Dalee1104 Posted September 18, 2017 Share Posted September 18, 2017 So for the 2 years that I've owned this car and the maitanence I've done to the thing being pretty much everything including head gaskets, master gasket set, and then bottom end work with new clutch and such. All this maitanence and I've been chasing this same issue that never seemed to go away. The car wouldn't go through it's power ban smoothly, it would kind of lurch at about 3k and it was just really really slow. After finding nothing over and over i gave up and dealt with it. Last night as I was driving home from restoring some jdm projector beams I got a cel, I ran it with a little obdII reader and came up with the p0420 code. Most common cause is the bank 1 O2 sensor according to the torque pro app. But it can't be that those sensors are brand new, the whole exhaust is. So I dig around some more and find a thread of a subaru mechanic who logs his information that he works on and gave a list of potential causes of this issue Basically how he described it is that the efficiency of the engine is below threshold and the bank 1 O2 sensor is what's picking up that lack of efficiency (in my case I think the excessive fuel as I run very rich, about 13 mpg). The list consisted of thing like fuel pump, fuel filter, air filter, MAF, O2 sensors, catylic converters. I'm going through all of this list and checking off each one as I've done all of that maitanence but then I see him note the engine voltage being too low will cause that code to show up. So I think to myself well let's try it out, I put the car on a deep charge, slow cycle 2amp overnight charge. I just got back from driving around for some errands and the car felt absolutely different. The power was smooth and responsive and the car had a lot more balls then I was used to. It solved what I've been chasing forever. I'm unsure if this is getting me stronger spark to help my gas mileage and the running rich issue. But my thought process is that something has to be faulty then, there has to be something in the system that is causing that voltage to drop and make my car run like crap. So my question to you wonderful people is what should I try to counteract these issues? Alternator? Grounding kit? Msd coil pack for funsies? Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 18, 2017 Author Share Posted September 18, 2017 Oh also side note, once I charged the car the cel went away so it's almost for certain a lack in voltage Link to comment Share on other sites More sharing options...
Brighton96 Posted September 18, 2017 Share Posted September 18, 2017 Maybe a dead cat? or partially blocked up Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 18, 2017 Author Share Posted September 18, 2017 The cat is brand new also actually. But when I charged the battery over night, the car is noticeably better this morning so wouldn't that mean it's something with the voltage in the engine? Especially considering even my passenger who doesn't ever notice anything noted the car feels smoother today. Basically charging the battery fixed my issues, but I want it to be a permanent fix so I'm unsure what to tackle first Link to comment Share on other sites More sharing options...
Brighton96 Posted September 18, 2017 Share Posted September 18, 2017 Have you had the alternator bench tested if it isn't new? If it isn't supplying enough power then the car will primarily running off the battery which would make it act inconsistent. Link to comment Share on other sites More sharing options...
doublechaz Posted September 19, 2017 Share Posted September 19, 2017 Pretty much all of the sensors that the ECU uses to know what is going on are electrically powered. The ECU has a voltage sensor in it that it uses to try to adjust the calibration of the sensors based on what voltage you have. Usually this is full charge, nice day, lights off vs. cold winter night, lights on, after a hard start. I bet if you have something pretty serious with your electrical that the voltage is outside what the ECU can correct for. This would make sensors read 'wrong' and the ECU would be completely confused and do all sorts of yucky things like give you 13 mpg. As to what is actually wrong, you'll have to baseline the battery voltage and then check it a few days later using the same conditions. If it is slowly sagging then you probably have a charging problem. If it is the same, but it's always low then you probably have bad grounds, rotted wires, a messed alternator, probably some other things that someone else will point out. The bench test mentioned above it also a good place to start. We'll all work on this and get it figured. Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 19, 2017 Author Share Posted September 19, 2017 Okay so I didn't have time to do much of anything to the car yesterday. The alternator has never been bench tested or tested of any sort at all except 2 years ago. When I bought the car the alternator was out so I got one from a junk yard and at the time it put a charge out of like 14 volts around there but that was 2 years ago and the car does have a sub without a capacitor and I know that can take a toll on an alternator, also the car has died a couple of times and I've just push started it and never charger it. That being said the battery is fairly new and in good condition but if the alternator was out my car would be dying everywhere wouldn't it? I charged my car the night before last and then yesterday it drove wonderfully, like perfect actually, no cel, driving almost all day. So i didnt charge it last night however and now this morning I started to notice a bit of inconsistency at 3k rpms, where it's always dropped off it's power normally, making my car thoroughly slow. Along with the inconsistency I also got the P0420 code again. What I'm genuinely stuck at is what I should try and tackle first. The list from that code ranges from air and fuel filters, to fuel pumps, to voltage, to 02 sensors, and then the one that seems like is most common the cat. But I've replaced everything in that list except the fuel pump as it tested good pressure and haven't done anything with the voltage including no coil pack upgrades or anything Link to comment Share on other sites More sharing options...
doublechaz Posted September 20, 2017 Share Posted September 20, 2017 I haven't heard of an alternator failing in a way that would charge the battery enough to keep starting day after day but would leave a serious undervolt, but there are a lot of things in the world that I haven't heard of. First would be to get a multimeter on the battery while the car is off. It should be 12.7. Then you would do the same test with the engine warmed up so that idle will be as slow as it goes. I'd say 13.5 would be borderline and with any rpms above idle you should be in the low to mid 14s. A more likely problem would be bad grounds. If the engine ground were bad it would make the coil and other items mounted metal to metal on the engine see a 'fake' lower voltage. If your elternator is making 14.0 volts and your ground is bad getting pulled up by 2.75 volts, then the coil would see 11.25 volts. You can test ohms from the neg battery post to various points on the engine block with the engine off. You should get basically 0 ohms. You can also do this by checking with the engine runnings and look for volts between the neg battery and various points on the engine. You should get 0 volts. If you can get those checked then we'll keep working out what is going on. Link to comment Share on other sites More sharing options...
twisty Posted September 20, 2017 Share Posted September 20, 2017 bad grounds is my guess as well. also, in regards to your sub. how big an amp is it? what lighting upgrades have you done? did you do any cable upgrades when you dropped the sub in? have you done the big 3 ground mod? i have a 1500w mono amp pushing a couple 12" subs, along with a 250w 4channel pushing 4 mid grade door speakers. i also have some upgraded fogs and HID headlights. my stock alternator held up well for a while, but it couldnt take the load more than a couple months. i ended up changing out for a 125A alternator and adding some extra grounds as well as running a 4ga direct to the alt from the battery to try and balance the load and charge capability. even with all that, the alternator at idle will dip under 13V when the bass drops hard and the lights are all on. i need a second battery to keep the system stable. check your grounds. look up the grounding mod here in the forums and do that, regardless of whether you find a bad one. Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 20, 2017 Author Share Posted September 20, 2017 I was thinking about doing that grounding kit everybody talks about. The sub is a 1400 watt sub but only a 1000 watt amp, the door speakers and rear 6x9 have a peak of 700 or 800 watts but their rms is a lot lower. The door and rear speakers have quite a bit into them, their high quality Rockfords. Other then that the jdm lights are in but I'm not using HID or anything and as of right now that's about it. In the near future I'm attaching some 500ff hella series rally lights to my basket rack, there's 4 of them so I'm not sure what kind of power those would pull Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 20, 2017 Author Share Posted September 20, 2017 Okay tested the voltage and the resistance. When the car is off the battery is at 12.1, when the car is on and even at low idle the alternator makes 14.1 and the battery is at the same. Revving the engine makes it go up to 14.2 but that's it. Measuring the resistance I went from the negative post on the battery to various grounds and just pieces on the engine and almost everywhere got ranging -.87 to -1.04 Link to comment Share on other sites More sharing options...
doublechaz Posted September 21, 2017 Share Posted September 21, 2017 The battery voltage with car off is a bit low. You may have a damaged cell. Running is OK. Last one was Ohms or volts? With a negative in front of it sounds like you were doing volts. I'd pull and wire brush all the grounds you can find and check that again. You'll want something about 10 times closer to zero. Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 21, 2017 Author Share Posted September 21, 2017 Tbh I'm a solid noob so I googled what the ohms was on the multimeter I was using and it said I had it right. Idk it's one of those free ones from harbor freight Link to comment Share on other sites More sharing options...
twisty Posted September 21, 2017 Share Posted September 21, 2017 im confused, you went from the neg terminal to other ground points and got a voltage signal? if that is true, you have a shorted positive hanging somewhere. that would be the cause of the drain. 14v at idle is nice, what is it while the subs and headlights are on? turn them all on, then run the ac fan at the max speed and see how the system holds up at idle. Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 21, 2017 Author Share Posted September 21, 2017 Yes you are correct on the first statement so that means i should be looking for a shorted positive wire somewhere? Would it be in the engine or just anywhere in the car, that could be a pita if it's anywhere in the car. And I don't have a.c. but I'll run the music and headlights and update you guys momentarily Link to comment Share on other sites More sharing options...
twisty Posted September 21, 2017 Share Posted September 21, 2017 start pulling a fuse at a time, doing the same test until you dont have a draw. that should narrow the search for the short. Link to comment Share on other sites More sharing options...
Dalee1104 Posted September 24, 2017 Author Share Posted September 24, 2017 So I took the car to the subaru dealership just out of curiousity just to see what they would say. They wouldn't take any other option other then that since my exhaust is aftermarket and much more free flowing with the aftermarket exhuast also that my ecu is reading too much air flow through the exhaust that it's not used to and the only way to fix it is to get an ecu tune for a bigger exhuast. Myself personally haven't gotten the cel back after clearing it just to see if it would come back. The car is back to it's lurchy self again though, haven't had time to try and find that stray positive wire. I'm gonna charge it tonight and see how it acts in the morning. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.