turk56 Posted July 15, 2014 Share Posted July 15, 2014 Info about the car: 2008 Legacy SE 2.5i, auto transmission 123,xxx miles Timing belt, water pump, thermostat replaced at 115k Plugs, wires, K&N air filter, MAF cleaned, and PCV replaced at 120k Has been tripping the P0420 code for awhile now - few instances of stalling out at red lights etc, difficult to start sometimes. After the plugs and PCV valve replacement the light stayed off for ~2000miles. Did have an instance of a battery leaking acid all over the wire that goes from the battery to the starter and alternator a few years ago, some corrosion present but not tons. See attached for the data from my scanner, I have also attached 2 screenshots of the graph comparing O2 sensors. My initial thought is that the front O2 sensor is bad, since it doesnt seem to be changing much while driving (side note - when the scanner is set on lambda it doesnt change at all) and the Voltage doesnt read on the scanner - but at the same time, the rear O2 sensor should not have such a drastic wave form. Here are my questions - - is it possible to have both O2 sensors go bad - what would that look like? - could the corroded battery wire have anything to do with this? Voltage is 12.8V - should I bite the bullet and get a new cat? - I have a new front OEM O2 sensor I bought from the dealer, thinking of putting it in and seeing what the difference is... Any thoughts or advice would be greatly appreciated!!CSVLog_20140715_182109.csv Link to comment Share on other sites More sharing options...
FknBoss Posted July 15, 2014 Share Posted July 15, 2014 A p0420 code by itself should cause stalling unless the cat is actually melting or broken and clogged. 420 is just a cat efficiency code. That rear o2 only determines how well the cat is doing its job. If it's stalling their has to be another code. If not cat is clogged. Link to comment Share on other sites More sharing options...
turk56 Posted July 15, 2014 Author Share Posted July 15, 2014 A p0420 code by itself should cause stalling unless the cat is actually melting or broken and clogged. 420 is just a cat efficiency code. That rear o2 only determines how well the cat is doing its job. If it's stalling their has to be another code. If not cat is clogged. Thanks, The other code that it is throwing is P0340 - which just started today after it stalled out at a red-light. The P0340 only comes on after it stalls, i clear it and it goes away, but the 0420 comes back. Link to comment Share on other sites More sharing options...
FknBoss Posted July 16, 2014 Share Posted July 16, 2014 The p0340 is a cam sensor. Possible your car goes into o pen loop rich because of th bad sensor and too rich for the cat to keep up. Test cam sensor or replace first before cat. Link to comment Share on other sites More sharing options...
turk56 Posted July 16, 2014 Author Share Posted July 16, 2014 The p0340 is a cam sensor. Possible your car goes into o pen loop rich because of th bad sensor and too rich for the cat to keep up. Test cam sensor or replace first before cat. Possibly so - what would be the best way to diagnose that at this point? Thanks for your help so far Link to comment Share on other sites More sharing options...
turk56 Posted July 16, 2014 Author Share Posted July 16, 2014 Here are a couple videos I took tonight which might help. What is normal Cat Temp? I would think at least 1000F? If the cat was bad, wouldn't the temp be low? Link to comment Share on other sites More sharing options...
FknBoss Posted July 16, 2014 Share Posted July 16, 2014 If the cat was bad it would be high. When they clog they'll glow red. Also if it's way to rich unburned fuel can make it to the cat and ignite inside and ruin the cat. Test resistance on the cam sensor. Link to comment Share on other sites More sharing options...
jdtrager Posted July 16, 2014 Share Posted July 16, 2014 Is it a PZEV? If so the cat has more material and clogs easier. My wife's 08 Outback 2.5i kept popping up with that code, tried o2 sensors and ended up having to do the cat. Just my experience, hope that's not what it is for your sake because they are not cheap. As of 2 years ago you could not get an aftermarket replacement for it either. Link to comment Share on other sites More sharing options...
turk56 Posted July 16, 2014 Author Share Posted July 16, 2014 Is it a PZEV? r. No, it's not a PZEV. Guess I'll start calling around to get the quotes on getting the cat replaced.... Link to comment Share on other sites More sharing options...
turk56 Posted July 16, 2014 Author Share Posted July 16, 2014 If the cat was bad it would be high. When they clog they'll glow red. Also if it's way to rich unburned fuel can make it to the cat and ignite inside and ruin the cat. Test resistance on the cam sensor. That makes sense about the cat temp and unburied fuel. How do I go about testing the cam sensor resistance? Link to comment Share on other sites More sharing options...
FknBoss Posted July 16, 2014 Share Posted July 16, 2014 Set a multimeter to ohms and put one to 1 pin one to the other Link to comment Share on other sites More sharing options...
turk56 Posted July 16, 2014 Author Share Posted July 16, 2014 So here is an update - Last night after running the diagnostic, I cleared both codes. Since then, whenever I come to a stop, the car shutters and will almost stall - only stalled once. No CEL. This is worse when the car is cold, and doesnt really happen after driving for 15-20 min. If I shift the car into N, it doesn't shutter or stall - only in D. Almost seems like the car is not getting enough (too much?) fuel when coming to a stop. Is this symptoms of a cam sensor problem? I am going to reset the ECU and see if that changes the shutter/stall..... Link to comment Share on other sites More sharing options...
turk56 Posted July 19, 2014 Author Share Posted July 19, 2014 Anybody? I suppose I'll take it to a mechanic this week and get a new cat... Link to comment Share on other sites More sharing options...
FknBoss Posted July 20, 2014 Share Posted July 20, 2014 Sounds like the cat MAYBE clogged.. unbolt the exhaust before the cat and see if it still shutters Link to comment Share on other sites More sharing options...
turk56 Posted July 20, 2014 Author Share Posted July 20, 2014 Set a multimeter to ohms and put one to 1 pin one to the other Got it, what should the normal value be? Link to comment Share on other sites More sharing options...
FknBoss Posted July 20, 2014 Share Posted July 20, 2014 I can't remember. What I can do is test 2 of the cam sensors I have when I get home tomorrow. I had to make a 1000 mile trip to Florida for a family emergency. I'm heading back in an hour or so. Link to comment Share on other sites More sharing options...
turk56 Posted July 21, 2014 Author Share Posted July 21, 2014 Ok. Mine tested at 2.27 Link to comment Share on other sites More sharing options...
FknBoss Posted July 21, 2014 Share Posted July 21, 2014 Ok I'm using my auto ranging bluepoint multumeter. On ohm testing the 2 pins closest to the head my one is reading 23.8 and the other 24.2 Link to comment Share on other sites More sharing options...
FknBoss Posted July 21, 2014 Share Posted July 21, 2014 Not sure on your car but mine has 2 cam sensors one on each head. Link to comment Share on other sites More sharing options...
turk56 Posted July 21, 2014 Author Share Posted July 21, 2014 Yeah, just retested to make sure we are on the same page. My car only has one sensor, at the very front of the engine near the timing belt cover (see pic). Tested at 2.35 kOhms this time. I tested the wiring harness that plugs onto the sensor, reading at 23.85kOhms. What do you think? BTW - Thanks for all your help so far - based on what I've been reading, I am def having a timing or sensor issue - likely unrelated to the P0420 code - which I am getting checked out by a mechanic later this week. Link to comment Share on other sites More sharing options...
FknBoss Posted July 22, 2014 Share Posted July 22, 2014 It can be related to the p0420 code. That code is a catalyst below threshold meaning the rear o2 is sensing the cat is not performing as it should. This can be caused by 2 things. 1 the car running extremely rich so much that the cat can not keep up or it is bad. I would try a cam sensor first. It's quick and easy and may fix the issue. Rule number 1 of mechanics. Fix what's broke. If you think you diagnosed 1 issue then fix that issue first. Because they seem they aren't related sometimes they are. Link to comment Share on other sites More sharing options...
turk56 Posted July 22, 2014 Author Share Posted July 22, 2014 It can be related to the p0420 code. That code is a catalyst below threshold meaning the rear o2 is sensing the cat is not performing as it should. This can be caused by 2 things. 1 the car running extremely rich so much that the cat can not keep up or it is bad. I would try a cam sensor first. It's quick and easy and may fix the issue. Rule number 1 of mechanics. Fix what's broke. If you think you diagnosed 1 issue then fix that issue first. Because they seem they aren't related sometimes they are. Couldn't agree with you more. The only reason I think they may not be related is that the P0420 code has been popping up for quite a while now. But, I'm going to replace the cam sensor first. Do you know if it is ok to use an aftermarket sensor or does it need to be OEM? The AAP by my house has a BWD, or I can order the OEM. 25$ difference. Link to comment Share on other sites More sharing options...
FknBoss Posted July 22, 2014 Share Posted July 22, 2014 For 25 bucks if go oem. Link to comment Share on other sites More sharing options...
turk56 Posted August 12, 2014 Author Share Posted August 12, 2014 So just an update in case other people are having similar problems - - I replaced the camshaft position sensor with an OEM replacement. PITA. After driving for a few hundred miles, the stutter and stall problem was much better, but still there. - I took the car to the mechanic, who confirmed that the downstream O2 sensor readings indicated a new cat. I bit the bullet and 800$ later got a new cat installed. - After the cat install, and maybe another 100 miles, the stutter is gone, no stalls, smooth idle. Acts like the car can finally breathe again. Gas mileage has increased from 24mpg to 28.7 mpg Hope this helps someone else. Thanks again FknBoss for the advice and help. Link to comment Share on other sites More sharing options...
FknBoss Posted August 12, 2014 Share Posted August 12, 2014 No problem Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.