Check Engine Light

[halston2006]

2001 Outback, 90k miles. Check enginge light (cylinder 4 misfire) has been on for approx 8 mos. Car periodically idles rough. Repair shop changed coil, wires, plugs, which did not fix problem. Second repair shop changed wires & plugs 3 months later which did not fix problem. Went to dealer 4 mos. later. Dealer checked fuel volatility, which was 3.5. Used 4 tanks of premium fuel from brand name stations, went back to dealer with light on. Dealer had car for 3 days, could not find problem, even though they contacted Subaru New England about problem. Ultimately changed the o2 sensor, but the light came back on 2 days later. Dealer says volatility is still about 3.5, but I'm using the best gas (premium) I can find from the major stations. Any Ideas?

[Subie Gal]

do you have the code that keeps popping up?

 

the CEL code?

 

that would help a lot with diagnosing

 

seems like the only thing left is a bad cat....

 

Jamie

[tcspeer]

I had a cyclinder # 3 misfire that turned out to be the E.C.U. unit. If you will buy a set of noid lights you can check your injectors connectors with them, and they are very cheap at most auto stores. If the light dont work on # 4 (and it did not light on my #3) check and see if you have current to the wire that goes to that injector, if you have current then you will be where I was and the E.C.U. fixed my problem.

2001 Outback, 90k miles. Check enginge light (cylinder 4 misfire) has been on for approx 8 mos. Car periodically idles rough. Repair shop changed coil, wires, plugs, which did not fix problem. Second repair shop changed wires & plugs 3 months later which did not fix problem. Went to dealer 4 mos. later. Dealer checked fuel volatility, which was 3.5. Used 4 tanks of premium fuel from brand name stations, went back to dealer with light on. Dealer had car for 3 days, could not find problem, even though they contacted Subaru New England about problem. Ultimately changed the o2 sensor, but the light came back on 2 days later. Dealer says volatility is still about 3.5, but I'm using the best gas (premium) I can find from the major stations. Any Ideas?

[friendly_jacek]

I had a cyclinder # 3 misfire that turned out to be the E.C.U. unit. If you will buy a set of noid lights you can check your injectors connectors with them, and they are very cheap at most auto stores. If the light dont work on # 4 (and it did not light on my #3) check and see if you have current to the wire that goes to that injector, if you have current then you will be where I was and the E.C.U. fixed my problem.

Noid light, what a silly name.

I had to check if you didn't make it up.

[frag]

I had a cyclinder # 3 misfire that turned out to be the E.C.U. unit. If you will buy a set of noid lights you can check your injectors connectors with them, and they are very cheap at most auto stores. If the light dont work on # 4 (and it did not light on my #3) check and see if you have current to the wire that goes to that injector, if you have current then you will be where I was and the E.C.U. fixed my problem.

 

Can I ask a question prof? (This is my car fixing university...)

Would it not be when you do not have current going to the injector that the ECU becomes suspect? If not the case, could you explain?

[tcspeer]

I put the noid light to the injector plug and found it would not light, so I checked the other three and they would. So someone here on the board told me to check and see if current was coming to the connector so I checked that and found 12 volts. ( I think it was 12 volts ) The noid light dont light from the current from the battery it flashes with the signal from the E.C.U. if I remember right. So I had current going to the plug but it was not getting the information from the E.C.U. to do what it was suppose to. That is why it became the suspect. But dont forget I came here asking for help with this and had many lead me to the final answer so I am sure someone here can better answer your question than me. (

Can I ask a question prof? (This is my car fixing university...

Would it not be when you do not have current going to the injector that the ECU becomes suspect? If not the case, could you explain?

[halston2006]

do you have the code that keeps popping up?

 

the CEL code?

 

that would help a lot with diagnosing

 

seems like the only thing left is a bad cat....

 

Jamie

 

The code is P0304 - cylinder 4 misfire. I spoke to the dealer today. They still think that I'm using bad fuel, although I have been using nothing but brand name premium from a station other than my regular station. Today they told me to use nothing but 89, and stay with one station. I'm not believing the low volatility diagnosis, especially since they told me that the light did not go off during my 3 tankfulls of premium gas because of the volatility of all of the gas could be questionable. That would be believable if they had other vehicles with the same problem.

[halston2006]

I had a cyclinder # 3 misfire that turned out to be the E.C.U. unit. If you will buy a set of noid lights you can check your injectors connectors with them, and they are very cheap at most auto stores. If the light dont work on # 4 (and it did not light on my #3) check and see if you have current to the wire that goes to that injector, if you have current then you will be where I was and the E.C.U. fixed my problem.

 

The noid light idea sounds good. I'll try it this weekend and re-post. Thank you.

[idosubaru]

i think i'd first replace the spark pack with a used one for $25.

 

if it's a cylinder mis-fire then first isolate that cylinder - what are cyilnder dedicated items - plug, wires, spark pack and injectors. not gas, that would show up elsewhere, that's crazy talk.

 

cylinder mis-fires on these EJ motors are typically ignition related. are the spark plug wires Subaru OEM wires? if you had an independent mechanic replace the wires, there's a good chance they are not subaru wires. get subaru wires and NGK spark plugs. these 2.2 and 2.5 motors are sensitive to having perfect ignitions.

 

plugs - wires need to be OEM and carefully installed. they are easy to check and replace, so start there. you can even swap the bad cylinder plug and wire with ones from a good cylinder. if the error code "moves" or changes to that other cylinder then you know the plug or wire is bad.

 

that you've replaced the wires twice is the reason i said i'd replace the spark pack first. but make sure they are OEM wires.

[OB99W]

Can I ask a question prof? (This is my car fixing university...)

Would it not be when you do not have current going to the injector that the ECU becomes suspect? If not the case, could you explain?

Oh man, does that open a can of worms ! First, we have to differentiate between "current" and "voltage". Then, we can discuss how the injectors are switched on/off.

 

To begin, here's a bit of "Basic Electricity 101":

1) "Voltage" is the difference in electrical potential between two points. Even if not connected to anything else, a charged car battery has a little over 12 volts of potential difference between its two terminals. However, no current flows if nothing is connected between the battery terminals.

2) "Current" requires the flow of electrons in a circuit. If you connect a light bulb from the positive to the negative terminal of the battery, there is then a complete circuit. The bulb lights because the current flowing through it heats the filament, which brings us to "resistance".

3) "Resistance" is the characteristic that determines the relationship between voltage and current. A fellow named Georg Ohm figured that out, and we measure resistance in "ohms".

 

See: http://en.wikipedia.org/wiki/Ohm%27s_Law

 

Now, to get back to the injector operation:

All the injectors have one connection to +12V at all times that the ignition is on. They are activated, when appropriate, by making a ground connection to the second lead, completing the circuit and causing current to flow. That ground connection is made by an electronic switch in the ECU.

 

While more-sophisticated test equipment can be used to verify that the proper voltage and switching are available at the injector, a "noid" light can simplify things. If it doesn't light, and +12V has been confirmed at the injector terminal, that leaves only the ECU itself (or a bad connection to it) as the cause.

 

I hope that helps, and doesn't muddy things further .

[halston2006]

i think i'd first replace the spark pack with a used one for $25.

 

if it's a cylinder mis-fire then first isolate that cylinder - what are cyilnder dedicated items - plug, wires, spark pack and injectors. not gas, that would show up elsewhere, that's crazy talk.

 

cylinder mis-fires on these EJ motors are typically ignition related. are the spark plug wires Subaru OEM wires? if you had an independent mechanic replace the wires, there's a good chance they are not subaru wires. get subaru wires and NGK spark plugs. these 2.2 and 2.5 motors are sensitive to having perfect ignitions.

 

plugs - wires need to be OEM and carefully installed. they are easy to check and replace, so start there. you can even swap the bad cylinder plug and wire with ones from a good cylinder. if the error code "moves" or changes to that other cylinder then you know the plug or wire is bad.

 

that you've replaced the wires twice is the reason i said i'd replace the spark pack first. but make sure they are OEM wires.

 

 

 

By "spark pack" do you mean E. C. U. unit, or is it something else? Spending $25 to eliminate that issue sounds like a good idea. How difficult is it to replace and where on the car do I find it? As for the plugs and wires, the last time they were replaced, Subaru wires and NGK plugs were used. I am not sure about the first time, but even at that point the light was on and the plugs and wires were original. Sounds like time to get the aftermarket manual. Also, I agree about the gas. If the issue was as prevalent as the dealer is saying, there should be a line of cars with the same problem, instead of my one car that has them scratching their heads.

[tcspeer]

I think he said he replaced the coil pact, is that the same as the spark pack? When my # 3 misfire showed up, I took the cheap in line spark tester and was able to see the fire was getting there so no further test was need on the elc. side of the misfire. I dont know if he has done this, but it also would be a good ideal. I agree with you I think the gas suggestion is a bit crazy.

i think i'd first replace the spark pack with a used one for $25.

 

if it's a cylinder mis-fire then first isolate that cylinder - what are cyilnder dedicated items - plug, wires, spark pack and injectors. not gas, that would show up elsewhere, that's crazy talk.

 

cylinder mis-fires on these EJ motors are typically ignition related. are the spark plug wires Subaru OEM wires? if you had an independent mechanic replace the wires, there's a good chance they are not subaru wires. get subaru wires and NGK spark plugs. these 2.2 and 2.5 motors are sensitive to having perfect ignitions.

 

plugs - wires need to be OEM and carefully installed. they are easy to check and replace, so start there. you can even swap the bad cylinder plug and wire with ones from a good cylinder. if the error code "moves" or changes to that other cylinder then you know the plug or wire is bad.

 

that you've replaced the wires twice is the reason i said i'd replace the spark pack first. but make sure they are OEM wires.

[tcspeer]

This is very good OB99W, I asked the local mechanic about the details of how the noid light works and you have nailed it.

Oh man, does that open a can of worms ! First, we have to differentiate between "current" and "voltage". Then, we can discuss how the injectors are switched on/off.

 

To begin, here's a bit of "Basic Electricity 101":

1) "Voltage" is the difference in electrical potential between two points. Even if not connected to anything else, a charged car battery has a little over 12 volts of potential difference between its two terminals. However, no current flows if nothing is connected between the battery terminals.

2) "Current" requires the flow of electrons in a circuit. If you connect a light bulb from the positive to the negative terminal of the battery, there is then a complete circuit. The bulb lights because the current flowing through it heats the filament, which brings us to "resistance".

3) "Resistance" is the characteristic that determines the relationship between voltage and current. A fellow named Georg Ohm figured that out, and we measure resistance in "ohms".

 

See: http://en.wikipedia.org/wiki/Ohm%27s_Law

 

Now, to get back to the injector operation:

All the injectors have one connection to +12V at all times that the ignition is on. They are activated, when appropriate, by making a ground connection to the second lead, completing the circuit and causing current to flow. That ground connection is made by an electronic switch in the ECU.

 

While more-sophisticated test equipment can be used to verify that the proper voltage and switching are available at the injector, a "noid" light can simplify things. If it doesn't light, and +12V has been confirmed at the injector terminal, that leaves only the ECU itself (or a bad connection to it) as the cause.

 

I hope that helps, and doesn't muddy things further .

[sea#3]

2001 Outback, 90k miles. Check enginge light (cylinder 4 misfire) has been on for approx 8 mos. Car periodically idles rough. Repair shop changed coil, wires, plugs, which did not fix problem. Second repair shop changed wires & plugs 3 months later which did not fix problem. Went to dealer 4 mos. later. Dealer checked fuel volatility, which was 3.5. Used 4 tanks of premium fuel from brand name stations, went back to dealer with light on. Dealer had car for 3 days, could not find problem, even though they contacted Subaru New England about problem. Ultimately changed the o2 sensor, but the light came back on 2 days later. Dealer says volatility is still about 3.5, but I'm using the best gas (premium) I can find from the major stations. Any Ideas?

 

2 things you might want to check

1) timing mark alignment (especially the right cam pulley ) belt might have jumped a tooth which can throw that code

2) valve lash , clearance may have closed up ,your close on mileage when it's suppose to be check

 

Hope this helps

SEA#3

[OB99W]

2001 Outback, 90k miles. Check enginge light (cylinder 4 misfire) has been on for approx 8 mos. Car periodically idles rough. Repair shop changed coil, wires, plugs, which did not fix problem. Second repair shop changed wires & plugs 3 months later which did not fix problem. Went to dealer 4 mos. later. Dealer checked fuel volatility, which was 3.5. Used 4 tanks of premium fuel from brand name stations, went back to dealer with light on. Dealer had car for 3 days, could not find problem, even though they contacted Subaru New England about problem. Ultimately changed the o2 sensor, but the light came back on 2 days later. Dealer says volatility is still about 3.5, but I'm using the best gas (premium) I can find from the major stations. Any Ideas?

First, I agree with others who have said that the fuel issue is probably bogus; your engine isn't likely to "complain" about the gas in only one out of four cylinders .

 

Having said that, I'm wondering about what standard the dealer is using to determine the volatility. The usual is RVP (Reid Vapor Pressure), but the number you quote (3.5) doesn't make sense on that scale. RVP typically averages about 8 psi, and winter grade of gas is often over 12. Gas of 3.5 RVP probably wouldn't work too well in any of the cylinders, possibly even in summer. You might want to ask the dealer what standard and method the "3.5" is based on.

 

By the way, premium gas often is less volatile than lower grades, so using it to minimize misfire due to low volatility is going the wrong direction.

[frag]

Sorry!

[frag]

Oh man, does that open a can of worms ! First, we have to differentiate between "current" and "voltage". Then, we can discuss how the injectors are switched on/off.

 

To begin, here's a bit of "Basic Electricity 101":

1) "Voltage" is the difference in electrical potential between two points. Even if not connected to anything else, a charged car battery has a little over 12 volts of potential difference between its two terminals. However, no current flows if nothing is connected between the battery terminals.

2) "Current" requires the flow of electrons in a circuit. If you connect a light bulb from the positive to the negative terminal of the battery, there is then a complete circuit. The bulb lights because the current flowing through it heats the filament, which brings us to "resistance".

3) "Resistance" is the characteristic that determines the relationship between voltage and current. A fellow named Georg Ohm figured that out, and we measure resistance in "ohms".

 

See: http://en.wikipedia.org/wiki/Ohm%27s_Law

 

Now, to get back to the injector operation:

All the injectors have one connection to +12V at all times that the ignition is on. They are activated, when appropriate, by making a ground connection to the second lead, completing the circuit and causing current to flow. That ground connection is made by an electronic switch in the ECU.

 

While more-sophisticated test equipment can be used to verify that the proper voltage and switching are available at the injector, a "noid" light can simplify things. If it doesn't light, and +12V has been confirmed at the injector terminal, that leaves only the ECU itself (or a bad connection to it) as the cause.

 

I hope that helps, and doesn't muddy things further .

 

Thanks! Only the second part was necessary, but too much explanation beats too little almost anytime.

When's the exam?

[OB99W]

Thanks! Only the second part was necessary, but too much explanation beats too little almost anytime.

When's the exam?

You're welcome, and sorry if the first part was too basic; it was for general consumption, not directed towards anyone in particular. I kind of cringe when terminology is misused, and sometimes tend to over-react.

 

Exam? Next week, but relax, it's open-book.

[Olnick]

Hey OB99W, don't apologize for being "too basic!" If it's something I know, then it's a great refresher. If it's something I don't know--which is ususally the case--then I learn.

 

That's what I love about USMB land . . . all the sharing and caring!

 

Aloha.

[OB99W]

Hey OB99W, don't apologize for being "too basic!"[...]

Okay, but it's sometimes like this...

http://www.netapp.com/news/report/feb-mar03/images/balancing-act.gif

[Olnick]

Ain't it the truth!

[frag]

Okay, but it's sometimes like this...

http://www.netapp.com/news/report/feb-mar03/images/balancing-act.gif

 

Is that a Brighton?