When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My '02 V6 has been out of commission recently for the CrisisCavalcade™ so it's nice to have it back on the road. Repairs included new struts and a upper A-arm in the front end, a remanufactured transmission, coolant hose, and a new fuel pump. Prior to all this recent work, I was getting an intermittent P0301 code, along with oil leaks from the valve covers. I had the intake plenum off, and replaced all 6 plugs and coils with name brand parts. I found a good amount of oil collected in the plug wells, so thought I had found the root cause of the P0301. Turns out this wasn't to be. The same P0301 has returned very intermittently, plus I'm getting a little bit of rough running that wasn't previously present. Details of my previous work here:
Any suggestions for a plan of attack? The new rough running? I'm not ruling out a new coil bad from stock, or a bad spark plug. However, it's seems like very thin odds to get a bad new part and unknowingly install it in the same troublesome location. I plan to swap the suspect coil and plug to different cylinders in the other (easily accessible) bank, but I'm not holding much hope for that.
If not bad parts, could my recent work have induced a P0301? No evidence of a vacuum leak when comparing fuel trims at idle and 2500 RPM. No other codes, BTW. The rough running happens mostly at light throttle settings, and things are generally fine at higher RPM. Fuel trims, MAF, and fuel pressure are all looking good on my scanner.
In addition to swapping the coil and plug, I plan to smoke test all vacuum and crankcase breather lines. I previously did a smoke test after reinstalling the plenum, but that doesn't guarantee something hasn't failed since then. I also plan to watch the fuel trims while feeding propane or carb spray all around the intake plenum and manifold. I also plan to replace the PCV valve in case that is sticking. Although fuel pressure shows good on my scanner, I will also verify the reading with a mechanical gauge.
Any other thoughts? Is it worth swapping injector positions and see if the fault follows? Value of doing a compression test? If so, how best to do one with the plenum removed to allow access to the hidden bank?
Here's what Jaguar lists as possible causes for P030X codes:
Have you checked the wiring loom to the injectors? The loom connectors become brittle with age and sometimes don't provide a good connection at the injector.
Of course it's also possible the injector for cylinder 1 is not spraying correctly.
Have you checked the wiring loom to the injectors? The loom connectors become brittle with age and sometimes don't provide a good connection at the injector.
Of course it's also possible the injector for cylinder 1 is not spraying correctly.
Agree, check the connector to the injector on Cyl #1 - also with the oil leaking into the coil plug well you need to pull the valve cover and change the coil grommet on the cover.
Personally I'd change all the rubber plugs on both valve covers.
Finally, odds are high you could have a coil bad out of the box. P0301 (cylinder #1) will be the worst misfire code to contend with.
But do all of the above and all should be well again soon.
also with the oil leaking into the coil plug well you need to pull the valve cover and change the coil grommet on the cover.
Personally I'd change all the rubber plugs on both valve covers...
One step ahead of you. Already been done, when I pulled the valve covers to fix an oil leak. I had been getting an external oil leak, with the occasional drip onto the hot exhaust manifold. I also found lots of oil collected in the plug wells. I replaced the outer and inner seals, plus the grommets around the VVT solenoids. I gave the valve covers a good smoke test when done and all passed with flying colors.
Some progress to report. I had an hour or so free yesterday afternoon, without any ice or rain falling from the sky. I ran some preliminary tests with interesting results.
1) Fuel pressure is low as measured with a mechanical gauge. With my scanner, I'm seeing 55PSI engine off, and 40PSI running. This is normal, right on spec. My mechanical gauge showed only 32PSI with the engine running. I was skeptical of the gauge reading, so tested my gauge against two other gauges. Can't guarantee I don't have 3 bad gauges, but they were all consistent so I'm going with an actual fault present on the car. I've ordered a new fuel pressure sensor. Best I can determine, the existing sensor is reading high and the control module is happily commanding to match this feedback, totally unaware the actual pressure is low.
2) Gave the intake manifold and vacuum system a good dousing with carb spray. No change in fuel trims. Maybe just a smidge at the IMT valves, hard to say. I have new Jaguar green O-rings and will change them as a precaution.
3) Also discovered excess AC ripple in the charging system. Normally this means a bad diode in the alternator, but it can also be from a marginal battery. One function of the battery is to act as a giant capacitor to smooth normal voltage spikes from the alternator. As a battery ages, this ability drops off. The present battery is 7 years old, so it's getting up there. I've been thinking of replacing it anyway as a precaution even before these recent troubles, so am planning to pick a new one after work. I ran out of time to confirm the AC ripple with my oscilloscope, so will also do that if the weather cooperates. I'd like to test with the new and old batteries and see if there's any improvement. It's possible the alternator is also at fault, but I'm going to replace the battery first due to age and go from there.
Is low fuel pressure THE problem? Can't say for sure, but it's definitely A problem that needs attention. The AC ripple? Less likely to cause this particular issue, but also needs some love. Sometimes these problems are like peeling back an onion.
I like NBCat's suggestion about the injector wiring. I guess the coil wiring could also be suspect.
Another possibility to consider is that when oil leaks into the spark plug wells and works its way down the threads of the plugs, it can bake into the threads on the plug and the threads in the cylinder head. This is the ground path for spark, so any added resistance in this ground connection can cause intermittent misfires, especially if your charging system is not always providing full voltage to the ignition coils. It would be worth removing the cylinder 1 spark plug and cleaning the threads in the cylinder head with a brass-bristle bottle brush and throttle body cleaner or carburetor cleaner. If necessary, also clean the threads on the spark plug (I use a bench-mounted wire wheel taking care not to touch the precious-metal electrodes).
Another thought is that I have found that a localized air leak in the camshaft cover can cause isolated lean running and misfires in a nearby cylinder or cylinders. So in this case, a leak at, say, the VVT solenoid seal or crankcase vent (PCV) valve seal could allow umetered air to be inhaled into cylinder 1 past leaking valve stem seals.
And here is another bunch of thoughts I had:
Blocked injector? You could remove it and clean it with carby-cleaner (pressure input) while applying 12V or 9V to injector.
Fuel contaminated?
You had now quite number of issues with you S-Type / I assume you did not drive much with it lately - thus: How old is the petrol in the tank? Do you know that petrol can go bad? In extreme cases already after 3 month. The effect of bad, old fuel on my Fairlane NL is always that it kills the fuel pump due to the glue-like consistency of the petrol. And when the electric motor in the fuel pump is glued solid, there is no pumping action anymore. This is just to describe, who bad old fuel can be, I am sure it can also stuff up other components, like e.g. the injectors, "Glue" in those little openings would be very bad.
And I take it you just swapped the cam-cover gaskets? As Don wrote, a small localized leak in the camshaft cover can cause localized lean running and misfiring. So, even if you have now new cam-cover-seals: Assuming that your '02 cam covers are possibly the same fail-design as on my X204s: Are your cam-covers also made from Magnesium? Magnesium is self-destructing in the engine in the vicinity of Aluminium and steel: Galvanic Corrosion! Did you thoroughly check the cam-covers, to see if the cam covers are still in one piece, with no "mouse-bites" off it missing?
PS: Actually, scrap my last thought: I can't see how an air-leak in the cam-shaft area could have an effect on just one cylinder, and not the others next to it: The combustion of the fuel/air mixture takes place "one story below"...
Last edited by Peter_of_Australia; 12-30-2022 at 05:17 AM.
Reason: added PS
Installed a new battery yesterday. I had a few minutes to test AC ripple voltage with the new and old batteries. Found lots of varying advice about how much is acceptable, anywhere from 50 to 500MV.
With the 7-year-old battery, I measured about 430MV. With the new one, the value dropped to 190MV. Depending which reference I'd use, these numbers were in a gray area although there was definite improvement. I was very careful to repeat the test conditions identically. No other parts were changed, etc.
Right away, I noticed the idle was MUCH improved. Previously, after a battery disconnect, I noticed the rough idle right away, so this improvement was not due to the relearning process starting over. I went for a quick test drive (5 miles?) and overall smoothness was also much improved. I had high hopes this had fixed everything. Visions of sugar plums danced in my head at bedtime. Alas, it was not to be. On the drive to work this morning, I still had a little bit of shudder under the same light throttle conditions, but I'd guess only 25% of what it had previously been. I'm still quite pleased with this partial improvement. No codes, even pending.
Although the new battery has obviously helped, it's probably just as well it wasn't the final fix. We all know I'd be insufferable, even more so than usual. Misfire code? Change your battery! HVAC problems? Change your battery! Ashtray stuck? Change your battery!
I should mention I ran out of time to physically check the fuel pressure last pressure. The new fuel pressure sensor is due to arrive today. If the weather cooperates, I'll install it after work.
Installed a new battery yesterday. I had a few minutes to test AC ripple voltage with the new and old batteries. Found lots of varying advice about how much is acceptable, anywhere from 50 to 500MV.
With the 7-year-old battery, I measured about 430MV. With the new one, the value dropped to 190MV. Depending which reference I'd use, these numbers were in a gray area although there was definite improvement. I was very careful to repeat the test conditions identically. No other parts were changed, etc.
More progress!
I don't know the "official" acceptable range, but I find that on most of the healthy systems I test, the AC ripple is less than 100 mV and typically in the 35-65 mV range, so at 190 mV, I would consider your voltage regulator/rectifier diode bridge to be borderline.
Here's my half-baked theory on the importance of low ripple, especially for older vehicles: the ECM, TCM and other modules have filter capacitors in their circuits to help smooth supply voltage ripple. But over time, the capacitors degrade and lose their smoothing ability. Electrolytic capacitors often have a service life of only 10 years. Given that the ECM relies on critical sensor signals that vary in hundredths and tenths of a volt, variations in supply voltage might cause the ECM to misinterpret signals from the TPS, ECTS, MAFS, HO2S, IPS, EOTS, EFTS, CHTS, FTPS, IATS, etc. With ripple of nearly two tenths of a volt, perhaps your ECM is not always able to optimally manage fueling and timing?
93SB (01-07-2023),AD2014 (01-07-2023),EssOess (01-07-2023),kr98664 (12-30-2022),MountainMan (01-12-2023),XJRay (01-12-2023) and 1 others liked this post. (Show less...)
I don't know the "official" acceptable range, but I find that on most of the healthy systems I test, the AC ripple is less than 100 mV and typically in the 35-65 mV range, so at 190 mV, I would consider your voltage regulator/rectifier diode bridge to be borderline.
Agreed. I plan to revisit my work this afternoon if the weather cooperates.
Part of the problem may be operator error. The oscilloscope I used is a fantastic toy, but I don't need it very often. When I do use it, I find myself fumbling around for the first few minutes trying to set things up. I wouldn't be surprised if I hadn't used the best setting, or something like that. For the values I recorded, I am treating them with a bit of healthy suspicion. But I was very careful to keep the test conditions identical with both batteries. There definitely was an improvement, with both the values and engine behavior. I'm thinking of repeating my test with my Fluke 83 digital meter, as that may give more predictable results. Could be the new numbers are fine, and the scope was being too finicky.
Originally Posted by Don B
Here's my half-baked theory on the importance of low ripple...
No, no, not half-baked at all. Makes perfect sense to me. I found myself hoping AC ripple was high and was skewing the feedback from the fuel pressure sensor. I was thinking of testing this theory by comparing scanner PSI to a mechanical gauge with the engine on and off, to see if there's a difference with AC ripple completely out of the picture.
When it comes to smoothing AC ripple, the long cable run to the battery in the trunk doesn't help, either. Most references suggest measuring AC ripple directly at the alternator. Here's one example from Fluke. See page 5, figure 4:
With my Fluke 83, the AC ripple measured 185MV. Turns out the scope reading was accurate. Still not sure if 185MV is considered acceptable or not. I played around and compared the fuel pressure signal to a mechanical gauge. The scanner display was still reading high (40PSI) compared to 30PSI actual at the gauge. Engine on or off, no change. I even disabled the alternator field by pulling fuse F11* under the hood and then ran the engine. AC ripple dropped off to 3MV, basically nothing. Same results.
I replaced the fuel pressure sensor. Kinda tight back there, but doable. The bottom bolt was tricky to handle. Once loose, remove it with a magnet. To install, tie a thread to it. Once started, pull the thread to break it and finish tightening the bolt. You can expect to drop this bolt, so don't risk losing it.
With the new fuel pressure sensor, the mechanical gauge now showed the correct 40PSI to match the scanner value.
With high hopes, I went for a test drive. Alas, still not better. Got the occasional light chugging and P0301 eventually returned. Not sure how long the relearn process takes, but I've driven 30 miles with 2 cycles, with only minor improvement. I'm thinking of disconnecting the battery to speed up the relearn process, but not holding much hope. If the weather cooperates, I may even try a short test drive with the alternator disabled, to completely rule out AC ripple.
Next step is to do a good check for leaks with carb spray and a smoke machine. After that, I guess it's time to dive under the intake again. It's actually not that much work to pull the foolish thing, but it still irritates me. If I don't find anything obvious, I'll swap the injector, coil, and plug to different cylinders on the other bank.
*With fuse F11 pulled, you'll also get fault codes for the heaters on all four O2 sensors, so don't be alarmed.
Been hemming and hawing on this one. What is the best way to do a compression test? That annoying intake plenum has to be removed for access to cylinders 1-3. No way to run the test with the engine warm.
Yes, there is no practical method to conduct a compression test on the 3.0 litre unit with the engine still warm.
Remove the upper inlet manifold and use a small amount of oil in each cylinder whilst conducting the compression test. Although, I'd be surprised if low compression in cylinder one is the cause of the misfire.
Have you used any Techron or other fuel system cleaners to help injector performance?
That annoying intake plenum has to be removed for access to cylinders 1-3. No way to run the test with the engine warm.
A cold compression test would be better than nothing. If you have five cylinders with 160psi and one with 100psi, that knowledge could potentially save you a lot of hassle and wasted time and money on parts you don’t need.
Normally, it would be a no-brainer to do the compression test. It’s only the awkward intake that is pushing you away from the desire to do it.
Battery disconnect to force a learning reset was no help, but not surprised.
Stopped ten miles from home and disabled the alternator by pulling the fuse for the field. No change, so I’d say that rules out AC ripple causing trouble.
Stopped five miles from home and reinstalled the fuse. Only codes were for the O2 heaters, as expected. Had to punch the gas to get back into traffic. Maybe 3/4 throttle until up to speed. And then the engine ran beautifully all the way home. What in the Wide World of Sports is happening? As the man with no legs said, I’m stumped.”
A relative compression test uses starter motor current or relative inter-cylinder crankshaft speed to measure the compression of all cylinders, so the intake plenum doesn't have to be removed. I don't know if this is true on the S-Type V6, but the crank speed test can be done very easily with a scan tool. On others, you need a current clamp and an oscilloscope with relative compression test capability.
93SB (01-07-2023),AD2014 (01-07-2023),kr98664 (12-31-2022),MountainMan (01-12-2023),NBCat (12-31-2022),XJRay (01-12-2023) and 1 others liked this post. (Show less...)
12-28-2022, 11:03 AM
P0301 Plan of Attack?
