I have an '02 3.0L S type with about 89,000 miles on it. I am getting a little engine shake, almost like the engine wants to die. It happens when the engine is warm, and I can feel it in the car, like a 'hestitation' or 'stutter'. It has never dies. It does this while running at 60mph too. It does it with the transmission engaged or in 'N' or 'P'. When it starts happening, it happens once or twice within a few seconds, then may not happen for minutes. Sometimes it will 'stutter' 10-12 in a minute. But the engine runs up fine to 80+ mph. Even at higher speeds, it can be felt from time to time.

I have also gotten 3 codes over the last 2-3 months. Each time it was the P0420 code - "Catalyst System Efficiency Below Threshod Bank 1".

Could these be related? What does this code mean in terms of an S-type? Do I need to replace the C-converter?

Could it be something else? A coil not igniting and sending unburnt gas into the exhaust? Other?

I hope one of you great 'Techs' on here will help me out. I do not have a Jag Dealer for 70-80 miles. The other car just blew a headgasket and I am looking at $3K to repair it...

My wife would be in much better spirits if you all can help me nail this one down.

Thanks in advance. Greg

 

BugDoc, sounds like an ignition problem to me. What I would tell you to do is the code is associated with bank #1. If you open the hood/bonnet and are looking at the windshield, it will be the side of the engine to your left. Now, remove the cover on the engine so you can look at the coils for each cylinder. If you look at the top of them, you will see an epoxy coating on top. If you find one that is cracked, replace it. This sort of problem is aggravated when it is wet outside (water gets inside the coil and causes the coil not to be able to fire properly). After that, do a look at the side of the engine block near the exhaust manifolds. Do you see any broken studs for the exhaust manifolds or any black powder around the edge of the manifold. If so, what you may be experiencing is an exhaust system leak. Unfortunately, this repair is a bit more involved as the manifold needs to be pulled off the engine, new gasket installed and then tightened down at a minimum, if not more work than that (dependent on the problem). if in doubt, you can take a piece of rubber tubing and place one end up to your ear and run the other end at the joint of the exhaust manifold to the engine. If you hear a chugging sound, you have an exhaust gas leak.

Hopefully someone else will come by and be able to give you a few other things to look at to help narrow things down for you.

 

Each bank (half) of the engine has its own cat. Each of those has a sensor before and after it. They're different types but in effect each provides a waveform that the PCM uses to decide in detail what to do about fuelling. It's also reading other sensors such as throttle position to figure out waht you want the car to be doing.

P0420 means the sensor waveforms look to the PCM as though the cat isn't working right. It could be a faulty cat but it could be a faulty sensor or an exhaust or air leak that then confuses the sensor. (Probably some more things are possible.)

Diagnostics (OBD - google it) allow a fair few of these to be checked but also checks need to be done for leaks and anything else that could be the cause. A cat's a bit too expensive to swap without first being rather careful to check other things.

One of the things the diagnostics can read are misfire counts stored in the PCM. Do NOT disconnect the battery or clear the OBD code(s) until such counts have been checked because they're cleared too!

Generally, don't clear codes. Figure out the problem, fix it, and the codes will clear because the cause has gone. When that's happened and there are no more codes, do a clear to reset things like misfire counts if you wish.

In case it's a misfire, coils are the common cause but even they're a bit expensive just to swap and hope.

Of course, if you're paying someone to work on your car it can make sense to swap cheapish things to shorten the time they take.

But I would NOT clear codes unless I was an expert (such as Jag-trained).

OK - i might if I'd investigated, could find no apparent cause and thought the code was unexplained. But you've kinda done that already.

 

oops, "waht" = "what"

 

It has not rained here in Texas in months, but I will look for cracks in the coils. I'm actually thinking that while I am in there that it is probably a good idea to go ahead and change out the plugs. I assume they have been in there for nearly 90,000 miles. I can get a full set of coils on eBay for $130, with a two-year replacement warranty. Should I just order those too?

QUESTIONS: How often does Jaguar suggest the coils and plugs be replaced? Based on the condition of the air filter and the cabin air filter when I bought it 7 months ago, it has never been serviced by a Jag authorized dealer.

Is there anything special one needs to do on the 3.0L S-type when changing out the plugs and coils? Any special seals? Other? Please let me know.

I'll give this a try. I have a mechanics stethiscope too. Is there anything I might hear with it on the engine, throttle body, etc. that I might recognize as a problem?

Thanks for your suggestions. The "shake" does not seem to hinder the engine too much. It still gets about 23mpg on the highway, but I don't want to do any more damage to the engine.

 

One parts place guy told me that a bad Cat. converter will actually glow red on the outside if it is plugged. I have an infrared thermometer. Would I be able to detect a temp difference from underneath that might indicate it is plugged or malfunctioning?

I have an OBDII code reader. I unfortunately cleared th codes yesterday and it did not throw a code in the 5-6 drives it has been on so far. Next time I get a code, I will post all the "freeze frame data" here too.

Can one read any of the other sensor data with one of these readers, or does it require a special reader?

OOoopps! Too late.

I found a full set of coils on eBay for about $130 delivered. Should I just go ahead and change them all out? How long are they expected to last in the blazing heat of Texas?

I reset them, because the Code did not seem to impact engine function other than the slight 'stutter'. But if/when it comes back, I will record all the data reading here for the Techs to see and make suggestions.

Thanks again. PLEASE help me sort this out. Just blew an engine in the van last week! Cannot afford much more at this point!

Thanks

 

The good news is that the PCM will try to protect the cat. (The bad news is that it may not succeed.) A failed cat need not block the exhaust or may partially (or wholly) block it downstream of where it used to be (due to being blasted there by exhaust gases). Infra red may tell you something but if it's "clear" really that just means "no data".

Some OBD readers will tell you lots, others are rather limited. Can you get mode 5 & mode 6 and do you know how to use the data? How about mode 7? Can you graph the O2 sensors?

Read about "drive cycles". Your code probably hasn't had time to be reported.

Change the coils if you feel that's likely enough to be worthwhile. I believe you about Texas but the only time I was there it was snowing

Remember to check for those leaks (air & exhaust).

 

BugDoc, the plugs only need to be changed every 100K miles. Since you are at 90K, probably a good time to do that anyways as it is possible one of the plugs could be cracked and causing this too. As for the coils, they are a "run till fail" part. You don't replace these until they break. But, if you feel it necessary to replace them, doing that is easy and if you are doing the plugs at the same time, it will add no time to the job.

The mechanics stethoscope will not help you in the case for the most part. You might be able to put the stethoscope on the head itself near where the valves are and see if you can hear a "clack" sound that is different than the other cylinders. This would indicate that there is a different amount of backpressure on that valve, meaning an exhaust leak. But, normally, it will make the engine sound like a diesel engine because of that valve noise.

 

So my manual says something like this:

Do you have any idea what this means in terms of an '02 S-type with a 3.0L engine?

Also, I went out to try and find leaks this evening. I cannot hear any in the vaccum system or the exhaust system. The cat converters on both sides read about 120-150oC depending on where I measured. They both seemed to be about the same temperature. The exhaust pipes just after the converters on each side were about the same temp as well.

In looking at the 3.0L engine, it seems one bank of plugs/coils will be easy to access. Does the other set require the removal of the intake manifold? I cannot see a way to access them without removing it.

The JTIS states:

To remove the intake manifold the JTIS takes you to the process for removing the engine. That sounds like fun, but is it really necessary? I am hoping not!

Can someone who has worked on the 3.0L coils/plugs on the right side (passenger side) please tell me what the steps are for getting to them?

Thanks.

 

No one answered my questions about accessing the coils and plugs on the passenger side in an 2002 3.0L S-type.

Please see message above with questions. Thank you.

 

The passenger side coils are covered by the intake manifold. They are long devices that sit inside the head (long tubes) therefore there is no physical way to pull them out even if you were able to wiggle your fingers under the intake and unbolt them without pulling the intake. Instead of worrying about it being hard work, look at it as an opportunity to really check things out in there.

 

I just talked with one repair place and they said "It has to be the catalytic converter. A bad coil will not act like that."

It only stutters when warm. It never dies, it just kind of has a momentary shake/stutter. It will run fine up to 100mpg, but the stuttering can be felt even when it is at higher speeds, in "N", "P", sititng at a light for rolling, A/C on or off.

Does it sound like a coil/plug issue or a Cat?

What does the converter cost for the 3.0L S-type? Any place to buy it cheap?


Thanks again.

 

BugDoc, I have indeed replaced a valve cover gasket (passenger side) which required removal of the intake. Simple process. I replaced my spark plugs as well. YOU will need new UPPER intake gaskets (6), might as well replace the (2) IMT gaskets (O-Rings)too. I had to purchase through dealer under $100.00. Whole process about an hour and a half.
You sound as if you are mechanically inclined, I would do the head gasket myself. Just a note I like to start major operations on a Friday night to get through the full removal process and then Saturday morning, start the reinstall (works for me)! Incidentally Auto Zone offers FREE removal and install process if you join their website (very useful). I also have a subscribtion to alldatadiy.com to compare their version of repairs.
Good Luck
Rick