So I recently did my headgaskets on my 99 forester. 5 speed, 116k on it. Any gasket that can be replaced was with Subaru parts. New plugs, wires, timing belt, water pump, tensioner, 2 smooth idlers and 1 cogged all replaced. So I've gotten a front o2 code (p0130), which I've replaced now twice with Subaru sensors. So I've got an annoying issue that I cannot figure out, when warm, my idle will bounce and won't stay steady for about 5 minutes after coming to a complete stop. When I drive from my house in Minneapolis to golden valley it's at operating temperature. I have 2 video that I'm going to post to show what it idles like once stopped. Any thought or ideas as to where to continue with my diagnosis would be so greatly appreciated. Any more info that someone may want to help I will happily provide. Cheers Mitch
That looks funky.. did you double check all wiring harnesses after rebuild? I've missed a few in the past that have caused all sorts of stupid codes etc.. I remember a rebuild once I did. Missed a connector for front o2 sensors. Threw a code and had some other issue. Was baffled after replacing both sensors. Ended up double checking and missed a harness that was tucked away out of sight. I would maybe start by checking the wiring. Did you remove motor from car?
I did pull the engine, I will double check all the connectors and bulk harness points tonight. Will respond this evening or tomorrow.
Try going over a checklist of everything you may have touched. Hoses. Everything! Tbh. I have rebuilt a few 2.5s for headgasket leaks. Haven't speant a whole lot of time diagnosing issues other than obvious things. Leaks etc.. Maybe someone with more experience could chime in too? I would start by double checking everything.
I've seen this type of behavior before. Here's a few questions for you to consider and help you out. Did you remove the Intake Air Control Valve (IAC or IACV sometimes) to clean it at all? If you did, you nearly always have to replace it with a new O-ring gasket as the constant vacuum on them makes the gasket swell when the IAC is removed and the gasket is exposed to atmosphere. Also make sure the connection is corrosion free and tightly connected when done. Have you cleaned the Throttle Body passages? Checked to make sure the throttle cables are not binding? Checked your connection on the Throttle Position Sensor for tightness, corrosion, and the proper voltage?
I actually replaced the IAC valve when I did the headgaskets. So it's brand new, with a new o-ring. Throttle body was thoroughly cleaned as well.
OEM iacv. No issues with it, just something I wanted to replace for preventative reasons. I'll double check everything this evening
All connections checked, including harness', vacuum lines, fuel lines, everything. Any more help or thoughts?
Check for an intake gasket leaking. Seen it quite a few time where they dont get cleaned perfectly an a little piece of old gasket can cause a leak
Lol oops forgot about that. How did your intake manifold gaskets look? Did you realign the manifold carefully onto the heads and bolt accordingly? Are you located in the cities?
I replaced the intake manifold gaskets, thoroughly cleaned both the heads and intake manifold itself prior to new gasket installation. I'm in Minneapolis on the border of Richfield and Edina
This is starting to look more and more like a vacuum leak. Might be time to get some leak detecter and start checking hoses.
Is there any possibility a clogged/bad catalytic converter causing too much back pressure do anything? I'm still getting a po130 code, any thoughts?
Hey Mitch check this out. http://www.subaruforester.org/vbulletin/f88/99-forester-warm-rough-idle-issue-105549/ May give a another option. Other then what has been stated previously. Another thought occurred to me did you have the heads and valves checked while the heads were out?
Isd your catalytic converter clogging up? That may,be far,fetched, but if the hg's were leaking that would deposit a lot of coolant in the exhaust potentially. If the cat is partially clogged it seems conceivable to me that the back preasure could have that 02 sensor flagging a problem.
No, that's true for sure, but I am suggesting is that the cat isnt clogged yet, but is becoming clogged or even has had the honeycomb break up. I have seen that before, even without codes (clogged up pipe as an exampe). Also, its possible that its really the rear 02 sensor throwing things off so the front 02 is telling the ecu that there is a problem, I have seen that too. Since this is a 16 bit ecu and I dont think you can log it efficiently, the best way to figure out if the 02 sensors are crazy is to put them on an osciliscope (whe have one at work). There is a reason the ecu is flagging the front sensor, got to get to the root of it. None of this necessarily preculdes other suggestions; valves, intake gaskets, erc. I would try this experiment. Clear codes, disconnect rear 02 sensor and see if the front code comes back (the rear code will pop for sure), rear 02 sensors can make the frontcsensor go crazy (seen this several times on wrx's, and the system is grossly the same). If both codes pop, try opening up the flange between the cats and see what happens then. Basically see if you can "mechanically" isolate the sensors.
Well, it's a bit crude, but I believe you have a two piece cat on that car, id so, you can start separating exhaust flanges and see if things change. Otherwise you would have to remove it and bench test if with an adapter for pushing compressed air through it. Not sure this iscthe right road or not, but it could be a valuable expermint since you have tried other things already. I personally would start by unplugging the rear sensor and see if anything changes.
so i unplugged the rear o2, it ran and idled well. So should I remove the cat and drive it? May be a stupid question but anything from here on out sounds good haha.
gonna swap exhausts tonight w/ my buddies catless 2.5rs exhaust. see how it works. experiment and catless FTW. will update this evening.
If you can find a spare rear 02 sensor, know to be good of course, that might be worth a try. Since unplugging it seemed to change the pre and post cat air/fuel monitoring it could just be a faulty sensor that isn't throwing a cel. Going catless is worth a shot too, but it could just be a sensor that isn't doing it's job right.
I pulled the trigger yesterday and just grabbed a new rear o2 sensor. After installing I went on a 20 mile drive and when I came back home it still was doing the same idle bouncing stuff.
Wouldn't a vacuum leak be constant and not related to temperature? Because it idles just fine when cold
Vacuum leaks tend to not be so noticeable when cold because the ECU is commanding a higher idle as well as being in open loop operation which tends to ignore some sensors, basically. Once the engine is warm and ECU is in closed loop, that's when sensors are read and ECU makes adjustments as needed. That is when an unmetered air leak (vacuum leak) causes havoc!
Just curious did you have the heads milled and resurfaced when you changed the gasket? Possible that there is a warp in the head (if you had some over heating when the gasket went) and now you still don't have a perfectly flat sealed surface on the head....?
I did not have them resurfaced, it overheated very shortly which made me immediately decide to pull the trigger and do the headgaskets. More diag will continue!.....
