The Stumble/Stutter Thread

Possibly a failing neutral switch. You can see this in romraider. Very odd though. Kind of acting like the old IACV is failing, but you dont have one.

Possibly a failing neutral switch. You can see this in romraider. Very odd though. Kind of acting like the old IACV is failing, but you dont have one.

 

 

 

EXACTLY like all the symptoms point to a bad IACV. Found the N switch removal in the uh "vacation pics" lol not too bad but ill have to see it for myself.

Edited January 19, 2013 by GEE-OTTO

The stumble I experience seems to be discussed quite a bit less. No problems with acceleration on my bone stock 09 5MT LGT.

The speed limits in my town are all 15mph and I struggle to find a way to cruise at low speeds without the MPG needle bouncing back and forth. I do feel the resulting jerkiness too. I assume it comes with e-throttle territory, but I have to think that a tune more sensitive to low speed input could help?

Thanks for the wisdom!

Hey man I feel you driving at low speeds isn't easy (stop n go traffic or creeping traffic) it bucks so I have to use a lot of clutch when in another manual car ( 2006 civic) I can just creep along no problem

I finally have some direction with my car.

 

Yesterday I was able to witness and log Cylinder 4 Roughness incrementing between 2100-2300RPM with no load, at one point reaching as high as 9. I swapped #2 and #4 coils to see if the roughness would follow, but it did not. Next step is going to be swapping injectors in the same fashion. If that also is inconclusive, I'm not sure if I should focus on mechanical (compression & leakdown) or electrical (ECU, harness, etc).

Interestingly cyl #4 with LWFW or even slightly slighter than stock tends to throw misfires more than anything, many cases of this are on this thread, I've experienced this as well and I've tried swapping everything and replacing the plugs, etc.

**Update

 

So tested N switch voltage was good. Call Mach V and found out that the surge is just rolling RPM speed. The ECU anticipates a take off so it holds the RPMs steady. This makes sense for me b/c it only happens while coasting then drops to normal below 2 MPH to stopped.

 

So it seems that ill need my friends at Mach V to tinker with the ECU map to get this changed which is fine b/c i also want to smooth out the throttle modulation at lower speed.

Thanks GEE OTTO! Let me know how this goes.

Swapped #2 and #4 injectors on Sunday and changed the AP datalog list to include the cylinder roughness values. The first log I ran with the RPM steady around 2100 showed intermittent roughness on all four cylinders, not just #4 like I thought I saw before.

 

What are the odds that I have multiple bad injectors?

If you have an Accesport, I would check the condition of your voltage with the car running. When my alternator was going bad, my car ran horribly and I was seeing multiple misfires on all 4 cylinders. On a good alternator at idle, you should see at least 14 volts.

If you have an Accesport, I would check the condition of your voltage with the car running. When my alternator was going bad, my car ran horribly and I was seeing multiple misfires on all 4 cylinders. On a good alternator at idle, you should see at least 14 volts.

 

Thanks for the input. I thought of that too, and at least at the battery it's around 14-14.5 volts. I don't remember if I checked it at the ECU with AP or not; I'll definitely double back on that.

 

I also had the thought that a bad rectifier diode might be causing a sine-wave output from the alternator, but my (cheap and basic) oscilloscope showed clean voltage.

So last night I started the car up, and it was stumbling a lot at idle, and the check engine light and cruise light came on. Don't have a code reader, and I found a thread about the gas cap, so I made sure it was tight, then pulled the positive battery terminal. Started back up, seemed ok, no check engine light.

 

Now this morning on my way to work, it was stumbling at idle, and it almost stalled a few times, but still no check engine light. Any ideas? Seems like the common issues are ignition coils and/or fuel injectors, how do you tell which is the problem?

 

I have an appointment with the local dealer on Saturday. I bought the car from them, and they had fixed both heads due to a burnt valve before I bought it. Now I am worried that they never fixed the original problem and it's going to happen again, and with no warranty it won't be cheap.

I fixed mine going to a stage 2 map and had the tuner adjust the idle rpm. Done with that.

You need to scan the code.

 

My guess is "system too lean" caused by a vacuum leak, but you shouldn't rely on a guess - scan the code. That's what OBD2 is for.

does the car still store a code even if the check engine light hasn't come on?

Had a stumble coming to a complete stop.

Cleaned out my MAF and my throttle body. Problem solved.

 

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For me it was a tune (raised rpm) and timing belt.

 

Need to do spark plugs to fix a 'sputter'

Changing the intake O-Rings finally cured mine.

 

aaahhhh.....so much better now. Sitting at stoplights

and in stop & go traffic used to be nerve wracking.

Always thought she was gonna stall when the motor would

randomly feel like it misfired.

Mine just comes and goes. It doesn't make any sense. No cels or lights.

Although one time I got a cel for about 100ft and it was blinking with no cruise light action. It was struggling to get past 2k rpm last night and when it did ( having the gas pushed more ) it finally took off like crazy. I've had everything checked multiple times, but not since the cel light.

Edited April 25, 2013 by Brprs

Um.. my understanding is the blinking CEL is very bad, either airlock in the fuel line or bad gas, etc. But it's bad enough that it can destroy your cat in your UP.

Blinking CEL is Subarus way of telling you not to ignore the CEL and to get it repaired immediately.

Its going to the dealer next Wednesday. Airlock? explain? It only blinked for a few seconds and then went off and never got it again? Earlier today I sprayed down the maf with maf cleaner and it seems to help. Either way its going back to the dealer. Next month should be the time get my up and downpipe installed along with my wideband o2.....finally. Edited April 26, 2013 by Brprs

No expert here, but just doing reading/learning about this issue. On another forum, they attribute the stutter or stumble which seems to occur at around 2500 to 3000 rpm is due to a some type of fuel line resonance.

 

Many have had reported success after adding 3 feet of fuel line between the fuel rail and the fuel damper, and after zeroing out the Load Compensation table and/or reset of the ECU.

The "problem" is getting confused/diluted/etc. The "stumble" in an 08+ LGT is associated to a harmonic in the fuel lines. A few members here have complained of this issue. But not too many. I own two 08+ LGT's and none of mine have it. But, an 08 has different fuel lines than an 05-07 LGT. 05-07 LGT is entirely different as to the cause and "repair" of the stumble.

The "problem" is getting confused/diluted/etc. The "stumble" in an 08+ LGT is associated to a harmonic in the fuel lines. A few members here have complained of this issue. But not too many. I own two 08+ LGT's and none of mine have it. But, an 08 has different fuel lines than an 05-07 LGT. 05-07 LGT is entirely different as to the cause and "repair" of the stumble.

 

Can you please provide any more info on the cause of the 05-07 stumble? I know there's been a lot of discussion about it in this and other threads, but is it something you could summarize for us please? Luckily I don't seem to have it in my 05, but others might. Thanks.