I have a 1997 Subaru Impreza Outback.

 

Example of whats happening.

 

Typically it starts just fine. I drove for almost two hours the other day and the car ran fine. All of the sudden it begins having a significant loss of RPM's, like it's stalling but catches itself before dying. It only lasts for a second but will happen multiple times. At this point, if I shut the engine off the car will not start back up. It will turn over but no ignition will take place. If this happens when I am at idle the car will sometimes die. This has happened multiple times. There is NO CHECK ENGINE LIGHT. 

 

I've changed the plugs, wires, and coils, fuel pump, fuel filter.

 

I was doing a search and saw someone describing what is happening to me and they changed the knock sensor so I pulled that off and put a multimeter on the knock sensor and the wiring harness on the motor side. Both check good. 

 

I'd like to get some advice on where to go. I havn't ruled out the knock sensor since this is an intermittent problem. 

 

Thanks for any and all help. Mike. 

Fuel pressure regulator possibly? Working most of the time but every so often throwing the fuel/air mixture way off. 

does it have a MAF? maybe tap around on it while idling - some soobs have intermittent MAFs.

 

scan for codes after it happens. could be a 'pending' code that would be helpful.

Edited January 28, 20179 yr by 1 Lucky Texan

Classic symptoms of the  MAF  failing . They don't seem to throw a code until they fail completely . I can't recall if 97 used them but 96 did.       Edit)  just saw this is an impreza most likely it is a 2.2  pretty sure you have a MAF on this,  look for the square unit with a large electric connector in the fresh air supply  just past the air filter. Usually have a green sticker on them. If you have one ... change it out . Go to wrecking yard or ebay and get an original equipment one, better used than a cheep china part.

Edited January 28, 20179 yr by montana tom

Thanks for the input. I'll check that out and let y'all know what I come up with it. 

An update thus far with new condition.

 

I have not been able to get to a junk yard yet to see if there is a MAF I can grab. Hopefully in the next two or three days. 

 

Now when I start the car the engine is right away idling at 2,500-3,000 RPM's at idle. It will NOT come down. 

 

I kept reading about the MAF sensor and what was happening to the car. I took a multimeter to the MAF, knock sensor, and TSP. They checked good except for the TSP which wasn't reading right on the multimeter so I changed that. There has been zero change since installing it. 

 

Do y'all think I should still be heading in the direction of the MAF after this new symptom of the car idling so high at idle? I havn't driven it since this new problem started. Not sure what would happen. 

 

Thanks again!

I've suggested the following many times but it seems to rarely be a problem.

 

Engine Temp Sensor - if it is bad in such a way the ECU thinks the engine is cold - it may be trying to 'choke' the engine and keeping rpms boosted while mistakenly warming-up.

 

but your rpms seems too high even for that.

I never had a 2.2 engine all of a sudden over rev but I sure had the MAF fail.  Just change it ASAP.

 

I don't know what a TSP is, but if it is a throttle position sensor, be aware that they are kind of tricky to calibrate.  There are good DIY's to instruct you. 

Yes i was referring to the throttle position sensor. 

 

I changed the MAF. still no change other than if I let the car just sit there and idle it will eventually lower rpms. Today I let it idle for about 30 min and it eventually got the rpm's under 1,000. I put it in reverse and drive just to go up and down the drive way to see what would happen but the car died as soon as it started moving. It started right up again but I hadn't anymore time to look at it for the day.