Gloyale Posted October 24, 2017 Share Posted October 24, 2017 Anytime AVLS malfunctions, it throws a code very shortly after. well, not always. The system has no way of detecting a mechanical failure. One of the springs or clips in the rocker assembly could fail. I am not saying this is it, just a thought. It's worth at least checking under the valve covers if the issue is as bad as OP says. I still bet carbon buildup Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 24, 2017 Share Posted October 24, 2017 I have not seen any EGR issues that caused pinging. Exhaust gasses are devoid of oxygen so they can't lean your mixture. Additionally the EGR only functions under part throttle cruise conditions in closed loop operation. It is not used during open loop acceleration as it would negatively impact engine performance. GD Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 24, 2017 Author Share Posted October 24, 2017 Thanks GD. I appreciate you talking through this. Here is what I am thinking. Purpose of the EGR system is to cool combustion slightly. Since all of the timing and blending and ratio stuff is interconnected, taking away that cooling effect could cause an increase in combustion temperature and... bingo! If, as I think it should, the ECU ignores the knock sensor at low RPM and load conditions that would further explain why there is no automatic correction happening until the engine speeds up. You are 100% correct about when the EGR is functioning. I did not know before but I have been looking into this over the past few days. EGR is closed at idle and WOT. All the rest of the time it is passing a small amount of exhaust gas and the system is tuned to allow for it. Only piece that is missing is the P0401 error code. If I had that I would be certain. Anyway, I flushed the EGR system last night so I am sure there is a good flow and we'll see how she sounds today. As I mentioned, the car's performance is exceptionally smooth with better than expected fuel mileage. Only the pinging sound is at issue. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 24, 2017 Share Posted October 24, 2017 Yeah the system can easily detect lack of EGR flow so I'm fairly certain it won't make a difference. Doesn't hurt to rule it out though. I can say that I've never had to clean a Subaru EGR with the one exception being a carbed EA82 that had a clogged pipe many, many years ago. The EJ systems (unlike Honda) never seem to clog. GD Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted October 24, 2017 Share Posted October 24, 2017 can't reacll if you mentioned the trans, but wonder if an input shaft bearing or , a cracked flexplate might do this? Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 24, 2017 Author Share Posted October 24, 2017 They do have a massive exhaust passage compared to those tiny tubes used on early systems. When I bought the car it had two issues that were confounding each other so no one was figuring out the problem. One was the EGR valve that was so full of carbon that it would not close. Add a MAF sensor that was off but not setting a check engine code. It made for poor driveability and no one was quite sure what to do. Those two corrections took a pig of a car and made it the pleasure to drive I always knew it could be. Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 24, 2017 Author Share Posted October 24, 2017 That is an interesting thought Tex. I am so glad that I brought this problem here. You especially have come up with the best ideas. And I keep hoping that the solution lies somewhere other than piston rings. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted October 24, 2017 Share Posted October 24, 2017 what trans do you have? Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 24, 2017 Author Share Posted October 24, 2017 4AT automatic. We'll,cleaning out the EGR system had no effect. Changed plugs tonight in case I was mistaken but ones I took out were identical. Ping does not happen when engine is cold. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted October 25, 2017 Share Posted October 25, 2017 GD - bad engine temp sensor? - but I haven't read of pinging being a symptom.....? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2017 Share Posted October 25, 2017 GD - bad engine temp sensor? - but I haven't read of pinging being a symptom.....? Never seen that, and coolant temp sensor failure on EJ's is almost unheard of. Easy to check in live data though. GD 1 Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted October 25, 2017 Share Posted October 25, 2017 oil pressure's gonna be higher cold Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2017 Share Posted October 25, 2017 oil pressure's gonna be higher cold True - could be mr. rod knocking. Wouldn't be the first one of those I've seen. GD Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 25, 2017 Author Share Posted October 25, 2017 The Subaru service manual does address rod bearing knocking so it is a known problem. Bearings have a different sound, they are consistent, and they don't go away at higher speeds but do change with engine RPM. Now that I cannot blame EGR I almost have to stay with the carbon. Blaming dislodging carbon on my newly acquired P0420 code. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted October 25, 2017 Share Posted October 25, 2017 lab analysis might help (blackstone , polaris ?) - metals or too much fuel, etc. in the oil would point to a bearing failing or weak rings allowing too much blow-by I guess. Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted October 25, 2017 Author Share Posted October 25, 2017 An oil analysis does make sense. I never had one done but talked extensively with someone at a local lab about doing this on Amtrak's road fleet when I worked there. We never followed through because the Director of Equipment did not believe it was cost effective. In this case it just might yield definitive answer as to whether it's time to start looking for another car. I ordered the Blackstone collection kit. Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted November 15, 2017 Author Share Posted November 15, 2017 Just a short follow-up. Changed the oil right after valve cover gasket replacement. After 1500 miles I am pleased to report the oil level reads slightly over full, just as it did when freshly changed. Pretty amazing for an engine with 237k on the clock. I've noticed that some days the ping is almost nonexistent and other days it sounds like a diesel. Also some days gas mileage is spectacular, occasionally achieving 30 mpg on my journey home, and other days it's closer to 25. In either case operation is very smooth. Lastly, it looks like the inefficient catalyst CEL is here to stay. Perhaps the bargain Pace Setter catalytic converter is not such a bargain. --Ken Quote Link to comment Share on other sites More sharing options...
kkingcqe Posted August 25, 2018 Author Share Posted August 25, 2018 It appears that I finally have a resolution. Check engine light reading P0171 had, within the past month or so, become very consistent about every 25 miles. I recently replaced a cracked PCV hose and bought a pressure gauge to check fuel pump pressure. No difference. Finally asked at a pay forum that features certified mechanics because I had run out of things to try. He suggested that the next step was to check or replace MAF sensor. Although the OBD Auto Doctor software that I also recently purchased showed acceptable MAF readings at idle he said that I should replace it anyway. It appears that the MAF sensor was the problem. No check engine light, no knocking. Still idles rather roughly for a modern engine, but I've put up with that for 5 years so I guess it's okay. Thought you might like to know. Thanks for the help! --Ken Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 25, 2018 Share Posted August 25, 2018 You can perform a volumetric efficiency calculation to check the MAF. And yes a lean code would certainly implicate it baring any vacuum leaks. Fuel trims would show positive numbers greater than 5 for sure. Takes 25+ to throw a 171. Glad you got it resolved. We see quite a few MAF failures from that era. GD Quote Link to comment Share on other sites More sharing options...
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