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Old 06-26-2017, 02:23 PM   #1
SeanRS203
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Default 05 WRX throttle hesitation and misfiring

Alright, yes there are a lot of threads like this and yes I've searched and read but none seem to have the problem I'm having. A shop is working on it with me and I'm just trying to get more input so we can figure it out.

Car: 2005 WRX
3 in high flow cat down pipe
3 in car back
Cobb EBCS
Cobb accessport
Cobb intake
Stage 2 tune
Act lightweight flywheel

All of this had been on the car for for about 5 months before any issues started. The flywheel has been on the car for about a year and a half. It's had the stage 2+ EBCS tune and EBCS for about a month before the issues started.

When I started my car one day I noticed it idled rough but I figured it was just an odd day and it would smooth out. But a little later the CEL came on as a cylinder 4 misfire then a bit later a cylinder 3 misfire. I got back home and cleaned the MAF sensor. Went to start it later in the day and it idled super bad and almost died. It was backfiring real bad so I just shut it off and left it. The next morning it started ok but still idled rough. The throttle also has a weird hesitation. The only way I can explain it is when I press the throttle is it kinda blips before the revs climb, that's in neutral. When it's heavier throttle and higher RPM it's perfect no problem. Between 2 and 3k rpm it bucks some if I cruise there. I did a little bit of checking with the tools I had (spark plugs, MAF etc.) then to the shop I went. Here's what they checked:
Spark plugs
Coils
Compression
Smoke test for vacuum leaks
Fuel pressure
Injectors
Cam sensor
Crank sensor
O2 sensor

Aaand nothing helped. They swapped parts from cylinders 3 and 4 to 1 and 2 to see if the misfire moved and nothing. Swapped MAF and O2 with known working ones. Nothing. Brand new cam and crank sensors. Compression was below spec but not too low, around 130s. But the compression was even across all cylinders.
After swapping the O2 sensor codes for all four cylinders misfiring came up. I cleared them and drove some more and only cylinders 3 and 4 came up. Took it to the shop for the cam and crank sensors. Drove it more and codes for all four cylinders misfiring came back.

Anyone have any insight? Anything would be appreciated because I'm running out of options
Thanks
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Old 07-02-2017, 05:59 PM   #2
SeanRS203
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Bump anyone had something like this?
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Old 07-07-2017, 02:43 PM   #3
SeanRS203
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Another bump...any advice would help
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Old 07-07-2017, 02:51 PM   #4
GroceryGetterL
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Did you log any of this on the Accessport?
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Old 07-07-2017, 02:51 PM   #5
SeanRS203
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Yes I have
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Old 07-07-2017, 02:52 PM   #6
SeanRS203
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Haven't really looked at it much other than watching the rpms drop as soon as I press the throttle
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Old 08-01-2017, 06:19 PM   #7
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Bump...had work done with the valve buckets as they weren't in spec. Still have the problem..
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Old 08-01-2017, 06:20 PM   #8
SeanRS203
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If anyone has any insight it would be really helpful
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Old 06-15-2018, 05:50 PM   #9
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Bump for the problem still occurring no matter what I try
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Old 06-15-2018, 06:53 PM   #10
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I know you've said the flywheel has been on there for a while but with all the things checked it seems to me that it's worth checking if you can do the work yourself so it's not a huge expense
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Old 06-15-2018, 07:45 PM   #11
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did you try the injectors?
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Old 06-16-2018, 08:15 AM   #12
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Quote:
Originally Posted by snow_bound26 View Post
I know you've said the flywheel has been on there for a while but with all the things checked it seems to me that it's worth checking if you can do the work yourself so it's not a huge expense


Yea I thought about that. Unfortunately I donít have the tools to do the work. Would the flywheel cause a code coming up without a symptom? I ask because the car definitely isnít running right and my gas mileage is suffering bad
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Old 06-16-2018, 08:18 AM   #13
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Quote:
Originally Posted by subaru_gc8 View Post
did you try the injectors?


My mechanic swapped injector 2 and 4 because the misfire is most prominent in cylinder 4. But the after resetting the codes it still came back in cylinder 4. So it didnít seem to make a change. But at this point Iím considering just replacing everything haha
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Old 08-17-2018, 07:26 PM   #14
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Update:

So now at idle I am running very rich. Like 11-12. (The reading is coming from my accessport, yes I know itís not near as accurate as a wideband O2 but hey its something right?) I am even getting the engine code of extreme rich fuel trim. This means either the car is getting too much fuel or no enough fuel is being ignited right? Iím thinking the latter is probably the problem. However when I step on the throttle it starts to rev fine but when it hits about 4K rpm, the car goes super lean and you feel a lack of power. I usually get out of throttle then so as not to run lean. However for the mechanic to see the problem and for a data log I have held the throttle down and when it reaches 5K rpm the fuel ďcatches upĒ and I run normal AFR all the way to redline.
Again any suggestions or comments are welcomed.
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Old 08-18-2018, 01:37 PM   #15
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have you checked the fuel pressure and made sure the fuel pressure regulator is doing its job?

maybe one injector is stuck causing the rich reading on the o2 at idle which would cause the other injectors to reduce output to correct. that would explain why it leans out under more load then rich back up to an extent once it goes into open loop. maybe let it idle a bit then look at the spark plugs and see of one looks different.
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Old 08-23-2018, 08:24 PM   #16
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Yea I thought maybe the regulator was messed up. But i replaced it a few months ago and nothing. Huh never thought about that. I have injectors I know are good. Maybe I should get them put in.
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Old 08-23-2018, 11:24 PM   #17
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Iíll post some data logs of whatís happening. So when I go WOT sometimes itíll start leaning out but then sometimes the fuel will randomly cut back in and pulls fine. This is very odd and very annoying. Thanks for all the suggestions.

After I figure this out I will write a book and become famous
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Old 08-25-2018, 01:15 PM   #18
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Pleas read, just went thru this clusterfu*c with an 05, 02 read good resist. no CEL, just for your info.

R/Mac

https://forums.nasioc.com/forums/sho....php?t=2883089
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Old 10-05-2018, 09:36 AM   #19
SeanRS203
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Awesome thank you for the link. I read through it. My mechanic has an 03 WRX and heís swapped the O2 sensors and MAF sensor from his car to mine and I still had the problem. I need to post those datalog soon lol Iím about to have my mechanic replace my injectors to completely eliminate that problem.

Quick question, does anyone know what symptoms a faulty wastegate would have?
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Old 10-06-2018, 10:06 PM   #20
CarmelValleyWRX
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faulty wastegate would not boost very well or if it was stuck it would over boost.
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Old 11-15-2018, 11:43 AM   #21
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Awesome thank you. Could a wastegate be ďstickingĒ at certain point maybe? Causing irregular boost? Iím not sure how accurate some of the data from the COBB AP is but the wastegate % looks like itís all over the place.
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Old 11-15-2018, 12:20 PM   #22
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what do your coils look like? how do the know that they are still good? I had a hesitation when I got into boost for a year before my cel came on. so just because you switch doesnt mean they are still good
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Old 11-15-2018, 01:14 PM   #23
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Quote:
Originally Posted by SeanRS203 View Post
Awesome thank you. Could a wastegate be ďstickingĒ at certain point maybe? Causing irregular boost? Iím not sure how accurate some of the data from the COBB AP is but the wastegate % looks like itís all over the place.
i guess its possible. look at manifold absolute pressure to see if your boost is steady. wastegate duty cycle will move around a bit to keep the boost controlled.
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Old 11-16-2018, 07:28 PM   #24
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strange question here but do you have an exhaust leak? also check the TGV or the wiring to the coils, I have read alot of similar issues caused by an exhaust leak, faulty TGV or weak power to the coils all worth a check!
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Old 11-16-2018, 11:16 PM   #25
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Quote:
Originally Posted by CarmelValleyWRX View Post
faulty wastegate would not boost very well or if it was stuck it would over boost.
if you hvce a faulty wg it would either have no boost or lot of boost, I still hold to my original diagnostic. its your coils
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