Which scan tool can read individual cylinder misfire live data on the S-Type? I have several ELM327 adapters, and an iCarSoft. Many live monitors are available but not misfire monitors for each cylinder.

I've been chasing a fish bite misfire, only occurring when engine is hot under load at low RPM. No codes are being set in the ECM but the misfires are clearly there. Replaced all plugs and coils, no change. I suspect a faulty injector but it would be nice to know which one is the culprit before diving in.

 

UPDATE: I was finally able to get SDD/IDS working with an original Mongoose cable I bought a while back. Unfortunately, even IDS does not contain any misfire counters. Does anyone know a method to identify which cylinder is misfiring (in the absence of any codes) using only IDS and a multimeter? As a last resort, I suppose I will have to acquire a 2-channel oscilloscope and do it the hard way - probe the crankshaft sensor signal and use frequency math channel to see where the crankshaft slows down.

 

Something odd is going on. The PCM is normally very good at detecting misfires. It can detect ones you can't feel - and commonly does.

Yet you can feel them and it's not reporting them?

If so, the usual reason would be that one or more OBD monitors are unset (thus preventing codes from flagging) or not running CL (closed loop).

You can check monitors & CL/OL status via OBD.

Don't clear codes as that also clears all the monitors (as does loss of battery power).

 

I use an icarsoft i930 and go to the obd2 function. In it is the monitor data for all obd2 monitors including individual cylinders another scanner i know but well worth it getting your car specfic one. The one i have does jaguar and landrover to 2008

 

+1 on that!

Maybe the transmission is shuddering just a little bit?

 

i had a saga where the ecm detected no misfires but watching the misfire monitor i could see them. The big difference is OP already changed coils and plugs. Hope they were oem. The trans will react to misfires sometimes before the ecm. Tough to diagnose when there are no codes. I learned the hard way. Possible vacuum leak. Not too familiar with the 3.0

 

Essentially, many misfires cause tiny jerks and yes those can upset the trans.

 

The misfire only happens in a specific scenario as I explained. Typically, a single fish bite miss under load at low RPM in closed loop with the engine fully warmed up. It never happens in open loop while the engine is cold. Car switches to closed loop normally. No CEL, all OBD monitors are set and no permanent nor pending codes are stored. There must be many misfires before the ECM sets a code.

I already own the iCarSoft and it works well. There are many live data monitors but for the S-Type, there are no live monitors/counters for misfires, let alone individual cylinder misfires.

No, this car has a manual transmission which rules out any shudder typical for torque converted slushboxes. A single misfire happens in any gear under load (WOT) at low RPM (under 1500 RPM). It is very noticeable, fish bite like.

All coils are brand new, Delphi brand, as the OEM Denso's are no longer available. 99.99% confident the issue is not with coils. 100% not a trans issue, this car has a manual 5sp Getrag gearbox. Vacuum leak is a possibility but unlikely as my short-term and long-term fuel trims are perfect at near 0% on both banks. How did you watch misfire monitors? What tool?

 

UPDATE: Making some progress! Still unable to pinpoint to one cylinder but it looks like the root cause may be the battery and charging system. After a full battery charge (13V at rest) with an external charger last night, I didn't experience any of low RPM misfires today. I tried many times to make it miss by lugging the engine and it didn't happen even once. This is after many months of getting the low RPM misfire on my daily commute.

I always thought the charging system was a bit suspect. But it never caused any electrical issues or codes so didn't pay much attention to it. According to JTIS, the alternator should start at 15.3V and then drop to 13.6V. My OBD scanner reports 14.4V after startup and it drops to 13.1V after ~5 minutes and it stays there. This seems insufficient to keep the battery fully charged. Even after a long drive, the battery voltage is only 12.5V at rest and 12.2V with ignition on. My hypothesis: It appears that this state of charge is insufficient to meet the demands of the ECM in the specific scenario - hot engine (meaning reduced charging voltage), low RPM (low amps from alternator), WOT (high ECM power demand), causing a misfire.

I will be putting my battery on the charger every night for a few days to confirm this actually fixes the problem. If confirmed, what (if anything) can be done to fix this? Is my alternator behaving normally or not? Do I need a new alternator? Possible bad ground? What voltages (high/low) on the OBD scanner is everyone else seeing? For full disclosure, battery is 2 years old. Test "OK" with my rudimentary tester. I will get it tested with a professional tool.

 

Typical "professional" tool is outdated.

These cars with COPs (coil on plugs) need a very fast high current. Only a battery can react that fast. The alternator is great (or should be!) with charging over longer periods (i.e. not spikes of millisecs).

12.5V is low but not awful.

I still do not understand why the PCM isn't flagging misfires if you can feel them. Normally it's the opposite! (You can't feel them but it can.)

 

Ooh, an excellent observation. By any chance have you also noticed any fault messages for the handbrake, cruise control, or DSC system?:

https://www.jaguarforums.com/forum/s...attery-193787/


Your voltage readings do look a little low, but I'd repeat the test with a regular voltmeter at the battery. IIRC, the OBD connection is at the end of a long branch circuit of marginal wire size. With normal electrical loads on the rest of a branch like that, it's not unusual to see the voltage a smidge low. I'd test directly at the battery to be sure before condemning any components.

What kind of battery tester are you using? I have two. One is an old-fashioned resistive load tester, aka toaster, an ancient artifact similar to this one:




It works great, but you must be aware of its limitations. The battery must be fully charged, for example.

My second tester is an ANCEL BA101, which set me back maybe all of $40 on a popular online vendor named after a particular South American jungle:

https://www.ancel.com/products/ancel-ba101


This little marvel is slicker than a toddler's mitten during a Minnesota winter. It does some electronic wizardry to test a battery's overall health, not just state of charge. I highly recommend one, or a similar product. I have several vehicles and I'll test all batteries about twice a year with both testers.

If the battery is not getting a full charge from the alternator, one possibility is excess AC ripple from the alternator. All alternators put out a choppy supply instead of straight DC, and the battery acts as a giant capacitor to help smooth these normal ripples. You can have a bad diode (in the alternator) causing ripple in excess of what the battery can smooth out. You can also have a defective battery that can't smooth out normal ripples. Or you may have a combination of the two. Our cars are especially suspect to this issue due to the distance between the alternator and battery. You wouldn't think it matters, but it can. The directions for most testers say to take the readings directly at the alternator, as the ripples tend to dampen out the further they travel.

If you have a tester like the ANCEL BA101, it has a special feature to test for excess AC ripple. Or if you have your charging system tested at an auto parts store, ask the kid running the machine to report the AC ripple. If he doesn't understand your request, just smack him and look at the printout. It's usually on there. If not, ask for somebody who knows how to run the machine as it is typically an automatic feature of the test machine you will find at any parts store.

 

i use the icarsoft i930. When it boots up a menu appears. I use obd2 diagnostics. Then it enters the system and shows a current status. I hit ok and another menu appears. I choose on board monitoring and from there i scroll until i get to the total misfire monitor or you can choose individual cylinders. The higher the number the more misfires has been picked up. It is not a one to one counter but an algorithim i have read. On my snap on modis i can see the monitors in real time as the counter goes very fast. The icarsoft is where i first saw and began diagnosis. Never set an ecm misfire code. Never

 

Perhaps the logic on the V8 ECM is different but on the V6 it takes a large number of misfires to trigger codes.

I have the iCarsoft LR 2.0 scan tool. I see a total of 90 monitors under OBD2/View Data. Unfortunately, on the V6, there are no misfire counters.

 

not familiar with that model. Does it have a menu item of on board monitoring

 

Not a great pic but this is from the icarsoft manual for your scanner. Number 7 is what you use for the monitors. It is accessed via the obd2 diagnosis function

 

So I gets to thinking. Misfires seem to be occurring at a rate below which codes are set. You could pull out your hair trying to get more details from the scanner, but maybe it is incapable of telling you.

Instead, what if you were to duplicate the fault conditions and drive long enough like that to set a code? For example, climb a long grade on a hot day at low RPM.

 

I looked through all the menus and misfire counters are just not there. I'm starting to think this is not the scanner's fault. It looks like the V8 ECM has more diagnostic features built in.
Interesting idea. My normal commute route in the North Austin area is totally flat so I may just have to visit "The Hill Country" to see if I can find a long grade!

 

In case uphill at some speed (maybe 50mph) causes more misfires it's nearly always due to coils.

 

there is no misfire counter until the PanPAG ECM came out in 06.

big doubt on battery voltage. these cars are not sensitive in any way, i once drove an s-type with a busted alternator for 3 hours. you have to drop under 11.8 while running to get a christmas tree and weird stuff happening

 

I had a similar problem with my car five years ago, or something. I took the car to a local mechanic and with his portable Snap On device he was able to check the car out in real time while I drove around and was able to pinpoint the problem pretty quickly. It didn't cost very much for him to do it and the problem was a pretty easy fix. It seems much better than buying a bunch of equipment that you don't have experience with. the Snap On device is probably more sophisticated than most too.