Low RPM Stutter / Hesitation

Seems to have just recently started, got just over 135,5xx on it, done the Tranny flush at 110k, thought it was the tranny at first, but it will do it in park, anywhere from idle to 2500ish rpms, all seems to be if I just ease on the throttle, I've seen posts about the GT's doing it, but this is only a 2.5i, hate to take it to the dealer but I need to get it fixed, trying to sell the car and a persepective buyer wasn't impressed.

 

The ECU hasn't been recently reset at all, ran full synthetic oil in the car since I bought it just about at 21k. Head gaskets were replaced last year.

 

Check engine light is not on.

So I took it to a local dealer, they did a throttle body, and injector cleaning, charged me almost 213$ and said front 'a/v' sensor, replaced the upstream O2 and the car still hesitates... any other suggestions besides the knock sensor, sick of throwing 100$ bills at it for it to continue to run like garbage.

When was the last time the spark plugs/wires were changed?

August 11 prob 20k miles. They supposively checked that. They did the plugs with the headgaskets, timing belt, water pump, tensioner, heat shields and cat last year. Transmission was serviced by a local tranny shop and they pulled the pan and used a gasket so the dealer fixed that a few months back so the tranny fluid isn't or shouldn't be dirty which was one of the things they said they got off the Subaru techline even tho it's in the motor. At an idle at a stop it almost feels like its misfiring but still no CEL..

And I have now replaced both O2 sensors and I still have a hesitation... this car is about $1 away from being set on fire!

Spark plug tube seals?

Spark plug tube seals? Think I'm getting oil in one of the plugs? I had the headgaskets done a year ago isn't this something a good tech would check? I also have an update anyway. After replacing the second O2 I drove it hard and got a CEL of misfire in cylinder 3, gonna pull the plug and check it out if it looks good gonna do a bump test and see if it's getting spark but at least I now have something to check into that I hope is in the right direction.

I had the headgaskets done a year ago isn't this something a good tech would check?

 

Never assume a good tech works on your car, trust noone!

 

My Outback had a head gasket replaced at the dealer years ago before I owned it, and the spark plug tube seals were totally shot. The plugs were soaked in oil, the tech re used the old gaskets.

That's for sure... I bought wires from the Subaru dealer since they were cheaper then aftermarket with the discount I get and low and behold when I pulled wire 3 it broke inside and the inside of the wire stayed connected to the plug. Was a pain to get out but no more hesitation. CEL didn't shut of after around 200 miles so I reset it last night. I'll probably be driving a bit today to see if it reappears. Called the Subaru dealer and suggested the next time someone brings in a car with no CEL you check ALL the plugs...

Good to hear it is working again!

You ever have any stalling issues? My wives wagon is going through the same problems with an occasional stall while stopped. Was thinking it's the cat but maybe the plugs after reading this.

 

thanks

It never stalled on me. RPMs at idle were pretty low. If it was in neutral and you let it sit for 20 seconds and tapped the gas not too hard you could feel it hesitate. It's slowly coming back and I had had the dealer do the fuel cleaning which is the BP 40 or something I've heard people rave about but at the next tank I also did Lucas too. The wires were deff shot. The cat I did the year before at 110-115ish as that had been playing peekaboo with my CEL for years before it finally stayed on long enough to get it to the shop.

Hmmm... I'll pull the plugs this weekend and take a look at them. Now I just gotta sort out the cat...damn OEM ones are pricey!!!

Yes they are. I paid 972$ for an unloaded one for my 05

I know this post is older and I had started it, but again I'm getting a misfire, and I didn't get a CEL, checked the pending codes and low and behold I get misfire cylinder 3 again. I'm going to try and compression test it this weekend, and at the same time I am a little hesitant at doing the valve adjustments like I've heard others talk about. Wouldn't this misfire screw with a compression test? I mean if it's running lean per the dealer and I can smell it, that means to me that it's not detonating right which suggests the compression test wouldn't be 100%, or am I wrong? I have new Subaru plugs to put in it too even though it has 146k now and had them done at 115k, wires were done between the two with Subaru wires. I also don't notice any power loss, it still feels strong through the whole RPM range, yet seems to be misfiring at a larger range, originally it had to be idling and then a quick stab of the gas and it'd misfire, now it varies, sometimes it does it, sometimes it doesn't, yesterday I got stuck behind a car doing 30mph on the dot and it consistently did it.

 

It's not the transmission, it does it in park / neutral it's definitely a misfire.

What came of this?

Wondering about this as well.

 

I'm getting what feels like misfiring as well with no CEL. I've only had the car for the last 11k miles of it's 104k life, so I'm doing my plugs and checking wires second, I've already replaced my air filter hoping that it was just an old clogged filter and cleaned the Air Flow Sensor. Haven't replaced any sensors yet, and really hoping I won't have to just guess at random sensors until it goes away.

definately sounds like a leaking spark plug gasket. I had the same issue and its hard to see without a good flash light. If you run it with a misfire for long it will destroy the catalytic converter like mine did. The seals were poorly designed and subaru has redesigned them since then. The valve cover bolts are pretty hard to get off if they are corroded.

Just FYI, I was having the same sputter, in park and on hard take offs. I put in NGK iridium R plugs, and I am set to go. Paid 101 bucks at the Subaru dealer. I did have my own plugs. Had them check the bots and they put seals in also. Car runs great.

Reviving the dead thread. Having this issue as well, and the car even threw a check engine light. There's oil on my spark plug leads so I assume that's causing issues with fouling the plugs. Would changing the plugs and wires (haven't done that in like 75k km) be enough for now or would I have to do the plug seals and valve cover gaskets? Is it a hard DIY? I've done my own timing belt and a bunch of other stuff but nowadays I'd have to borrow garage space to do this.

Reviving the dead thread. Having this issue as well, and the car even threw a check engine light. There's oil on my spark plug leads so I assume that's causing issues with fouling the plugs. Would changing the plugs and wires (haven't done that in like 75k km) be enough for now or would I have to do the plug seals and valve cover gaskets? Is it a hard DIY? I've done my own timing belt and a bunch of other stuff but nowadays I'd have to borrow garage space to do this.

 

Change the plugs and wires, I personally never use OEM parts but a few big ones (Alternator) . People will swear to use OEM Subaru parts. I have never done that. I used NGK wires and plugs. It's easy to do, there are many youtube vids on it.

Change the plugs and wires, I personally never use OEM parts but a few big ones (Alternator) . People will swear to use OEM Subaru parts. I have never done that. I used NGK wires and plugs. It's easy to do, there are many youtube vids on it.

 

Yeah, did that the other day and it's sorted right out. Kinda sucked in -7C weather though...

 

Mostly just wondering if this will become more frequent if I don't address the valve cover gasket