misfire
 

My 2001 s type 4.0 has developed a misfire. It is not noticeable until the engine is completely at normal operating temperature. I have had it analyzed at two different repair shops, one of them specializes in European cars.They could not find any codes to indicate the problem.It is most noticeable at idle in gear but also at approximately 2500 rpms. It is intermittent and most of the time the engine runs smoothly.The car has 56,000 miles and has never been tuned.Maybe the Jag dealer is the next place to take it unless I can locate the problem.
I will appreciate any suggestions.

Are there no codes? Not even pending ones? (Get an OBD too with live data and check for yourself, they're cheap enough.)

misfire
 

Thanks for your response.
Both repair shops said they did not see any codes.I probably will order an OBD2 code reader as it will help in this and future problems.Unfortunately I am 79 and can't do much work on my car .I sure miss the days when I could do just about everything a car needed. However those were the days of carburetors ,distributors,points and condensers.I owned two cars with hand cranks,a 1928 Dodge with rumble seat and 1930 Chevrolet.

Either purchase a COP tester or possibly one of the shops have one. Since the misfire is happening upon full warm up - have the coils tested then. The COP tester will isolate even an intermittent misfiring coil.

I have had two instances of an intermittent misfiring coil under load that had no OBD codes associated (pending or constant) but was immediately picked up by the COP tester.

misfire
 

Bought an OBD2 code reader and read the codes on my SType.Actually,I did not read the codes as the reader indicated no codes stored.
It still has an intermittent miss at idle but speeds above idle ,the engine runs very smooth.
I will take it to Jag dealer if the misfire continues at idle.
Thanks for the responses.

Do not overlook a Cat conv. that may not be functioning at peak. Hard to imagine that you do not have codes.

Try a quick and easy test- go about 10 miles and hour and then do 2 quick 3 seconds pops to the floor on the accelerator and see what happens or if you get a flashing cel.

Just a suggestion based on recent problems of mine.

Tom in Dallas
05 S-Type 3.0 76k

misfire
 

I did the two pedal to floor acceleratopn tests for approximately 3 seconds each.No flashing lights or light of any kind.Car accelerated smooth and very fast.It did have the misfire at idle when I got home.I will take it to dealer soon and let everyone know the results.
Thanks for the responses.

It was just something found that was a quick force test. Good then. Hard to believe you are getting misses and not even pending codes. Are you looking for those or just hard codes? Whatever you do, do not erase any info with your reader A good Jag mechanic will have the proper software and can look at all sorts of info we cannon and can even see the number of misfires on each cylinder.


Have you run it at a warm engine at idle and and at 2500 rpm and looked at fuel trims (if your reader can do that?)


Tom in Dallas

misfire
 

Took my 2001 S type 4.0 to the dealer today for a diagnosis of the misfire at idle.
Dealer said that it had no codes and gave me an estimate of $1,600 for new coils and plugs.They charged me $107.00 for the diagnosis.The service man and mechanic said to drive it until a light comes on and then they can read the code.I asked if it would harm the catalytic converters to drive it.Their answer was no.Said it would have to have a very bad miss and be driven for a long time before any damae the cats.
I have taken it to three shops and all have said the same.Apparently they cant diagnose a problem unless they can read a code.Alternative is to spend lots of money and hope they find the problem
I think I will continue to drive it until I get a better diagnosis than I have had so far.
I will inform you when and if I solve the puzzle.

My previous Jag was a 2001 S type 3.0. Every time I had a misfire it did NOT throw any codes. Replacing the bad coil each time fixed the problem.

The car was under Jag extended warranty so I had to pay a deductible and down the road I went. They would only repair one coil at a time due to warranty rules.

I don't know if you have replaced any coils but with the car being around 14 years old you might bite the bullet and change them all at one time. On mine it seemed like I was changing one every few months until all were replaced.

Also change the plugs if you are at 75000 miles or over. Try to buy OEM coils, if you can and change them yourself or get a independent shop to do it.

Buying the coils yourself and taking to the mechanic will be cheaper as well.

Possibly a vacuum leak.

This is nuts and typical of the liars at the dealership.

They have software that can read the "backdoor" of the system and pull up misfires /voltages/ ohms on every cylinder- even if not enough to feel or throw a code.- as cars have some level of misfire all the time. The idea of coils and plugs would be $1600 is a silly as a brake job on the s-type that the dealer wants to charge $1600 for. That would give them about $1200 labor and still profit on parts for a 45 minute job.-

I do not know about the 4.0 engine, but do not think anything close to the manifold has to be removed as on the 3.0.

Do you get a flashing CEL at all?

Do not discount that you have a short or crimped wire as I did. Have you ever gotten a CEL and do you have any pending codes or even own an ODB scanner. Even a cheap one from Harbor tools is better than nothing.

Do yo hear any pre-detotantion in the engine?

Do you smell any gas or exhaust. What is pickup and mileage like?

Remember that coils can test fine, but under load might not preform correctly. Could even be dirty fuel injectors or water in or around coils and plug, heats up becomes steam, can't escape and goes back to water.

The dealer should have been able to test for a vacuum leak with a smoke machine or just running the car at idle and then 2500 rpm and see the fuel trims and know if there was a leak. I would not trust the dealer anymore than Bernie Madoff.

Tom in Dallas

Plugs not due till 100K on 4.0, are they?

Doesn't sound at all like plugs anyway...

Does not sound like plugs unless there is oil or water causing a problem with contact.

They say they are not due until 100k, but at 76K with high maintenance, mine were a black mess (not my problem) but away they went.

Tom in Dallas

But yours is a 3.0 I thought, with different lower-life plugs.

Yes should check plug wells but that's essentially to check for coil damage not plug damage.

yes- mine is a 3.0, but jag dealer (when I was under extended warranty) said they did not need to be replaced until 100k. Mine were and are now the NGK Laser Iridium Spark Plug.
Sometimes you can strange ohm reading from plugs, but I really do not think it is oldmaned's problem. I am suspecting something like a weird wire problem.


Does he not have a slightly different version/level of the ODBII system than later models? I still cannot belive that the dealer could not use their software to get behind the front part of what we see. Perhaps he did and found nothing, which might rule out a number of normal things.

Tom in Dallas

misfire
 

Thanks for the responses.
The invoice from the dealer today says:connected SDD and checked for codes-none present.
I had a cel light but it was a thermostat code and I had the thermostat and housing replaced for approximately $700 and no lights since then.
Car accelerates and runs normal,except when idling and occasionally misfires at very low speeds.No gas or exhaust odors present.
I bought an OBD scanner and checked for codes with the same results---no codes.
Car has 57,000 miles and has actually been over maintained as it is not driven frequently.My wife loves this car and wants to keep it forever.I haven't noticed a change in MPG but haven't checked it to see if their is a difference.
Thanks again for the responses and I will appreciate any suggestions.One of the repair shops did state that they checked for vacuum leaks and did not find any but not sure how they performed the check.

V8 only. Your dealer was wrong. V6 models are 70K miles as per Jag maintenance sheets.

I was able to get my hands on a full set of OEM coils brand new for $300 and another $60 for plugs. Replaced them myself and haven't had a problem since. My issue started out just as you described and eventually got so bad it would cause the car to stutter and shake at 50mph.

About 50mph uphill seems to be a harsh test

The 4.0 and original 3.0 (pre-2003) have a different OBD system (PCM is Visteon) via SCP (aka J1850 PWM). Later cars have Denso via CAN/ISO. Doesn't matter with most OBD tools but some cheap ones don't like something about the Visteon. But they tend not to communicate - they don't wrongly say no codes.