After hearing reports of fuel trim normality and excellent pressure, I drive out of the dealership (1/3 of a tank poorer, and 100 miles more on the odometer). 2 days later, my CEL and RP lights are on again. It's been to the dealer 4 times, 1st time they assumed I needed an MAF, and I got one... didn't work (I'm demanding a refund this time, no more screwing around) and there is clearly something wrong. i have had fuel filter, and oil/filter changed since btw.

Unusually, every single time I post these problems on the forum (PO172, 175) I get 0 responses, basically. So, I'm trying again.

P.S. According to an exhaust test, the car is putting out lean exhaust (and yet throws out rich codes)

 

The JTIS OBD code chart provides the following for your posted codes. Since they seem to come and go I would begin at the bottom of the list looking at electrical connections.

What kind of fuel mileage are you getting?

 

Putting an exhaust probe in the pipe and even passing an emission test does not always tell you how well the mixture is being controlled. The engine mamagement system has parameters of correction to the base fuel strategy. The air/fuel ratio may be correct, but, the system is having to correct beyond the normal parameters and this throws the code.

Your exhaust may look clean but if you were to look at the data with a capable scan tool, you may see that the correction is beyond 20% or so. Without having all of the information, I can't say that your dealership is doing anything wrong. However, with only the information you provided, it seems suspect.

I work on cars for a living and sometimes the information gets diluted or distorted every time it moves from the customer to service advisor to mechanic. Or in the opposite direction. If the dealer you're working with is asking for more money to fix the same problem, they have some explaining to do. Be persitent.

There are many possible causes to your problem. More data like mileage on the engine, fuel pressure, maintenance history, other test results would be helpful. I remember seeing a few Jags with plugged part load breathers causing mixture codes. Poor maintenance resulted in the pcv system plugging up. Many other possibilities.

A tech needs to look at all the info and come up with a correction. Otherwise, your just going to end up having more parts thrown at it hoping for a hit.

Good luck,
Joe

 

Thanks for the replies. I can say that the car had a poor maintenance record prior to my ownership. I bought it at 41,000 and is now at 52,000.The fuel pressure is reported as normal by the dealer. I had asked about the possibility of dirty injectors, they said that was not it. They haven't charged me for any of the latter services, but it costs me time, gas, and my car (they don't give me a loaner, I'm a minor).

The mpg seems to be suffering, probably about 3 or 4 miles to the gallon. It's hard to make a direct comparison under different driving conditions though. I have personally changed the oil 4 times, changed the fuel filter (took absolute ages, it got stripped and cross threaded by quick lube people), beyond that it has only had cosmetic repairs I think. Headliner, wheels, etc. I wanted to do a transmission service, but I have a feeling the trans will die if I do. I know it must be low on fluid, and getting the gunk out of there might seize it up.

Another symptom I can report is an erratic start/idle. It turns over a totally random number of times on cold starts, between 3 turns and 6 turns. When I lived in Florida, it turned over 3 times and fired up every time. Also, at idle, after a cold start, it will sink in RPMs for no reason.and then go back up. The idle has also gotten a bit rougher (but not really rough, like a passenger might not notice).

Thanks again,

Ian

 

The P0172 & P0175 leads me towards a rich fuel. I would be checking the air filter and the passage to the throttle body for blockage. The MAFS could be part of the problem and I would see if you can swap it out with another before spending $200 +/- a few on one. Also check the plug clean and connections tight. I would then go the TB and check all the connections and see that they are tight and clean. Did you check the fuel pressure? If so what was the reading at the Schrader valve and did it fluctuate at all when testing?

 

Ian,

I read that the light came on 2 days after you left the dealer. I think you're assuming that the same codes are stored. Are you checking the codes yourself? It is possible that you have a different code now. You need to verify.

Sometimes a failure of one sensor or system can prevent other self tests from running. If the dealer is right and the fuel trim is now normal, other OBDII monitors(self-tests) that could not run before may be running now and showing a fault in another area. The "catalyst monitor" is an example of a monitor that won't run if the fuel trims are not normal.

I suggest you dive in to learning slowly but carefully about diagnosing and working on your car or take it to someone you can trust. If you do it yourself, you will save money if not this time, in the long run. If you enjoy doing it, it's not work. It's a hobby. If you hate it, pay someone to do it.

If you lose faith in your mechanic. you need to find a new one. If you still trust them, give them another shot. Perhaps one of the members of this forum can lead you to a shop in your area if you choose to pay someone to fix it.

If you want more feedback on your current issue, can you confirm that current code or codes are the same as before?

Joe

 

Is your battery in good condition? Everytime I disconnect my battery on my car, the rpms drop (and almost seems like it will stall, but it never does) when I start it and then it increases to normal. Maybe your issues are due to a low voltage from the battery and/or alternator?

 

I agree with rechecking the codes. I would say the best way to figure this out is with a trending scanner. You need to figure out if you really have rich burn or an incorrect rich indication, given the reference to the exhaust test. A dirty or bad MAF can cause the fuel control system to wind up the LTFT, then saturate the other direction when the throttle changes. Again, you can figure this stuff out by watching trend charts of the lambda sensors and fuel trims. A

And from the wild *** guess department- You don't suppose someone put new lambdas meant for an AJ26 engine in your AJ27, which requires wide band sensors?

 

Quick thing to do that may or may not affect your issue: unplug and clean the TPS connection using Radio Shack contact cleaner and lubricant, both sides of the connection... corroded TPS connector pins can cause the varying idle speed that you mention and was one of the possible causes defined by the OBD code definition.

It certainly fixed mine.

 

You know, it has been PO172, PO175 all 3 times, and the symptoms are the same. So, yes, I guess I am operating under an assumption. I have to get it checked when an auto parts house is open. I had not considered the throttle positioning sensor, I will have a look tomorrow.

Burmaz: I called the battery manufacturer, it is under 2 years old, and I believe it is in okay shape.

Gus: My suspicion was that the MAF was an unnecessary repair, and the service manager agreed to compensate me for that. I did replace the air filter about 5k ago, so that isn't it, I don't think. They never mentioned the Schrader valve.

sparkenzap: The dealer put a MAFS on there, which I believe is for a slightly different engine. But they assured me it was correct. I believe it is from a slightly newer installment of the AJ-V8. The lambda sensors were never replaced.

The tests I did myself, such as the exhaust gas test, seem to be accurate. Fuel pressure tests were done by Jaguar of Tulsa.

I will have the codes confirmed, but I'm 95% sure it's the same exact thing.

Thank you,

Ian

 

Well, then, I stand by my recommendation that you get software (AutoEngionuity, Autologic, Ids, Some ELM software) that can chart trends for the OBD parameters and monitor them relative to your exhaust analyzer.

Did you understand my statement about a transitional lean condition winding up the LTFT (or vise versus)?

Did the car run nomally when you first got it, then begain this behavior ?

Until then, checking the connectors seems like a good start.

 

Ian,

Sounds like you're determined to tackle this. Good for you!

The process is summed up "Concern. Cause, Correction."

Verify the concern. In your case the MIL (malfunction indicator lamp(s)), and your driveability concerns.

Determine the cause. Put all of the facts in front of you and the rest of us. Codes, test results, scan tool data, repair and maintenance history,observations and whatever else may be pertinent. You or we can evaluate the facts and confirm or hypothesize the cause. With the help of this forum, this will thankfully be easier than on your own. You've already recieved some great suggestions.

Perform the correction. Change the part or repair the system. Verify the repair.

We wish you success.

Joe

 

a 2 yr old battery says nothing, test it for assurance. I have brand new batteries fail. its not as big an issue on your car as later electronic laden
cars.
Pull the air filter and make sure there is not a squirrel or mouse/rat nest in there. Its a cosy spot and I say that cause why? Ive seen it many times before.
forget exhuast test, there is a reason to have catalytic converters, to clean the exhuast. you need to monitor short/long term fuel trims.
Now heres another issue. IF long term fuel trims were not cleared, the car can continue to try to fix a problem no longer there are continue to have faults that will SELF correct. <<<EDIT, THAT SHOULD READ NOT SELF CORRECT BEFORE RESETING A CEL
I would drive the car monitoring fuel trims, and fuel pressures off the rail(shraeder valve)
Dont assume(they should either) the correct spray patterns of the fuel injectors. THE only way to properly diag this is to pull the injectors and have them cleaned and flow tested. That way the company doing the test and cleaning can tell you what the spray patterns look like on the BEFORE flow run. I have found many issue by doing this. I use this company locally and he charges $18ea and has a 1 day turn around.
Fuel Injector Cleaning Service : Injector Cleaning Service : Injector Cleaning : Clogged injectors : Injector Flow Testing : InjectorRX.com

 

Brutal is correct in his assesments.There are only a few things that can cause this concern: Excessive fuel pressure, bad MAF, Blocked air filter or housing, or incorrect inputs from sensors like TP, Intake Air Temp, Etc, leaking or stuck injectors, or bad PCM. I would use a scanner to check the inputs that the PCM is seeing, especially MAF, O2 sensors and IAT. Let us know what the fuel pressure is also.
Good luck!

 

@ sparkenzap; I currently am "over-budget" on repairs, so automotive softwares are out of reach atm. The car ran perfectly when I first got it (in fact, given its history it was incredible)

"Did you understand my statement about a transitional lean condition winding up the LTFT (or vise versa)"

I actually was unclear about what you meant. With this technical stuff, I'm probably only about 1% as knowledgeable as many of you guys lol.

@brutal; I just went out to the Jag and checked the air filter, no animals (lol) and the filter is pretty clean. The MAF is new, and it was originally assumed to be the problem (hence, they replaced it, evenn though it is now obvious it was not the problem).

@limelight, brutal; I am not personally able to test fuel trim, although the dealer has put about 60 miles on the car with equipment on, and are reporting normal fuel trim.

@jchavez76, thanks for all the general advice

@Quad Maniac; Where are the TPS mounting pins? I know where the throttle body is, but idk about the pins.

I'm going to Autozone now to have the codes read, so I'll update in a bit

UPDATE::: The codes I pulled just now are the same, Po172 PO175. Same as the prev. 4 times, so now I have a confirmation of that

Thanks very much,

Ian

 

Ian:
You mention Arizona- And your location says central Fla. I suppose you have moved. Just wondering if someone with trending software near where the car is will put the chart on it for you. If you were in Atlanta, I would be happy to have at it. My IDS is currently in Orlando, so you could have a go at it with my son if you were there. The following suggstions should be considered the "poor man's approach to sorting your problem.

The throttle body has a connector on either side ear the top. Disconnect both, look for corrosion and clean with contact cleaner even if no corrosion is apparent. and reseat the connectors, making sure they are fully seated.

In lieu of trying another battery, note the off condition battery voltage, then the crank and note the idle voltage after it is running a few minutes. If the running voltage is more than .9 or 1.0 volts above the off charge voltage, there is a good chance you have noise on the DC system.

So, the dealer has told you several things it is not. What are they saying could be the possible causes? Did they recommend a new throttle body yet?

Although not the best injector leak test method, you can observe the leakdown rate at the test port aftetr shutting off the car. It should hold pressure for quite a while- Mine holds for hours or days. Do you have a fuel pressure test guage? (About $40.00 at Harbor Freight).

Does your engine temperature guage seem to operate normally? It would sure be good to read the parameters given in the pinpoint test- back to borrowing scanning software.

Is there a Tuscon Jag club. Maybe you can find help there, Most clubs will have at least one person with engine control tools and experience.

And, keep your chin up. These cars ain't magic, although they appear so sometimes. Make friends with some scanner software and you will figure it out.

 

Even though I'm sure the dealer has already tried this, but have you tried resetting the codes, and/or disconnecting the battery to reset the fuel trims?

My car is currently running lean with an intermittant RP light. My lean condition used to be much worse with the ECU cutting the throttle to the point I could hardly drive on the freeway. The culprit (Well partial culprit)? A missing screw on the valve cover! I still don't understand how that caused the problem.

Have you tried an independent mechanic?

I wonder if your slow starting problem is caused by a leaking injector that is slightly flooding the engine while parked causing slow starts. Does the exhaust smell like fuel? Have you tried flooring the gas all the way to the floor when you start it? This tells the ECU to stop the fuel pump, and lets the engine start on its own without additional fuel (such as a flooded engine condition). If your car starts faster with the throttle floored, maybe this points to a leaking injector being a problem?

Others know more than I do though.

 

We've confirmed this car has codes indicating it's running rich. Does anyone know if this vehicle uses a fuel rail mounted fuel pressure regulator? Or is this the type that uses pulse width modulated fuel pump control?

If it has the diaphragm type, is the diaphragm connected to intake vacuum? If this diaphragm is rurtured, It could leak fuel through the vacuum hose and cause a rich condition. This would also cause extended cranking times before start-up. Pulling the vacuum line to check for fuel dribble is an easy check.

If it's the PWM control type, the fuel pressure sensor could be reading inaccurate always or intermittently. This could cause the fuel pressure to be too high and run rich. Kinda tough to check without a scan tool or pressure guage.

Ian- Even a relatively inexpensive scan tool that could read fuel trims would help. And I agree with sparkenzap on the fuel presure guage. It would be great to be able to rule that out.

Hang in there.
Joe

 

The '02 has a fuel rail pressure regulator but I do not think that it has a vacuum connection. Corrections appreciated. It does not have a PWM pressure regulation system.

 

You know, I do want to take it to my independent (whom I found after I had already dropped $700 at the dealership) but I can't afford another $90 Diag. + the repair. Maybe if they will give me a full refund at the Jaguar Dealer, I can take the car to my independent.

In fact, I have floored the car from a start (I did not mean to.) But I remember it turning over a normal number, like 3 times. I will ask about a leaking injector when I take it in tomorrow. I know for a fact, that doing that on a start (esp cold, like I did) is hideously bad for your connecting rod bearings, and just about everything. But the exhaust does smell like gas. Which is why this sounds suspiciously right.

By the way, yes, the dealer has reset the codes every time I had it in their shop.

Thanks Jon.

@sparkenzap: Hahaha you say Arizona... I know I'm in a flyover state but its is Oklahoma not AZ lol. I am in the Jaguar Club, but the folks I know mosty specialize in the V12 and XK (I6). (and I don't know them that well yet either)

No worries though. On to other car stuff

I really appreciate the offer to use your IDS, but sadly I had booked a flight a month in advance. Another thing is, I'd hate to put 1300mi on the car in this state (fouling up spark plugs, etc) and get 20-23mpg average using my new-found "granny" driving style (trying to save some of Iraq's oil in reserve).

We barely talked about the throttle body at the dealer. I actually, for the first time, am really going to talk technically with them about it... and spend a few hours at the dealership, rather than just leaving my car with them again. Unlike my independent, they seem to want to keep me pretty far from the technical stuff (probably assumptions based on my age). But they owe me, now that I've spent all this time (and money) taking the car there, and I can't just take it somewhere else atm.

The temp gauge does seem to be working normally. It seems like the car actually starts normally if the engine is at temperature (even at the bottom of the gauge). I suppose this hints at a battery problem with the starts (like Burmaz has mentioned), but that doesn't seem to link up to the codes or gas smell at all. I will ask them about the temperature gauge at the dealer.

If the dealer just pays me off, then I will ask to use someone's garage/ testing stuff. Then, if I fail, I shall go to my independent.

@JChavez76 and test point, I will ask about a possible vacuum leak if the fuel pressure regulator is, indeed, connected to a vacuum line.

If I left something unadressed, please let me know (I'm trying to read properly, I may have missed something)

Thanks guys, I really do appreciate it

Ian