Ian:
I admire your attitude about the codes being caused by a reason. Cause and effect are not recognized by many folks. However, Jaguars are different,in my experience. Some things just fall into "S**t Happens".

In fact, the Italian tuneup might have cleared a plug, valve seat or burned something from a lambda sensor. Sometimes it just causes whatever is the problem to destroy itself so you can find it!

Anyway, at this point, your mileage numbers look right and you have no codes, so for now, "Don't worry, be happy".

 

Factory ait intake, filter is a Purolator. What is the symptom( the symptoms) that line up with a throttle body fault? The car was throwing PO172-175... rich codes. I know it must be a fuel pressure issue (which seems to be intermittent), but I don't know where the fault is.

 

I assume you have looked at the "Possible Causes"?

Blocked air filter
Fuel system return blockage
Leaking fuel injector(s)
Fuel pressure regulator failure (high fuel
pressure)
ECM receiving incorrect signal from one
or more of the following components:
ECTS, MAFS, IATS, TPS

The TPS is , of course, located in the throttle body, and the connectors are known for intermittent problems, among other TB issues.

 

I have indeed looked at all the possible causes. My main suspicion, the leaking injector, was shot down by the master tech at Jag. They never suggested the TPS, but I suppose it is possible.

For the record, I changed the fuel filter 1-2k miles ago, for the first time. It had never been changed for 50k, and there was mud in it. I suspected fuel contamination until the CEL came back a few hundred mi later anyway. It hasn't come back in a while, but despite there are some intermittent drops in performance (lower mpg, weird starts, feels down on power) . (Maybe its the throttle body, or maybe its in my head??) The RP light has yet to come back in 300mi. the MAFS is new btw.

@ sparkenzap... lol I keep these boxes open a long time, so I keep missing posts... but thanks guys for the help! If I really think it's gonna be ok, I guess I should ask to have my money refunded from t he dealer.

 

I would not bet on the injector, since you say you had rich codes for both banks. I would rather put my money on the regulator, although they are seldom reported to fail, but could give the code.AND, it could cause the fuel mileage computer to give high readings for mileage.

 

That makes sense (both banks). However, if the regulator were failing now, it may have had to fail at 41000 miles, because I've gotten the same fuel economy since I bought the car, never have I experienced any weirdness about the car until this started throwing the CEL 1k ago. on my first drive in it, I averaged 24.6mpg, and 25.1 was my highest long-term average. And that was with the car down 1qt on oil, on all different tyre pressures, and a few other things I fixed when I got home. that was avg. of a 240 mile journey.

I never did hear of an AJ-V8 fuel pressure regulator failing, but I guess it's a likely candidate given my current symptoms

 

I am sorry I am not sure what we are trying to do on this thread, I lost track. I understood that you had a P0172 & P0175 that is equal to “A” & “B” bank rich combustion and the possible causes are Blocked air filter Fuel system return blockage Leaking fuel injector(s) Fuel pressure regulator failure (high fuel pressure)ECM receiving incorrect signal from one or more of the following components: ECTS, MAFS, IATS and TPS. You say the Air filter is OK, the MAFS was replaced, Fuel filter has been replaced, An exhaust test revealed a lean condition (I do not know how accurate that is – I must assume it is accurate).

You say the MAFS that was installed is like the original but was slightly different.
The fuel pressure was ok, but what was it?
What are the fuel trim readings?

The way I see it is that you may have
1. Air blockage
2. High fuel pressure regulation
3. Poor fuel related plug connection (TB)
4. Poor fuel presentation to all cylinders
5. Improper plugs or improper install
6. Throttle Body
7. Or the O2 are connected backwards
As for a true MPG test I do not bank on anything less than 100miles, on the same road under the same conditions.

Get yourself an ELM Scan tool connect it to your computer and take the car for a run. Record your 02 readings, fuel readings and anything you can record and let us see the results. It is obvious that the people you are dealing with at the shop have no idea what is going on and we are trying but we do not have any readings to go by.

 

Lol thanks for reading in Gus. Sorry if the thread has lost a bit of track.

The fuel trim and pressure readings were done by the dealer. They did not give me specifics other than that it was "good" within their whole time running tests. I could call and ask if they kept the readings as records, but I doubt it. I personally do not have any fuel pressure monitors. The exhaust test was accurate, I used an analyser a friend from the Jag club had and I assume it was reading correctly.

I've just looked up ELM scan tools... I definitely will want to buy one ASAP. Any recommendations on the brand? I'll be getting one soon, looks like I could definitely use it.

I want to get more data for you guys, sorry... lol I'm the same as a guy with tech support on the phone, and only a vague idea of what he's talking about.

 

Jaguar should have all the information documented, in fact it should be on your bill/statement. As for the ELM Scan 5 go to Amazon and pay less and get it in a few days. You could use Ebay if you wish. As for us we all want to help but going at it with no real information is a shotgun approach and that approach will run you in circles. Get the facts and stay on track.

When were the plugs replaced?

 

I just checked the Jaguar of Tulsa receipts, no actual fuel pressure data. I will call and ask during the dealer's hours tomorrow.

Spark plugs were never replaced.

 

They could be part of your problem. You should pull one and look, it could be the wrong temperature rating, gap or just old and need replacement.

 

Hi, have a look at this post about fuel trims. You have a car in which the o2 sensors are reporting a lean mix, but the tailpipe air/fuel ratio is rich. This would indicate a misfire, producing unburnt fuel and air, inducing the O2 sensors to think the engine is running lean, and adding more fuel. Bad performance and bad fuel economy. I would change plugs and check on-plug coils, and check all the points he makes in the article. https://www.jaguarforums.com/forum/g...ed-quiz-49317/
good luck
let us know the results
Pete

 

I don't have a reported lean condition. I have a reported rich condition, with an exhaust test showing slightly lean gases.
PO172 PO175

Will read the link tomorrow, bedtime now. (lol)

I just got the CEL and RP lights friday, so back to the dealership on monday.

Cheers,

Ian

 

I got the car back today.

They didn't refund me for the MAF part (which is what I wanted in return),
but didn't charge me for the "actual" fix, which is this hose. So far, so good. Low RPM torque feels better.

Apparently, its plastic collar had seperated a bit, and under a torque load it would leak unmetered air, and thus throw a PO172 PO175.

This time, for the first of 5 times, I ONLY got PO175.

I ended up not paying diagnostic time at least (or the $200 for this hose+install) . Lets see if it works.

What do we think?

 

OK, we'll see, but I'm not convinced.....

You are exactly right, that would allow unmetered air in, but that would also tend to cause a P0171 and P0174. P0175 is the other direction.

Good luck!

 

I have a theoretical question:

In your experience, if the LTFT adjusts for lean conditions at idle ( and richens the mixture), what is the chance of setting a rich code when run up to speed? (when the percentage of excess air is proportionally less) I know that if that happens and the LTFT windup is more than the STFT can correct for, the engine will run rich for a few minutes until the LTFT can unwind. But I have never seen a code generated in that condition.

Hoping for input from those with more actual experience than mine.

 

I'll say one thing, this was not what I expected, and I'm not going to be surprised if I see a CEL in the next few weeks... or days.

I'm just relaying what the service manager told me.

@Sparkenzap... I'm not sure if I can answer your question all that well, but I can report that the RP light only ever came on during city driving, under 40mph.

 

Ross,

Check out this post and screens from a while back, it may answer your questions. Also, if you haven't seen it, go back up the thread and see the Fuel trim primer I posted last year.

https://www.jaguarforums.com/forum/s...e2/#post352490

Then we'll see what other questions you have.

Cheers,

 

OK, Ross,

Your question shamed me into dusting off the paper on Fuel Trims I had promised one of the Mods last year. It elaborates on the example I referred you to in the last post.

https://www.jaguarforums.com/forum/g...17/#post463672

Hope it helps!