planemusic Posted April 6, 2015 Share Posted April 6, 2015 I have a 2005 Forester XS with 160K miles on it. This past summer I got stranded up in Maine with a bad spark plug. The spark plugs, wire, and coil were replaced. Following that, the car still didn't idle correctly. I disconnected the battery, waited about 30 minutes, re-connected the battery, turned the ignition to the on position for about 10 seconds, started the car and didn't touch anything and let the ECM relearn how to idle (as is a popular subject on these forums). The car seemed to run fine after that though I thought it idled a little rougher than before the fix. I drove the car though our rough Chicago winter with no problems. The first day that it got warm out the car developed a very rough idle - to the point of stalling at red lights. Now, if its cooler out it will start up normally but once the engine warms up it idles rough and usually stalls out. If its warmer out, as it was yesterday, the car is rough to start (you have to work the gas pedal) and idles really rough and then stalls out. It idles so low that the engine shakes the car uncontrollably. I cleaned the MAF, the throttle body, and the idle air control valve. That seemed to work for a day but it soon went back to idling really rough. What else should I check? Should I just replace the IAC? Quote Link to comment Share on other sites More sharing options...
lstevens76 Posted April 6, 2015 Share Posted April 6, 2015 Have you checked out the ECT? When it's idling rough try disconnecting it and see if the problem goes away. Also, vacuum leaks are a possibility. Quote Link to comment Share on other sites More sharing options...
planemusic Posted April 9, 2015 Author Share Posted April 9, 2015 Thanks for the tip. I did a little research on faulty ECTs with Subarus and it sounds likes it could be the culprit. I ordered a new one and it should be here tomorrow. I quickly tried to find it on my Subaru but came up short. Do you happen to know its location on a 2005 Forester? Quote Link to comment Share on other sites More sharing options...
wtdash Posted April 11, 2015 Share Posted April 11, 2015 (edited) You probably figured this out......but The ECT aka CTS (coolant temp sensor) is on the coolant crossover pipe that runs under the intake manifold (IM). It's on the passenger side, back of the IM...Usually hidden behind some wiring. GL, Td Edited April 11, 2015 by wtdash Quote Link to comment Share on other sites More sharing options...
lstevens76 Posted April 11, 2015 Share Posted April 11, 2015 That's about as rough as the ones on the 2.2L that you have to remove the air cleaning and all the PVC hoses to get to it. Another thing has your PCV Valve ever been changed? Also, what plug wires did they install? It seems that is a common problem with Subaru's and cheap wires as well. What plugs did they put in might be another issue? Before changing it you might unplug it and see what happens. Also, I use Torque (app for android) and a Bluetooth OBD2 scanner myself on all OBD2 cars. It makes life easier because unlike a normal scanner you can see real time fuel trim information along with real time coolant sensor and MAP information. A cheap temp reader ($25 or so) at Harbor Freight could tell you if it's reading correctly or not. Just some other thoughts. I do my own mechanic work out of necessity and sometimes by choice. Necessity = cost and choice = fun. Quote Link to comment Share on other sites More sharing options...
planemusic Posted April 19, 2015 Author Share Posted April 19, 2015 Thanks for the advice, guys. Sorry for the delay. I ended up replacing both the coolant temp sensor and the PCV valve. I checked and cleaned out the valve channel as some folks say it can also get clogged. After replacing the coolant temp sensor the car initially idled better but about ten minutes into a test drive the car started stalling at lights again. That was when I replaced the PCV valve - now the car idles better but not perfect. Though it doesn't stall at lights, it does seem to idle low and a little rougher than I think it should. How much truth do you folks think is in letting the car's ECM relearn how idle? Quote Link to comment Share on other sites More sharing options...
lstevens76 Posted April 19, 2015 Share Posted April 19, 2015 Do you have a check engine light on? A rough idle will usually cause one. Also, what plugs/plug wires? It is possible that with a bad etc and pcv you could have fouled a plug. Quote Link to comment Share on other sites More sharing options...
wtdash Posted April 19, 2015 Share Posted April 19, 2015 Hi, I'd look up ECU RESET and do it. That 'should' speed up the relearning. But if the original problem still exists it'll come back. Quote Link to comment Share on other sites More sharing options...
planemusic Posted April 23, 2015 Author Share Posted April 23, 2015 I replaced the plugs and wires with nice NGK stuff. Same problem. There's no CEL on either. Could it be the idle air control valve? Quote Link to comment Share on other sites More sharing options...
lstevens76 Posted April 23, 2015 Share Posted April 23, 2015 (edited) I replaced the plugs and wires with nice NGK stuff. Same problem. There's no CEL on either. Could it be the idle air control valve? It could be anything, and unless you like dumping money into parts lets take a step back. First, if you use an android phone I would pick up an inexpensive bluetooth reader and the torque app. That will help. Next, do you have an FSM (Factory Service manual)? If not find one online or pick one up. Once you have an FSM most of the time (someone else might correct me) they contain sensor specs and ways to test things like the IACV beyond what may be listed in the forums. And before putting more money out I would also consider things like a compression test, etc... to try and trace it down. Maybe do a run test on the cam sensor? Edited April 23, 2015 by lstevens76 Quote Link to comment Share on other sites More sharing options...
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