit strange:
- When iddling (700 RPM), tension is approximately 1 volt
- When accelerating to 4000 RPM, tension seems to occilate between 2 and 3 volts.

On the tutorial, the guy had a maximum tension of 4 volts. Are all the MAFS the same tensions ?

One strange thing:
- yesterday when I removed the connectors from the MAFS, the engine stalled
- Today, I did the same and nothing happened. The engine kept on renning the same way

I have also been looking for air leaks in the intake manifold and I found nothing. No split tube or so. And with carburator cleaner spread around, the iddling did not change. So I think there is no air leak.


I have another question. What about the Intake Air Temperature Sensor that is located near the MAFS ? May it be related to my issues ?

What do you guys think ?

Next:
- clean MAFS
- add a fuel check valve
- Clean and test Intake Air Temperature Sensor ?

Please let me know.

Best regards

Julien

 

Hi everyone,

To days was an other bad day for the jag' ...

I have cleaned and tested the MAFS: the output voltage is OK and the reading of the signal by the ECM is OK too/ I have looed ate it while driving with the OBD tool.

I also added a fuel check valve and it did not change anything...

I feel really really disapointed and now, I don't know what to look for...

To summerize:
Fuel pressure regulator: OK
MAFS: OK
Fuel check valve: OK
Air leak: not found any

Do you have any idea of where to look for ?

Your help will be precious

Julien

 

Julien

If you have OBD Live Data there are a few things you can check that might point you in some direction.

Firstly, check the fuel system status i.e. Open Loop or Closed Loop. You should be in Closed Loop fairly soon after start up. If not then there is a fault somewhere.

Secondly, check the LTFT and STFT. I expect these to be high given your 1178 code but Live Data should confirm this. Max STFT is somewhere around 24% I think. These are Fuel Trim (Long Term and Short Term) measured in Percent and are a measure of how much the ECU is increasing (+) or decreasing (-) the fueling. Your code suggests that the ECU has adjusted as far as it can and still sees lean fueling.

This could be caused by a bad O2 sensor. The O2 sensor voltage should fluctuate high (rich) to low (lean). The ECU normally responds to these fluctuations by constantly changing the fueling. I'm sure you can find volumes of stuff on the net for more in depth explanation.

If O2 sensor was just returning low voltage then ECU would see that as lean mixture and keep trying to go rich until it gets to limit.

You should be able to see the O2 sensor voltages on your OBD tool. If you can graph it it should have a fairly consistent fluctuation low to high about every second.

 

Hi Julien It is interesting to follow your diagnostic process. Have you checked the possibility that the O2S connectors could be swapped ie 123 sensor plugged into 456 socket?

 

Hi Everyone,

Thanks for the suggestions.

I will look at this this week end.

The O2 sensors have be changed by the garage so they are brand new, but I have no idea if they did it properly and they might have swapped connectors.

I have also seen on youtube that you can diagnose air leaks with the LTFT and STFT and a cigar .... I will looks at it too.

Thanks for the help !

Julien

 

Hi all,

Today I have been checking O2 sensors and all seems OK. I explain.

The 2 sensors are brand new.
I have checked the harness: On the upper sensor, the blue wire is to ground. The red wire has an output of 4.7 volts. The other blue wire has an output of 12 volts, so is the white wire.
For the second 02 sensors, the value are the same.

So I believe everything is OK on the O2 sensors side.

Are my measures correct ?

I also tried to swap both connectors and it was even worse.

On the MAFS side:
when the car is running and if I disconect it, the engine is about to stall but then does again, with no change (or even an improvement but it might be a placebo effect)
I diagnosed it with a multimeter and the OBD tool. The values seems to be in the right range (for example 2.26 volts for an output of 0,026, and 2,60 volts for an output of 0,050)

Are my measures correct ? Maybe I should try to go for a 15 mn ride withe the MAFS diconected. But I doubt.

I also checked for air leaks with a "smoke machine" and did not find anything. I will deaper investigate with a more advanced one but I believe there is no air leak.

I checked for LTFT and STFT with OBD diagnostic tool. Here are the data I found:
STFT = 24.2%
LTFT = 36.7%
Fuel system = CL (closed loop)
Load PCT = 15.3%
SPARKADV = 14°


Do you have any idea of what I should investigate ? I have run out of ideas....

Thanks in advance for the help

Julien

 

As expected your FT figures are way out. But you should have 2 sets of figures for Bank 1 and Bank 2. Are they the same/similar? This might help isolate whether there is a general engine problem (fuel or air supply) or just one or two cylinders (injectors?).

If your O2 sensor output is constant 4.7v then that is not right. As per my previous post, the voltage needs to swing high/low about every second (I think from 0.1 to 4.7).

Although you have new sensors are you sure they are the correct type? Is it possible the garage fitted generic sensors and messed up the cabling (they have to be patched to the original plug) or perhaps just the wrong type?

You really need to monitor the O2 voltage on your OBD tool rather than a multi meter. That way you are seeing what the ECU is seeing.

 

[QUOTE:

You really need to monitor the O2 voltage on your OBD tool rather than a multi meter. That way you are seeing what the ECU is seeing.[/QUOTE]

Brendan, are you actually able to monitor 02 voltage on your '95? What device are you using to do so?

 

Dear all !

Sorry, I forgot to say that there are two series of data for the STFT and LTFT, but both are the same. So if I understand your explainations, this is a general problem ?

My explaination was not clear. This is the input from the electrical harness. That i what surprised me since there are 3 electrical inputs (2 of 12 volt and 1 of 4.7 volts) and one ground.
How can the O2 sensor "comunicate" with the ECM ?

I will check on the O2 sensor side today. They are genuine parts and not adaptable. But lets check to get sure.

How do you monitor O2 sensors with the OBD ? I tried to but the OBD doesn't seem modern enought.

Thanks a lot for the help !

Julien