Random misfire (P0300 & others + sometimes no AC)

[Rob]

2004 Marauder, approx 180K, well maintained. She uses some oil, but not terrible.

I have been battling this for a while in my spare time which is slim. I’ve had my mechanic friend with the uber expensive Snap-On computer look when it’s been happening too. Car could be great for a few weeks then occasionally and randomly I’ll get a P0300 (Random Misfire) along with some stumbling on acceleration and idle. Sometimes this is combined with other codes. Sometimes not. SOMETIMES when it’s misfiring I have no AC.

My diagnostic ability is limited because it will usually "fix" itself before I get back home and I can't find the problem if it's running great in my driveway.

At random, my symptoms are, and in various combinations:

Drive great, misfire a little, get worse, then smooth out and be fine
Instant light on startup and drive like poop, or light on startup and drive like eh, but drivable
Driving fine for a while and suddenly misfire with light immediately
Driving fine for a while and a light and misfire many miles later or no misfire at all
Driving fine, misfire, park it, shut off, start up, and it’s all better…or not
Misfire, AC will blow hot for a while, magically come back
Fortunately I've never stalled out or been stranded because she always comes back like a Phoenix.

Over the last few months some codes that I recall have been:

P0352 – Ignition Coil B primary/secondary circuit
P0356 - Ignition Coil F primary/secondary circuit
P0305 – Cylinder 5 misfire detected
P0316 – Continuous misfire detected on startup first 1000 revolutions (Showed up a few times over a few days but not before)
….Replaced crank position sensor, then later got…

P0315 – Crankshaft position system variation not learned (This one has not come back since shortly after the new CPS)
This past weekend when I was replacing the coils and adding Granatelli connectors, I noticed a little oil in #6 hole so I did the cover gasket. In retrospect I realize I didn’t pull the plugs. Oops! But after I did the coils, it has some issues finding a good idle, but eventually settled down. Took it for a spin and drove AMAZING like it got a shot of adrenaline and I loudly whooped “She’s BACK!” Drove it for a couple days and all good. Big smiles. Happy dance. Then this morning, 5 min down the road, light, misfire, flipped it around and drove the Jeep to work with my head down in shame.

So to recap, replaced plugs, factory coils, few COP connectors had exposed/green wires so soldered and replaced and replaced cam cover gasket on PS, new PCV and hose. (The PCV to cam cover detents where the PCV turns and locks into the ‘grommet’ are a little worn so the PCV is possibly cocked a tad. Can’t find replacement ‘grommet’ part that bolts into the cam cover). Cleaned MAF & air filter. Did injectors a while ago when this first started. Techron a couple times in the past. With my mechanic's Snap-On, he's actuated/tested all the stuff he can like EGR, etc.

As my last act, I’m going to pull the plugs this weekend, again, and put in a new set of XP104’s. That way I can be 100% sure it’s not the COP/plug. Again. Kind of.

I haven’t ruled out things like the PCM or an intermittently broken wire somewhere and if this were persistent it’d be a different story, but it’s RANDOM, and goes away on its own. And coupled with the AC issue, I just don’t know. I've been playing with my various 4.6L's for something like 18 years so I know my way around the platform. This has me stumped. After years of fiddling with a seriously annoying problem, I’m about ready to call it quits. I trust my Jeep and Suburban more and I know FAR less about those vehicles.

Thoughts?

[Agent2006]

Age and brand of battery? If it's not a Motorcraft and if it is 2 years old or older, then....these days it is highly suspect....

Bad ground is the other idea.....

[Rob]

Diehard (Platinum?) and I'm not certain of the age. Few years. Terminals are clean and tight.

The obvious chassis grounds are good. Removed, cleaned, and re-bolted. Does anyone have a map of all of them? I don't think I missed any though.

I considered the battery but I have noticed no voltage drop, dim lights, or startup issues ever. Alternator is new as of maybe 4 or 5 years. I suppose I can have my mechanic put his tester on next week for giggles.

Also, I had a chuckle when I read this thread about batteries. They are all largely made by the same company, but I respect where you are coming from.

https://www.mercurymarauder.net/forums/showthread.php?t=72318&highlight=battery

[musclemerc]

Sounds like you already replaced the usual suspects. Dont spend another dollar till you do a compression or leak down test.

[Invective]

Bad ground is the other idea.....

With phantom electrical issues I also locate and clean every ground - always use dielectric grease afterwards. Unplug and replug electrical connectors and pack with dielectric grease. Intermittent tells me it isn’t a major failure (obviously). When was the last time the OP pulled the negative cable off of the battery for several minutes? (pcm reset). Always negative first - positive last and reattach in reverse order (negative last). Basics first, especially with a 15yo car.

[Rob]

Right, it's not a major catastrophic failure because it will drive for weeks just fine, the not.

Compression was done last year with no findings.

When I did the driver side cam cover I had to disconnect the three main harness connectors. I checked for anything untoward and they were good. I was going to do a dab of dielectric grease but it slipped my mind.

Battery has been disconnected and let sit, I dunno, hundreds of times over this whole diagnosis period. Every time I made a change. The last time was when I did the COPs this past weekend.

[Turbov6Bryan]

how much does a cam sensor cost for one of these?

All those previous codes are a wash once you correctly installed the new coils, replace the plugs and lets see how it drives once you have new plugs and coils, new cam and crank sensor.

I would look at the ground wire on the passenger front timing cover, make sure its grounded well.

Report back and we can try and help out. Do you have anyway to log this experience?

[Rob]

Tomorrow (Sat) is supposed to be a nice day so it's plugs and recheck grounds. Timing cover is first in the list.

Cam sensor is under $30 and I'll have one before the end of the week.

I did have a documentation plan. My cheapo Innova 3130 is only so good so I wanted the AutoEnginuity scan tool and Enhanced Interface for Ford-family (EI01). Yummy mode 6 data. My plan was to start to log data on my laptop literally every time I started the engine. I don't mind the investment in diagnostic tools, but phantom issues are not really scan tool level. Better than nothing though, unless anyone has a 100+ channel lab scope I can borrow for a few months.

Thanks everyone. You people are a very fine bunch. :nworthy:

[Grimrepairman]

Vaccum leak?
Could be dirty or sticking IAC or EGR.
Rubbed harness behind heads?
This is interesting, please keep us updated.

[Rob]

My findings on Saturday:

Tore into wire loom starting from PCM and moved outward. To my delight, all the connectors looked clean and wires were good. However, found totally sliced slightly larger red wire going to cruise control. Don't use cruise so not surprised I didn't notice. Soldered, heat shrinked and rewrapped it all. Why is there a black pin hole test plug on the cruise and another random wire? Plus an epoxied shut one from the PCM? Didn't get to the harness towards the back of the DS head but it looked ok with no chafing. I hate chafing, but there are creams for that.
Re-checked COP connectors for more bare wires. They all looked good.
Re-seated the Granatelli connectors to the COPs. Anyone else notice they like to pull out and remain firmly seated on the plug necessitating retrieval via needle nose pliers, and require heroic efforts and just the right angle to seat?
AGSF32WM plugs looked OK. New as of maybe 10K miles ago. No unusual fouling or red flags. Replaced with XP104 just because. Gaps carefully verified as identical.
PS timing cover ground admittedly looked rough. I was sure I checked it before, but clearly I didn't. The rest were removed and again re-cleaned for due diligence.
Found two slightly cracked rubber hoses. One was the ~4" rubber piece that goes from the intake to the hard plastic tube that goes to the purge solenoid. I couldn't read the numbers on the label to order a new one and the parts diagrams were vague. Anyone have that PN? Also the hose from the intake tube to the DS PCV grommet had a few little cracks where it slipped over the nipple. I didn't have the appropriate tubing in my stash of goodies so I wrapped some electrical tape around the offending areas. Neither hose looked particularly bad and it's more likely me manhandling them caused them to actually crack.
Started up. Ignition circuit H insta-light. Rough idle. Re-seated COP. Disconnected battery for a while.

Started up again. Better idle, still not smooth. Inspected COPs. Thought I was having a plug blow out. #3 COP appeared to be pushing up and out and I had to push it back in like a hernia. Commenced to freak out. Shut off car. Cry in corner.

Saturday night:

Get super stressed thinking I'm having a blow out and look into Time-Sert. Held off clicking the 'checkout' button.
Sunday:

Caffeinate
Re-re-inspect all components. Clean the snot out of the plug holes and threads. (Anyone have a clever method of doing that besides a bottle brush and paper towel taped to a dowel?)
#3...I think it was the pressure of the squeezing bulging gasket that fooled me. When I got the car I noticed the PS valve cover has a couple bulging plug gaskets (2, 3, 4). Hack before me probably over tightened. Why?! They don't leak so I'm leaving them be for now. Makes changing plugs interesting because my plug socket sometimes gets stuck on them. Also, my PS plug cover has a mostly stripped bolt so it's not holding the COPs in/down tight. That was my fault on Saturday. Really annoying since that's the side with the migrating COPs. I will be retapping and getting that secured. I think it's the only thing holding in my COPs on the PS. Yikes...
Drove about 20 min to Dunks and back and Hallelujah! I don't think she's ever driven as smooth. No codes, smooth idle. Code scanner showed only the EGR and CAT left to learn. I had other things to do so I didn't want to be out too long.
Started car few hours later and....maybe little rough idle. No codes but didn't feel as smooth as before. Hung head in shame and put my tools away.
De-stressed by petting one of my hens that loves to roost on humans. She's like a lap dog.
I drove the Towncar to work this morning. Yeah a 4.6 that doesn't give me constant grief. :depress: Before I rely on her to actually get me from point A to B, I want to thoroughly test close to home and make sure its actually a problem and not me being neurotic and way too sensitive to normal still-learning PCM weirdness. And I want to make sure that cover bolt is re tapped because that's really stressing me the way the cop wanted to wiggle out.

So, my take away is, I'm just not sure. The questionable vacuum hoses could have been a factor, but that it would ride great, take a dump, then go back to business as usual all in the same drive makes me think it was something else. I discovered a few issues that may be causing me grief NOW (bulging plug gaskets, moving COPs, and unfortunately stripped bolt that should be holding my COPs in that sort of isn't). But those threads were damaged on Saturday so the cover should have held those COPs down firmly all this time, thus a non issue? Yes, I want to replace the cover gaskets on the PS at some point, but I really don't want to because it's a super pain. Plus, it wasn't just the PS that was misfiring originally, unless a few occasionally misfiring COPs would cause a cascade even on the DS side? I don't know how sensitive the ignition system is but I always thought if one failed, then only ONE failed.

Also, can someone please tell me why my AC would sometimes blow warm when I was having a misfire? Is there some emergency system that causes the compressor to shut off thus alleviating additional engine stress when there is a misfire?

I realize I fired birdshot at the paper and hit the 10 ring, but I've had this kind of semi success before. I think everything's great for a few days, then not. I'm reserving judgment until the weekend when I can do some meaningful cruising and highway runs.

I suppose I could replace the EGR but I am not looking forward to that EGR nut and she misfires as much at idle as driving so I believe the IAC is a non-issue at the moment.


In the meantime, any other suggestions?

[BLACKMARAUDER04]

You might have a burned exhaust valve. If there is carbon buildup on the edge of the valve ( or the chrome / silver on the valve is blackened), when it goes down, it's not seating properly.
Those codes can come up because of this. I would get a leak down test on your engine. it may pinpoint the problem. My Silver had a burnt exhaust valve on #6.

[Mackdombles]

Your compressor will shut off during a misfire FYI. Ac will temporarily shut down

[Rob]

Ok good, so it is going into a protection mode and I don't have mysterious cascading electrical failures.

[Agent2006]

Suggestion: take the battery out of the Town Car and install it in the Marauder.

I don't have long distance diagnostic powers, in fact the ones for my own heaps in my driveway are pretty lame, but when I first got my LS1 Firebird, after a short time the thing would run fine, then run rough...then OK...like it was possessed. The car became that fun but crazy chick we all knew in high school, couldn't say goodbye ...

Replaced the battery ---purred like a kitten. Must have a been a loose cell plate, or something, could never get a bad battery reading from it, seemed to start just fine, but going down the road....:mad2:

Would be interested to hear the compression test results if you do that test...

[Grimrepairman]

I'm not the smartest guy ever, but I don't think a compression issue would be intermittent.
In my personal experience, intermittent means electrical.
Could still be vacuum related. May be worth getting a smoke test.
Your friend with the scanner should be able to actuate the iac and egr in functional tests.
If you're lucky, the misfire counter will point to a specific cylinder. If not, try a contribution test.
May be worth trying to back probe the cops and checking voltage under load.
If you want to get really fancy and have access to the equipment, can back probe the cam and crank sensors and check that they are triggering correctly.
Kinda want to get my hands on it, but I'm at least 3hrs away.

[justbob]

A simple noid test to the cop terminals is an cheap easy test. My own car had cyl 8 misfire and it ended up being a kinked wire right at the terminal and the insulation looked perfectly fine. Couldn’t see it but the noid light easily spotted it.. Them wires are tiny.


Sent from my iPhone using Tapatalk

[Rob]

When this was first happening, after the usual suspects were check and replaced with no lasting results, my guy went through EVERYTHING and actuated it ALL. Literally the whole Snap-On menu, every function, every applicable screen. Nothing red flagged otherwise he would have addressed it. So maybe, lets say, the EGR wasn't sticking at the exact moment he was testing it. Doesn't mean it is 100% functional. He obviously caught the vehicle on a good day and all the actuating in the world would be moot.

A smoker, noids, and lab scope. Not too expensive. Can always loan the stuff out to folks in need too. My guy did all that in the beginning, but like I said, nothing was acting up AT THAT MOMENT. I'd need to have all this equipment in the car all the time and pull over at the first sign of misfire. Pop the trunk and it's like the MiB car but instead of cool shiny alien weapons, it's wires, boxes with blinky lights, and tools.

No harm in swapping the battery.

[ncmm]

and after the battery swap?. . .

[decipha]

Excluding any mechanical problem which I think you've ruled out
there is only 5 possible causes for your issues and they are as follow:

1> If RPM does not exceed 1500 rpm at cold start you could get false misfire codes
2> If cold startup enrichment fuel is insufficient (weak pump or dirty injectors)
3> Excessive oil in the intake manifold
4> Wrong oil filter (use motorcraft only)
5> Weak coil(s)

I am basing this on my 03 marauder which had the exact same codes and did the exact same thing. Mine was usually quick to set a check engine light on cold startup though and idle like poo.

btw, the autoenginuity scan tool was a waste of money. You could get a moates quarterhorse that has far greater diagnostic abilities. That's how I diagnosed and fixed this same problem on my car. Been over a year and hadn't had a problem yet.

[Rob]

Alrighty sorry for the late replies fellas.

SPRING UPDATE:

New battery - no change. The old one was dead. I was a bad boy and didn't start it all winter, and no trickle. Oops.

After the new battery, it ran pretty nice for around 50 to 75 miles. Tiny little shake on idle after a few min of running to warm it up, but not bad. Cleared fresh PCM jidders perhaps. All in all, pretty smooth idle and steady at around 600 rpm. Next morning, after about 45 min of driving to work (around 30 miles of a 40 mile trip) the light came on while still on the highway and at speed. P0300. No change in performance really. Cleared code in frustration en route. Started to drive home that afternoon, about 10 min and 5 miles on back roads later, same code. Cleared. Drove this morning, after a while code.

Still must register a serious enough error because the AC compressor is shut down after first code and it's getting warm out so it really sucks.

My next line of attack:
-Smoke engine. Again. Recommendations on personal smoker I can afford? I want to do it myself not have my mechanic do it.
-replace EGR (even though it's been actuated via snap-on tool previously)
-TPS? I notice the throttle sticks just a touch and I have to goose the peddle ever so slighty when it's closed sometimes. Gonna clean throttle and grease the cable/pedal.
-fuel filter, oil, filter (regular maintenance)
-Did old battery die because of a weird hidden ground? And no, before someone asks again, the harness behind drivers side cover is fine. I de-loomed it, inspected, wrapped and zip tied out of the way last fall. All the grounds I can find have been disconnected, cleaned, dielectriced, rebolted.

I'm due for MA state inspection by June 30th latest and they will fail with a light so she's gonna be grounded unless I can fix this asap. Not to mention I want my car working.



1> If RPM does not exceed 1500 rpm at cold start you could get false misfire codes
2> If cold startup enrichment fuel is insufficient (weak pump or dirty injectors)
3> Excessive oil in the intake manifold
4> Wrong oil filter (use motorcraft only)
5> Weak coil(s)


1> Engine starts normally every time. I dunno 1800 or 2k rpm rev? Whatever is normal.
2> Injectors are new as of a few years ago when the random light started. Haven't changed pump, but why trip code after many miles? No performance issues at low or high speeds. She moves well.
3> As I stated in my first post, the PCV grommet detent retaining bumps on the valve cover are slightly warn causing my PCV to cant slightly. It seems tight though. I will seal with RTV and wrap the snot out of it with electrical tape.
4>Filter is Motorcraft
5>Coils (Motorcraft), plugs (XP104), electrical connectors (generic but soldered and heat shrunk), and Granatelli connectors are NEW. See post 1.

[Agent2006]

according to http://www.myautorepairadvice.com/p0300.html

What Causes a P0300 Code?
Low Fuel Pressure
Vacuum Leak
EGR system malfunction
Internal Engine Problems (such as low compression)
Less Common Causes
Faulty Coil
Faulty Spark Plugs and/or Wires
Camshaft or Crankshaft sensors
Ignition module
Computer

Does your scan tool report fuel pressure as the car is running?

[Rob]

Alrighty, so the latest. Thought I updated this thread weeks ago. My mistake.

-Replaced EGR
-New cam position sensor
-Removed, inspected, and re-clamped some vacuum lines just because
-Cleaned MAF
-Oil, filter, fuel filter
-New Crankcase Ventilation Retainer (the thing the PCV valve 'clicks' into on the valve cover. Mine wasn't clicking)
-New crankshaft position sensor (I looked back in the records. CPS "may not" have been replaced since it wasn't on my mechanics slips. Swore it was. Did it again anyway.)
-Disconnect battery, sit, drive
-AC tested and recharged

Now it's several hundred miles later. Maybe 15+ cold cranks or more

Still getting:
P0315 – Crankshaft position system variation not learned
P0300 - Random Misfire

Still not right. Sometimes engine shakes a little at idle like I have lopey cams, sometimes a specific COP showing misfiring. Never the same COP. Swapping COPS does nothing. Sometimes she drives perfectly, as in: put a glass of water on the engine and no ripples. Other times like a giant poop.

I'm reading conflicting information on the "crank relearn" procedure. What is the drive cycle on this?

Pretty much fed up. Guys, I'm not new to these cars. I know them. New PCM? AT this point, I almost have nothing left.

Anyone in New England want car?

[EMAS]

From what I've read the crankshaft variation is learned during deceleration fuel cutoff when speed has been above 60mph. So you need to clear the codes and find some place where you can get it up to 60+, take your foot completely off the accelerator pedal and wait until the car slows down to 40 mph or below. Do it 3 times and it should learn that.

Instead of spending the big bucks on the AutoEnginuity system with the enhanced Ford package consider ForScan. OBDLink is a good communication device. Personally I use the MX as it will read the Medium Speed CAN that some of my newer Fords have but a LX will do everything that can be done on a Marauder. ForScan will give you almost all of the functionality of IDS, including Mode $06 and the ability to change some settings on some vehicles. The software included with the OBDLink will also give you Mode $06 for all brand vehicles.