picky with 02 sensors

[95subiblu]

http://www.rockauto.com/en/moreinfo.php?pk=991852&cc=1269806&jsn=349

 

So, when I got my subi it had a p0420. i'm not so sure if its the converters or not but that's going to be one of my last things to try. there isn't any exhaust leaks- i checked. At any rate I changed the old 02 sensors (front and rear) with the one on the link (DENSO) in hopes that it would solve my 130 miles per tank poor mpg problem, but it didnt do anything. as far as I know the o2 sensors that it comes with are also Densos- are the ones I got too cheap? I hear that these cars are picky with the o2 sensors. Any suggestions as to what I could do to fix my issue. I'm going to change my coolant temp sensor tomorrow to see if that helps.

 

I still don't know enough about these motors and stuff to post more contributing posts, but as I learn more I promise to post less like this and be a better member of the 'scoob community, thanks!~

[Brighton96]

How many miles are on the car? If it's over 200k then I may suspect a dead catalytic converter. But if you are getting horrible gas mileage then that pretty much proves it's bad O2 sensors. You can do NTK or Denso but replace both the front and back sensors at the same time and just make sure to match the brands (don't buy one ntk and one denso) I got them off amazon and it saved me about $60 vs my employee discount at Advance Auto. It takes about 30 minutes to replace them yourself and it's pretty painless as long as you buy/loan the O2 sensor sockets (parts stores rent them to customers)

[Osei]

When was the last time plugs were changed?

If necessary you can put a spacer on the rear O2.

 

O.

[95subiblu]

I changed them both. and at the same time changed the plugs, the oil, and the valve cover gaskets. It has 143k miles

[doublechaz]

How is the performance besides the terrible gas use?

[RumbleRumble]

If you can disconnect the cat and see if it runs better.

[95subiblu]

How is the performance besides the terrible gas use?

 

 

to be honest, I wouldn't be too sure on that since the car has been this way since I first got it. but, when in 5th traveling 60mph or so, if you mash the pedal all the way it isn't doing much but making noise- accelerates pretty slowly.

but If in neutral I can rev it up to 5k no problem. i do feel it a bit slow, even it is already an under powered car.

[Brighton96]

It sounds like the O2 sensors are toast. When mine went bad, MPG was the first thing to go bad and then it would stall out when slowly coasting up stop signs and what not.

[95subiblu]

It sounds like the O2 sensors are toast. When mine went bad, MPG was the first thing to go bad and then it would stall out when slowly coasting up stop signs and what not.

 

 

that's what I thought. but, I just replaced them with the DENSO ones about last week I think, and it changed nothing. I just changed the coolant temp sensor (the one behind the motor by the IACV) it I'm not so sure it did much.

 

my reasoning behind that is that maybe the old sensor was going bad so it would give a false reading making the ecu think that it was always cold- causing a rich fuel mixture.

[Brighton96]

Did you reset the computer after the install? Just disconnect the battery and leave it off for 15 minutes or so

[95subiblu]

Did you reset the computer after the install? Just disconnect the battery and leave it off for 15 minutes or so

 

 

Yeah, I changed the valve cover gaskets the while changing the sensors and I removed the battery to get to the driver side valve cover. but it turns out it might be the crank or cam seals that are leaking.... this car was abused before I got it apparently. but a '95 OBDII 2.2l non interference dual port 5mt is a great powertrain to have.

[Brighton96]

The cam and crank seals are a pretty easy job, just have to deal with taking all the timing junk off. And yeah I wouldn't mind having the 5MT instead of the 4EAT.

[95subiblu]

The cam and crank seals are a pretty easy job, just have to deal with taking all the timing junk off. And yeah I wouldn't mind having the 5MT instead of the 4EAT.

 

is it really? the valve cover gaskets were super easy in comparison to the 1.8t on a passat. I f*****g hated that car lol. I did the timing on a '03 mits 6g72 and it wasn't too bad, this car being a 4cyl should be simpler right?

 

how much do you think a shop could charge for it? it's winter in Juneau so the weather is extra shotty, and I moved up recently so I don't have all my tools at my disposal.

[Brighton96]

We have the same motor and I've had the timing junk off 3 times (one time was a parking lot timing belt service) and I just did all the gaskets on my car which included and cam and crank seals. The shops in my area in WV charge between $300-600 to do the timing belt job, so I figured it'll be around that cost, it's a few hours of labor but it's not a really difficult or tricky job. When I did my timing service it took me 3 hours and 45 minutes.

[doublechaz]

Things to check when the O2s are good would be jumped timing belt and plugged exhaust. Unless you are used to driving 'vettes you shouldn't feel like this car is so underpowered. It's not a racecar, but I wouldn't call it underpowered.

[95subiblu]

Things to check when the O2s are good would be jumped timing belt and plugged exhaust. Unless you are used to driving 'vettes you shouldn't feel like this car is so underpowered. It's not a racecar, but I wouldn't call it underpowered.

 

how could I check the belt? haha yeah, it's just not very fast.

[doublechaz]

That would involve getting all the accessory belts off, remove the pulley on the front of the crank, then take off the 3 timing cover sections. Then you would check the little marks on the cam and crank pully to be sure they are all lined up. For me, checking exhaust pressure is easy since I have an extra O2 port up front that I can screw a pressure gauge in to. I don't know how a normal person would go about checking it, but it can make a huge difference if it's not flowing free.

[MilesA]

A clogging catalytic converter could cause a lot of backpressure which would account for poor power and fuel economy. The power drop gets worse as more load is put on the engine. It can lead to overheating, also.

 

Checking belt timing is correct involves remove the timing belt cover and aligning the crankshaft on the 12 o'clock mark. Then checking the timing marks on each sprocket are aligned.

[Setnev]

The P0420 code is a tricky code to fix. I used to have a 05 Hyundai Tucson that would throw the code whenever I went on longer road trips. They replaced vacuum lines, intake gaskets, O2 sensors, etc. They finally investigated further and found ethanol corrosion in the fuel lines, fuel rails, and on the fuel injectors. They replaced everything under my extended warranty. They were going to replace the catalytic converters but the warranty company wouldn't cover them. Two weeks later the check engine light came back on a 100 mile trip. I was getting the P0420 code and Lean Fuel Mixture code. On a recommendation, I performed a fuel system pressure test and found out that the pressure was dropping drastically under load. It was effectively leaning out the fuel mixture by actually starving the motor, throwing the O2 sensors off balance and then getting a false reading. I replaced the fuel pump and the filter and the code never came back.

 

I have no issues using Denso sensors. Most OE sensors are made by either Denso or Bosch.

[twisty]

A clogging catalytic converter could cause a lot of backpressure which would account for poor power and fuel economy. The power drop gets worse as more load is put on the engine. It can lead to overheating, also.

 

we just had a 1980 corvette in for rough engine and power loss. while idling in the shop in a lift spot, the catalytic apparently got red hot from being so clogged and burned the paint on the lift brace. i once started a field on fire with a 1984 chrysler lebaron with a red hot cat as well. fun stuff.

[95subiblu]

That would involve getting all the accessory belts off, remove the pulley on the front of the crank, then take off the 3 timing cover sections. Then you would check the little marks on the cam and crank pully to be sure they are all lined up. For me, checking exhaust pressure is easy since I have an extra O2 port up front that I can screw a pressure gauge in to. I don't know how a normal person would go about checking it, but it can make a huge difference if it's not flowing free.

 

would a timing light save me the trouble of taking everything apart?

[Brighton96]

You can't do the old school timing light and rotating the distributor. The cams and crank have one grove cut in the pulleys so there's only one way to time it and it's really easy to set.

[MilesA]

would a timing light save me the trouble of taking everything apart?

You're thinking of ignition timing. Checking the belt is for the valve timing. Not the same.

[95subiblu]

You can't do the old school timing light and rotating the distributor. The cams and crank have one grove cut in the pulleys so there's only one way to time it and it's really easy to set.

 

You're thinking of ignition timing. Checking the belt is for the valve timing. Not the same.

 

Oh man- I guess I have some more learning to do about these motors. haha

[doublechaz]

To elaborate, all the cams in an engine have to be quite precisely lined up with the crank as far as rotational position. Our engines have twice as many cams a most engines because of the two cylinder banks. If any of these is out of line then the valves under that cam will open and close at the wrong time with up to devastating results to power/efficiency. Think of the engine's suck/squeeze/bang/blow cycle. If the intake valves open early then exhaust may push into the intake and displace good air. If they open late they won't inhale fully and may even blow back into the intake during squeeze. If the exhaust open early the bang will go out the tail pipe instead of through the crank to the tires. If they open late the exhaust may go into the intake again.

 

Contrast that with spark timing. If that is early the bang will push down on the piston while it is trying to come up wasting power fighting itself. If it happens late the piston will be running away from the bang. Both result in reduced power, but for different reasons.

 

Either of cam or spark timing can cause damage if they are far enough out.

 

As a specific example my 2.2 "single cam" meaning two cams, single for each bank, had the driver's cam jump two teeth. I've done a deal of mods and believe I'm running about 165 HP to the 135 stock, but with the one cam just two teeth out or about 20 degrees I was making, no kidding, 20 HP. I couldn't even get up a mildly steep driveway under my own power.

 

(Usually people only talk about spark timing becuase that used to be adjustable to just about anyone. Cam timing has never really been adjustable without fairly serious engine mods. That builds the bias to assume spark when someone just says timing. But with todays toothed timing belt systems it is possible and for some engines even common for timing to jump a tooth. Hence the need to examine if that has happened)