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HELP' loss of power 15mpg....


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42 replies to this topic

#1 legend01

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Posted 22 March 2013 - 03:23 PM

Hi all,few months back my impreza wrx 2001 started to loss power every now and again then its got worse so now its running bad all the time,it drives like its lost 50bhp idles fine mpg is also down to about 15mpg,then i get cel for front o2 sensor so thought that was the problem & purchased a denso o2 so no cheap sensor doesnt make any difference,even when i had the lasr map tweak for uprated fuel pump mapper asked had i done anything else as he got another 3degree's of timing which is alot but hadnt done anything that day car ran great the next it was terrible again,as this has gone on for a few months its started to drive me mad so has anyone got any ideas i can try?

 



#2 nipper

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Posted 22 March 2013 - 04:31 PM

How many miles?

 

I would start with a good old fashioned full tuneup including the PCV valve. Throw a vacum gauge on it and see if the exhaust system is clogged. Check the operation of the engine coolant temp sensor. Also reset the engine map to stock and see what happens.

 

How old is your timing belt?



#3 aprezzal

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Posted 23 March 2013 - 10:32 PM

I would agree with the vaccuum check to see if your cat is partially clogged from the bad O2. Doesent take much when the sensors go south to do it. Good Luck with the repair!



#4 1 Lucky Texan

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Posted 23 March 2013 - 11:45 PM

in addition to the above suggestions;

 

clean the MAF sensor (use proper cleaner for that)

 

possible knock  sensor problem too I guess.


Edited by 1 Lucky Texan, 23 March 2013 - 11:46 PM.


#5 legend01

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Posted 24 March 2013 - 03:26 PM

Thanks for replies,i also forgot to ad that on my boost gauge at idle the vacam pressure is -8 my gauge goes from 0 done to -8 which i thought was low,i have cleaned maf,i think il go with what you are saying & do pcv vavle,the strange thing is i get no cel codes apart from the two ive have ie:0420 the day before my last map but mapper told me no problem as he was turning that sensor off & as it hadnt been mapped before i thought it was because of turbo back exhaust,then the only over code was for the front o2 which ive changed.well soon as the snow clears up il take a look at the things you have advised me of &let you no.many thanks...



#6 legend01

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Posted 24 March 2013 - 03:28 PM

oh & my timing belt is up for renewal,how would that efect things unless its jump a tooth?Thanks to all...



#7 nipper

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Posted 24 March 2013 - 03:35 PM

Lets get a cheap vac gauge from autozone of pep boys, as I don't know what that -8 means. Normal should be 18-20 IN Hg at idle.

 

http://www.classictr...cts/vac/uum.htm

 

I don't know why your mapper shut off the second O2 sensor (or did he just clear the code?) as it monitors the performance of the cat, unless the mapping was actually pissing off the cat and got you where you are today?

 

For all you know you may be getting a code and it is the 2nd O2 sensor, but since it was shut off, who knows. 

 

I would suggest some mechanical things too, like one or more brakes dragging, a huge vacum leak?



#8 legend01

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Posted 24 March 2013 - 05:35 PM

thanks for reply,as it got a turbo back exhaust for some reason they turn off the sensond sensor over hear (im in england by the way) as the exhaust gives the cel 0420 .my boost gauge does shows in' mercury it starts at 0 then goes down to -8 which is bottom of scale it still seems to boost to 1.2bar no probs thats what it was mapped too, il double check its not ment to be -80 & let you no.the only thing with the 0420 code that was already on when i got car & someone had cut the cel light instead of getting it tunned properly.ive rebuilt both front calipers wjth new pistons & they are fine now as they were seized.

i always use 99octane fuel which it is tunned for.also the car started to play up before i had it mapped at first it would lose power now & again but now its the opposite loss of power all the time then once in a while runs great ,its like it runs really rich.i was also advised to change the neutral switch which i did.

is there a good way to do a vacum test if your cat is blocked?

Advise is really appreciated many thanks.


Edited by legend01, 24 March 2013 - 06:06 PM.


#9 nipper

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Posted 24 March 2013 - 08:50 PM

Look at the link I posted, it tells you how to use a vac gauge to test for a clogged cat among other things Being down on power and running poorly, is your turbo operating? IS your turbo gauge in PSI or BAR.

 

The vac gauge is really under appreciated as a diagnostic tool, so simple and very informative.



#10 hp_pants

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Posted 25 March 2013 - 09:26 AM

Look at the link I posted, it tells you how to use a vac gauge to test for a clogged cat among other things Being down on power and running poorly, is your turbo operating? IS your turbo gauge in PSI or BAR.

 

The vac gauge is really under appreciated as a diagnostic tool, so simple and very informative.

 

My thoughts exactly-the TD04 turbos are starting to wear, finally, on the WRX/Foresters. Do you get any smoke at startup or idle? Most people don't see the smoke, so it's best to get out and look.



#11 nipper

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Posted 25 March 2013 - 09:29 AM

Check now, and I mean now, to see if you are consuming any oil from a blown oil seal in the turbo.



#12 hp_pants

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Posted 25 March 2013 - 05:49 PM

Check now, and I mean now, to see if you are consuming any oil from a blown oil seal in the turbo.

Yeah, you can lose 2-3 quarts past a worn piston ring in a turbo. Your piping before and after the turbo's cold side should have a little bit of oil, but if there is a black deposit, no bueno.



#13 legend01

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Posted 26 March 2013 - 12:47 PM

Hi, no car doesnt use any oil at all,boost gauge reads in bar & boosts to 1.2bar thats what its mapped too,also my boost gauge does read vacum (in' mercury) it goes down from 0 -1-2-3 ect to -8 & the -8 is where the gauge sits when at idle.i have had two times where ive had a very slight bit of smoke come out of the exhaust this was last year when we had extremly hot weather & was sat in a traffic jam but none since then,i do have sort around the tip of exhaust which got worse when my problems started but ive put this down to running rich.Thanks for the replies.



#14 hp_pants

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Posted 26 March 2013 - 01:02 PM

Hi, no car doesnt use any oil at all,boost gauge reads in bar & boosts to 1.2bar thats what its mapped too,also my boost gauge does read vacum (in' mercury) it goes down from 0 -1-2-3 ect to -8 & the -8 is where the gauge sits when at idle.i have had two times where ive had a very slight bit of smoke come out of the exhaust this was last year when we had extremly hot weather & was sat in a traffic jam but none since then,i do have sort around the tip of exhaust which got worse when my problems started but ive put this down to running rich.Thanks for the replies.

Well, if it smoked, something was going on. I rebuild and sell turbos for a living, so I know a few things.

A turbo that is out of balance due to wear will show imbalance (and poor performance) at a certain RPM range. If a turbo is completely gone, it will show imbalance at every range, but if it is just worn, it will fail to perform either at low RPM, mid RPM, or high RPM. So, a worn turbo will lose power usually at low RPMs or high RPMs, but usually not both.

Doesn't mean it's your turbo at all-do you have a K&N filter by any chance?



#15 legend01

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Posted 26 March 2013 - 01:42 PM

no k&n just dry panel filter,its really strange as the car does go really well once in a while,& the loss of power is all through the power range,its running rich i just dont no why thought id found the problem when i got the code for front o2sensor changed that with denso one but no different.thanks



#16 hp_pants

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Posted 26 March 2013 - 03:23 PM

no k&n just dry panel filter,its really strange as the car does go really well once in a while,& the loss of power is all through the power range,its running rich i just dont no why thought id found the problem when i got the code for front o2sensor changed that with denso one but no different.thanks

well, the turbo is a pain in the rump roast to get to on those engines-if you can get the air inlet hose off the turbo so you can inspect the compressor wheel and give it the shaft test I would....



#17 nipper

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Posted 26 March 2013 - 04:37 PM

I'm going to sit back and listen on this one, as it has been a while since I have a turbo to diagnose. Intermittent can be a pain. to diagnose. But lets get a real vac gauge on there just to check out the basics. No need to drive with it connected as we are looking for responses with the car just running in the driveway.



#18 hp_pants

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Posted 27 March 2013 - 02:02 AM

I'm going to sit back and listen on this one, as it has been a while since I have a turbo to diagnose. Intermittent can be a pain. to diagnose. But lets get a real vac gauge on there just to check out the basics. No need to drive with it connected as we are looking for responses with the car just running in the driveway.

well, because I am a turbocharger rebuilder, it's always the turbocharger. The problem, as I see it, is that the turbo is going to be worn at that mileage. Turbos are like brakepads-they wear and need to be serviced at about 30,000 miles. They will hang on until 130,000 or more, but if we get a turbo in the shop, it allways shows wear.

I think it's important to rule out any electrical or sensor problem, and I wish some mechanics would chime in, because a turbo, with this kind of mileage, will be in need of service, but without a bigger picture diagnosis, we can't say that the turbo is the source of the problem.



#19 legend01

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Posted 27 March 2013 - 06:50 PM

yes i agree that the turbo with over hundred thousand miles on it will be worn,&  if the problem started a bit different to how it did i would be more inclined to investigate  mechanical parts.ok today a used one of them elm 327 devices after eventually getting the software for it i got a few logs il try & put them up on hear,there's one thing that is bothering me on the o2'sensors i dont get no info on o2 1-1  then i get voltage on o2 1-2 which for what i can gather the o2 1-1 would mean bank1 sensor 1 & o2 1-2 would be rear sensor could someone confirm this please?but o2 1-1  which is new if that is the first sensor & im getting no readings have i got a knackered new sensor or more likely is there a wiring fault to this sensor? any thoughts on this?

still dont get any cel codes & did speak to the place wear i brought the o2 from & was told he had never nown of a new denso sensor being faulty,so tommorrow im gonna try 7 test the wiring to sensor anyone no of the best way to go about this?& do a vac test too. Thanks to all.


Edited by legend01, 27 March 2013 - 06:51 PM.


#20 hp_pants

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Posted 27 March 2013 - 07:41 PM

yes i agree that the turbo with over hundred thousand miles on it will be worn,&  if the problem started a bit different to how it did i would be more inclined to investigate  mechanical parts.ok today a used one of them elm 327 devices after eventually getting the software for it i got a few logs il try & put them up on hear,there's one thing that is bothering me on the o2'sensors i dont get no info on o2 1-1  then i get voltage on o2 1-2 which for what i can gather the o2 1-1 would mean bank1 sensor 1 & o2 1-2 would be rear sensor could someone confirm this please?but o2 1-1  which is new if that is the first sensor & im getting no readings have i got a knackered new sensor or more likely is there a wiring fault to this sensor? any thoughts on this?

still dont get any cel codes & did speak to the place wear i brought the o2 from & was told he had never nown of a new denso sensor being faulty,so tommorrow im gonna try 7 test the wiring to sensor anyone no of the best way to go about this?& do a vac test too. Thanks to all.

yeah you would think there would be a CEL....try to pop off the air intake and at least rule the turbo out, too....



#21 nipper

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Posted 27 March 2013 - 08:30 PM

This may be a combination of things. Vac gauge will also give you an idea of engine compression,

 

Hrmm .. i wonder... Maybe we are barking up the long tree. A dying fuel pump or fuel pressure regulator can cause these issues and wont throw a code.



#22 hp_pants

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Posted 28 March 2013 - 10:16 AM

This may be a combination of things. Vac gauge will also give you an idea of engine compression,

 

Hrmm .. i wonder... Maybe we are barking up the long tree. A dying fuel pump or fuel pressure regulator can cause these issues and wont throw a code.

Which would mean a lean mixture vs a rich mixture. Yeah, if there was a way for him to check his afr-tailpipe sniffer, etc.. 



#23 1 Lucky Texan

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Posted 28 March 2013 - 10:39 AM

oh & my timing belt is up for renewal,how would that efect things unless its jump a tooth?Thanks to all...

 

 

OK, fess up, how close to renewal are you?



#24 legend01

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Posted 28 March 2013 - 11:57 AM

Hi all,belt is next to do after i fix this problem,ok i took off the pcv & its as clean as a whistle,also put a vacum gauge on & it idles at 12' when i blip the gas to over 2000rpm the vacum gauge goes up then drops to about 5 then rises back to 12' also held rpm at 2000rpm vacum went up then dropped to about 5' then i let it idle it & went back to 12' .& fuel pump was replaced last year with uprated one,i do have a new fuel regulator was thinking of putting it on to see if it maid any difference,soz i forgot to take air inlet off to check turbo will do this later or in morning. .so guys what do you think?


Edited by legend01, 28 March 2013 - 12:07 PM.


#25 nipper

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Posted 28 March 2013 - 08:05 PM

Thats not good, thats really low.It should be idleing about 20 inhg turbo or not. At idle was the needle steady or jumping. Sounds like a huge vacume leak






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