I have a 2001 Subaru Legacy Sedan 2.5-liter 4-cylinder with 61,000 miles. I took it in for its 60,000 mile service just 4,000 miles ago. I first noticed the problem just recently when accelerating on to the freeway. Though my foot remained constant on the gas pedal, the car reacted a couple times as if my foot had come off slightly. When it was happening, the car had a slight hesitation and minor loss to the acceleration. When it happened the second time, I carefully watched the RPMs, which did not change in anyway. It does not happen when running at a constant speed.

Now with the recent colder weather, it has also started to chug when idling – feels like it wants to die. The RPMs are still staying steady though. Since it has just been in for the 60,000 mile service, I assume the fuel filter and sparks plugs are new and not the issue. In searching the web I see other possibilities include catalytic converter, fuel pressure regulator, fuel pump, oxygen sensor, etc. I am also wondering if it could be as simple as bad gas and am running the tank out and will fill up and see if anything changes. Any thoughts on how to narrow down the cause or how to approach this would be very appreciated.

any cell showing up, autozone will read it for free, i kinda had the same problem , bad coolant temp sensor, real pain to change ,

Sounds like a misfire. Is the Check engine light on?

 

Did you buy gas at a shady gas station?

The check engine has not come on. The gas was from Costco. I just ran the tank down and filled it up at Exxon with the middle grade to see if it will change anything. I will report back my results.

that sounds exactly like what my 99 2.2 automatic is doing. see my "cutting out while driving" post. I still have it but am planning to do my timing belt service before I continue since it is way overdue and don't need the headache of that breaking. I replaced the TPS and the knock sensor as well as cleaning throttle body and IAC valve. My next suspect was this neutral switch. I get the P1507 code occasionally now.

My problem turned out to have an easy fix… spark plug wires. I replaced them and now the car is running awesome.

My problem turned out to have an easy fix… spark plug wires. I replaced them and now the car is running awesome.

 

Keeping a good set of plug wires on your Subaru is one of the very best htings you can do to make it happy:)