A bit of help with my BG5

Hello lads.

I drive a 96 Legacy wagon 2-liter N/A MT. And MPG had been not really great for me. Latest measure was 145km per 23l petrol (about 14.7 US MPG?). Also it idles kinda rough, sometimes you can feel whole car shaking a little. Previous owner said it was busted engine mounts so I had them replaced but it still has this (to smaller degree though).

 

What I did:

• Replace MAF
  
• New spark plugs
  
• Replace spark plug wires (one wire was shorting so replaced all)
  
• Replace throttle body (I busted throttle position sensor by accident so my fault)
  
• Replace fuel filter
  
• Replace fuel pump (old one had low pressure - 2 bar instead 4.5 bar for new)
  
• Replace engine oil and gearbox oil (not really related but had to do it anyway)
  

 

Now I've read the MPG FAQ and one thing remains is cleaning the IACV, I haven't done it yet but I've read online that bad knock sensor can cause bad MPG because it retards ignition timing. Is this true or I should'n waste time on it? I never noticed a CEL light up. Also I'll try to use fuel system cleaner product next time I fill up.

One more thing, my car has DOHC engine and the manual says it uses 95 octane fuel, is this true? I've been using 92 octance.

Thanks in advance

I don't think the IACV does much while driving, I think it's only really used at idle/closed throttle. Cleaning it won't hurt but don't think that'd solve your issue. Also that difference in octane won't do much, we typically run our cars on 87 here and NA subaru's don't seem to care. Oil viscosity plays a larger role than you'd think with MPG, I ran 0w-20 just as a test once and got up to 23mpg highway where the previous best was around 20 mpg (using 5w-30.) Also, I average 17/18mpg with a slightly refreshed engine so you really aren't that far off. I'd just chock it up as a tired engine and maybe injectors that aren't spraying properly.

I get 29 highway, and in the city, with the racecar switch on, I get 22. I would call 22 highway broken.

 

Have you done anything to diagnose the car? The most common cause for bad mpg is either oxygen sensor problems, or exhaust leaks ahead of the oxygen sensor making the computer confused about what is actually happening. I was able to get my mileage that low once when I had an exhaust leak where the pipe joins the cylinder head. It sounds like a lifter tick, but on the bottom of the engine instead of from above. Once I fixed it the car was back to normal mpg. With modern scanning gear you can see what each sensor is telling the computer.

Hi again. Something weird started happening a few days back.

When I start the car in the morning it worked fine for a minute and then rpm really dropped down and car almost stalled and CEL lit up. This lasted for a few seconds and then rpm became normal and CEL went away. Now today something different happend: it started stalling and CEL lit up again but then the car actually stalled. I started it again but CEL didn't go away now. I thought I'd deal with it later and drove off. I went to the gym for about 2hrs and when I came back CEL was still on but the car runs fine.

What happened there?

Hi again. Something weird started happening a few days back.

When I start the car in the morning it worked fine for a minute and then rpm really dropped down and car almost stalled and CEL lit up. This lasted for a few seconds and then rpm became normal and CEL went away. Now today something different happend: it started stalling and CEL lit up again but then the car actually stalled. I started it again but CEL didn't go away now. I thought I'd deal with it later and drove off. I went to the gym for about 2hrs and when I came back CEL was still on but the car runs fine.

What happened there?

 

update. when I left work tonight it idled really weird. it got quite a bit colder now where I live and usually when I start the car it has this cold idle higher rpms for a few minutes but tonight it just started with "normal" idle as if engine wasn't cold. maybe a thermostate issue or temp sensor? dashboard temp gauge works fine

When things come and go it is often that there is a bad electrical ground that gets better and worse as it jiggles and as temperatures change and such. This can cause various engine sensors to read incorrect values and then the computer makes all kinds of weird decisions based on the bad data. Like weird idle speed behavior, stalling, sputtering, you get the idea. If the car has ever been driven on a road with salt, I would say that bad grounds is way behind schedule.

When things come and go it is often that there is a bad electrical ground that gets better and worse as it jiggles and as temperatures change and such. This can cause various engine sensors to read incorrect values and then the computer makes all kinds of weird decisions based on the bad data. Like weird idle speed behavior, stalling, sputtering, you get the idea. If the car has ever been driven on a road with salt, I would say that bad grounds is way behind schedule.

 

well now CEL stays on all the time and usually when I start the car in the morning it has "cold idle" a bit higher rpm but now it just idles at normal rpm from the beginning as if engine wasn't cold. and also this morning it had a bit of trouble starting

It would help to know the codes that are set.

Hi again lads. It was freezing these few days (-15 C at night) and yesterday my car couldn't start in the morning. I called for emergency start service and they managed to start it. What they said is I had bad spark plugs. They were new but I bought cheapes ones, Denso brand but I accidentally bought plugs for SOHC engine (I have DOHC engine). Right plugs cost 2.5x the ones I bought and also are platinum plugs. Yesterday I took my battery home so it wouldn't discharge overnight but today morning it didn't start either. Are these plug really bad or is my battery bad? I don't know how old is it and it's cheap ass noname brand and it says 60AH and 500 CCA. When starting voltage drops to 8.41 volts. I'm planning to call emergency start tommorrow again and get a good battery (95AH VARTA brand and it has 830CCA). Would this fix my issue or do I have to get the right spark plugs also?

 

Here's how I was trying to start it after -15 C night https://youtu.be/WgAjJze9Ns4

1. Computer controlled fuel injected cars do not need you to continuously stomp on the gas pedal while starting. In the old days of carburetors a shot of startup fuel was delivered by the accelerator pump when you stomped on the pedal. No such device has existed for about 30 years. You may, however, be confusing the computer by flapping the throttle vane back and forth. Just let the computer do the starting.

 

2. The starter motor is not designed for continuous cranking for minutes at a time. If the car hasn't started in 15 seconds you are not going to get it to start by holding it longer. In non-freezing weather you might actually burn down your car doing that.

 

3. If your battery can support that huge amount of cranking it is not the problem, unless that huge amount of cranking done repeatedly has worn out the battery since the video.

 

4. Spark plugs couldn't cause what you show in the video unless they are 100,000 miles past needing changed, or they are installed wrong. Wrong plugs may cause detonation once warmed up or other such problems, but they won't prevent you from starting.

 

4. As to the actual problem, it sounds like you have uneven compression which is never good for starting.

 

4. It sounds like you got a couple sputters from it so perhaps severely abused fuel injectors through running cheap gas. This presents more in cold weather. If it didn't fire at all, then injectors probably are not bad. Also a fuel delivery problem could be a bad fuel pump or completely clogged fuel filter. When was the last fuel filter change? Have you done anything to verify fuel pressure.

 

5. It sounds like the bad compression changed from the first few rotations so perhaps you have valves hanging open. Are you running the correct oil for cold weather?

 

This car desperately needs to see a real car doctor. Rather than swapping parts at random they can do tests to see what is wrong and let you know what needs to be done and how much it will cost. A first critical test is to read what codes are making CEL stay on. Perhaps you only have a bad ground that is preventing spark. Or perhaps your injectors are full of gunk and getting it running with a fuel system cleaner will fix it. Certainly you want to use the correct parts. If you have stuck valves it may not be worth fixing if it is caused by lack of oil changes. If it is caused by wrong oil only, then it would be trivial to fix.

 

Anyway, if we are going to help you, we will need solid actionable info. If a service garage is your path then they should be able to figure it out quick and easy.

1. Computer controlled fuel injected cars do not need you to continuously stomp on the gas pedal while starting. In the old days of carburetors a shot of startup fuel was delivered by the accelerator pump when you stomped on the pedal. No such device has existed for about 30 years. You may, however, be confusing the computer by flapping the throttle vane back and forth. Just let the computer do the starting.

 

2. The starter motor is not designed for continuous cranking for minutes at a time. If the car hasn't started in 15 seconds you are not going to get it to start by holding it longer. In non-freezing weather you might actually burn down your car doing that.

 

3. If your battery can support that huge amount of cranking it is not the problem, unless that huge amount of cranking done repeatedly has worn out the battery since the video.

 

4. Spark plugs couldn't cause what you show in the video unless they are 100,000 miles past needing changed, or they are installed wrong. Wrong plugs may cause detonation once warmed up or other such problems, but they won't prevent you from starting.

 

4. As to the actual problem, it sounds like you have uneven compression which is never good for starting.

 

4. It sounds like you got a couple sputters from it so perhaps severely abused fuel injectors through running cheap gas. This presents more in cold weather. If it didn't fire at all, then injectors probably are not bad. Also a fuel delivery problem could be a bad fuel pump or completely clogged fuel filter. When was the last fuel filter change? Have you done anything to verify fuel pressure.

 

5. It sounds like the bad compression changed from the first few rotations so perhaps you have valves hanging open. Are you running the correct oil for cold weather?

 

This car desperately needs to see a real car doctor. Rather than swapping parts at random they can do tests to see what is wrong and let you know what needs to be done and how much it will cost. A first critical test is to read what codes are making CEL stay on. Perhaps you only have a bad ground that is preventing spark. Or perhaps your injectors are full of gunk and getting it running with a fuel system cleaner will fix it. Certainly you want to use the correct parts. If you have stuck valves it may not be worth fixing if it is caused by lack of oil changes. If it is caused by wrong oil only, then it would be trivial to fix.

 

Anyway, if we are going to help you, we will need solid actionable info. If a service garage is your path then they should be able to figure it out quick and easy.

 

Thanks. So installing better CCA battery won’t help me right?

Fuel pump and fuel filter change was about a month ago

Oil is 10w40

At this point from all the way over here I would say your battery sounds fine. 10w40 should be ok. The two things I want to know are what codes are in it and what is the compression test for all four cylinders. After that would be time to verify fuel pressure and verify spark.

 

A very simple easy check you can do is pull the crank sensor and make sure the sensor end is clean, and then do the same with the cam sensors. They sometimes build up a layer of iron filings because the sensor is magnetic and that debris can cause them to send bad data to the computer. But I don't think that will be your problem in this case.

So I bought correct spark plugs this weekend (1 plug cost more than 4 old plugs lol. Old set was $10.26 and new set was $46.64). It did start in the morning but it was still difficult. Also I started it at night to see if plug wires were shorting but didn't see any sparks on them. Also put 95 octane petrol in it. This morning I read error codes and it said 13 - camshaft position sensor. Could this be my problem? Also somebody recommended me to use 5W30 oil. Should I bother changing it now? My 10W40 did less than 1000km since last change.

5w30 might be better if you have temps much colder than freezing, but it is not your problem listening to it crank.

 

A cam sensor problem certainly could do this. First would be to pull it out and check if it is dirty. Next would be to use a meter to check if the sensor works. Third would be to verify that the wires are all good. The sensor working sometimes and not other times indicates a wiring problem more than anything else, but the first two are easy and quick. Fourth would be to make sure the engine to frame ground and intake ground are good. These age and are likely not OK anymore if they haven't been worked on since 1996.

 

13 sounds like a first gen code. Second gen should be OBDII and the code would be something like P0340 from a scanner.

So I've been saving worst for last. Cam sensor was good, I've disconnected it while car was running and it stalled so it definetely works. One more thing I noticed is despite I've replaced spark plug wires one of them was still shorting (if I touched it I would feel a strong discharge). I thought bad coil pack so I found a know good but used one and got it replaced. Don't know about fuel economy yet but power has noticably imporved. Car now goes 60kph in 3rd gear @ about 2500-3000 rpm so that's nice. This morning however tempreture was just about freezing and cold start wasn't easy. Also replaced starter motor cause I busted original one. Still, while idling, car is jerking and I think missfiring probably? Tomorrow I'll go and check fuel injectors and I hope it's the problem and also I'll check compression.

Now about bad compression. I really hope it's alright BUT if it's not... That means piston rings right? Really expensive job

Also. I've messaged my local subie group chats and three people said it looks like temp sensor issue. One guy said he had same problem

Bad compression can come from a few things, all of them quite expensive. It's not usually bad rings as they would have to be so bad that other symptoms would have been present long before. Same with cylinder walls. Head gasket is probably most common and least bad. Valve damage can do it as well, but that usually would result in zero fire on that cylinder. But let's get spark and injectors fully tested before we worry too much about compression.

didn't mean to send this twice sorry

Bad compression can come from a few things, all of them quite expensive. It's not usually bad rings as they would have to be so bad that other symptoms would have been present long before. Same with cylinder walls. Head gasket is probably most common and least bad. Valve damage can do it as well, but that usually would result in zero fire on that cylinder. But let's get spark and injectors fully tested before we worry too much about compression.

 

Yeah I really hope it's fuel or temp sensor thing. Cheers

So I changed coolant temp sensor hoping it would fix cold starts cause a few people messaged me they had same problem. This morning temperature was just below freezing, about -2 C and very humid, and car didn't start easily. Now it used to throw an error for coolant temp sensor (code 21) and when changing I didn't disconnect the battery so maybe error was still in the memory? On my lunch break I went and disconnected battery for a minute and then scanned for errors and it didn't have any codes whatsoever. In the eveninng when I went home car started fine, temp was about -6 then. Also one thing I noticed: turns out my off-brand MAF was causing all this poor idling and jerking. I took an old original MAF from a guy i know and put it in my car and all of a sudden it idled a LOT better. Still a bit rough but probably that old MAF was faulty cause it was just lying around in his garage in a box of random junk. Also checked for head gasket leak symptoms and coolant was clear no signs of emulsion, oil dip stick had normal oil in it. Something I also saw online is you could open coolant reservoir cap (not radiator cap) and look for bubbles and I didn't have any. So I guess head gasket is fine?

 

Now all this got me thinking, could my bad MAF cause these poor starts? Cause ignition is fine, fuel systems seems fine, head gasket seems fine, car has decent power now after I replcaed coil pack. One thing that is known bad is MAF. Also didn't have a chance to run a compression test cause I personally don't have the tool and the guy I planned to lending it from was out of town.

Sounds good so far. MAF can cause a lot of problems. You could try gently squirting it with MAF cleaner and no other product to see if that helps. If it is dirty from being on a shelf... Also, you could try running a tank or two of premium name brand gas. Many years ago, before I knew better, I was running Citgo gas and it got where I could barely start it on cold wet days and it would run like crap until it warmed up. Literally one tank of Shell 92 and it was like a new car. At that time Citgo had little to no injector detergents in it. I don't know if that is still the case.

So.

I really hoped it wasn't a compression problem.

A few days back I went to a local subie repairs shop and they diagnosed bad fuel injectors and I've told them about coil pack and IACV and MAF stuff. So we ran a compression test and voi la - cyl#1 has 6 bar and others have 9 bar out of 11 normal. They proposed a theory that car was running too rich all the time because of bad fuel injectors and it caused piston rings to wash out and degrade. So I used this product for piston rings:

 

and changed oil after that and also used this

oil additive.

Don't know how good it's gonna be but I hope it gets me through winter and I'll probably sell this car then. Thank for your help @doublechaz

That's not ideal, but we can't always have what we want. A friend of mine has an old 4runner daily driver that has been running on 3 instead of 4 for a couple years.