Flat/Sluggish spot in engine when driving

[Shibe]

08’ Impreza 2.0R manual, 214xxx k’s.

I have had the car for about a week and I’ve noticed when driving it that the car has a slow/flat/sluggish spot around 2000 until  2500 rpm where it struggles to accelerate. The revs kind of fluctuate up and down around and it slowly climbs until it hits around 3k rpm and it accelerates fine. Some days are worse than others, sometimes it happens, sometimes it does not. 

 

My first guesses are are spark plugs and leads or something wrong where it’s starving it from fuel? Maybe a fuel pump or the likes of. 

 

Any ideas?? Thanks guys.

 

Edited January 13, 2018 by Shibe

[Subru]

I had exact same car a year ago and I noticed it had very little power down low but idk about the revs etc.

[THUNDA]

I had a similar problem ages ago, ended up changing a whole lot of parts for no reason, Could be alot of different things but will likely be pinpointed accurately by a subaru specialist with a ecu scanner, if your in auckland pop into @Subirex Automotive

 

Otherwise check/ replace the basics

Spark plugs/ coils/ HT leads, fuel filter, air filter etc

 

Good luck  

 

[Shibe]

I should also add that when downshifting and engine breaking the revs drop really low to around the 300-400rpm mark and feels like the car is going to stall 

3 hours ago, Subru said:

I had exact same car a year ago and I noticed it had very little power down low but idk about the revs etc.

 

Yeah I think they generally don’t start making much power until around 3.2k rpm but mine is suuuuper hesitant before then 

[Guest]

Is it only when cold?

[Shibe]

3 minutes ago, evowrx said:

Is it only when cold?

 

Nope, cold and warmed properly. In fact I think it might be worse when it’s warm but it’s quite hard to tell since it’s qute inconsistent 

[Gripless]

Sensor or intake leak post MAF sensor. Maybe alternator supply issue at low rpm.

 

does it rev freely and smoothly when in neutral? Is it a load based issue, more people in the car makes it worse.

 

Like @THUNDA said if you don't have a obd2 dongle or cable to log data take it to a shop. Or you'll blindly be replacing parts.

[Shibe]

2 hours ago, Gripless said:

Sensor or intake leak post MAF sensor. Maybe alternator supply issue at low rpm.

 

does it rev freely and smoothly when in neutral? Is it a load based issue, more people in the car makes it worse.

 

Like @THUNDA said if you don't have a obd2 dongle or cable to log data take it to a shop. Or you'll blindly be replacing parts.

 

Idle in neutral isn’t the best. It tends to fluctuate the revs a bit and shake when it drops 

[Gripless]

Idle control can get stuck or fail or not sure if the non turbo has the TGV (but the 08 upwards run the TGV at idle and maybe light load not just cold start like the older cars). But logging shows what the Ecu is trying to do.  

guessing it's a throttle cable not electronic, still learning Subaru. 

 

could still be coils or plugs but they tend to sound lumpy almost constantly.

so many options until you start checking things off.

but check the voltage before you do anything else. Make sure it's 12v or higher.