Alright, I should have posted here a couple of weeks ago, but here goes.

A few months ago, my '04 X-Type started acting a bit strange. While under moderate acceleration after a stop, the car abruptly slowed down and I noticed that the Check Engine Light was on. (I eventually determined that the CEL was actually coming on while the car was stopped or at very low speed, prior to the acceleration anomaly. I believe the sudden loss of acceleration is due to the engine computer limiting the engine speed to 3000 RPM as a safety measure.) Letting off the gas and then easing back into it seemed to resolve the acceleration issue. I had the codes scanned and got either P0171 or P0174 (lean mixture) along with P1111 (self-diagnostic, from what I can tell). Within a couple of days, the CEL would shut off and nothing more would happen for a couple of weeks. This happened a few times (with the period gradually decreasing from several weeks to a few days) before I had a chance to take it to my mechanic. My mechanic has done the following:

1. Checked for and repaired a potential air intake leak
2. Cleaned out the MAF sensor
3. Replaced the MAF sensor
4. Replaced an O2 sensor
5. Smoke tested the engine and repaired several vacuum leaks
6. Replaced the throttle body, which was leaking

During the course of this work, the frequency of the problem increased from once every few days until it became a constant problem. Alas, I just got the car back this evening, and within 5 miles of driving, the problem reappeared. After 2+ weeks of living mostly without my car and spending over $1,000 chasing this issue, I am at my wits' end as to what to do. Any suggestions from the Jaguar gurus on this forum as to what should be checked next would be very welcome.

Thanks,
CarLuva

 

CarLuva, take a look at the plug going to the throttlebody on the driver's side of the car. Look at the wiring closely and see if you see missing insulation near the plug. In the past, some people have experienced a problem like yours and they had damaged wiring there which was shorting out the throttlebody positioner, causing the computer to limit the engine RPM and cause all sorts of issues.

After that, not sure what could be causing what you are seeing. I would say to get the codes read again and see if you are getting any new codes. That may help us narrow down where the problem lies.

 

Thanks Thermo! I'll check on the wiring and let you know if that takes care of it.

 

Buy yourself an OBD reader that gives fuel trims (I use Android phone + Torque app + a cheapo Bluetooth OBD dongle from EBay)
Then you can read codes and trims yourself and post them here.
Without this you're shooting in the dark.

 

Alright, I took a look at the wires going into the throttle body and could not see any visible issues. Is there anything I can do with a multimeter to check those for short/open circuits?

As for codes, I reread them and got just a P0171 (bank 1 lean).

By the way, I need to make a correction about P1111; P1111 is commonly said to be a self-diagnostic code, but Jaguar's description of this code is "Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage". It indicates an over-voltage condition; the first time I took my car in, my mechanic found that the alternator was putting out significantly higher than normal voltage levels due to excessive corrosion on the positive battery terminal. Since he cleaned the positive battery terminal, the P1111 code has not returned.

 

you still have a vacuum leak some where ...get a sniffer

 

The smoke test should have found all leaks with the cars vacuum system. Your list of things done by your mechanic is suited for a vacuum leak & MAFS but is that the same codes every time that is giving you the restricted performance? You could have another issue like a failing knock sensor. Do me a favor and plug in your (I hope you have one) OBD II reader and clear your faults leave it plugged in and drive the car until it goes into restricted performance then tell us what codes your reader captured.

 

Gus, the codes were cleared after the throttle body was replaced (the last work performed by the mechanic). The CEL came back on within 5 miles after I picked up the car; I read the codes within 5 miles after the CEL came on, and the only code present was P0171. P0171 and P0174 (banks 1/2 lean) are the only codes that have ever been observed (aside from the P1111 that, as I mentioned, was fixed by cleaning up the corrosion on the battery cables. Are you suggesting that there may be additional codes that are not getting stored or are getting masked by the P0171?

FYI, I don't currently have an OBD scanner. I've considered purchasing one several times, but running around the corner to AutoZone or Advance Auto Parts to have the codes read has always been convenient enough that I've never gotten around to it. If I do purchase one, it seems that I'll want to get one that is able to scan real-time data, as suggested by steveinfrance. If anybody has any suggestions, I'd welcome them. I'm currently considering , which appears to provide all of the functionality I would need (reads and clears DTCs, reads real-time sensor data). I don't have an Android phone, but I do have a Bluetooth-enabled laptop.

I'm going to be out of town on business travel for the next week, so I plan to drop off the car with my mechanic tomorrow afternoon to let him take one more look at it while I am out of town.

 

If you are confident that you have no leak then we can move on to fuel. Fuel presentation is as important and any restrictions could cause the same codes. Have you changed your fuel filter and have you used a fuel injector cleaner? If not replace the filter I replaced mine the other day and it was overdue. Along with that add a bottle of BG44K to your fuel and drive the car and see what takes place. If you have the ability to check the fuel pressure I would do that as well.

As for the OBD II reader I have a few that I use but the one I paid $30.00 for is the one I use all the time. I plug it in I get the codes if I need additional info I go for one of the others. It is worth every penny I paid for it.

 

Thanks, Gus. The fuel filter was replaced less than 10K miles ago, so I'm pretty sure that should be fine. I put a fuel system cleaner in my tank this afternoon. How long would you expect it to take before that would make a difference?

 

If you used BG44K you will see a difference all most immediately anything other than that it would be difficult for me to say because all I use is BG44K. I have noticed that it seems to work better on short trips so highway driving is not necessary. You should still try to get a fuel pressure reading.

 

Not being a mechanic, I don't have any way to obtain BG products, so I used a Gumout brand fuel system cleaner. Yesterday evening, I had to drive to a town about 45 miles away; this is the first time that I have driven the car more than about 5 miles in a single trip since this became more than an intermittent problem. Most of the trip was on roads at speeds of 55-60 MPH with occasional stops at traffic signals. When I was about halfway to where I was going (after perhaps 20-25 miles of running with the fuel system cleaner), I noticed that the car was no longer in "restricted performance" mode; the car performed normally for the rest of the drive. A few hours later, when I started the car up to return home, it was still driving normally, but a short time later, the "restricted performance" behavior returned. This lasted for 10-15 miles, after which the car returned to normal operation.

This morning, I drove the car to work (about 16 miles, most of which was on an unexpectedly traffic-free interstate at 65 MPH). It showed "restricted performance" behavior during the first few miles (prior to getting on the interstate), but when I got off the interstate, it was back to performing normally.

I really have no idea if the fuel system cleaner has had any effect, or if the returns to normal performance that I have observed are just a by-product of the engine having had time to get fully warmed up and/or having run at highway speed for an extended time. As I mentioned in my last post, I'm going to be out of town on business for the rest of the week, so I will have to suspend attempts at diagnosis until I return. I plan to order the Bluetooth OBD-II scanner mentioned previously so that I will be able to do DTC resets and provide details about fuel trim when I return.

Thanks to everybody for your help so far; I'll be back with more questions in about a week!

 

The P0171 is associated with vacuum leaks, so I don't think that should be ruled out yet. Not that long ago I had an intermittent CEL and part of it was traced to a clamp that had come a little loose on the accordion hose that attaches to the airbox. I also changed the MAF sensor because I also got P1301 I think it was, but you already did that. Maybe when the smoke test was done the issue wasn't there. Sometimes those sorts of things can be hard to find if they are intermittent. Good luck, I can only imagine how maddening this is getting, especially when you just want to do right by your car. Let us know what it ends up to be.

 

Thanks for the suggestion, Alfadude. Replacing that O-clamp on the air intake hose was actually the very first thing my mechanic did.

I'm back from my business trip, and the Bluetooth OBD-II scanner is on its way; I'm planning to see what data I can get from that before I take the car back to my mechanic.

 

My 03- 2.5 that I just posted a thread for acted similar, warning lite on at start up(the colder the worse and longer it acted up)after it warmed up the lite went out at highway sustained speeds but as soon as I stopped and idled it would come on and went out after highway speed was attained and got worse over time.I had replaced upper o-rings,tuning o-rings,brake booster line with the o-rings for the plenum, the problem stayed. The problem is now gone after the LOWER o-rings were replaced. Do the lower o-rings before throwing time and money into any components Buy the parts @ $10.00 uppers,$14.00 lowers PER SET, Valve cover set for $60.00, Plugs $6.00 ea., For $150.00 you will know for sure, Don't forget the tuning tubes o-ring $10.00. The lower o-ring leak is every hard to detect as I found out but that what it was. I also put in two Chinese hand cuffs(vacuum line adapters) which was included in the $150.00.

Good luck

 

Check the amperage (not just the volts) on the battery. You might have a bad battery. Getting worse over time points that way.

Getting worse when its cold out would point towards the upper and lower intake gaskets / orings need to be replaced.

 

Alright, got the scanner. DTCs currently present are the same old P0171 and P0174. I also got the freeze frame data from the time P0171 was stored; clearly the fuel trims on both banks are way too high:The code was triggered at low speed (2 MPH) and near idle (1347 RPM), which is consistent with my qualitative observations. I will try to get some objective numbers under varying conditions tonight and tomorrow. In the meantime, it really sounds like there may still be a vacuum leak. Unless something really jumps out in the data I get, I guess I'll have my mechanic give it another smoke test and possibly just go ahead and replace the lower O-rings even if he doesn't find evidence that they are leaking. I don't think he did another smoke test after replacing the throttle body, so perhaps the throttle body leak was masking some other leaks during the last smoke test.

Thanks for your continued help, all!

 

Would it be possible for you to get a fuel pressure reading? You say you have no vacuum leaks, you replaced the MAFS and O2 sensor and you replaced the TB and fuel filter the only thing I could think of is low fuel pressure.

Earlier I suggested you add a fuel additive BG44K and you were unable to find it and added another additive and noticed a difference but it was short lived.

The P0171 & P0174 are connected to vacuum leaks & fuel and fuel presentation is important. It could range from restricted fuel injectors, a failing fuel pump and or fuel regulator. If you seem to have a problem with my suggestion of a fuel problem then read the possible causes related to the P0171 & P0174. I know that your car is a 2004 and the chart is for a 2002 but the P0171 & P0174 are the same on yours.

Link http://jagrepair.com/DTCforms/X400_0..._OBD_II_R4.pdf

You live in Manassas go the any of the dealerships in your area and ask them for BG44K and also get a fuel pressure reading with your new OBD II reader.

 

Thanks Gus! I certainly haven't ruled out a fuel delivery problem. The fuel pressure from the P0171 freeze frame data is 54.8 PSI. I can't seem to find any information about what fuel pressure is "normal" for this engine.

 

I do not have the pressure requirements on that car but you pressure seems to be sufficient. What ever you find to be the problem please post it.