My 2003 Subaru Forester intermittently loses power

[steve_runner]

Hello Everyone: 

 

This is my first post on this forum, so I hope that things go right for me in this post.

 

For the past year, my wonderful 2003 Subaru Forester (actually my mom's car) is acting strange. When it runs, it runs great. However, what happens all too often is that the car loses power. When you step on the power, the RPMs go down and the car will sometimes not start after that.

 

I have done everything from change the spark plugs and wires to even changing the ignition coils. I have one backup ignition coil and even when swapping these back and forth, the intermittent problem keeps reoccurring. Sometimes I spit on the connector and it works for a short time then quits again. 

 

I used some contact paste on the contact and sometimes this worked, and sometimes it didn't. So, finally, the last week or so, I replaced the 4-prong connector going to the ignition coil. This worked for about a week, then low and behold, it started all over again.

 

I have a theory and i want your input. I believe the reason this problem is intermittent is because there is a shorted wire somewhere. From what I observed late last night when checking the connector with my ohm meter, the only wire in that setup of wires that should have zero to 5 ohms is the yellow/green wire. The remaining three wires are positive wires I am sure and should have infinite ohm readings when zeroing them out. However, the yellow wire on the terminal is actually reading 28.5 ohms and I am thinking that this could possibly be the intermittent short that keeps coming and going. Could I be right about this? I have HVAC/R experience in electrical troubleshooting and have run into similar things like this in my respective trade field. 

 

What are the ohm readings I should be getting when trying to figure out these four wires coming off the ignition coil wiring harness? I think only one wire should be a ground and the other three should have infinite ohms. 

 

I am super frustrated with this situation and your help would be appreciated. I don't believe I have an ignition coil problem or connector problem. Replacing the other one was probably a waste of time. 

 

By the way, yesterday I had a mechanic replace the alternator which was old and not charging, but I don't think this is related to the problem I have been having on and off for the past year. Please help me if you can.

 

One other thing: I noticed that some models of the Subaru Forester have a 3-wire wiring harness configuration going to the ignition coil. Did they remove this wire altogether seeing that it was a redundancy? I am thinking they did, but in any case, it does not relate to my exact problem.

 

I doubt this problem I am having is anything but electrical. The symptoms, again, seem like something (a wire) is intermittently shorting.

 

Steve

[1 Lucky Texan]

first, consider a new thread asking for a shop recomendation near you. Someone may know of a soob-friendly mechanic.

Is there a DTC after this happens? Even with no CEL, there could be a pending code. Have the computer scanned and post any codes here.

If the car has a MAF sensor, those sometimes have an intermittent failure inside. Also, a common failure point is old knock sensors, they can kill power and might not cause a check engine light. It's one area where cheap ebay sensors work for most people. Not hard to swap either if you want to just try something.

 

Any oil on the plug wire boots? leaking valve cover gaskets might put oil on the plugs causing missing. Old wires sometimes arc in moist/rainy weather too.

Edited March 12, 2018 by 1 Lucky Texan