I fixed it! …maybe, kinda… we'll see

"PowderHound" (PowderHound)
08/25/2016 at 16:11 • Filed to: None

I’ve been having a weird hesitation the past few weeks around 2500 rpm in my WRX that felt like a misfire, turns out it was. There were no CELs until yesterday when it was finally triggered for a misfire in cylinders 1 and 4. Interestingly enough, after the CELs came on it seemed to smooth out a little bit but it was still there. I got it home and began checking and cleaning a bunch of stuff; Cleaned the MAF and connections, cleaned the throttle position sensor plugs at the throttle body, cleaned the battery anodes and connectors, checked coil packs connectors and that they weren’t loose, and checked for vacuum leaks/disconnected hoses and found nothing.

I was about to bike to work this morning and decided it would be better to drive my car to see if it fixed anything and throw some fuel injector cleaner in it since that’s another possibility for misfire and I haven’t put any of that in there in a good while. Since the battery was out and reset the ECU, clearing the codes, I let the car idle for a few minutes to relearn idle (heard this helps from somewhere and it certainly isn’t hard). Well, the car drove great! No misfires, no codes, no stuttering, even holding it around that 2500 rpm mark in second/third it didn’t miss a beat.

I’ll chalk it up as another victory but I’m sure it will come back around to rear it’s ugly head. If that does happen I may have to go with changing the front 02 sensor, I changed it 2 years ago so maybe it’s seen it’s share of miles? Also, you may have noticed I never mentioned spark plugs, they were changed a few months and less than 10k miles ago so I am doubting that those crapped out on me within a year.

DISCUSSION (13)

HammerheadFistpunch > PowderHound
08/25/2016 at 16:18

Did they put new injectors in with the rebuild? I had a stumble/misfire on my FXT that turned out to be a bad injector.

PowderHound > HammerheadFistpunch
08/25/2016 at 16:28

They didn’t, and I doubt they cleaned the old ones. Did your stumbling happen at a specific rpm? That is the only thing throwing me off. I could see it if it was happening all over the rev range

HammerheadFistpunch > PowderHound
08/25/2016 at 16:29

Is it all the time? or just sometimes?

PowderHound > HammerheadFistpunch
08/25/2016 at 16:33

It was pretty much any gear 1-4 between 2300-2700 rpm. Fifth was fine and fourth wasn’t as bad as 1-3 second was the worst

HammerheadFistpunch > PowderHound
08/25/2016 at 16:42

hmmm, maybe not an injector then. Trouble is you will just have to wait until it throws a code.

DipodomysDeserti > PowderHound
08/25/2016 at 17:15

I started having a misfire on our van at work. The spark plugs were old so I figure I’d check those first. Somehow three had backed their way out and were sitting in there loose. If it comes back, maybe check the plugs (I know how much of a PIA it is on the EJs).

PowderHound > DipodomysDeserti
08/25/2016 at 17:41

Definitely will look at that as a possibility if it continues to misfire

TahoeSTi > PowderHound
08/25/2016 at 19:48

Did you do any Data Logging with the issues? That would help really help. Hesitation is usually something to do with the ECU pulling timing. Data logging could help you figure out why it’s pulling timing.

Also, I replace my plugs every 25,000 miles I think the service interval is something like 30k if you haven’t replaced them in a while it’s worth doing.

PowderHound > TahoeSTi
08/25/2016 at 20:05

I didn't. I have been meaning to get an old windows laptop and everything to data log. Spark plugs are within 10k miles probably a good bit less

You can tell a Finn but you can't tell him much > PowderHound
08/26/2016 at 09:14

Were the coils replaced on the rebuild? I had to replace one of my coils at around 30,000 miles because it went bad.

PowderHound > You can tell a Finn but you can't tell him much
08/26/2016 at 10:51

Didn’t get new ones. Not sure if we used the replacement engines coils or the ones from my blown one. Either way, that’s a lot of miles on the coil packs. It could be that as well, I just hate throwing money at the problem and not knowing what it actually is

You can tell a Finn but you can't tell him much > PowderHound
08/26/2016 at 11:18

Yeah, I would drive it with the fix you did for a while and see if it throws a code again. If it does, swap the coil packs and see if the misfire follows the coils. At something like $200 a piece you don’t really want to be swapping those out just in case. Plus they are a PITA to change.

Khalbali > PowderHound
08/27/2016 at 01:16

If it comes back, say it's a misfire on cylinder 3, take the #3 plug and swap with #2, and take the #3 coil and swap with #4. Then see where the misfire goes, #2 change plugs, #4 change coils, #3 means probably injectors, though you could try a cleaner before you replace them.