Need help with a high rpm misfire

[b57]

I've got a b7 w 150k miles that's misfiring on one bank (driver side). Car runs fine in general and idles fine, but misfires / gets flashing CEL at high rpm- 3500+. just about all cylinders on that bank misfire- at different times i get a different mix of cylinders misfiring, but all have misfired at some point.

i'm also getting a p1071, running lean on the other cylinder bank.

Here's what i've done-
- i've swapped the coils from one bank to the other. the problem stays in the same cylinder bank (as i did this, i noticed a bit of oil higher up on the coils coming from a couple of the problem cylinders)
- i replaced the maf

the spark plugs are about 6 months old.

i also hear a ticking right over the airbox.

any help appreciated.

[jakeoboy67]

I have to ask : what kind of downpipes do you have ?

It's a long shot , but something similar happened to me about 2 years ago:
It started as a loss of power at high rpms (4000+)
then I had misfires in the 3-6k rpm range (same as you), they were becoming worse and worse
the misfires were all on 1 bank , and did not follow the coilpacks or spark plugs
I also had a lean condition code( I forgot which bank)


only codes were misfires/lean/SAI insufficient flow.

I had a clogged cat and very little exhaust flow was coming out from that side's exhaust

[b57]

I neglected to mention. I just switched to piggie pipes.

the problem predated the switch. i figured going with piggies might fix the issue. it hasn't, though the car is running much better at idle than it had been

[Lucca M]

Fuel filter ?

[b57]

changed about 40K back.

would it be fuel filter if lean codes are for only one bank?

[VinnysS4]

My first thought was a clogged cat. It is always possible your main cat on that bank could be clogged. Do you have vcds? A few things that "could" cause it:
Plugs
Injectors or injector seals
Coils (you addressed this)
Fuel pump or a leak in a fuel line (always possible if a line got damaged during fuel filter removal)
Dirty MAF sensor
Clogged air filter
Timing could be off on that one bank due to a broken guide or what not
Faulty 02 sensor? Not sure this would affect high rpm enough to misfire, unless it is calling the ecu to lean out or go rich?
Valves not seating fully ( have you run a compression or leak down test?)
Broken valve spring? UNLIKELY if it is misfiring on multiple ful.
Air leak? An intake vacuum leak is UNLIKELY to cause it when the throttle is opened due to there being little vacuum while the throttle is opened
Faulty ecu
Have you checked for readiness or stored codes? Freeze frame data?

[b57]

Thanks!
Should I start with the plugs? They've only got about 8k miles on them but I also found a cpl of them (on the problem bank) to have oily residue when I swapped out

Could a leaky VC cause this? (The oily plugs and misfiring). This particular VC is def leaking

[jakeoboy67]

misfires all over a single bank are usually caused by excessive cam adjuster wear or a clogged cat
that's the only things I can think of right now

OP , a fuel filter would lead to a fuel rail pressure drop ,at the point where there is the most demand for fuel, and would(normally) affect both banks.

[b57]

Here's what I'm getting for fuel trims
ST1, 19.53%
LT1, 11.72%
ST2, -14.84%
LT2, -8.59%

Bank 2 is where I'm getting misfires

[Epetes]

Did you look at the main cats when you had your downpipes out? I have almost the same thing going on right now. I pulled my pipes to look and both precats looked good so I figured I had some other problem. When I went to drill out the precats I noticed some chunks of debris in my main cat o2 bung hole. I stuck a borescope in there and found my main cat was starting to fall apart. My misfires are all on the bank with the bad cat and it is throwing a rich code and my other bank is lean (with no misfires). My misfires only happen above 4k RPMs. I recommend pulling the left rear o2 sensor and sticking a camera in there (I got one for $10 or $20 on amazon) and inspecting the face of the main cat if you didn't look at it when you made your piggies.

I don't know why my precat wouldn't have melted away before the main but who knows.

[b57]

i actually bought the piggies pre-made (my downpipes were in rough shape) and they looked fine when i checked them out.

something weird happened this weekend- i didnt misfire at all in 100 miles of driving, after making two unrelated changed.

i replaced the battery, bc it was dying. and i replaced the charcoal cannister with the bypass hose, bc i was having issues filling up the tank. i'm still getting the p0171 for bank 1, but the misfires are gone.

[drinkbrew]

I'm having the exact same problem all with bank 2 misfires (5-8) at 4k+ RPMS. It started after some other unrelated repairs to the front crankshaft seal, alt belt, SAI vacuum line and fan. It lasted a few days then went away for a week now it's back and the misfire is worse and loosing power even at lower RPMS. I'm getting very little exhaust flow out of the drives side exhaust.

[2004B6S4]

I just wanted to say in regard to the ticking you mention near the airbox, that could be your n80 purge valve. If you touch it while it's making noise you can actually feel it click. I'm not sure if that's normal or not but I've noticed recently that mine does that. I haven't had misfires but I've also been trying to figure out why my 02's are reading lean at higher rpms and causing me to lose power above 3-4k, and I just started getting codes for sai insufficient flow and for a very small evap leak. Not sure if any of that stuff is related or not

[b57]

the misfire is back. happens under hard acceleration (wherever i am in the RPM range).

I'm thinking i should swap the injectors and see what happens

[b57]

the misfire is back. happens under hard acceleration (wherever i am in the RPM range).

I'm thinking i should swap the injectors and see what happens

Not finding a diy for removing fuel injectors. Does someone have a write up handy?

[2004B6S4]

it's pretty simple. remove the 4 bolts holding the fuel rail to the manifold, then just pull up and it will come out. then remove the clips holding the injectors to the fuel rail and you can pull the injectors straight down out of the rail. Relieve the fuel pressure first, and I'd order new pintle caps from jhm ahead of time since the old original ones always break

[b57]

OP here, finally had a chance to work on the car this weekend. Running out of things to try out and considering selling the thing.

To recap:
- I'm getting a misfire on Bank 2 whenever i gas it hard. no misfires on Bank 1.
- when in neutral, i dont misfire until 6K or so; in first gear i misfire around 4-5k; in 4th or higher i start misfiring at 3K
- i dont misfire at all if i SLOWLY increase speed. so if i'm on the highway on cruise control and i slowly up the speed-> no misfires. and i've done this up to 6k rpm
- Bank 1 has been consistently running LEAN (but i can't tell if this is a symptom of the misfires, the cause of the misfires, or altogether unrelated)

Here's what i've done so far
- first theory was that the precats were clogged. took it to an indy who confirmed via boroscope. bought and installed a pair of pre-made piggies. car felt better but it didn't address the problem
- replaced the MAF
- swapped coils across banks
- swapped injectors across banks
- swapped plugs across banks
- replaced both upstream O2s
- tightened the intake manifold bolts as someone suggested above (they were loose)

it hasn't thrown any timing related codes, but since this is happening across an entire bank, i'm wondering if it's timing related.

any suggestions on what to do next?

[s4nicetry]

Well I would check the compression and leak down test, where if that doesn't answer the problem it's probably time to go after the timing components ie. worn cam adjuster.

[b57]

I forgot to mention i did a compression test. Bank 2 cylinders are a bit low:
1: 140
2: 145
3: 140
4: 145

5: 125
6: 135
7: 135
8: 150

could this explain the misfires?

[b57]

And this morning i got these codes.

http://imgur.com/a/lNaUA

http://imgur.com/a/6RnZX

Makes me wonder if i'm got a wiring issue going on here. Any help appreciated. This thing is driving me nuts