The Stumble/Stutter Thread

[Thinking out side box]

Ok, I'll bite. I'll help make your question(s) easier to understand. You won't get any answers here though, you'll need to post in the correct section. Don't take offense, I'm just trying to be helpful. I recommend creating a new thread in the Turbo Powertrains section. That would be the perfect place to discuss your unique problem, and a really great place to show us pictures of exactly what you're talking about.

[Turbodad]

My car is bone stock, and I get the hesitation and stuttering in the usual 2500- 3000 rpm range. If I floor the pedal, it'll move past that and run fine. A couple of observations:

1. I recently went for a period of time with a driver's side oil control valve that seemed to be working but was throwing a CEL. No stuttering during that period of time, but it has returned after I replaced the OCV.

2. When the car is misbehaving, the engine seems to have very little power, which makes me wonder if the engine controller has the ignition timing at full retard? Or is the OCV in the wrong position for power in that rev range?

3. If I use the steering wheel buttons to initiate a downshift, I see the transmission is usually in a gear that one or two higher than what it seems like it should be for the engine load. For instance, going up a steep hill toward my house, it'll be in 3rd gear, when 2nd is what's really called for not to be lugging (to the point of bogging down) the engine.

 

Those are my 4-cents worth, that it seems like overly retarded timing, and/or a transmission in too high a gear, probably for mileage purposes. Plus OCV misbehavior.

[Skidude]

My car is bone stock, and I get the hesitation and stuttering in the usual 2500- 3000 rpm range. If I floor the pedal, it'll move past that and run fine. A couple of observations:

1. I recently went for a period of time with a driver's side oil control valve that seemed to be working but was throwing a CEL. No stuttering during that period of time, but it has returned after I replaced the OCV.

2. When the car is misbehaving, the engine seems to have very little power, which makes me wonder if the engine controller has the ignition timing at full retard? Or is the OCV in the wrong position for power in that rev range?

3. If I use the steering wheel buttons to initiate a downshift, I see the transmission is usually in a gear that one or two higher than what it seems like it should be for the engine load. For instance, going up a steep hill toward my house, it'll be in 3rd gear, when 2nd is what's really called for not to be lugging (to the point of bogging down) the engine.

 

Those are my 4-cents worth, that it seems like overly retarded timing, and/or a transmission in too high a gear, probably for mileage purposes. Plus OCV misbehavior.

 

I am also bone stock, and have sort of suspected a cam timing thing for a while, but I have no way to really check that. My car is a 5MT though, so I generally know what gear I am in, and my RPM is solidly correlated with my wheel speed in any gear.

[bochuck]

UPDATE: Problem came back with force. I was driving apx 50mph and the car lost power and throttle response for a few seconds. CEL came on and car regained throttle response. P0340 for the camshaft circuit. Took it in and they tested the circuit and found that one of the signal lines was showing something like 10Mohms of resistance. This is probably what was causing my issues from the get go, but it never threw the code. Having them test the harnesses to see if it is only the one wire. Hopefully it doesn't decrease the weight of my wallet too much.

Problems still persistent as ever. The lead tech and technician at Subaru were so certain that they had found the problem. Told me it was the ECU. Had diagnosis sheets and everything. Gave them a known good ECU and had the keys registered to it. Bought a Cobb AP and got an e-tune. Everything was going fine until today. Code popped 3 seperate times. Caught it on a datalog. Any reason the camshaft would just shut off like it did? Other than being a faulty sensor? Line 1392 at the 125 second mark.

[bochuck]

Problems still persistent as ever. The lead tech and technician at Subaru were so certain that they had found the problem. Told me it was the ECU. Had diagnosis sheets and everything. Gave them a known good ECU and had the keys registered to it. Bought a Cobb AP and got an e-tune. Everything was going fine until today. Code popped 3 seperate times. Caught it on a datalog. Any reason the camshaft would just shut off like it did? Other than being a faulty sensor? Line 1392 at the 125 second mark.

 

Better snap shot.

[heiche]

Problems still persistent as ever. The lead tech and technician at Subaru were so certain that they had found the problem. Told me it was the ECU. Had diagnosis sheets and everything. Gave them a known good ECU and had the keys registered to it. Bought a Cobb AP and got an e-tune. Everything was going fine until today. Code popped 3 seperate times. Caught it on a datalog. Any reason the camshaft would just shut off like it did? Other than being a faulty sensor? Line 1392 at the 125 second mark.

 

Which code, the P0340 you mentioned earlier? Did you ever change the cam sensor itself?

[bochuck]

Which code, the P0340 you mentioned earlier? Did you ever change the cam sensor itself?

 

Yes. Same code. Never changed the sensor. The techs were both certain that wasn't the problem. It's a $100 toss up though. It would suck if it didn't fix the problem. Always good to have an extra though if it ends up being good. AVCS dropping to zero is also cause for concern.

[heiche]

It's possible that if the ECU doesn't see the signal from the cam position sensor, it puts that side in a "failsafe" mode and deactivates the AVCS, which might be why it drops to zero. Wonder if someone might have a used sensor for cheap?

[Tuning Alliance]

Could be sensor, cam sprocket or AVCS solenoid issue. I have seen the solenoid break and they can send metal into the oil system. I would remove the solenoid and inspect, possibly replace it.

[bochuck]

Thanks for the reply Mike. This is the reason I haven't sent any logs recently for my e-tune. Didn't want to bother you with it at UConn when I spoke with you and Brian. Figured I could look it over first. Car actually died on the way there. Had to turn around and get my wifes car. I will be checking the sensor when I get a chance. Got one on order just in case.

[bochuck]

Could be sensor, cam sprocket or AVCS solenoid issue. I have seen the solenoid break and they can send metal into the oil system. I would remove the solenoid and inspect, possibly replace it.

 

How much oil am I expected to lose by taking one of those AVCS solenoids out? Doing this in my apt parking lot. Is it even a good idea to try it, or should I take it in? APTs are anal as hell with their vehicle maintenance policy and fluids.

[m sprank]

How much oil am I expected to lose by taking one of those AVCS solenoids out? Doing this in my apt parking lot. Is it even a good idea to try it, or should I take it in? APTs are anal as hell with their vehicle maintenance policy and fluids.

 

About 1 tablespoon of oil.

[bochuck]

Thanks. I will deffinately be replacing then. Not too expensive to change both out. Those plus that cam sensor "should" fix my issues.

[bochuck]

Replaced the camshaft sensor today. Damn is that thing hard to get to. Removed the airbox and a couple breather tubes just to be able to barely get my hands to it. The one bolt the holds it on was loose. Took a little doing, but was finally able to unscrew it with my middle finger and index finger. Impossible to use your thumb, so good luck if you have to change it. Putting the new one in was loads easier. Tightening it is doable with the smallest 10mm socket and ratchet. Took the car for two test drives on seperate occasions. Nary a problem. I know the ecu needs time to relearn everything, but it was throwing the code after two minutes of clearing it before. Now it is running pretty smooth. Also found a possible vac leak after the maf and fixed it. Only time will tell now.

[BAD-WOLF]

Since I replaced my shortblock and valve train it's been doing pretty well, just some minor stutter here and there. Thing has just over 500 miles, and I replaced the downstream o2 sensor last night to see if I could smooth out the inconsistent idle. Since then it's seem a little beet more stumbly when I roll into the throttle. But I haven't driven it a whole lot since I installed it, maybe 10 miles or so. Possibly needs to learn new trims? What do you guys think.

 

I'm waiting until the 3k mark when the engine is completely broken in to tune, so I'm running stock tune with a GS Uppipe, but pushing it little by little here and there, breaking it in the way I want to drive it but never revving over 4500-5000.

[Max Capacity]

Since I replaced my shortblock and valve train it's been doing pretty well, just some minor stutter here and there. Thing has just over 500 miles, and I replaced the downstream o2 sensor last night to see if I could smooth out the inconsistent idle. Since then it's seem a little beet more stumbly when I roll into the throttle. But I haven't driven it a whole lot since I installed it, maybe 10 miles or so. Possibly needs to learn new trims? What do you guys think.

 

I'm waiting until the 3k mark when the engine is completely broken in to tune, so I'm running stock tune with a GS Uppipe, but pushing it little by little here and there, breaking it in the way I want to drive it but never revving over 4500-5000.

 

FWIW, I did the street tune at 500 miles on the ej257. No need to wait.

[BAD-WOLF]

FWIW, I did the street tune at 500 miles on the ej257. No need to wait.

 

That's great info, tell me more! How's the engine doing, how was the tune, what do you suggest? I'd like to ditch this stock tune ASAP, to me that thing is poison.

Edited May 10, 2016 by BAD-WOLF

[Max Capacity]

That's great info, tell me more! How's the engine doing, how was the tune, what do you suggest? I'd like to ditch this stock tune ASAP, to me that thing is poison.

 

 

See my sig. the car will turn 225,000 miles tonight. The ej257 has over 72,000 miles. Runs great.

 

Contact my Tuner www.tuningalliance.com for your e-tune. He really is that great. Tell Mike I sent you.

[Redslaya]

TYPE OF STUTTER/STUMBLE

Steady throttle/Increasing throttle/Both: highway speed crusing

 

MODS

Intake: K&N Panel filter

Exhaust: catless up, OEM Down, Catback

Fuel: Stock fueling, 93 octane

Turbo: VF40

Engine Management: Cobb OTS Stage 1 91

Tuner and revision of tune(if you don't mind):

 

MAINTENANCE

Sensors changed: none, going to clean MAF

Plugs changed: went 1 step colder

Coil Packs changed: changed all last year

 

OTHER SYMPTOMS

Check Engine Light: none

Etc: Bad idle at times, not always and at differing amounts of shaking

 

RESULTS

What has and hasn't worked for you: filled it up with fresh gas, didnt come back for 10 miles. also had a bad idle that comes and goes.

If something worked, how long has it been working for:

 

 

any idea at what the problem could be?

[m sprank]

The cold plugs and the standard issue related to fuel delivery.

[Redslaya]

The cold plugs and the standard issue related to fuel delivery.

 

i was recommended swapping to colder plugs by a reputable shop after i was having this issue with OEM plugs. i also had a downpipe and cobb OTS stage 2 tune and had this problem as well. downpipe swap was unrelated and had to do with emissions.

 

what is the standard fueling issue?

 

edit: seemed to have fixed it. decided to clean the MAF and in doing so found my filter covered in motor mount grease. since i had done the milkjug delete when the mount blew the fluid inside it got all inside the airbox. cleaned the filter and MAF and it seems to be gone.

Edited July 16, 2016 by Redslaya

[m sprank]

Glad you got it figured out.

 

FYI, we do not recommend cold plugs until raising compression and/or tracking the car. I think we are a "reputable" shop.

 

http://www.infamousperformance.com (the shop)

http://www.delicioustuning.com (our tuner)

[flip213]

TYPE OF STUTTER/STUMBLE

Steady throttle/Increasing throttle/Both: Rapid increasing throttle, WOT

 

MODS

Intake: K&N Panel filter

Exhaust: STI up, LP Down with O2 out of the flow and high flow cat, stock after downpipe

Fuel: Stock fueling, 91 octane

Turbo: Stock

Engine Management: Cobb OTS Stage 2 91 v300

Tuner and revision of tune(if you don't mind): COBB AP v2

 

MAINTENANCE

Sensors changed: none, MAF is clean

Plugs changed: NGK Iridium IX with approx. 40000km on them

Coil Packs changed: yes last week

 

OTHER SYMPTOMS

Check Engine Light: none

Etc: Car stumbles/shutters under WOT under 3000-3500rpm with no backfire or black smoke. not sure if i'm hearing popping out the intake. no stumble on light throttle or steady throttle.

 

I've done a datalog and sent it to COBB with a response saying i should do a compression leak check. Datalog also shows knock indication and reduces boost because of knock. Knock normally occurs just before peak boost which reduces boost. Boost target is 16.2psi once under full load and passed rpm range of the stumble, the boost will stabilize and peak at 15.7psi. I don't believe its boost leak.

 

Pulled spark plugs and they all indicate good burn. one had slightly more carbon deposit but acceptable. No really white (lean) no really black (rich) plugs, all nice light brown.

 

The knock isn't caused by lean mixture (plugs would be on the whiter side)

 

I've had the same setup for 3yrs without a problem

 

RESULTS

What has and hasn't worked for you:Nothing

If something worked, how long has it been working for:

 

Anyone have any ideas? How long do the iridium IX last for generally?

 

cam sensor or knock sensor possibility on the way out? OCV?

Edited July 17, 2016 by flip213

[m sprank]

You asked Cobb for advice. They gave it. You have not followed it, yet now you ask for advice here.

 

If you dont want to take the advice, dont ask for it.

 

Compression and leak down check. Your "stumble" is not what is being cataloged in this thread. You have a mechanical issue that was not there before. Something has physically changed. Cobb gave you good advice.

 

Iridium plugs are supposed to last 60000 miles. But you say you are not misfiring, so it should not be plugs. As plug gap just begins to get too large, you should experience a misfire at the top of the RPM range under WOT.

[STidriver86]

Hey guys. Forgive any oversight and feel free to ask questions if you need more info.

 

TYPE OF STUTTER/STUMBLE

Steady throttle/Increasing throttle/Both: Both. More noticeable at increasing throttle. Steady throttle makes my fuel economy gauge wag back and forth a tic or two like a flag in the breeze.

 

MODS

Intake: Cobb SF (no air box) w/ Gimmick turbo inlet

Exhaust: Tomei EL, Tomei UP, Cobb DP, Cobb turbo-back exhaust

Fuel: ID1000's, Aeromotive 340 (installed 3k miles ago), no aftermarket FPR (93 octane pump gas)

Turbo: Blousch 440XT (8 cm inlet) with FMIC & Perrin BPV - Less than 10k miles on the block as a whole. Turbo, headers, injectors have about 5k.

Engine Management: AccessPort

Tuner and revision of tune (if you don't mind): Procom Racing Protune by Lou (in person). Last tuned & dyno'd July 9, 2016.

 

MAINTENANCE

Sensors changed: None

Plugs changed: No. NGK 1-Step Colder currently installed w/ 10k miles.

Coil Packs changed: No

 

OTHER SYMPTOMS

Check Engine Light: No

Etc: Only happens under light throttle increase or steady light throttle (maintaining speed on residential street). Hard acceleration is much less prevalent (so far). Car stutters more noticeably at low rpm's on residential streets than at highway speed.

 

RESULTS

What has and hasn't worked for you: Let the car rest overnight. Will fill up with fresh fuel later today. Planning to reset/reload tune if no change tonight.

If something worked, how long has it been working for: Nothing yet.