Hello, I own a 2002 Jaguar X-Type AWD Sport 3.0L with Manual Transmission and has about 134,000 miles on it. I inquire help on my current Engine System Fault, obviously.

The Problem:
Car enters limp mode intermittently. This happens one of two ways, either when I'm idling at a stop light or I'm cruising, but very rarely if I'm accelerating.

Symptoms include a Check Engine Light, a Engine Systems Fault warning, and a loss of control of throttle. The tachometer will read from 1000 rpm to about 2250 rpm. Sometimes it will be at 1000 in gear and out of gear, and some times it will be 1000 rpm in gear and 2000 out of gear. And rarely it would rev itself. I can still shift, knowing it probably bad to, but I can still shift and accelerate very slowly and get up to 30 mph (all the way to 5th gear).

To start, when I first bought the car, after about 200 miles or so, it started leaking coolant out of the "T-Junction" on the radiator hose. So to cut costs I simply patched it up with some JB Weld, and it worked just fine and didn't leak. Next thing to go out was the clutch, so I brought it to a shop to get that replaced, and it didn't leak there.

However, when I got the car back, the alternator and battery were bad. So I replaced the battery and alternator and didn't hassle the shop I took it to for the clutch since I had to move a couple days later. I replaced the battery with a brand-new battery and an alternator with a used one (had about 80,000Well, I drove it for about 2,000 miles straight to Massachusetts, and that's when the first time Check Engine Light came on. When I got to Massachusetts, I retrieved a Catalytic error code (forgot the number). And I was driving in Massachusetts when the first time this Engine System Fault appeared. I pulled over and restarted the car after pumping the gas pedal three times, and the symptom cleared.

I then had to drive another 3,000 miles in it shortly after, which I did without a hitch. And at about the 2,000 mile mark the Check Engine Light went off. I finally got to my destination, here in Yuma, Arizona. And I believe the city driving is what drove it to go bad, since in Massachusetts was city driving too.

Anyways, I'm in Arizona and the fault starts picking up, first at a couple times a week, then a couple times a day, since my commute is only 8 miles a day (to and from). The coolant leak came back and worsened significantly, and I was forced to fill it up with water until the radiator hose I ordered came in. I then installed said radiator hose assembly (hole upper assembly with "T" junction).

For the first couple days it didn't pop-up. My first suspicion was that the steam/evaporated coolant was making it up into the Air Filter (since the box is directly above that "T" junction) and thus creating multiple faults with ignition, emission, and air-fuel mixture getting all messed up.

But then the Limp Mode started again. This time in two's. I would get the fault, pull-over restart the car and pump the gas pedal three times. And I'd get about 50-100 feet and it would do it again. Repeat and it didn't pop up for another 50 miles or so.

I noticed that if I drove like a maniac (getting above 3,000 to 3,500) then idle or stay below 2,000 that's when the fault would pop-up. Making me suspect that the fault only showed up after I replaced the alternator, and making me think that the regulator isn't having enough time to adjust to lower rpm's (I'm not a huge mechanic buff, so I'm not how sure my logic is here).

So today, I brought my car down to the local AutoZone to get my OBD II codes taken and check my battery/alternator. Alternator test came back good, and my faults, had four of them (I didn't get the codes written down or printed, forgive me). They included P1000 and P0420, and I know the AutoZone employees usually don't know much, but he told me to clean my Mass Air Flow sensor, which I will do tomorrow, as well as bring my car back there to see what the alternator is doing when it's in Limp Mode (today was a busy day, and out of courtesy I didn't want to take long due to the long line).

So my inquiry, is that if anybody has any idea how to fix this (I'm trying to avoid a high cost replacement) or has any prior history on this that would help. I did some research on here, and saw that someone had a similar problem and he fixed it by replaced a Throttle Position Sensor, cleaned the Mass Air Flow sensor, and sealed a vacuum leak on his intake manifold (I believe). However, I'm not sure if his problem was 100% up to par with mine. I'd just like a second opinion, please. Thank you for your time if you actually read all that because I know I probably put too much unnecessary information and maybe too little necessary information.

Once again, thank you for any help.

 

Update:

Today I got a flat tire on the way to work and changed it with the full spare I had, and then drove to work, obviously. Well, it did not fault today at all. When I got out of work, I drove directly to Pep Boys to get brand new tires since the ones I had were very bald.

Well, once I got my car back, Pep Boys obviously cleared all the codes on my computer, and the check engine light was off when I got back into my car. I was expecting it to come back on once I drive for about 30 minutes or so. BUT IT DIDN'T. I kept driving around, grabbed a late lunch and everything. I drove it for about an hour or so, and still no fault.

I opened up my hood to inspect for a vacuum leak, since this car is notorious for it. And I could hear a leak very loudly, kinda like an air hose leaking. It was right on top of the intake manifold (now, I'm not a mechanic buff, so forgive me for not describing it well) where there are two sensors on two different of what looks like valves. Well I sprayed some throttle body cleaner in there, and the rpm's went up very very little... bare noticeable.

I decided to kill time and drive around some more, like a maniac since that would be usually to cause it to trigger. Still no effect. I got back and a mechanic buddy of mine told me that Mitsubishi (he has barely any experience with Jaguars, thus does not know the design) has two valves that fluctuate for high rpm's and lower rpm's, and this leak is what could be causing it, confirming my suspicion of a vacuum leak I got from a little research here.

Anyways, I showed him what I meant and he started spraying some throttle body cleaner in there, and it stopped the leak. No more sound, no more feel of a vacuum or air rushing out. We bullshitted for a bit and went our separate paths. So I drove for another 2 hours, and I'm amazed that it has yet to fault. The Check Engine Light is still even off as I speak/type.

I'm just wondering if that by changing my tires and now having correct alignment and tread and proper shock absorption through tires, does that put less stress on the engine making these fault gone? Or is this just a coincidence that it fixed itself. Or was it doomed to fail eventually until my buddy cleared the leak (yes, that sounds stupid)?

 

Outcast, from what you are describing, it sounds like you had a loose wire going to one of the wheel speed sensors and when you had the tires mounted, the mechanic was nice enough to put the wiring back in its mount. This then causes the computer to see the speed sensor all the time, leading to proper operation.

If you need more information, let me know.

 

Thank you very much Thermos. I do appreciate your advice, and I do not mean to belittle it at all, so I apologize if this seems deceptive or unbelieving. But I today the fault popped out only twice (one after another). Much better than it did before the tire change. All my codes were having to do with emissions, however. Two of them for a Too Lean Emission, one of them P1000 and the other P0420.

The two faults did trigger the Check Engine Light. I drove for about 5 miles and it went off. I drove to AutoZone and back to fix another problem (windshield washer nozzles/hoses). When I was testing my windshield nozzles the Check Engine Light came on and the vacuum leak was there before the light was. I'm not sure if any fluid reached the leak on the Upper IMT Valve or if the fluid did anything. I will return to AutoZone to scan the codes again later tonight.

I know I have to take off the Intake Manifold to get to the spark plugs, so I thought I could kill two birds with one stone and take it off, replace the IMT O-rings and replace my spark plugs. I ordered the O-Rings last night, and waiting for them to arrive.

 

theoutcast, do not worry about it. I bet you had P0171 and P0174 for the lean conditions. Those are complements of the vacuum leak. If you are replacing the IMT valve o-rings due to hearing sound in the area, then you are probably on the right track. As for the P1000, that is simply saying that you had a problem, the condition cleared and the computer has not had enough time to complete a drive cycle to verify everything is now running properly. As for P0420, that is an inefficiency code for the catalytic converter. It can be caused by the lean condition, can be caused by an O2 sensor that is starting to go. Fix the vacuum leak and see what you have then.

 

Thank you Thermo. That was going to be my plan to the T, actually.

I went back to AutoZone today only pulled 3 codes today. P1000 = diagnostics did not finish = negligible for this condition. P0420 = cylinder 2 misfire or failed ignition coil or catalytic inefficiency. and not sure of the number but, Bank 1 of too lean.

I took off the intake manifold, with the Throttle Body, IMT Valves to replace the spark plugs. I also cleaned the entire assembly as best I could. The IMT O-rings did not come today in the mail, so I didn't get to replace those, but I did a thorough cleaning of the entire intake manifold/IMT valves/throttle body. My spark plugs did need the replacing, and as for the 0-rings, they do too, just by a quick inspection. Every other o-ring was perfectly fine.

I did find another line that feeds from the back cylinder area to the area between the throttle body and air filter. The end that connects to the engine was easily removed and half of the plastic tabs on the connector were broken off. What is that line called? So I can find a replacement.

After reassembling after the spark-plug change, the vacuum leak was still present. Tomorrow, hopefully the o-rings come in, and I should be able to replace the top one (the only one giving off an audible leak) in a jiffy. I will also replace the ignition coil for Cylinder 2 when I do a little research and find out which one it is and order the part.... baby steps.

Once again, thank you Thermo.

 

So I used somebody else's picture for the first to demonstrate where I found this line and wonder what it's called. Pictures should demonstrate themselves.

 

Today I finally got my IMT Valve O-Rings, and only got to replace one of them since I was at work and didn't have time to unscrew my Intake Manifold.

The car's running better than it has ever before. However, I finally got the liberty to download a no-**** Jaguar OBD II codes, so I wasn't just guessing on what other sites/AutoZone says.

The three codes I get are actually quite simple:
P1000 = System (OBD) check not complete since last memory clear
P0420 = Catalyst converter system efficiency below threshold - bank 1
P1344 = APP Sensor sense circuits APP1 and APP2 range / performance

Now, P1000 is negligible since it pops up when any other fault is detected, and that's it's only purpose really.

P0420 can pop up from a number of things, however, it has to happen twice for it to turn on the Check Engine Light. It can be caused by HO2 sensors failing or disconnected, catalyst failure, engine misfire or more commonly on an X-Type, a vacuum leak.

P1344, however, is the fault that creates the Engine System Fault and causes the car to go into "limp home" mode. For default action, it lists:
ECM Default:
– APP angle default value used
– Speed control inhibited
– APP adaptions (wear,variance) inhibited

Those right there, describe limp mode, or at least in my case. It does have to happen twice to cause the Check Engine Light to pop up. And for possible causes, it lists:

APP Sensor to ECM sense circuits:
short circuit, open circuit, high resistance
APP Sensor sensor supply circuits:
short circuit, open circuit, high resistance
APP Sensor sensor ground circuits:
open circuit
APP Sensor failure

I'm not 100%, only 95% really, that APP stands for Accelerator Pedal Position [sensor], but I can't find any references that state it as such. It does make sense though, the ECM isn't receiving an input from the Accelerator Pedal Position sensor, so it makes sense that it would default the value and not allow any new input from a now proven faulty sensor.

I however, just reset the ECM by shutting down the engine and pumping the gas three times to continue with my day.

My next step, for now, is to veer off chasing this vacuum leak and to check my connections to my Accelerator Pedal Sensor to the ECM/Throttle Body (if they exist) and if they are all good, I am going to replace the Accelerator Pedal Position Sensor.

So for a question for re-assurance.... Does APP Sensor mean "Accelerator Pedal Position Sensor?" Thank you for all your help.

 

outcast, yes, APP is just what you think it is. You would be one of the first to actually have that fail. Normally when people think it is that, it is is actually the throttlebody (but you have different codes that what they normally get). You should be able to get that from the local auto parts store. Granted, you may want to do a once over of the wiring under the dash to see if you managed to damage the wire with your foot. That could save you from having to put in new parts.

As for your vacuum issue. I would need to look at my car and follow that line. I do not recall what that line is for.

 

Today I finally got the chance to change out the other IMT O-ring, and no vacuum sounds arised. I sprayed some throttle body cleaner in and the RPM's neither went up or down, when I sprayed anywhere on the top of the engine.

I also checked on my APP sensor down by my feet, and I disconnected the cable leading up to it, and got the limp mode "Engine System Fault" as well as it normally does. I then reconnected, made sure it was nice and snug and restarted the ECM by restarting my car and pumping the pedal three times.

So it's very very plausible that the problem is from there. So on my way to AutoZone I kinda put my accelerator pedal and sensor through a mild torture test. I revved it up fast then slow both three times. Tried to pull it back, and push it side to side, just to see if the sensor was having issues when a physical force hit it the wrong way. I also tapped the side of the side with my foot, and when stopped I pulled at the cable, wiggled it, and couldn't set a fault.

At AutoZone I cleared the two codes I had P1000 and P0420 and they have yet to pop up again. So perhaps I stopped the leak and we'll see about the sensor in the next week or so.

 

Been trying to follow your issue and would like to get a little additional information. Do you have all the codes you pulled from the beginning of your trouble? As for a vacuum leak, is your 3.0 the same as the 3.0 that is in my 2000 S-Type? I have information on vacuum leaks on my page under S-Type and throttle body rebuild under XK8 sections of my page that might help. I am not sure at this point that you have a problem with the TB it could be poor plug connections.