Car loses speed and engine RPM

[Mohammed Moawad]

HI all esteemed forum members,

I own a 2012 Subaru Impreza, it has 18,700 miles on the clock and it has had all services done routinely and maintained regularly according to the service schedule in the manual. Nevertheless something strange has happened recently, on a really hot summer day while I was cruising at normal speeds the car has suddenly started losing RPM as well as speed, accompanied with a sense of choking but with no apparent unusual noises. Even after pushing the accelerator pedal the engine didn’t start gaining RPM whatsoever, I had to then pull over turn it off and start it again, afterwards everything went absolutely fine.
It has done this once almost a year ago but all I had to do then was pushing the pedal a bit further down and for longer and it gained RPM normally again.

An additional bit of info that might be helpful.. After a long park in the Sun the engine took longer to start, and didn’t actually start untill pushing the gas pedal (it has never done this before and it starts normally without pushing the pedal).

Another point to be taken into consideration, I regularly use octane boosters and fuel system cleaners (STP). Everything esle is operating perfectly.

Any help will be extremely appreciated.

Topic

[Brian]

The symptoms sound completely random and not possible to duplicate for a dealership. I’d take a look at the TSB’s for it to make sure nothing falls under this category

http://www.automd.com/recall-tsb/search/?m=Subaru&mm=Impreza&y=2012

[Its me]

Interesting problem.. Have you pulled any codes? Even if there is no Check engine light, check for pending or historical codes… Possibly a misfire code (may be a P030X problem)

How clean is the air filter and plugs?

I would start by pulling pending and historical codes…

In the absence of this I would look for a fuel delivery issue. A clue may be when it took a while to start and it started after you pushed the pedal in. (engine is flooded, depressing the pedal to the floor often is the clear flood mode).

One may think a leaking fuel injector (internally). Reading the fuel trims may yield a clue as well…
Also the ambient air temperature sensor (readings with a scanner) and MAF should be looked at..

Also it could be as simple as some bad gas if this has just happened a couple of times…

Also FWIW octane boost is nothing but snake oil and is a waste of money IMHO, in tank fuel injector cleaner is also a waste of money as well… The only pour in treatment that I think has any merit is Techron (this is added to some brands of gasoline as well)

Good luck

-Karl

[Mohammed Moawad]

I’ll try pulling any pending codes and update with the findings…
Appreciate your help

[Lorrin Barth]

My guess is some outlet is still selling winter gas and you got some.

Yeah, octane booster doesn’t work. The only place more octane is available is at the pump. In tank fuel injector cleaner I saw work once. Use it sparingly – once a year.

[EricTheCarGuy]

You might check for an exhaust restriction.

What you describe sounds similar to those symptoms. Also, I don’t think you need to use octane boosters and injector cleaners on a regular basis like that. Sometimes overuse of those products can actually damage the fuel system. More info on solving performance related issues here.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Good luck and keep us posted.

[Author]

Replies