I'm about to dig into an issue I've been having. A while back, the Mass airflow sensor was slightly out of spec. I cleaned it, and it didn't complain anymore.

After a while, however, I began to receive 02 sensor codes. The first code simply suggested a new 02 sensor, so I replaced it and cleared the code; only to find more codes related.

It's been running rich for quite some time now, and I'm not entirely sure it hasn't been for the 2,000 miles I've owned it.

I'm wondering whether or not the MAFS is still there, causing issues, even though it might be technically within specification for an average sensor, and not throwing it's own code anymore.

I've got three codes, all for 02 sensors, and it's running rich. Logic suggests that anything affecting both banks has to be before both banks. Still, I have to wonder.

I'll post the codes themselves shortly. I've lost the little piece of paper I put them on.

One more question:

If I indeed have to buy a MAFS, is there a place that I can get one at a reasonable price? I've so far found one for 1,600 dollars, and that's a bit stupid. At the very least, that sensor must have been fitted to some other vehicle, not just the Jags, where the cost might be lower.

 

Look for Part# LHE1620AA

I found one on eBay for less than 50 british pounds. I found used ones for less than $400.

I'm sure with some time you can do much better than me.

 

Yeah, I've been on the hunt. I've run into two dead ends so far. Used on Ebay, I'm not willing to pay much, as it's a total wash if it's trouble. The thing is, the 1996 sensor seems to run incredibly higher than the others. There may be no difference, but I haven't found out yet. I've still got channels to exhaust, however, before I am out of luck.

Here are the codes:

P 1191
P 1192
P 1194

Off the top of my head, I can't remember precisely which is which, but whatever they are, they are related to the running condition.

At the moment, I don't know what to do with that. I do know that I had a direct 02 sensor code before. These are unfamiliar to me, as is how they might be affecting my rich running condition.

As I said in another thread, I've lost my repair disc, and I'm still in the initial stages of examining the issue. So, if anyone knows what to do about these codes, or what they are suggesting, it might save me quite a bit of trouble.

 

That part number seems to have really, really helped in my search. It's amazing what a number will do for you. Thanks!

Hopefully this thread will help me determine if this is the cause of the constant reporting and rich running. I've got to get this sorted.

With the prices I'm seeing on that sensor with the part number, I'm actually hoping it's the sensor now. They are FAR lower than I have been seeing before.

 

I'm glad that its helped. I think I saw a used one on eBay for about $25. Its used, but it seems like a pretty minimal investment. Might help you decide whether you want to buy a new one or not.

Please make sure to come back and post a summary when you get your problem resolved. There are too many threads that have people diagnose a problem, promise to post the result but never do.

I'd like to make sure that the next guy that has a similar problem can learn from your issue.

Thanks.

 

It appears that the problem was very simple.

I replaced all four O2 sensors. When that was done, the engine did sound better, but it suffered random misfires, as well as bogging and surging at ranges between 1700 and 1900rpms.

So, I reasoned that it must be the mass airflow sensor. The symptoms matched. Since I had already cleaned the factory sensor, and scoped it at barely within specification, I decided to replace it. I scored a rebuilt unit for around 400 bucks.

When the problem was not solved, we then really, really looked at it.

Bank 1 was running incredibly rich, and bank 2 was running incredibly lean.

Looking at it logically, it couldn't be the injectors, plugs or coils, as the misfire was indeed quite random. That was confusing enough, but there was more.

It couldn't be the O2 sensors, either. I would have to have bought two sets of two sensors, both polar opposites, both incredibly out of specification, and managed to install each bad set on the same bank.

Let's just say that would be about the most unlikely coincidence of all time, so I wrote that option off entirely.

Well, that leaves us with things on the intake side. There is not one component that could cause such a discrepancy between banks, as well as the random misfires. Nothing could possibly be broken.

As it turns out, nothing was.

I performed a propane test, to no avail. For those that might not be familiar with the practice, it involves introducing propane gas to the exterior of every seal, gasket or hose on the intake side of the engine. There was no result. Everything was fine.

So, I was fed up with the whole affair, and had someone smoke test it, which is essentially the exact opposite of the propane test. Nothing. No result.

Now, this was frustrating for everyone.

As a matter of course, given that they knew I'd spring the cash, they did a thorough and full cleaning of the entire system before the combustion chambers.

You know what came out of the intake manifold? All kinds of nastiness.

After that, as well as making sure to clean the entire system as best as possible without taking it apart, she ran perfectly.

So, in the end, it was simple filth that was causing the bad running conditions. The other parts needed replacing anyway, as we never would have found the issue without them, but it was nastiness inside the intake that was screwing everything up.

I don't know why I didn't think of it. I normally clean that stuff out when I buy a car.

Right now, at a stop light, you can't even feel that straight six running. The only evidence that it is running is the slow burble from the exhaust.

Perfection.

I told you I'd post the results.

 

That's an interesting find. I found that same solution, but it was causing a different problem. My car was stalling out occassionally. Initially it only occurred while parked. One day when I was driving home, it stalled out as I was making a low speed turn in my neighborhood. That's when I took it to the Jag dealer. I wasn't getting any codes, so taking this problem to a mechanic without being able to demonstrate the problem would have been difficult.

I ended up paying about $150 for the dealer to tell me that I needed a new throttle body ($2,300) and, since they were difficult to take off, a new Throttle Position Sensor ($1,200). I took the car, armed with that info, for a second opinion to my local mechanic. For $50 he cleaned out the throttle body and all has been fine since.

 

I've found I still have a few little issues, but I think they may be a byproduct of freeing up all that crap. It's quite cold outside, and naturally things are going to be a bit off from a cold start, but there are still some issues.

Twice now, from a cold start, my power brakes weren't functioning. No worries, I can drive without the assist, but it lends itself to a vacuum problem. Now, that being the case, it's not surprising that when the engine is cold it still stumbles intermittently at stop lights, especially when braking with no assist. It did stall out once, tonight, but I was able to restart it.

Right now, I've got a full can of Seafoam in the tank, and I expect it will help clear the lines and injectors.

As for whatever problem is causing my vacuum issues, that will have to wait until I get back from PA. It's not the smartest thing in the world, but I'm taking her up there from NC tonight.

I'm hoping that the extra hours on the engine will help clear it out. If not, I'll have to look into it.

Given the improvement from the cleaning, I am willing to wager that there are still a few issues to sort out in that arena. If the intake manifold was that bad, it stands to reason that other things are as well.

I'll wait for any codes on the drive, and then proceed to sort out any issues as they crop up. I expect it's filthiness and vacuum related, given the effect on the brake accumulator.

Still, so far as warm running is concerned, it's worlds better, and feels new.

I don't think these new issues are anything different. I think they were masked by the other problems, just as the filth was masked by the bad 02 sensors, which was probably caused by the filth in the first place.

I just wasn't there to see it caused.

 

I will confirm that after the cleaning, I still had some intermittent problems, stuttering idle, etc, but that all went away after a few thousand miles. I don't know if I ever had the full stall out again though.

 

You might want to check your coolant temperature sensor...see if it's within specification. A digital volt-ohm meter is the tool to use.

 

I'll be happy to test it, if you can tell me what the specifications is.

I'm having more issues here and there.

When it's chilly out, the engine misfires severely for a while after ignition. Eventually, it calms down, but still suffers minor fluctuations in idle speed and an occasional miss.

Upon depressing the accelerator pedal, there is a drop in RPMs and a hesitation before the vehicle reacts appropriatly.

Several things have been done to the vehicle in an effort to sort the issue. There was decent logic behind each of these practices, so it's not a case of simply tossing parts at her.

1: Two smoke tests were performed, another propane test, as well as several attempts with ether to root out a vacuum leak. No leak has been found.

2: Fuel pressure regulator has been replaced. Seemed like a good idea at the time. No result.

3: Crankshaft position sensor replaced. I've heard they go out slowly over time, so I gave it a shot. No dice.

Now, during that hesitation upon depressing the pedal, a bit of a hiss comes from the engine, near the EGR valve. I did not clean or replace the valve. I removed it, and noticed nothing awry, aside from a slight, unexpected rattle when it was shaken. I called a supplier and had them shake a new one. They said it rattled as well. As for the valve, it depressed very easily and smoothly with finger pressure, and returned when pressure was relieved.

I've never toyed with an electronic EGR valve before, so I'm not sure if those results are good or not. I removed it at a racing shop, and while none of us are experts in computer control systems, we didn't see anything patently wrong. Still, I might be missing something, here.

The entire issue really feels like some sort of vacuum leak, but it may not be. The only indications of a leak are the brief hissing noise, as well as an occasional hiss from the barely functional climate control system in the cabin. That's intermittent, though, and does not appear to correspond to any engine misbehavior.

Overall, the engine feels a bit down on power and misfires enough when cold to worry me about using it for anything other than long drives. It doesn't sound very happy, and being a long straight six, I'd rather not sit there and watch it misfire like that.

The last code I cleared was indicating a lean condition on one bank, as well as misfires. I have seen both persistent and random misfire codes.

Any more ideas? It's about to get a fuel filter and a fuel pressure measurement. Can't think of much else at the moment, but there are clearly things I need to check.

 

Hello Kennith;

As far as the Coolant Temperature is concerned, I personally would not even bother wasting my testing it,. Its part number LHE1600AA , costs less than 100.00 at the dealer, probably less online, and like the CKPS, it should be replaced anyway. The EGR valves are typically stuck open or closed with carbon. Yours sounds OK, so I would revisit that after looking at some other things

Based on your description of your misfire, I would look at :

1-Ignition coils , spark plugs and associated wiring-The Ignition coils are a weak point in the AJ16 engine. Look for cracks on them, sometimes if you take the coil cover of in a dark place, you can actually see them light up as they misfire. For your plugs I would suggest you research which ones work best on the AJ16 engine. After trying the Jaguar specified RC12yCC Champion gapped at 38 thou, I have been very impressed with NGK Iridiums BKR6EIX installed directly from the box..they come gapped at 30 thou

2-Throttle Body-have it removed and cleaned by someone who works on AJ16 engines. If you can not do it yourself. These can gum up and be problematic. Like the crank sensor and coolant sensor, this should be done on an AJ16 anyway. Make sure the intake in clean, as it tends to build up with oil and can drip down to the TPS and fry it

3-The Idle Speed Control Valve-can cause the kind of flaky idling you describe. Clean or replace. Some guys can clean it, other buy new. Again, not a very expensive part. Would correspond to your fluctuating idle

4-The Throttle position sensor.- I would change that last. It cost more and you have to have the car reset by a Jaguar PDU. These have different failure modes but could also correspond to your symptoms, problem is that flaky ones will test OK. Mine tested OK 2 times I only solved an intermittent stall I had (car would cut of completely in when decreasing speed from say 70 to 65 in the highway) Problem was solved when I decided to throw a new TPS at her. That was over 2 years ago.

5-Look for water on your ECU connectors. If a pin has been compromised it can cause intermittent and deteriorating symptoms , including over-fueling, etc.

6-Almost forgot!!-Thermostat-- is she reaching operating temperature??

Do you have any other codes??

Good luck!!

 

1: I've replaced one coil already, so it's reasonable to assume others are approaching end of life as well. That said, this would be a nearly immediate secondary failure. Coil diagnosis can be a deceptive practice.

The vehicle will soon hit the 100k mark. I'll go through the coils soon, but I want to eliminate other variables in the meantime.

I'm using the Iridium plugs already, and I took the time to gap them properly. I like those plugs in general, but I made a point to use them here because of the harder, smaller electrode. The engine was running rather rich when I took delivery.

2: The throttle body was cleaned by an import specialist who's seen a few XJS cars. That said... I never did trust that bugger. He was simply the closest shop around, and I didn't have time to do it myself. I didn't watch him do it, so there is no telling what qualified as "cleaning".

I can't see anything gummed up and nasty in there, but a good cleaning may well be on the menu. It's annoying, but if it's got to be done, so be it. Good time to have something else in the engine bay powder coated, if nothing else.

I personally cleaned everything from the cold air inlet to the bellows at the throttle body. There was plenty of gunk in there when I did so.

One thing I'm not sure of is how the crank case ventilation works on the AJ16. I couldn't find any note of a conventional PCV valve. Rather, all I see are ventilation hoses. I had the cam cover off for coating when I was working on other areas, but I don't remember what was under there at the vent point.

If there is an aspect of this system that requires routine service, please let me know. I'd also appreciate a rough description of where the heck the valve is.

3: I'll just buy an idle speed control valve, unless I believe I can sufficiently restore it to a degree of operation that requires no mindfulness.

4: I've considered this. I don't want it to be faulty, but it's on the back of my mind right now. Does it have to be reset as it's replaced, or can it be driven after replacement to a facility that can reset it?

5: I'm on it. Hadn't considered that, of all things.

6: Well, the temperature gauge says she is. Seems to take a while in cold weather (may be a result of all that missing), and in hot weather I worry it's going to overheat. It used to, but that's because the electric fan switch didn't work. I've got a replacement, but I haven't felt like draining the system, so I am using a manual switch.

Will it overheat now? Heck if I know. It seemed to be fine, but it's darn close to the edge, it seems. I'll be able to tell better when I get her running properly and it warms up outside. I'm not sure how much I can expect out of this cooling system in NC summers. I do know they crowded the radiator area...

No further codes at the moment.

 

In the past, the vehicle displayed a few symptoms that might be attributed to a coolant temperature sensor.

In one instance, the engine behaved very badly. Unfortunate smells were produced, the missing reached a new high, and black smoke was indeed present. Very, very nasty indeed.

I unplugged the MAFS in an attempt to shove it into limp mode, and succeeded. I drove it back, and the next day it was fine, having thrown all manner of codes.

Nothing was changed, and it never happened again.

 

Kennith;

As far as finding a mechanic goes, make sure your guy works on AJ16 engines and is familiar with them. If he's a good man on XK's or V12's or even AJ6''s or conversely with the modern V6 and V8 Jags, but does not know about particulars of a X300 or XJS powered AJ16, he's no good for you. Remember although similar, a 93/94 6 Cylinder XJS is NOT the same as a 95/96 and does not have the same failure modes...Again, you want a guy who deals with X300/95/96 XJS's and had the appropriate equipment to reset the car.

Did the guy who cleaned the throttle body take it all out completely out for cleaning. I think this is important, because if he did, you can probably write that of.

Some advise when getting new coils to avoid further grief. Whoever you are buying them from ask if they have a transparent "Made in Japan Sticker" on the coils. if they do, they are made by the original manufacturer that made them for Lucas. The Chinese/Taiwan copies are garbage and fail rather quickly. Also make sure that the Coolant Temperature sensor is the correct part number. DO NOT let some parts guy "match up" numbers for you. Go to JDHT, find the correct part numbers for your vin and find the part number. I have ended up with AJ6 parts when people "match up" parts in their systems.

There is no PCV valve in the AJ16. Jaguar had a recall to install some kind of valve on the X300's but apparently that did not work out well as some owners reported pressure in cam cover resulting in leaks. Solution is to yearly or bi-yearly remove the intake and clean.

As I said previously the TPS is going to be hard to diagnose, that being said, I do believe that most guys who have had it fail as I did, had problems like the one I described: You are driving in the freeway at 75, you ease on the pedal down to 70 and boom!! its like someone cut the lights out. Car just dies right there in the middle of the highway, then kicks on after 3 secs. I am not saying that it's not your problem, but it seems failure modes within the same engine tend to be similar (obviously not all the time, but..)

The ECU on the XJS can be accessed in 20 minutes or less. Do check it.Here is a write up from a gentleman from England who found water on his X300 ECU pins after a long while of intermittent issues. :

Jaguar XJ6; Jaguar X300; Jaguar XJ6 3.2 Sport; Engine Control Unit problems; ECU

On my XJS I had the very same issue, my connector looked just like his. In order to avoid future failure my well versed AJ16 mechanic and I took the following steps on my car:

First we wrapped all the ECU wiring harness along the firewall, leading to the ECU with tape. Water drips into those cables and they go straight down to the pins;



We then sealed the rubber boot entrance with silicone:



Then the connectors on the new ECU recieved a healthy dose of dielectric grease inside and outside, specially on top of the female connector right by all the wires come into the connectors.:

 

If your power brake assist is not working properly, and you are running lean ... how about taking a look at the booster check valve and the associated vacuum hoses? If it is worse during cold weather that would be because plastic and rubber are not as flexible when cold.

 

As soon as I get back to NC, I'll wait for a slightly warm day to check that ECU. I'm visiting someone in PA at the moment, and after looking in the ECU area, that's a bit more stuff than I want to remove in a town-home parking lot.

Aside from that, it's cold here, and I don't have what I need to tinker with it.

Darn good idea, though. I'd never have thought to check the ECU. Never had trouble with one before. Of course, this engine is a bit on the strange side to begin with. Even for me. I don't mean the actual engine, of course; just the various control systems. The engine seems tough as nails.

I mean, it's got the bits it's supposed to have, but something about everything is just slightly different that I'm used to (sloooooowly failing crankshaft position sensor, anyone?). It's left me scratching my head quite often, and I'm no stranger to British vehicles.

Bah. Everything is a learning experience.

 

Here's the engine code for reference: 9 L P F L B 14081

I've had to bounce around the parts references you listed.

9: Jaguar

L: 4.0L-1994.75

P: Petrol

F: Not a selection in XJS parts reference. Under X300, it's listed as 4.0L N/A.

L: Emissions A

B: Not a selection in XJS parts reference. Under X300, it's listed as spec range-1995

Ignoring the few odd digits, the serial number should be enough to order the right coolant temperature sender, so I'll get right on it.

 

I swapped the crankshaft position sensor. I drove it twice that day, and nothing improved.

The next day, she stopped stumbling. Well, it's seen a few miles now, and the issue hasn't presented itself again, so maybe it's gone. I've got a 333 mile drive coming up in the next few days, which will provide more data.

I cleared a lean and misfire code after the fact, so we shall see what crops back up. I'm going to try to put enough miles on it to throw some codes before I leave.

It still feels a bit... Restricted. Almost as if the air filter is clogged. I'll see what codes are thrown, if any. Given the way the SAI behaves (on, off, on, off), I'm wondering if that coolant temperature sensor is indeed stuffed.

It's cheap, though. I'm going to order one when I get back to NC. Can't hurt. At least I'll be sure it's good.

If the running conditions are cured without codes for two cycles, I'll swap the plugs again, as well. They've seen hell, after all.

We shall see.

 

I've done a few more things, but with a lack of time to really get into it, I dropped the vehicle off at an import specialist shop. The owner seems to actually care about his customers. He handles Jags frequently and takes his time. Seems the sort of guy that may actually bother to research issues he is unfamiliar with.

We shall see what happens.

Hopefully the diagnostics won't cost too much. Either way, it's all going to be done more quickly than I'd have been able to. I've got other vehicles to finish, and some of these finicky issues take too long to sort, as I'm unfamiliar with the vehicle.

I'm learning, though. Once I find out what the issue is, I'll have learned quite a bit about the car, and will be better equipped to deal with future problems. I'm a fairly capable mechanic, but this thing's had me scratching my head quite a bit.

I forgot to check the ECU, but I'll make a point to mention it to him, if he isn't already familiar with the potential issue. I wish I'd have remembered.

Right now, it reports a lean running condition, but it's subtracting fuel from the mixture. He's got a few ideas, but I'll ask about the ECU.

Whatever the heck the problem is, I'm sure the vehicle will be wonderful once it's sorted.