I’ve been researching for weeks. Haven’t posted because i’m doing everything that could possibly be suggested. But maybe not and now we are here. I have consistent cylinders misfiring. 1,3,7. Occasionally an even numbered cylinder will miss as well. Plugs new IFRN10 NGK. Coils have resistance. What’s the correct reading for ohms? The first 2 pins if anyone knows? Also have a P0355 misfiring coming from ecm primary or secondary from coil ect. with a P0316 all misfire related. And the occasional P193 fuel pressure. This is the 3rd sensor all give the same code. With all those codes related help me rule out. Fuel pressure ranges in the 50’s sometimes 40’s which is about right. Compression is all even. i even re torqued the head as i just recently had it off about 500 miles ago so i figured it had its time to stretch bolts and maybe coolant was leaking through cause the misfires and overheating. Along with a combustion smell in tank from head gasket i believe! Don’t quote me yet need to do the test.

Overheating is fixed. I read an article here of a guy who had the same problem misfire wise and understanding the fact the cats are really close to the combustion process may fail. Also all misfires being in the same bank all or almost all cylinders. Now he never mentioned if everything still ran smooth because mine does there is no rev limiting, if i put my hand back there or rev its constant no break ups. But his issue was a melted cat trapping the exhaust from leaving the engine causing the misfires. He took his O2 sensor out and said voila done deal fixed.. I did that and all i did was created an obnoxious exhaust leak. When i drove like that i did have no codes tho.. but it drove bad.. so was hard to tell. Usually if i turn the car on the ecm cycles after 2 mins it will reflect problems and throw codes. Another thing after that 2 mins if i don’t put it in drive it will go into RP. even with the 02 sensor out i let it idle in Park for 2 mins and it still went to RP. If i drive normal then mash the gas, immediately RP. I’m constantly resetting this car to drive it. The ole battery restart. Also always re calibrating my throttle body i swear it was never a problem until i read people going on about it. All the times after i didn’t do it and started car it was fine. I saw that and ever since have throttle issues if i don’t do it, tell me how that works. Anyways...

i need help guys what can i try

 

Anyone there ?

 

Your dense lengthy text is hard to read and leaving out digits does not help. Getting some of the details wrong also does not.

You need a COP tester, forget using a meter.

It should be no surprise that you need working O2 sensors in the correct place.

I got lost trying to tell if you've followed other posts for the codes and the workshop manual likewise.

 

From the workshop manual, P0355 will only be caused by the following:

Ignition coil open/short circuit.
Ignition coil insulation breakdown.
Damaged harness.
Connector pins bent or corroded.
Damaged ignition circuit ground.
Damaged engine control module (ECM).

Have you worked through the pinpoint tests in the workshop manual including step 1 in Pinpoint test A 'Replace the suspected faulty coil with a good one.'

Here is a link to the workshop manual: http://www.jagrepair.com/images/Auto...M-Workshop.pdf

Mellow

 

Yeah, we're just hiding. Sorry, but the start of this thread sounds like you're throwing a bunch of frantic Hail Marys, in desperate search of a quick fix. I hate troubleshooting with an eleven-foot pole. When I saw your comment about driving with the O2 sensor removed, um, well... Let's just say I've never heard of that before, let alone to consider that a valid troubleshooting technique.

If worried about a potentially clogged cat, there are specific back pressure tests you can do. I'd put that way down on the list of probable faults, though.

At some point, you'll have to just systematically work through some normal troubleshooting. Follow the fault codes and do exactly what the workshop manual calls out before convincing yourself of some exotic fault.

Have you tried swapping coils between the good and suspect cylinders? If the fault follows the coils, then you'd know they are bad, without having spent a dime for troubleshooting.

Did you ever resolve the compression question? From your other thread, you said compression was down around 100-120psi. That can't be normal, is it? Does the supercharged engine have such low compression by design? Can anybody else chime in on that?

 

Based upon a friend's 2003 XK-R (which is in really good nick) the compression for the 4.2 supercharged V-8 should be in the range of 160-165 PSI. 100-120 PSI is decidedly not normal for an engine with a compression ratio of roughly 9:1...

 

I was trying to let everyone know what i have done and answer all the questions i know you all would throw at me. If i checked this, checked that, ect. Yes i have the electrical guides because of my 250amp mega fuse short last week. i’ve been studying it.

Yes i have new coils, i’ve gotten new plugs. Swapped around and it doesn’t make a difference. The same cylinders are consistent. Cylinders 1,3,7 and again every once in a while and even bank cylinder will miss as well.

The compression i’m still waiting on an answer for. I’ve read in the manual that it’s supposed to be 160psi i believe which i don’t see it being. Mine are consistent at 120. My 7th cylinder was at 90psi because i repaired a dropped valve seat and didn’t fix the rings. It is now at 115psi with some engine restore liquid which really did the trick and the fact the remaining cylinders only jumped to 121/122 at highest 120 is my number and my buddy’s supercharged motor on his 05 str.

With the new info on the p0355 code you posted for me i will started checking grounds and my ECM which i believe it may be.

 

The reason why I mentioned the O2 sensor was because a gentleman on here have the same problem with the same cylinders misfiring all on one bank he figured out that it was the catalytic converter that was clogged so he said he pulled the O2 sensor in the car ran like a dream if you searched it I’m sure you would find it it does not make sense to me but I will post the link so you guys can read ithttps://www.jaguarforums.com/forum/s...arms-up-63446/
i have those symptoms as well so it’s hard to tell. After a battery disconnect all is good. Once the computer cycles and starts to realize that it has faults it will then throw the codes. No matter what if I mash the pedal at any time in any mode I will get Restricted Performance. Also the check engine light flashing indicating misfires and that the cats could be damaged I get a lot of as well I’m sure because of the misfires but I figured this car has overheated multiple times in the past which is why the valve seat dropped and it’s been miss firing for a very long time that maybe it was a possibility.

 

https://www.jaguarforums.com/forum/a...ajv8-specs.pdf

 

180psi????? doesn’t say for what variant. There is no way. if that is the case what could be causing my STR to be running 120 EVEN across the board ? I searched for compression numbers no one likes to post them.

 

wait sorry ... that’s the wrong engine. 3996cc displacement the STR is 4200cc or is it. someone educate me

 

After reading all the posts. If your car experienced over heating, and as you mentioned you had to replace the head? or gasket? Then very likely you got coolant into the cat. If you did, that would almost surely plug it, and could very easily cause most, if not all of these symptoms. That could also be the reason removing the O2 sensor makes a difference, because the exhaust now has somewhere to go, and it is not backing up into the engine. Kinda like shoving a potato in the tailpipe. The car won't run with a blocked exhaust. My guess is that all the miss fires are on the same side as the head? or gasket? that was replaced, and the cat is plugged. That's my best guess. Hope it helps.

Jack

 

I am pretty sure that 180 PSI is for the normally aspirated variant with a 10.75:1 compression ratio. Yours is 9:1. As I indicated in my post above, my friend's Supercharged 4.2 runs in the low 160s in terms of an actual measured compression reading.

 

The old gasket was good and fine. Only removed the head because the 7th cylinder dropped a valve seat. Yes i understand that that is simple mechanics. I mentioned by removing the O2 sensor all it did was create an exhaust leak. So i was try to reference the link i posted of the gentleman who had the same issue. I don’t understand how his car ran “perfect” by removing the sensor. As for codes i have to double check if it still throws them with the sensor out. So with the car normal if i turn it on and don’t touch it for a couple minutes it goes into restricted performance. When I took the O2 sensor out I started the car let it idle and it did the same thing went into restricted performance. When I restarted it and then took it for a ride I did not get any codes but I’m also not sure if I drove it long enough either and I didn’t want to drive it any longer because of the exhaust leak it sounds obnoxious and there is no performance obviously. I’m beyond this. I’ve tried everything. Swapping coils the problem doesn’t follow it stays same cylinders. It’s 5 cylinders usually but there is a main 3 which are 1,3,7. i know my car isn’t running on 3 cylinders even 5. So they are working just randomly or weakly.

 

So the 7th had a compression problem caused by a valve seat.
1st question, did you have the same or indeed any fault codes before the mechanical fault in the engine?

If not then you need to start to re-trace the steps you made repairing the valve seat, including visual inspection of all the wires you moved and even checking you have the the cam shafts correctly timmed using the cam shaft setting tool 303-350. (Or if you dot/scratch marked evertything, as I probably would, that they all line up.)

Use the workshop manual and work through each stage of each recomended pin point test. This is what they would do at the dealers.

Mellow

 

Yes they were there. No this engine is clockwork to me. I’ve taken this engine apart 10 times or more down to the block. I know every bolt secret and trick to tearing down and rebuilding this engine. Timing is not the issue. Cams are timed valves have been adjusted and gapped properly to spec. Mechanically the engine is good. Electronically that’s a different story.

 

In the kindest, gentlest manner possible, I'd have more confidence if you had successfully rebuilt this type of engine 10 times, and those 10 vehicles are out driving around with no issues. Unfortunately, all we have at the moment is you've torn down and reassembled this particular example 10 times. For all we know, there's some unforeseen issue causing a problem, and this same oversight has been repeated 10 times.

I'm not very familiar with this engine, but I can offer an example from a different type of engine. On older engines with conventional timing marks on the crankshaft pulley/harmonic balancer, it's possible for the inner rubber core to slip. This causes the timing marks to be inaccurate relative to the crankshaft, but this is not obvious at first. On other forums I frequent, I've seen this trip up many people, regardless of their experience level.

The low compression across all cylinders makes me wonder. There are many variables that can skew a compression test to read low. For example, a low battery or a tired starter reduces the cranking speed, which can give misleadingly low numbers. As an aside, I've been taught never to condemn an engine solely on a cranking compression test, but to run a cylinder leakdown test for confirmation. The cranking compression test is relatively quick to do, and if it passes, you're good there. But if not, spend more time with the slower leakdown test to be sure.

However, another possibility for low cranking compression is incorrect valve timing. The cylinders aren't able to breathe and compress the air properly if the valves open or close at the wrong time. This is one of those things that make me go, "Hmmm". Just thinking out loud here, but what if you had replaced the timing chains and the marks were inaccurate? You could repeat the assembly process 10 times, and consistently get the same erroneous results. I'm not sure how the cams are timed relative to the crankshaft, but is it via special marks on the chains?

While you're stewing on that possibility, I highly suspect you've got more than one fault active. The one that really grabs my attention is code P0355. See the explanation here, on page 35:

http://www.jagrepair.com/images/Auto...tos/P20003.PDF

This isn't just a generic misfire code, i.e. low power has been sensed from a particular cylinder. Those are codes P0301 through P0308. This is the computer saying I'm not happy with coil #5. This could be a wiring problem, but the most likely culprit, in my over-inflated opinion, is a bad coil.

Please note such a code would be totally separate from any possible compression issues. Even if your poor engine has zero compression but eight good coils, you should not have that P0355 code. You mentioned swapping coils around for troubleshooting, but did you move that one?

And just to be sure, please see page 3 at the same link above for cylinder numbering.


For giggles, please see this thread on an XJ8. The original poster had a long laundry list of fault codes, but one was P0355. He replaced that coil and all was good:

https://www.jaguarforums.com/forum/x...99-xj8-226755/

Important detail: The cylinder numbering shown in that thread does NOT apply to your car.

 

First I have to say that with your obvious skill set, this must be very frustrating for you. I know it would be for me as well. Do stick with it and please do not take any of the responses on here, my ones included as in any way patronising. That is not our intension, we are only trying to help you in any way we can.

As fault code P0355 this is for the coil on cylinder 5, not 7 where you had the valve seat problem, obviously the previous lack of compression on 7 has nothing to do with this fault code.

Have you change coil on 5 for a known good coil?

If so then just keep working down the list of causes, i.e. broken/damaged wires, damaged connectors etc.
I am sure that you know that it is not unknown that a damaged connector or wire could only just be making contact when static, giving the correct reedings on a meter, but when the engine starts to vibrate, or when the circuit starts to take power it loses contact. This could be hard to find.
The Jaguar recomended way to test a coil is to replace it with a known good one, not to try and get the static resistance reading from it as this can be misleading, as it may not show any differance from a good coil.

Mellow

 

When the chance is given i will get specific on my issues and codes as i know have been all OVER the place. Also to what i have done already.

Then en engine is apart again. supercharger valley hose bursted a second time because i didn’t buy another one. i simply repaired the second time by buying new fittings and clamps and sealant and created what was a fix that’s has lasted forever. Not sure where it bursted this time but that’s the main priority right now. When it’s back up and running i will do another compression test and give all trims for fuel ign spark load and codes as i constantly run the car with a scan gauge live display hooked up. Thank you everyone for your input and willingness.

 

I just created a new thread but being this is open if i get the answer first i’ll take it down. Being my compression problems and the head getting decked professionally and all the valves changed and springs changed everything changed and the seat dropped. Although i started i’m at 120 except for the cylinder that dropped seat. My local junkyard just equipped a beautiful 4.2 L naturally aspirated 2006 Jaguar. My next question would be is that head compatible to my car being it’s the same engine although I know maybe somethings may be different. are cams from my str compatible to it?