So I had a strange thing happen yesterday, after driving on several errands we returned home and parked the 2001 XJ8 VDP in the garage.
Thirty minutes later i needed to access the attic above the garage and had to back the car out to access the pull-down ladder.

All was fine until about 30 minutes later I went to return the car to the garage and when I tried to start it it struggled to run, and banged and clanked and generally sounded as though it was in real trouble. (it ran just like when a motor overheats and runs on after the ignition is turned off). I tried to start it after a minute or two, but the same thing.

I wondered if it was a failing fuel pump, and so removed the cap on the fuel rail shrader valve and when I depressed the valve I had fuel squirt 3 feet in the air......so plenty of fuel pressure.

There was no check engine light on, but when I checked for codes it had a "PIIII Intake air temp sensor circuit intermittent high voltage" message.

I left the car overnight and this morning it started up normally and ran as though there had been no problem.

So, what do you all think, my MAF sensor looks perfectly clean, do I need to replace it, or is it likely to be something else?

All input appreciated.

 

The air intake sensor is a thermistor that responds as increasing resistance means lower temp

This is the same as the engine coolant sensor and may be the same part # for swapping purposes

A dirty connector will simulate a low temp

See page 65

http://www.teacher.starenvirotech.co...%2005-2004.pdf

 

You can try cleaning the MAF and see if it helps resolve the problem. If cleaning doesn't help and occurrs again then I would replace the MAF. Since the IAT is part of the MAF.

 

If I do replace the MAF sensor, they are available from $30 thru $250, any advice on brand/quality/price etc?

 

On the middle wire you should see X voltage DC seeing that its alive

 

P1111 is NOT AN ERROR CODE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

The P1111 is a 'readiness' tests completed.

If you clear a P1111 you will get a P1000. Then you drive until you get a P1111 and you get angry because the car is happy but you think it is a fault with the MAFS or something so you clear it and the DTC changes to P1000 again.

So you drive the car until it is happy again and sets P1111 but you still think it is a fault so you clear it and get P1000.

STOP THE MADNESS!!!!!!!!!!!!!!!!!!!!!!!!!!

bob

 

Thank you for that Bob...............so what do you think was the problem I experienced? The car basically wouldn't run, not enough to actually move the car, all sorts of horrible noises etc. And then the next morning starts and runs as normal. I'm afraid to drive it in case the problem reoccurs.

Doesn't the "mass air sensor intermittent high voltage" message indicate that the MAF sensor is at fault?

 

So if when I check for errors I get an "Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage" message, but no P1108 OBDII code, what does that mean?

 

Was the DTC PIIII (P capital I which is Roman Numeral 4 or IV) or P1111 (One thousand, one hundred eleven?)

You typed a bunch of capital I's (eyes)

The GENERIC P1111 has NOTHING to do with the JAGUAR P1111.

DO NOT use generic DTCs for Jaguar DTCs.

The P1111 has NOTHING to do with the MAFS, Temperature or any other faults.

Use the Jaguar DTC guide and NOT the internet!!!

 

Bob, thank you for your continued response, I'm not sure.....when I checked with the scanner, it said there were no "generic" codes, but there was a manufacture specific code, this was the Jaguar P1111 "Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage" message.

I'm now completely unsure of what the error means, and/or if has anything to do with the fact that my vehicle would barely run, and yet now appears to run fine. I am cautious about driving the car in case the same situation re-occurs. I have no problem replacing the MAF sensor (with an original equipment Denso item) but don't want to waste money if it isn't the cause of the problem.

 

It seems that, as a generic code, P1111 means "Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage" but, as a Jaguar specific code it means "System checks complete since last memory clear". According to the Jaguar specific codes, the trouble with the IAT Sensor are codes P1112 or P1113. What is not clear is whether a universal OBD reader (with Jag database) will display the IAT trouble as "P1111" and whether, for the same trouble, the Jag VCM/IDS will show codes P1112 or P1113.

In any case, I would first inspect and clean the MAF connector pins. As a side note, no dielectric grease should be used on the pins of any connector. Otherwise, the IAT sensor is inside the MAF as shown on the pic.

 

I would take note of what Motorcarman has said..post 6 and 9.....

You could have been experiencing a bore wash problem..
Starting the car and moving it in and out of the garage with out letting it get up to full engine temp is not recommended.

 

There is NO "generic" P1111 because by OBD II definition all P1 codes are non-generic!

They are allocated by the car maker and could be (but never seem to be) unique per car.

Usually they are unique per make, so a Toyota P1111 (if they have one) could be "on fire" and Jaguar could be (and is) all OBD monitors have passed. Someone made it about their car's IAT - but not Jaguar!

Don't clear it without a GOOD reason where you KNOW why - because if you do then:
1. you may not get the OBD monitors to run properly so can fail smog tests
2. you inhibit many codes being flagged and diagnosis can be very hard

Many sites fail to point this stuff out because they want your clicks but could care less about really helping...

 

I began to wonder that myself, although I am always very careful to let the car reach operating temp if I back it out of the garage when cold, and in this case the car was hot when put away, and still hot/warm when backed out, and still warm when attempted to start an hour or so later.

So, I'm really not sure what the problem was, not why the OBD reader displays a "IAT sensor high voltage message", or if it has anything to do with the incident.

The car runs fine now, so I'll just drive it as normal and see if it re-occurs.

 

It seems you are having engine issues that are not generating a code. Bob cleared up the code issue, P1111 is a good thing to see. So I would look into things that cause rough engine issues that would NOT throw a code. That seems to be the situation you are in. In my experience that’s often fuel related issues, but thats just an idea...

The bore wash theory above has merit. I’ve never experienced that on any of my Jaguars but it’s certainly plausible and wouldn’t generate a code.

Honestly it sounds like a giant vacuum leak, but THAT would throw a code.

Good luck

 

Yes, it is strange, the car runs fine now, I went out in it today and it runs as it should. So maybe the bore wash thing does have merit, although it seems a little unlikely as the car was warm at the time. (Not been through any brief cold starts)

The only other thing I can think of that I did which was out of the ordinary is when I backed the car out of the garage, instead of removing the key and putting it on the "center waterfall" I left them in the ignition. The ignition was not turned on, but the keys were in the ignition for an hour plus. I can't think that this could have anything to do with it, but it was something I never do.

I will drive the car as usual and see if it re-occurs.

 

Okay, so the same/similar thing happened again. Drove for about 25 miles, stopped for a dental appointment, drove home, everything fine, stopped at a store near home, when I came out and started the car it started running rough, misfiring etc. Managed to make it home, just.

Checked codes and it showed a "P0174 System too lean Bank Two"

The possibles listed are:

Engine misfire
Air intake leak between MAFS and throttle
Fuel filter, system blockage
Fuel injector blockage
Fuel pressure regulator failure (low fuel pressure)
Low fuel pump output
HO2S harness wiring condition fault Exhaust leak (before catalyst)
ECM receiving incorrect signal from one or more of the following components: ECTS, MAFS, IATS, TPS

There are no signs of an air leak before the throttle body

Maybe it is the MAF sensor breaking down under hot conditions?

Or I'm wondering if the fuel pump is on the way out? Do they usually show signs of failure, or do they usually just quit?

Or, anyone have any better ideas?

 

I had a chronic P0171-P0174 'RESTRICTED PERFORMANCE' issue with my 2001 XJ8. I replaced the MAFS with my 1999 XJ8 (that runs fine) and the fault would recur every few days to a week. I replaced all 4 HO2 sensors.(no change). I tried several used MAFS I had in my toolbox.(no change)

I swapped intake manifolds/injectors with another spare engine I had in the shop.(no change)
I could watch the fuel trims creep up tying to compensate for the 'lean' running and finally trigger the 'lean-both-banks'.

No intake leaks so I saw someone here on the forums mention a WALKER brand MAFS so I bought one and THAT finally fixed the fault.
It's been good for several months now.

bob

 

Thanks for that Bob............

After an hour or so the car started and ran fine, so I suspected a MAF sensor that breaks down when hot, so I ordered an OEM Denso LNE1620CB ($131,00). I'm hoping it fixes it If not I'll look for a Walker brand!

Thanks again.

 

I might have spent the money for the OEM if I was certain that the MAFS was the fault but watching the LTFT and STFT as well as replacing related parts to see if it changed, I was not sure what part was faulty. It did take several days to a week to set the CHECK ENGINE when the fuel trims maxed out. I cleared the DTCs and pulled the ECM fuse to erase the fuel trims each time I tried a replacement part. (clearing the DTC does not reset fuel trims to ZERO)

The $30 Walker part (WALKER PRODUCTS 2451138) on RockAuto was just a cheap way to verify my diagnostics. I had tried at least 4 used MAFS from running cars to used ones I had in my toolbox. I just did not think that they could all be far enough off to set the stupid lean codes!!!!

bob