BobbyB13

Happy holidays EvoM members,

I’m getting a misfire at or near (varies) peak boost on my 2006 IX 9 SE. When I first drive it, it will reach peak = 23psi with “stumbling,” but as I drive it longer it stumbles / misfires / jerks hard around 20-21 psi. That’s it. Car idles fine, revs fine, boosts fine up until 17-23. It is not RPM related - I can slowly rev up to 5-6k with no issues.

Car is lightly modded (below), daily driven, and has 185k mi. I bought it at 50k with the mods below and never had any issues other than regular maintenance. Original owner is my best friend and these mods were probably done around 30k, so everything has about 150k miles (including fuel pump).
• Street tune
• Walbro 255
• K&N + hardpipe
• 3” TBE (high-flow cat)
• MBC @ 23 psi

Diagnostics / trial and error to date
1. Compression checked out at 150 psi +/- 2 psi every cylinder (sigh relief)
2. There are NO codes being thrown (pushing me toward “not a sensor”)… Is that a good assumption?
^ If it WAS a sensor but worked at non-WOT ranges, which one would it be? Crank AS, Cam AS…?
3. AFR at WOT = 11.0 – 11.5 and NOT steady…
^ At WOT, it used to read a steady solid AFR, (I could’ve sworn it was 10.x)… Now it does not – even during boost build prior to the hesitation / misfire it reads in the 11’s and 12’s jumping around.
^ Fuel pump dying? (it used to howl and doesn’t “seem” as loud anymore… I could be used to it though…). Also, in NY/NJ we recently just got into cold weather, which could also be prompting the FP to fail…
^ Bad fuel injector? Doesn’t that throw a code or wouldn’t I get a specific cylinder misfire code?
4. Ran a boost leak test and held 20+ psi for 10min with a slow loss through the PCV like normal.
5. The CEL does NOT flash (detonation count indicator)
6. Plugs have been swapped multiple times, and all plugs were gapped at .022-.025. It has always run on stock plugs at that gap w/ no issues. No difference.
7. Wires and coil packs have been swapped twice – one set was completely new. No difference.
8. MAF was swapped with a low mileage one. No difference.
9. Injector resistor pack was replaced with a brand new one, and that whole plate assembly was swapped with a low mileage one.
^ Based on inconsistent resistances I was getting, I was sure that was going to fix it but it didn’t.
10. Turbo spins super smooth, very minimal shaft play, burns very little oil.
11. I’m now on my second or third tank of gas since this started – I was “hoping” for bad gas. No difference.
12. Wire-wheeled major grounds in the engine bay and actually added in a couple more going back to the battery for good measure.
13. ***I also checked the timing marks of the cams and they lined-up with respect to each other. (I haven't checked the timing mark on the crank though. I assume if it jumped timing it would've done so at the cams.)

I believe I’ve read every misfire thread, and I tend to be self-sufficient with diagnostics, but I am pretty stumped here and just want to get this thing running right again. My personal experience / gut is telling me it is ignition = wires / coils / plugs, but that’s not fixing it. I’m considering electrical problem further “upstream” like the wiring harness or ECU, or because the AFR readings aren’t consistent maybe a bad injector or the FP. Car never sits for more than 2 days and gets regular highway miles, so I would be surprised if it was bad gas or water in the tank. I have a palm code reader but not Evoscan or reflash equipment.

Help please (options?). I am not one to ask for help, but I just want to get back to enjoying my car…
1. I’m about to hit “order” on a new Walbro 255. (Good idea? The parts canon is starting to run out of ammo… but what’s the big deal with another $100 during the xmas season?)
2. Anyone in the Rockland NY / North NJ interested in diagnostics? I’d be happy to throw you a few bucks / Guinness or craft beer / whiskey if you help me get this right.
3. Buy datalogging and reflash cable and software and learn about logging and tuning… (Not what I want Santa to bring me…)
4. Replace car, owner, or wife before wife does; (make the first move). She is not happy that I’m spending my nights working on this instead of watching TWD or Orange is the New Black.

Thanks in advance, everyone. If nothing else, maybe this thread will serve as a checklist for the other folks in the misfire club.
Cheers,
Bobby
Congers (Rockland), NY

IzzyRS

iTrader: (8)

You could try closing the spark plug gap a bit, try going to about .018-.020.
Can you find someone local with a Tactrix cable so you can log the car?
A weak/dying pump could cause issues but you should typically see your AFRs really lean out when the pump is not operating properly.

LetsGetThisDone

iTrader: (1)

Replace fuel pump and bypass the fuel pressure solenoid, hook the FPR up directly to intake manifold vacuum source.

4b11slayer

Might wana swap good known coils

Evo9_Dubai

You need to log your voltage during a pull.

I had a similar issue on a friends car and it turned out to be a voltage problem caused by a bad alternator.

BobbyB13

Thanks for the input, everyone. Some notes...

1. FUEL PUMP should be arriving today from Extreme PSI. I may try to swap that out tonight after the family is in bed. What about injector(s)? I had measured their resistances a few weeks ago and they checked out, but could 1 (or more) still be clogged or bad at high RPM / load?

2. COILS / WIRES I've got two complete sets of coil packs and wires: 1 set used and known good, and the other only a few weeks old. No difference in the problem.

Last night I checked the coil pack plugs for damage (none) and zip-tied them into place in case vibration of those plugs was triggering the misfire, but didn't help.

3. VOLTAGE I did replace the alternator this past summer. It could be a bad replacement, which has happened to me once before, but the battery is holding a charge and it was 15degrF the other morning and 25 today.... With regards to testing voltage, why do I need to log that during a pull? Are you suggesting for specific sensor voltage, or alternator voltage? If alternator, I can test it at the battery with the car off, then car at idle, and then car with partial open throttle? Yes - there's no "load" mechanically on the car, but electrically it only really cares about the RPM's. What does vary electrically is current and the output "pulse" for the ignition system at higher RPM's... (But again, I can drive at high RPM's - just not WOT.) ...I'm still going to check this though - good point.

4. ^ Leads me to WOT tuning feedback systems. I'm not "a tuner," but from what I read last night the Open Loop WOT tuning is done by logging pulls and adjusting the fuel map only. The only other feedback mechanism / sensor is the MAP and/or the MAF, depending on which one the tuner prefers to use, and this is all that is used to calculate the target AFR for which I'm tuned. (I believe my guy used the MAP sensor only.) So, at WOT the system goes into OL and uses the "tuned" fuel maps for the given RPM and the known manifold air pressure. (Is this correct so far?)

...Thus, if the car runs totally fine in CL and non-WOT boost (0-15psi), and if the car is measuring RPM correctly (sure) and recognizing WOT / triggering OL (which is does - I can see that on my palm reader), then the problem has be fuel delivery related (FP or F-inj) or MAP sensor... OR a freak electrical / ECU / harness problem(s) that would only happen to me.

I may just eat it and buy the Tatrix cable at this point if the FP doesn't do it.

My other option is Daily Driven Autosports is pretty local for me, and I did talk with Remy on the phone earlier this week, and he put a bet on FP. Otherwise he said bring it in.

Thanks, everyone... Keep the ideas coming!

BobbyB13

Thanks again for the input, everyone.

1. I replaced fuel pump with new filter, and I confirmed the fuel pressure regulator direct routing to intake manifold, no tears on FPR vacuum hose.

2. Alternator is holding a steady 14.2V at idle. Battery is 12.6V with the car off. I also charged the battery while doing the FP replacement. (No luck)

3. Tried a third set of known good plugs - no luck.

4. Cleaned both cam sensors, and crank angle sensor was replaced during timing belt change around 3000 miles ago... (Anyone ever gotten a BAD brand new CAS?)

I'm going to re-measure injector resistances tonight and stethoscope the injectors to listen for 1 that is different than the others. Other than that, I'm out of ideas.

CAM + CRANK SENSORS? Everything I've read about the cam and crank sensors is that when they go, they are gone and you get nothing... Is that correct? Has anyone ever had intermittent problems like I'm having with such a sensor?

Again - if anyone in Rockland / North NJ with datalogging capability wants to make a friend + few bucks / nice bottle of whiskey for the holidays, look me up...

LetsGetThisDone

iTrader: (1)

Cam and crank sensors "typically" causing hard starting. Your hiccup/misfire that is only relevant to boost would not be caused by those two sensors.

4b11slayer

Stock injectors? Maybe an injector is clogged or failing at high rpm.

BobbyB13

Agreed - that's what I found from my reading here... Car starts perfectly every time, especially with the new FP.

BobbyB13

^ This is actually exactly where I'm now at. Yes - stock injectors. I've checked the resistances of the injectors a month ago , but obviously that's a static condition reading, and this is only dynamic-sensitive, so I would not be surprised if this does not present any bad resistance readings with the car off.

Any other tricks to trouble-shooting the injectors besides multi-meter? (I don't have a spare bench flow tester laying around...)

4b11slayer

You can try and remove them and diy a clean rig.

a 2 volt battery to open the pintle and spray carb cleaner through.

Atleast remove them for a inspection.

Anything is possible at this time.

If you had the ability to monitor misfire counter it would be easier to diag it. To narrow it down to a specific cylinder.

If you have any sort of datalogger you can start logging stuff and see if you see anything out of the norm.

BobbyB13

Right on, 4b. I'll try pulling them tonight and hit them with sea foam. This has literally been a T&E process of every night trying something new after the family is in bed.

I also reached out to a local Evo / Sti shop last week, and they said try the FP replacement, and if NG, reach back out for a data log, (which I've done). Hopefully Remy isn't too busy this week

BobbyB13

Okay - now things have gotten interesting. Last night on my drive home I put on my big-boy pants, went WOT, and HELD IT through the stutter until I heard a pop as loud as a tire blow out. It felt, (yes - I felt it), and sounded like it came from under the passenger seat. Once my heart beat returned to normal, I found that the car still drove and boosted the same as it did before, though I did not repeat this experiment.

Laying in bed last night, I then recalled something my buddy mentioned in passing, "Maybe your cat is clogged." I originally dismissed it because it's a high-flow cat, but given that "pop" I heard, I think he is right. There is probably enough flow for non-boost and low-boost conditions, but under hard boost the car may be creating positive pressure between the cat and turbo which is essentially semi-stalling the car, and when I held it at WOT it pressurized until it blew out at a gasket.

If this hypothesis IS correct, hopefully that pressure wave did not make its way backwards past the turbo into in the engine > head gasket. Judging by the car driving absolutely the same as previously, I'm guessing this purged at an exhaust gasket (they are all old and have minor leaks) or purged its kinetic energy as sound and briefly spinning the turbo backwards.

I'm going to get the car up in the air tonight and see what's going on at the cat and check my compression again.

Has anyone clogged their cat (stock or high-flow) and what were your symptoms / experiences?

4b11slayer

I have seen a clogged cat cause a misfire at high rpms but was on a customers car and was non turbod.

remove the cat and go for a pull.