I need some sage advice as soon as you are able. After multiple random misfires and Restricted Performance mode this what we tired.

1. replaced sparks and engine coils. noticed oil...
2. replaced gaskets a year later problem returned
3. replaced Catalytic converter

now we have only 1 misfire - cylinder 4 on the drivers side plus restricted performance mode all the time. the diagnosis from a mechanic is to rebuild the engine to reshape the cylinder. given the proposed cost and the work already done.. i am skeptical...

I welcome your thoughts....

thanks

 

I had a Nissan engine in the past the consumed lots of oil and always had smoke on start up. Occasionally I could find oil globbed on the end of a spark plug. As it turned out, a failing catalytic converter spit fine pieces of ceramic into the cylinder and wiped out the rings. This caused a weird lack of power and misfire until it warmed up. I don't know if this is what has happened to you, the catalytic converter replacement you listed just made me thing of it.
I ended up re-ringing the engine and honing the cylinders (basically a full rebuild) and it runs great now.

If you haven't already, I would start off checking a valve cover gasket. My 2.5l X Type had a small leak that would allow oil to coat the end of the coil and spark plug. Have you done any compression testing or checked codes? I think restricted performance has to be triggered by something more serious than a misfire(ie the computer has a code for something to put it in limp mode). Have you tried resetting codes and seeing if they come back?

 

You mention the vehicle is a MY2003; is it a 3.0 litre or 4.2 litre?

Did the mechanic providing advice perform a compression test of the cylinder(s)? If so, what were the results?

What DTCs are stored? Post them here.

 

Umm, condemning the engine because...?
No compression or leakdown check and he just says maybe rebuild it. For what's likely an external issue such as intake leak or bad coil, wiring to coil or any other problem.
I'd try another shop, just to have someone else have a look and see what they find. Throwing parts at a problem is usually expensive without results. In this case very expensive.

 

I know my engine is a V6 but like you had multiple misfires mostly bank 2 did everything plenum seals, plugs, coils, last thing I tried was a compression test??

Guess what one bank had low compression on 2 cylinders, did a valve clearance check those cylinders had no clearance on exhaust valves.

Don't scrap the engine until you have done the basics its even worth putting a vac gauge on the inlet it can help diagnose a load of issues?

 

Ben, thanks for your insight.
A compression test was done but with "no" results.
The valve cover gaskets were replaces with the 1st tune up 7-8 months ago.

 

NBCat, thanks for your response. Compression test was done but no results. Jaguar 2003 S Type 3.0.

 

ok i have an appointment this morning with another shop

 

What does 'no results' mean? No compression? What were the actual numbers per cylinder?

 

Mikey, according to the mechanic, he ran a compression test but did not get a result. As if to say that the compression didn't happen?

 

hmm... guessing he failed (*) to be clear.... but perhaps meant all was good enough.

(*) sadly happens too often, the problem I guess being that most owners wouldn't understand the results if told them so they aren't told them

(Like with fault codes.)

 

Have the shop performing the work list the compression values for each cylinder. If one or more is more than 10% lower, have them provide you with the compression values after a small amount of engine oil is added to the cylinder(s) in question.

Post the results here.

Before proceeding with any additional engine work, the tappet clearances must be checked on any cylinders reading low if the addition of oil has not brought the compression up.

 

The problem has been fixed. Rebuild is unnecessary.
#4 Cylinder coil was replaced and the ignition coil was replaced. no more limp mode and no more misfire.

Compression was tested #4 142 lbs the others were between 124 and 130.

Check engine light is still on because of codes P1647 & P182 were found in history as "soft codes" did not return after repair and test drive. thanks all for your input. did i miss anything?

 

Was the number four cylinder coil fouled with oil, or did it simply stop functioning?

The number of miles on the vehicle is unknown, but given the age, I hope the spark plugs were replaced.

It is probably best you do not return to the mechanic or shop that told you the engine needed to be rebuilt to 'reshape' the cylinder.

 

This is such a common problem: a mechanic that is either too lazy, too stupid, or too crooked to carry out basic diagnostic techniques. While I wouldn't expect every owner to actually be a mechanic, it would behoove them to learn the basics, These haven't changed in over a hundred years. Thankfully due this internet forum you've got hundreds of "bros that got your back!" Don't jump any conclusions without checking with this forum first.

 

NBCat,

my Jag has 157,000 miles on it. as far as i know the coil was not functioning even though it was replaced less than a week ago with the spark plugs during the Cat Converter job. I think the last mechanic that diagnosed and fixed the problem is going to be my first call from now on. Shop #1 did say that after a Cat job it may take some time for the compression to build up and he is guessing that if he kept the car longer it would have happened. I did not tell him that on the advise of a friend I had the oil changed with high mileage oil and I used a Lucas fuel treatment. could that have had an impact on the process?

 

Jag Forum is a great resource.
thx

 

Engine compression is not related in any way to catalytic converter function. Either something got lost in translation or mechanic #1 is an idiot.


High mileage oils are a band-aid that sometimes might help on engines that are leaking or burning oil. Yours does not reportedly suffer either problem.

Jaguar specifically warns against using fuel or oil additives- it's in the owners manual. Most products are of no benefit or can cause problems if misused.

Modern fuels and oils already have more than enough additives to keep the engine running properly. Adding even more is a waste of time and money. In this case, the difficulty was a bad coil. No additive will fix that.