MisterMisfire

A plea for some expert guidance. I have danced all over the internet researching this and have looked over the Rennlist results that Google throws up. So, here are my car's issues:

All plugs and coil packs replaced 6 months ago. Now has a mysterious misfire. CEL comes on. OBDII showing multiple misfires, but it also highlights cylinder 6. Over the next few days the misfire migrates to 5 then 4, then 2 then 3. Had a local guy check it out. MAF needed replacing. So that was done. Oh, and the timing chain tensioner. But still the wandering misfire.

The CEL comes on and I have an OBDII reader and keep checking and clearing the codes.

Last week I pulled every plug - not one was at the regulation 1.1mm gap. So I gapped every plug and OMG I had my car back. Proper acceleration - I was thinking I'll lose my licence if this continues!

On my way back home CEL comes on. Cylinder 6 again. So I swapped coil packs 1 and 6. Still cylinder 6. So I swapped plugs 1 and 6 (1 pretty well never comes up as misfiring) so now the set up is coil and plugs from 1 and 6 are swapped and the rest are as they were.

Multiple misfires all over the place. I think there were 7 codes including the right bank running lean. And also the CEL flashes on hard acceleration so I am guessing fuel is making its way down the exhaust and messing with the O2 sensors.

So I swapped 1 and 6 back.

Wondering if plug in 6 is cracked so I bought a direct replacement and popped it in. Just got back from a drive and the misfire is still there but no CEL yet apart from the flashing when I accelerate hard.

I recharged the battery last night with my CTEK MXS 5.0 (did I mention that the LEDs on the comfort pack interior lights flicker?) so I know there are no battery issues. Alternator shows a steady 14 at all times.

But this damn misfire is doing my head in.

Any ideas. please?

Rod Croskery

I had this happen with my mother's Scion. Eventually in disgust I towed it to the Toyota dealer and asked him to fix it. $500 later the bill showed much testing and the replacement of one coil. It has run fine since.

MisterMisfire

Hey Rod. I am now tending to think it might be the Air/Oil Separator membrane or a vacuum pipe.

I had the car running earlier and tried taking the oil filler cap off. There was decent suction as I removed it and the car began to stall and misfire, and a load of codes came up on the OBD - exactly the same codes as when I run the car.

Normally on tick over the codes don't appear but when the car is in 4th or 5th and I try to accelerate then it complains, misfires badly and struggles to pick up speed. The CEL comes on and it also flashes to show the catalyst sensors are detecting something is up. This is why I think that the AOS membrane has a hole.

I have ordered a replacement from Russia of all places. I looked at the AOS unit and tried to prise the cap off but it is on pretty tight. I am waiting until the membrane arrives before I go for it proper. Meantime, tomorrow I will be hunting for vacuum leaks....

Rod Croskery

I'd still think coils, but what do I know? My only success diagnosing one of these was a couple of years ago when Ruby started to run very roughly while passing a minivan. I immediately diagnosed a driveshaft fault, did a Jimmi fix successfully, but still had a very rough-running Cayenne. My code reader blamed a misfire on #7. I looked at the price of coils and bought a pack of 8 from a vendor on Vancouver Island. #7 was easy to access, so I switched the coil and Ruby's ailments went away. So I did no more until today when I got energetic and did a tune up. Now it runs worse.

Rod Croskery

Add one more success to my record. Ruby had random misfires after a tune-up today. I kept switching old, cracked coils I had replaced with new ones (which proved to be 50% defective) into 1, 2, and 8 until I had three that worked. From this and the Scion mess, I can postulate that your plugs are fine. The high-priced mechanic looked at my re-gapped Scion plugs and left them alone. All of his efforts went into finding the single bad coil (6 months old, aftermarket from UAP) which caused all of the trouble.

Anyway, the Princess Auto CEL meter has proven correct every time it has identified faults on Ruby. This time it was P0300, 301, 302, 308. The 300 is a generalized fault. When I had fixed each of the others, but not until, the engine went from rough to a smooth purr.

What originally confused me during the Jimmi Fix misdiagnosis was how profoundly a single miss affects a Porsche V8. My son suggested that one missing cylinder confuses the O2 sensor and it thus affects the whole bank of cylinders. It's not the V8 from the sixties, which could run just fine with a plug or two not firing.

MisterMisfire

You know, you might well be right. I have been pulling the coil packs with my bare hands and the coil in cylinder 6 is flipping tight. So I have just ordered a coil puller set from Amazon (Prime is brilliant!) and I have got 4 coil packs left over from before. I have checked the primary resistance on them and they are all identical - 0.389 ohms - but I cannot work out how to check the secondary resistance because they are 4 pin coils.

Anyway, once the coil puller arrives tomorrow I will use cylinder 1 to check the spare coil packs and then start swapping them out with cylinder 6 which is my main problem one.

Air filter arrived this morning. I took the housing apart on my car and the one that is there is clean - car was service six months ago. So I will keep this new one until it needs replacing.

On another note, a previous owner put some after-market LED strips on the front of the car and in the process caused a fault with the side lights so that every time the lights went on a warning came up. So I removed the LEDs in the hope that this would correct the problem but it hasn't. Anyway, lights were fully off and when I started the car the side lights warning came up. Weird. And then the reverse sensors actually started to work properly which they never, ever do.

Electrical gremlins?

Rod Croskery

During my battle with the '08 Scion's coils I used my multi-meter in every way I could imagine to determine the good ones and the bad ones. It all came to nought, I think because you can't predict with a meter how the coil will perform when hot. I sent along with the car a sheet of readings on the four coils. The dealer's mechanic spent a long time testing according to the bill, and then simply replaced one coil.

On a Cayenne the coils are much harder to switch than on a simple in-line 4 like the Scion's. I have found the angled upholstery tool which comes with screwdriver sets is ideal for sliding down under the coil to lever it out.

deilenberger

I'll repeat what I've posted here numerous times.. when odd things start happening electrically on a Cayenne - the first place to look is the wire bundles under the driver and passengers footwells. Undoubtedly on one this old the footwells have been flooded, probably more than once. The splices in the wiring bundles do not like that at all, and they simply become non-splices (and copper oxide). It's time to look there.. and check the DIY and other posts here about how to, and what you're looking for. I'm not going to repeat the info here - it's well documented on the forum.

MisterMisfire

Thank you for this - I'll check those lists. I guess that's another job for tomorrow....

I haven't driven the car today and got back from a job earlier and decided to begin the short job of checking my spare coil packs in cylinder 1. I took the current one out and popped an old one in and started the car. Instantly I could hear a sharp 'suck' upon the first few millimetres of accelerator press. Again and again there was a clear suck noise. I got my father in law to listen out for it because I wondered if I had not refitted the air box cover properly but the sound was coming from the back of the engine block (nearest the windscreen) and where cylinder 6 is. We swapped places and he blipped the throttle and I stood in front of and to the side of the engine. Every time there was a clear sucking of air in from somewhere near the back of the engine.

I cannot work out where it is from. Any ideas? No CEL but then the car was only running for a matter of 3-4 minutes. I felt around the AOS but it isn't that. I felt around the pipes around there but can't feel anything.

deilenberger

I'm not familiar enough with the V6 engine to give any advice on it.. besides general things. You probably shouldn't hear a sucking noise back there. Possibility might be the vacuum line going to the power brake booster.. that's back there somewhere.

MisterMisfire

Checked 2 of the spare coil packs in cylinder number 1 and both were fine. I put the original pack back in cylinder 1 and replaced the coil in cylinder 6 (the main culprit). Started the engine and wasn't happy with the sound from number 5 so I replaced that one - I hasten to add that I stopped the engine for every coil change. Got in the car and the CEL was one with one code - misfire on cylinder 6, which I guessed had been from before I changed the coil.

Went for a drive and I had my old car back! Doing 40mph in 6th gear and no kangarooing as I gradually squeezed the throttle. No shuddering and juddering.

I know my car well enough to know that these fixes can be temporary. So I pulled over, stopped the engine and restarted. No misfire!

I totally ragged the car on the way home - CEL flashing so I guess it needs tuning as it is dumping fuel down the exhaust and upsetting the O2 sensor. Called father in law and he came round for a trip in my lovely quick Cayenne.

And the bloody misfire is back!

Now I am guessing that maybe there is a crack in a wire to the boot that fixes on to the coil pack. I have taken the plastic cover off and checked the wires visually - no sign of loose wires. I pulled the cover off boot number 4 for comparison and there was no problem.

Got the car going in to the shop next Friday. They need to hunt this gremlin.

Rod Croskery

What code does it read? Whatever it is, P0302, for example, means that coil number two ran fine cold, but engine heat caused it to misfire. You're not quite home yet, but you're getting there. You'll save a lot if you buy one new coil pack and it works.








Checking coil packs is the kind of fun you get setting your hair on fire and putting it out with a hammer. It feels so good when you finally succeed.

MisterMisfire

P0306 - the classic cylinder 6 code. And you're right about the difference between hot and cold. It is normally fine when it is cold, but once warmed up the misfire is very noticeable. That said, I was getting 6 or 7 codes - P0300 (various misfires), P0306, P0305, P0304, P0303, P0302 , P2189 (system too lean at idle Bank 2) so to only get P0306 feels like progress!

I've got a 60 or 70 mile round trip to do tomorrow morning so we will see what is going on. I have seen a set of 6 coil packs for about £122 including delivery from Germany and I am tempted to get the lot.

The 'old' coil packs that I found worked in cylinder 1 and popped into cylinders 5 and 6 seemed to be fine. Maybe I'll just get one branded pack and see if that works.

I do have a couple of anomalies on the packs. About three of them have the lugs snapped off so the boot isn't 'locked' on the coil pack. They are stiff, but I read another chap thinking that his misfire was caused by the boot loosening. The other weird thing is that the coil in cylinder 4 is upside-down in relation to 2 and 6. I doubt it makes a difference but it is odd....

MisterMisfire

I've noticed that the engine seems to be limited to 4000 rpm when in neutral. It revs freely through gears 1-5 but again is limited to 4000 rpm is 6th. Is this normal?

Did my 60 mile round trip. Within a few hundred metres of starting the CEL was on. I stopped 2 miles later and checked the codes - P0300, P0303, P0304, P0306, so multiple misfires plus cylinders 3, 4 and 6 misfiring. I restarted the car and did the 30 miles there without incident but with a definite misfire. Got to my destination, stopped. Restarted the car 15 minutes later and came home. Again, definite misfire but no CEL.

Had flashing CEL when hard accelerating.

But I couldn't get above 99mph on the way home as the car seems to be limited to 4000 rpm in 6th gear.

Saw some coil packs on Amazon last night for a bargain so have ordered 3. Delayed delivery but hopefully here Monday or Tuesday.

Getting bored of this.

Oh, and it is cool and rainy so my reverse sensors aren't working!

MisterMisfire

Bought 3 new coil packs and put them in cylinders 3, 4 and 6 - remember that 6 is the one that comes up most often. I have already replaced the spark plug in 6.

Got 6 codes straight up after starting the engine up - multiple misfires, cylinders 2, 4 and 6 plus bank 2 running lean. Cleared the codes and went for a drive - horrible jumpy misfire. Tried high revving it and got the CEL flashing again to show O2 sensors not happy plus the CEL lit up again. Cylinders 1, 3, 5 and 6 plus multiple misfires. Cleared the codes again. Turned engine off.

On the way home CEL came on. I dropped it a couple of gears and thrashed it for half a mile. CEL flashing. Then CEL disappeared. Still a bit of a misfire but the CEL is still off.

Like I keep saying - mysterious misfire....