Severe hesitating

[TulsaBob]

Hi , all. Hive mind question:

2001 Forester: Severe hesitating and terrible fuel economy. I've changed the fuel filter with no improvement. It will hesitate AWFULLY and then, sometimes, suddenly clear up. And then go right back into the practically undrivable hesitation.

I was thinking it could possibly be the ignition coil. Does that make sense?

Thanks, everyone!

 

[NazForester2016]

Does the CEL come on with the problem?

 

[TulsaBob]

Yes, the check engine light is on. Reports as O2 sensor issue. However, I find that most problems I have seem to report as an O2 sensor issue!

 

[Dick Foster]

Electronic engine management systems are strongly dependant on the first O2 sensor reading to determine how much fuel to give the engine (injector duty cycle) so that could very well be your problem. It's a good start, at least.

 

[TulsaBob]

Update:

Changed the ignition coil and fuel filter and the problem is still present.

it seems to start OK, badly hesitate and then get better from every stop.

 

[Dick Foster]

Let us know when you stop shotgunning parts and change the parts the car is asking you to change and the problem is resolved.
Just changing random parts until you stumble on the bad one is no way to fix a car, although many stealerships do exactly that because it's not their money and it's an expensive process.

 

[Malpaso2000]

This may sound odd, but in my 2007 Dodge Ram I was having a similar issue. The batteries in the remote were going dead. I discovered the solution when I used the spare set of keys, and the issue cleared up. The spare set is almost never used. It may not be related in a Subaru.

 

[chasfish]

Maybe a bad pcv? When was last time it was inspected cleaned or replaced?

 

[TulsaBob]

Let us know when you stop shotgunning parts and change the parts the car is asking you to change and the problem is resolved.
Just changing random parts until you stumble on the bad one is no way to fix a car, although many stealerships do exactly that because it's not their money and it's an expensive process.

My apologies. I'm not a car guy and I'm trying to get this fixed the best I can. the CEL disappeared when I replaced the ignition coil.

 

[Dick Foster]

My apologies. I'm not a car guy and I'm trying to get this fixed the best I can. the CEL disappeared when I replaced the ignition coil.

It's best to get a scan tool of some sort and let the car guide you as to what parts to change. Not just randomly change parts until you accidentally stumble across the problem.

I keep a Scangauge 3 plugged in all the time so I can read and reset fault codes anytime while also adding several gauges so I can keep my eye on things before they become a problem.

» ScanGauge III

www.scangauge.com

 

[TulsaBob]

Maybe a bad pcv? When was last time it was inspected cleaned or replaced?

I'm going to clean the MAF and change the PCV today.

 

[TulsaBob]

Well apparently, this model has a MAP sensor not a MAF. Does anyone know the location of the MAP sensor for the 2001 Forester?

 

[Dick Foster]

Well apparently, this model has a MAP sensor not a MAF. Does anyone know the location of the MAP sensor for the 2001 Forester?

It will actually have both, a MAF mass air flow typically found just after the air filter and a MAP, manifold air pressure (intake) . Can be found anywhere in the intake manifold.
A good book on electronic engine management helps a lot in un ravelling how today's auto engines work.

Here's one of the many out there and of course many e-books are avaliable on the topic too.

Amazon.com

 

[TulsaBob]

UPDATE

Cleaned the MAP sensor. Car accelerates much better, but it now shifts HARD. Anyone have a clue?