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Help with Mechanical Issues

check engine vacuum leak knock sensor

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22 replies to this topic

#1 cascadeclimbn

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Posted 25 March 2014 - 07:46 PM

So I bought a 1996 Subaru Impreza Outback Wagon a few weeks ago. For the most part it runs fine but I've noticed a few problems and the check engine light is on as well. For one it is not getting the gas mileage it should it's getting about 21mpg combined and thats because i have the FWD fuse in...it gets worse mpg when it's in awd like a good subie should be. Second, the engine seems to lack a bit of power and thirdly, which may also tie in with the second, it has over-revved twice on me on steep hills. Fourth, the transmission shifts a little rough especially in the first 10 minutes of driving. And fifth, there is often times (but not always) a slight burning smell coming from the engine bay (but no smoke). I took it to autozone today and had them run the codes  on the check engine light and it came back with 3:P0325--faulty knock sensor or circuit bank, P0106-MAP sensor performance (which says likely cause is vacuum leak), and P0301- cylinder 1 misfire detected (leaking or blocked injector). Anyone on this forum good at diagnosing over the computer based on observed issues and check engine codes pulling who can give me an idea as to what could be causing the listed problems and were to start looking at fixing them?



#2 heartless

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Posted 25 March 2014 - 09:34 PM

if your codes are posted in the order they were retrieved from the car, then start by replacing the knock sensor, clear the codes and see what, if anything, comes back. It is quite common for one problem to set multiple codes.

 

harsh shifting in the first few minutes, while still cold, is fairly common as well - how does it perform when fully warmed up?

 

When did the car last get a full tune up and/or timing job?



#3 nipper

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Posted 25 March 2014 - 09:44 PM

What he said. Check your transmission fluid condition and level too and let su know how that is.



#4 cascadeclimbn

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Posted 25 March 2014 - 10:36 PM

if your codes are posted in the order they were retrieved from the car, then start by replacing the knock sensor, clear the codes and see what, if anything, comes back. It is quite common for one problem to set multiple codes.

 

harsh shifting in the first few minutes, while still cold, is fairly common as well - how does it perform when fully warmed up?

 

When did the car last get a full tune up and/or timing job?

 

 

What he said. Check your transmission fluid condition and level too and let su know how that is.

Transmission fluid level and color/viscosity is good. The car still shifts a little jerky when warm but not badly and is a lot smoother than when first driving. Like I said in my OP though, it has over-revved a couple times on steep hills and wasnt getting any extra power when over-revving (might not be describing that well). I'm not sure in what order the codes were retrieved, I didnt know that was important or even a thing so I didnt ask. The guy I bought the car from said he replaced the knock sensor but I don't 100% believe him since he didnt seem like the most honest guy. Is there any way I can check the knock sensor to rule that out if it's working properly? I do not know when the last time the car got a tune up or timing job as there were no records when I bought it and the guy I bought it from said "he" tuned it but again I don't know if his word means much. What would be causing my poor gas mileage (even in fwd and not awd) and could any of these codes be related to that or the 0over-revving issue or the slight burning smell i described? How much does a tune up and full vehicle inspection typically cost. I can generally do a lot of different work on my own cars with a good starting point, help from google, my stepdad's tools, and a haynes manual but thats only b/c im good at following directions and figuring things out on my own...but i dont know a whole lot about cars in general and how to diagnose. The subie beast also has 238k mi on it if that puts anything into perspective.


Edited by cascadeclimbn, 25 March 2014 - 10:38 PM.


#5 nipper

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Posted 25 March 2014 - 11:09 PM

That over-revving is the transmission slipping which is not a good thing, as that rarely gets better. Do you mean the tach or engine revs climb but the car doesnt pick up speed?

 

When you buy a used car from someone just do everything like it has never been touched. 

 

Plugs are not too hard on this car. Filters are easy, and the pcv vale isnt too hard, thats a tuneup.



#6 cascadeclimbn

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Posted 26 March 2014 - 12:25 AM

That over-revving is the transmission slipping which is not a good thing, as that rarely gets better. Do you mean the tach or engine revs climb but the car doesnt pick up speed?

 

When you buy a used car from someone just do everything like it has never been touched. 

 

Plugs are not too hard on this car. Filters are easy, and the pcv vale isnt too hard, thats a tuneup.

Anything else you would recommend "tuning up"? I can figure out how to do most things so if it would keep everything in working order longer then I'd like to know about it. And yes, the tachometer goes up but speed doesnt. I'll have to let it off the gas and press again to even keep going. Its only happened twice out of maybe 20 times on pretty steep, long hills in the cascade mountains but it happens nonetheless. Would that just be a transmission issue or could it be an engine issue as well? Anything I can do to slow the demise of the transmission so I'm not having to replace it in 6 months? 



#7 heartless

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Posted 26 March 2014 - 06:51 AM

if the previous owner had no proof of any work, then yes, treat it as if nothing has been done and do it all.

 

complete timing job, including water pump, all timing components & seals, and an oil pump reseal - there are good kits on ebay for around $200 with everything you need. Mizumo Auto and The Import Experts are 2 trusted sellers there. a search here will turn up good directions on how to do the job yourself. the 2.2 is an easy motor to work on.

 

Complete tune up, including plugs (basic NGKs are all you need, dont waste your money on fancy plugs), wires (OEM or NGK only), pcv, filters, and possibly vacuum lines if they are hard/brittle. a couple dollars worth of the "by the foot" stuff of the appropriate size works well.

 

Knock sensors can be had pretty cheaply - $25 or so, again, on ebay - just make sure you are getting the correct one for your car/engine... not sure if there is a way to "test" it, but this can cause fuel mileage issues, as can the MAP problem.

 

tranny slipping - you can try a fluid flush and maybe adding a tranny additive - Lucas makes one that was used a lot in the older Ford Taurus trannies that had issues with engagement/slipping with good success - but generally speaking, slipping is not a good sign.

 

the slight burning smell could simply be an oil leak dripping onto the hot exhaust and burning off. common leak areas are the front timing seals (cam and crank), and the cam case cover seals (commonly called valve covers) - they use a rubber seal, not a gasket. the seal gets hard with age & heat and tends to leak. a new seat of seals with bolt grommets can be had at RockAuto.com for around $25 and change (I just bought a set for my 95 Legacy wagon).

Also check the axle boots for tears - especially passenger side close to the cat convertor - torn boots can allow the grease to fly out & hit the exhaust - this is usually pretty stinky, tho.



#8 1 Lucky Texan

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Posted 26 March 2014 - 08:44 AM

just to triple check - you are checking the trans fluid level while iding? on level ground and after moving the selector thru each gear for 5-10 seconds?



#9 tirod

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Posted 26 March 2014 - 08:50 AM

As for the gas mileage, we now see you are driving it in the mountains with long uphill grades under power. 21 mpg in those conditions is actually pretty good. Steep grades will upset the mileage.

 

The knock sensor potentially being defective means the ECU won't advance the timing fully, and that cuts power to prevent detonation. It would quickly eat a hole thru a piston or two, and they program it to default with less. It affects mileage by simply not having full power, which forces us to open the throttles more and waste gas.  

 

The code causing problems are fairly easy to fix, the slipping clutches much less so. Assuming it's an automatic, the fix is to replace the transmission. First option is a clean used one, and the installer will need a transmission jack. They will also need to be aware to not compress the pan at all, or the solenoid under the magnet dimple will be cracked and require replacement. 

 

A rebuilt transmission will be costly - nearly the price of the car. That is probably why the previous owner had it up for sale. We buy cars because we buy the seller. He couldn't be trusted, as said, and it was likely because he knew it had a major symptom of an expensive repair and got rid of it. Slipping clutches are expensive and only get worse. It's apparent he replaced a lot of fluid, and may have used a conditioner to get them to grab more, but the final result is he sold the car. 

 

I got no warning, it just went bang on a long uphill grade and went to limp mode in third with no reverse. Damage was that extensive. I got home, and spent three weeks taking it out and installing a used one in my spare time. It was just a month after I had installed a used motor. Sore subject at home. 

 

My advice - get the codes repaired enough to go away, detail it. flip it. 



#10 MilesFox

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Posted 26 March 2014 - 09:05 AM

in regards to knock sensor, try sea foaming the engine if there is excessive carbon causing knock, and try a higher octane fuel.

 

in regards to misfire, inspect the plugs and read their condition. this will tell you a lot. open the back of any haynes manual for a spark plug color chart indicating burn condition. also, consider replacing the ign wires with NGK brand. I was once foiled by bad plug wires resulting in swapping a bunch of sensors until new wires cured my toruble.

 

in regards to the trans, make sure the fluid level is correct. I had a pan leak, that once it leaked out enough, the shifting became delayed, didn't go into overdrive, and the rpms had to stall up first before the car would move. From that point, it took 4 qts(1 gallon) of fluid to bring it back up to a proper level. There is a cold and a hot level on the dipstick, and fluid level must be cecked in park while idling at operating temp.

 

Perhaps the trans cooler line is leaking onto the exhaust, causing the fluid loss and burning smell.



#11 nipper

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Posted 26 March 2014 - 09:38 AM

When driving in steep hilly areas, do not use D, use D3 to atke some stress off the transmission and maybe reduce shifting if the car cant seem to make up its mind what gear to be in (not unusual for a sooby). Change the fluid.

 

Everything else everyone has said is sound advice so I wont repeat any of it as my typing sucks.



#12 cascadeclimbn

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Posted 26 March 2014 - 01:39 PM

just to triple check - you are checking the trans fluid level while iding? on level ground and after moving the selector thru each gear for 5-10 seconds?

Im doing all that except I havent checked it after moving through all gears...just from Park to D. I assume your saying the proper way is to move it through all gears?



#13 1 Lucky Texan

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Posted 26 March 2014 - 01:44 PM

Im doing all that except I havent checked it after moving through all gears...just from Park to D. I assume your saying the proper way is to move it through all gears?

 meh - it's usually recommended. probably more important when topping-off than just 'checking'.

 

I am usually suspicious of 'mechanic in a can' solutions, but  CRC TransX or some other additive would definitely be worth trying.


Edited by 1 Lucky Texan, 26 March 2014 - 01:48 PM.


#14 cascadeclimbn

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Posted 26 March 2014 - 01:45 PM

As for the gas mileage, we now see you are driving it in the mountains with long uphill grades under power. 21 mpg in those conditions is actually pretty good. Steep grades will upset the mileage.

 

The knock sensor potentially being defective means the ECU won't advance the timing fully, and that cuts power to prevent detonation. It would quickly eat a hole thru a piston or two, and they program it to default with less. It affects mileage by simply not having full power, which forces us to open the throttles more and waste gas.  

 

The code causing problems are fairly easy to fix, the slipping clutches much less so. Assuming it's an automatic, the fix is to replace the transmission. First option is a clean used one, and the installer will need a transmission jack. They will also need to be aware to not compress the pan at all, or the solenoid under the magnet dimple will be cracked and require replacement. 

 

A rebuilt transmission will be costly - nearly the price of the car. That is probably why the previous owner had it up for sale. We buy cars because we buy the seller. He couldn't be trusted, as said, and it was likely because he knew it had a major symptom of an expensive repair and got rid of it. Slipping clutches are expensive and only get worse. It's apparent he replaced a lot of fluid, and may have used a conditioner to get them to grab more, but the final result is he sold the car. 

 

I got no warning, it just went bang on a long uphill grade and went to limp mode in third with no reverse. Damage was that extensive. I got home, and spent three weeks taking it out and installing a used one in my spare time. It was just a month after I had installed a used motor. Sore subject at home. 

 

My advice - get the codes repaired enough to go away, detail it. flip it. 

Thanks for all the helpful pointers in this! It is an AT btw. How much does a transmission cost and how much to have someone drop it in? I got the car for $1000 so if it is not too expensive it might be worth it for me to just replace it. Im hoping the couple times its over-revved isnt too serious. Do you think if i do a flush that it should hold up for at least 6 months?



#15 cascadeclimbn

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Posted 26 March 2014 - 01:47 PM

I just checked the transmission fluid again after having the car run for a bit and it actually looks like there is way too much transmission fluid...as in a half inch above the max line for hot. Could this cause transmission problems?



#16 cascadeclimbn

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Posted 26 March 2014 - 01:51 PM

in regards to knock sensor, try sea foaming the engine if there is excessive carbon causing knock, and try a higher octane fuel.

 

in regards to misfire, inspect the plugs and read their condition. this will tell you a lot. open the back of any haynes manual for a spark plug color chart indicating burn condition. also, consider replacing the ign wires with NGK brand. I was once foiled by bad plug wires resulting in swapping a bunch of sensors until new wires cured my toruble.

 

in regards to the trans, make sure the fluid level is correct. I had a pan leak, that once it leaked out enough, the shifting became delayed, didn't go into overdrive, and the rpms had to stall up first before the car would move. From that point, it took 4 qts(1 gallon) of fluid to bring it back up to a proper level. There is a cold and a hot level on the dipstick, and fluid level must be cecked in park while idling at operating temp.

 

Perhaps the trans cooler line is leaking onto the exhaust, causing the fluid loss and burning smell.

I didn';t have a code saying there is a knock the code just said faulty knock sensor (*and gave a list of other possible problems like fault with sensor circuit bank). There isnt any knocking or pinging with the engine that I'm hearing. The P0325 code just means faulty sensor right? It doesnt mean there is a knock, is the way I understood it.



#17 cascadeclimbn

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Posted 26 March 2014 - 01:52 PM

When driving in steep hilly areas, do not use D, use D3 to atke some stress off the transmission and maybe reduce shifting if the car cant seem to make up its mind what gear to be in (not unusual for a sooby). Change the fluid.

 

Everything else everyone has said is sound advice so I wont repeat any of it as my typing sucks.

Thanks for the tip!



#18 mikec03

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Posted 26 March 2014 - 02:29 PM

On the transmission fluid, you have to drain and fill three times to get a 90% replacement [because only 50% drains out at a time.]  I would do it immediately.  Will it help?  Probably not but you have to try something.  After that, you can also try some magic in a bottle mentioned above.

 

Is a high level causing your problem.  Probably not.  It's very difficult to measure the correct level in a subaru trans anyway so you may not be correct in that it overfilled. What I do is to measure the amount that I drain out.  It should be 4 to 4 1/4 qts.  Then I refill with about 4 and 1/8 qts. 



#19 nipper

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Posted 26 March 2014 - 03:10 PM

Actually over filling is bad. It can cause the fluid to get aireated. Hydraulic systems do not pump air well, It can cause slipping and other oddities. 


Edited by nipper, 26 March 2014 - 03:36 PM.


#20 cascadeclimbn

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Posted 26 March 2014 - 04:20 PM

So for a tune-up what Iv'e gathered so far is replace spark plugs, spark plug wires, pcv valve, and air filter? Anything else I should do or check? I'll plan on doing a tune up first and replace the knock sensor and then have the codes ran again and go from there. For the transmission it sounds like I should at least change the fluid but more so do a complete flush and add some kind of substance to the tranny fluid as well?



#21 cascadeclimbn

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Posted 26 March 2014 - 04:38 PM

Could a bad MAP sensor be causing my shifting issues? As that is one of the codes that popped up-- P0106.



#22 nipper

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Posted 26 March 2014 - 05:07 PM

It could, but we first need to get everything else at a normal baseline before we start pointing fingers. A bad MAP will not cause a tranny to slip.



#23 heartless

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Posted 26 March 2014 - 06:51 PM

It could, but we first need to get everything else at a normal baseline before we start pointing fingers. A bad MAP will not cause a tranny to slip.

 

^ this.

 

full tune up, maybe knock sensor.

clear the codes - can be accomplished by disconnecting battery for a half hour or so

drive the car and see what comes back







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