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Old 04-25-2022, 06:06 PM   #1
Boostedidiot
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Default Stutter/Stall Issue. I'm lost!

Well for the past 6-7 weeks i've had this weird issue where from a stand still my car will occasionally sputter (acts like a misfire) and either stall or correct itself, nothing i do with the throttle seems to help when it stalls, when it doesn't sometimes i can give it more juice and it'll go along just fine. Lately the issue has become more frequent (probably due to more stop and go traffic in downtown nashville) and occasionally when I'm downshifting i'll go to give it a rev match blip and it'll do nothing. The car idles perfectly fine staying right at 14.70 AFR with 0-1% correction consistently. I have tried to replicate it but it just seems to be completely random. I'll have days where it doesn't do it all and then days like yesterday where it stalled 4 times in an hour.

Things i've done so far:
1. cleaned MAF sensor, replaced MAF sensor
2. smoke tested for vacuum leaks (none)
3. Changed plugs and tried a friends coils
4. compression and leak down test (both passed with flying colors for 200k miles)
5. Cleaned the IACV (yes i replaced the gasket)

I'm sure I've tried other things but i can't account for the endless hours staring under the hood wanting to pull my hair out. Any help is greatly appreciated and i did grab a couple logs (probably the wrong info) to see if it would help.
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Last edited by Boostedidiot; 04-25-2022 at 06:18 PM.
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Old 04-26-2022, 07:41 AM   #2
Thabias
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What about testing/replacing crank/cam sensors?
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Old 04-26-2022, 08:46 AM   #3
Elbert Bass
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Have you watched your TPS value as you slowly open the throttle?
I have seen TPS sensors get a "bad" spot in the carbon film and give intermittent values just off throttle. Value should be 0.2 volts to 1.0 volts closed and then increase smoothly with no erratic readings to 4.2 volts to 4.7 volts WOT.
You can also measure resistance across the sensor as you slowly open throttle or measure the output voltage. Another thing would be check for voltage drop across the sensor ground - poor ground will cause the sensor to read erratic.
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Old 04-27-2022, 01:33 AM   #4
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Quote:
Originally Posted by Thabias View Post
What about testing/replacing crank/cam sensors?
I'm going to test them in the morning, today i went over all my grounds and cleaned them up. Was going to replace them to see if it made a difference but currently can't afford 110 bucks for 2 cam sensors and 30 bucks for the crank sensor lol

Last edited by Boostedidiot; 04-27-2022 at 07:12 PM.
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Old 04-27-2022, 01:34 AM   #5
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Quote:
Originally Posted by Elbert Bass View Post
Have you watched your TPS value as you slowly open the throttle?
I have seen TPS sensors get a "bad" spot in the carbon film and give intermittent values just off throttle. Value should be 0.2 volts to 1.0 volts closed and then increase smoothly with no erratic readings to 4.2 volts to 4.7 volts WOT.
You can also measure resistance across the sensor as you slowly open throttle or measure the output voltage. Another thing would be check for voltage drop across the sensor ground - poor ground will cause the sensor to read erratic.
You do this without the engine running i'm assuming. I did go over all my grounds and clean them today and check for any broken/frayed wires.
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Old 04-27-2022, 09:03 AM   #6
Elbert Bass
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Quote:
Originally Posted by Boostedidiot View Post
You do this without the engine running i'm assuming. I did go over all my grounds and clean them today and check for any broken/frayed wires.
Yes - those are KOEO tests - Key On Engine Off. Actually the ground I was referring to in my response is the TPS sensor ground which goes back to the ECM. Do you have a scan tool that reads live ECM data? That will show you the TPS value as you open/close throttle.
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Old 04-27-2022, 06:30 PM   #7
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Quote:
Originally Posted by Elbert Bass View Post
Yes - those are KOEO tests - Key On Engine Off. Actually the ground I was referring to in my response is the TPS sensor ground which goes back to the ECM. Do you have a scan tool that reads live ECM data? That will show you the TPS value as you open/close throttle.
So i set the TPS Volts on my AP and without touching it, it sits at 0.50 and increases smoothly as i press the throttle, the only thing is that at WOT it's 3.82 max
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Old 04-27-2022, 08:58 PM   #8
Elbert Bass
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Quote:
Originally Posted by Boostedidiot View Post
So i set the TPS Volts on my AP and without touching it, it sits at 0.50 and increases smoothly as i press the throttle, the only thing is that at WOT it's 3.82 max
Hey, one thing I forgot - and that reading made me think of it - is there a little bit of slack in the throttle cable at the throttle body? There should be. If the cable is tight it can hold the throttle open a very small amount. If you adjust the TPS that way you will have the range out of whack and can cause bucking.
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Old 04-27-2022, 09:36 PM   #9
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Quote:
Originally Posted by Elbert Bass View Post
Hey, one thing I forgot - and that reading made me think of it - is there a little bit of slack in the throttle cable at the throttle body? There should be. If the cable is tight it can hold the throttle open a very small amount. If you adjust the TPS that way you will have the range out of whack and can cause bucking.
Actually there was quite a bit of slack in it, i noticed when testing the voltage that the pedal felt like it was doing nothing for a bit then going so i tightened it up.
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Old 05-01-2022, 04:44 PM   #10
03,2.0Ljapwagon
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My car has kind of always done a similar thing. Every now and then after a cold start, my car just sputters and dies like it is losing fuel pressure for a second. After the car dies you can start it up and it runs great the rest of the drive. Just to clarify, This happens randomly. And sometimes you can start driving and the car starts to sputter, when this happens you can floor the car but it doesn't do anything. It just seems to prolong the inevitable. But recently I have found a solution, I can keep the car in gear (while rolling) without pushing the clutch and just turn the key to the off position and then on. It seems like the car just resets itself and is fine for the rest of the drive. I am not really sure where to check first. It kind of sounds like an ECU issue.
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Old 05-04-2022, 08:09 PM   #11
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Quote:
Originally Posted by 03,2.0Ljapwagon View Post
My car has kind of always done a similar thing. Every now and then after a cold start, my car just sputters and dies like it is losing fuel pressure for a second. After the car dies you can start it up and it runs great the rest of the drive. Just to clarify, This happens randomly. And sometimes you can start driving and the car starts to sputter, when this happens you can floor the car but it doesn't do anything. It just seems to prolong the inevitable. But recently I have found a solution, I can keep the car in gear (while rolling) without pushing the clutch and just turn the key to the off position and then on. It seems like the car just resets itself and is fine for the rest of the drive. I am not really sure where to check first. It kind of sounds like an ECU issue.
See mine is more or less doing it after it's been driven for a while. I have no issues at all from cold startup to about 30 minutes or even an hour after cold start up. After it's been warm for a while I start having the issues. I notice it most when i'm driving through areas with stop and go traffic and speed bumps every 15 meters.
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Old 05-04-2022, 10:13 PM   #12
03,2.0Ljapwagon
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Quote:
Originally Posted by Boostedidiot View Post
See mine is more or less doing it after it's been driven for a while. I have no issues at all from cold startup to about 30 minutes or even an hour after cold start up. After it's been warm for a while I start having the issues. I notice it most when i'm driving through areas with stop and go traffic and speed bumps every 15 meters.
Have you tried to factory reset the ECU?
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Old 05-06-2022, 11:28 AM   #13
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Originally Posted by 03,2.0Ljapwagon View Post
Have you tried to factory reset the ECU?
factory reset no because i'm on a tune, but i have reflashed my tune twice now
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Old 05-06-2022, 11:47 AM   #14
undyjr
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He may of been referring to disconnecting the battery and holding the brake pedal down for a few seconds. You will retain your tune.
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Old 05-06-2022, 03:39 PM   #15
03,2.0Ljapwagon
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Quote:
Originally Posted by undyjr View Post
He may of been referring to disconnecting the battery and holding the brake pedal down for a few seconds. You will retain your tune.

Yes, I meant that. Do you have an accessport? I assume you do because you reflashed the tune.
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Old 05-11-2022, 10:30 AM   #16
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Quote:
Originally Posted by 03,2.0Ljapwagon View Post
Yes, I meant that. Do you have an accessport? I assume you do because you reflashed the tune.
Yes I do. Would a factory reset still be a good idea?
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Old 05-11-2022, 11:49 AM   #17
03,2.0Ljapwagon
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Quote:
Originally Posted by Boostedidiot View Post
Yes I do. Would a factory reset still be a good idea?
If I were you I would uninstall the tune and see if anything changes. If nothing changes then you can reflash the tune back on.
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Old 05-11-2022, 09:41 PM   #18
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Quote:
Originally Posted by 03,2.0Ljapwagon View Post
If I were you I would uninstall the tune and see if anything changes. If nothing changes then you can reflash the tune back on.
Well i made some progress today. I noticed it was idling a little weird right before it stuttered and inevitably stalled so i stopped a friends house that was close and started touching clips and grounds while it was running and behold the connection to the coil pack on cylinder 2 is in some way shape or form messed up, i can't recreate it perfectly but playing with it causes the same rough idle into a stall
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Old 05-11-2022, 10:09 PM   #19
03,2.0Ljapwagon
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Quote:
Originally Posted by Boostedidiot View Post
Well i made some progress today. I noticed it was idling a little weird right before it stuttered and inevitably stalled so i stopped a friends house that was close and started touching clips and grounds while it was running and behold the connection to the coil pack on cylinder 2 is in some way shape or form messed up, i can't recreate it perfectly but playing with it causes the same rough idle into a stall
Guess it's time for some Coils! They were about 200 bucks for the 4, last time I changed mine.
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Old 05-11-2022, 10:12 PM   #20
03,2.0Ljapwagon
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Quote:
Originally Posted by Boostedidiot View Post
Well i made some progress today. I noticed it was idling a little weird right before it stuttered and inevitably stalled so i stopped a friends house that was close and started touching clips and grounds while it was running and behold the connection to the coil pack on cylinder 2 is in some way shape or form messed up, i can't recreate it perfectly but playing with it causes the same rough idle into a stall
Guess it's time for some Coils! They were about 200 bucks for the 4, last time I changed mine. Have you done a timing belt kit yet?
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Old 05-11-2022, 10:14 PM   #21
03,2.0Ljapwagon
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didn't mean to post twice
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Old 05-16-2022, 07:37 PM   #22
monkeyposeur
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Quote:
Originally Posted by Boostedidiot View Post
Well i made some progress today. I noticed it was idling a little weird right before it stuttered and inevitably stalled so i stopped a friends house that was close and started touching clips and grounds while it was running and behold the connection to the coil pack on cylinder 2 is in some way shape or form messed up, i can't recreate it perfectly but playing with it causes the same rough idle into a stall
Stuttering/hesitation/bucking can have so many causes and many of them can share the exact same symptoms which can be extremely frustrating as you have discovered.

I had a stalling/stuttering issue and it turned out it was the coilpack(s). NGK coil packs from RockAuto are great. They run about $62 each. I would advise against getting cheap ones.

Things I checked/replaced before the coil packs:
Checked ECU for stored codes
Reset ECU multiple times
Ran new ground lines
Checked fuel pump and fuel pump sock (there have been instances where the sock gets so clogged up it causes fueling issues)
Replaced fuel filter
Replaced fuel pressure regulator
Checked for boost leaks (found a loose intake coupler)
Replaced MAF with a new spare I had laying around
Replaced Spark Plugs.
Replaced alternator with new higher output voltage unit (had it laying around)
Logged during pulls - no knock detected.

I had no misfire codes which also made the problem hard to track down.

After I replaced all four coil packs the car was pulling like it used to. Replacing the coil packs was last on my list of things to do, so it was a frustrating process.

When I replaced the coils I wasn't even sure if it was going to help so I didn't bother and try to isolate which coil(s) were causing the problem. Do yourself a favor and just replace all four.

Last edited by monkeyposeur; 05-16-2022 at 07:44 PM.
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Old 05-20-2022, 01:20 AM   #23
Boostedidiot
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Quote:
Originally Posted by monkeyposeur View Post
Stuttering/hesitation/bucking can have so many causes and many of them can share the exact same symptoms which can be extremely frustrating as you have discovered.

I had a stalling/stuttering issue and it turned out it was the coilpack(s). NGK coil packs from RockAuto are great. They run about $62 each. I would advise against getting cheap ones.

Things I checked/replaced before the coil packs:
Checked ECU for stored codes
Reset ECU multiple times
Ran new ground lines
Checked fuel pump and fuel pump sock (there have been instances where the sock gets so clogged up it causes fueling issues)
Replaced fuel filter
Replaced fuel pressure regulator
Checked for boost leaks (found a loose intake coupler)
Replaced MAF with a new spare I had laying around
Replaced Spark Plugs.
Replaced alternator with new higher output voltage unit (had it laying around)
Logged during pulls - no knock detected.

I had no misfire codes which also made the problem hard to track down.

After I replaced all four coil packs the car was pulling like it used to. Replacing the coil packs was last on my list of things to do, so it was a frustrating process.

When I replaced the coils I wasn't even sure if it was going to help so I didn't bother and try to isolate which coil(s) were causing the problem. Do yourself a favor and just replace all four.
Well I'm really starting to lose my patience with this car lol.
I've now replaced all 4 coils and plugs with replacements from subaru (get a discount wife works there). Replaced fuel filter today to see if that was an issue. Still just getting nowhere. I did notice i'm running very very lean so i think it'll be going to the shop for a new tune. Not sure what changed but i'm tired of throwing money at things that clearly aren't helping.
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Old 05-20-2022, 06:09 AM   #24
undyjr
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iWire sells the replacement plug for your coil packs. They're cheap and worth a try at this point.

Last edited by undyjr; 05-20-2022 at 06:10 AM. Reason: it's early...
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Old 12-07-2022, 07:26 PM   #25
monkeyposeur
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Oops, double posted somehow.

Last edited by monkeyposeur; 12-08-2022 at 02:13 PM.
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