Hi guys

1.I have 2000 stype 4.0l. when you start the car rpm fluctuates between 690-715. when you sitting in the car you feel the body shaking a bit.Any idea's? No misfire codes.

2. Also every 60 or so miles i am getting P0420 codes. Ran lucas for 3 gas tanks, not much of a improvement.below are the fuel trims.

fuel sys-1 cl, fuel sys-2 n/a
load 40.8, ETC 192
STFT-1, 10.2,LTFT-1, 0.0
STFT-2, 1.6, LTFT-2, 0.0
FRP- 39.2, RPM 1406
VSS 42
Can some one shed some light what should be my next course of action? Cat convertor? Hard to find CA legal cats on google.

 

Can you post the fuel trims etc at idle?

It sounds like you have a misfire or possibly just an air (vacuum) leak. The idle fuel trims (if it's going CL) will tend to confirm that or not.

How many miles has it done? Have you changed any plugs? Any coils? Have you looked for any water/oil in the plug wells?

In case it is misfiring, it will bit by bit be damaging the cat(s) and if bad enough you'll get a code along the lines you are doing.

 

JagV8

1. I will post the idle, fuel trims when i go home.
2. I have replaced all the plugs with original jaguar plugs.
3. Replaced no-2 and no-3 coils( Pax side bank).During replacement of plugs chcked no oil or water leaks to the plug wells.
4. It has 65000 miles on clock.also replaced pax side o2 sensor-1 with lincoln LS( motocraft).

 

JAGV8

One more question for you.When i run diagnostic, it states misfire detection is ok. Also i do not get any misfire codes, or do not see MIL light flashing during idle or running on hwy.

I was told, it will put the MIL light or code, when the percentage rate of the misfires pass the theshold.when i took to a independant jag tech, he showed me a window in the computer with misfire rates.which type of scanner will do that, to see misfiring cylinders.i have a obd.com scanner which connects to my computer.

 

If that "misfire detection" is the misfire monitor and is Complete, it means something complicated (read jtis etc if you really want to know) but does not mean that there are no misfires.

Cars count misfires more or less all the time, some of the counts being what you and I would call false. It's very hard to detect a misfire so the PCM just does its best and is actually quite good. So, it turns out to be the rate/frequency of misfires that matters. A typical cheap OBD tool won't report them. The dealer-level tool costing $5-20,000 will. Some tools in between may also do, but you'd have to hunt to find which if any do for the S-Type of your era.

As I understand it, even the ELM327 could be used to report the misfires BUT you'd need special software to drive it and I'm not sure anyone has written it for the S-Type.

It's not certain that you have misfires (perhaps your fixes have cured them) but the P0420 suggests you've a damaged cat and often that's from misfires. But there are other causes (heck, they can just fall apart), such as an air leak which in turn can make the fuel trims all wrong which can then result in unburnt fuel entering the cat.

What does your indy jag guy suggest?

 

Hi Jagv8

He wanted to replace coils 2 and 3, then check o2 sensor grounds.Coils were replaced.i have not check the o2 sensor grounds as yet?

 

Jagv8

Here are the idle rpm fuel trims.
fuel sys-1 Cl, fuel sys-2 N/a
load- 27.1, etc- 194
stft1-0.8,stft2-0.8
ltft1- 3.1, ltft2- 3.1
frp- 39.6,rpm 695

Also in ref to your question, indy tech replaced no-2 and no-3 coils.I replaced all the plugs with original jag iridium plugs.

 

Those fuel trims are OK at idle, so you probably don't have an air/vacuum leak.

It's running CL, as it should.

Without a tool to examine misfires you can't be sure whether (or how much) it's misifiring. But your indy can do that.

I'd let him check the O2s as he can probably graph them and should know what to look for. If you can graph the O2s, the two upstream ones should switch regularly between about 0.2V and somewhere nearish 0.8-0.9V. The downstreams you don't really want to be switching much if at all. Ideally they sit at about 0.45V but if it's between the 0.2V and 0.9V they're likely OK.

The P0420 is a cat efficiency code (essentially: the downstream sensor is switching too often so the cat appears not to be using the spare O2 as it should) but could be due to an aged or failing O2 sensor, I suppose. Worth hoping for, as they're sooo much cheaper than a cat.

I wouldn't think you'd feel much shaking if the revs are changing 690-715. So, maybe it's a misfire. You'll see some variation in rpm if you have any varying load such as a/c on, so I hope you didn't
(But that still shouldn't feel like shaking.)

The other thing I've met PCMs doing is trying to "wake up" an O2, but the revs changed a lot more than by 25 and the car went OL for a short time.

Sorry to say this but I think you're out of DIY territory.

 

jagv8

Thank you very much for the info. I will take a visit to my indy tech, with an open wallet!