I Donated broknindarkagain Posted December 18, 2010 I Donated Share Posted December 18, 2010 This is kind of a weird one for me. I haven't come across an issue like this before, so I'm not really sure where to even begin diagnostics at. I drive a 1997 Legacy GT with a 5 Speed (EJ25D NA engine) My car starts and drives great. No issues except once in awhile. While I'm coasting in 4th or 5th gear, the car will bogg down sometimes. It only happens when I feather the gas to maintain speed. It never happens past about 15% throttle. It almost feels like I'm trying to pull a 50,000lbs trailer up a hill. To correct the problem, I can push the gas in a little more and about 2 seconds later it will kick back into normal operation after throwing me back in my seat a little bit....or I can push in the clutch, rev it up a little bit, and let off the clutch again. At first I was thinking something along the lines of the rear diff or the transmission having problems (low fluid level or something like that), but I've checked as much as I can check and it seems OK. Clutch is new (about 10k miles installed myself). I've recently done a tune up (less then 20K miles) using a Duralast wireset and Denso Double Platinum plugs. I've as well checked for vacuum leaks (via smoke machine) and didn't find anything. Throttle body is sparkling clean....blah blah blah. New fuel filter as well. My check engine light isn't on, and there isn't any codes. Part of me thinks it may be the fuel pump, but with intermittent problems only in certain gears seems kind of strange to be a fuel pump...especially with no problems starting the car. Has anyone ever come across this before? What possible repairs might I be looking at? -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
that97lgt Posted December 18, 2010 Share Posted December 18, 2010 have you replaced the knock sensor in your time with the car my gt did same until i changed it out btw 97 ftw Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 18, 2010 Author I Donated Share Posted December 18, 2010 a good friend of mine bought a 97 lgt after he saw mine lol I haven't changed any of the sensors. Wouldn't a bad knock sensor throw a code? -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 18, 2010 Author I Donated Share Posted December 18, 2010 And on second thought, isn't the a knock sensor for each bank? (one per side of engine). How would I narrow down what one is bad without any codes that I can pull. http://www.autozone.com/autozone/parts/Duralast-Knock-Sensor/1997-Subaru-Legacy/_/N-j9fnqZ93xni?counter=0&filterByKeyWord=knock+sensor&fromString=search&itemIdentifier=268130_0_0_ 75 bucks a piece from Autozone -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
Baddog Posted December 18, 2010 Share Posted December 18, 2010 You have ONE knock sensor. I believe yours is in between the throttle body and intake mani. http://www.porcupine73.com/pics/sensors/knocksensor3.jpg Browse around in there. You will find it. The binding in gears try to change out the rear diff oil and report back. I dunno if you have an LSD or an Open Diff in the rear. But I want to say they take 0.8qt's of oil. EDIT: To answer your question how to check it. Pull it out (sometimes it's a pain in the arse) and check for ANY cracks. If it has a crack it could be on its way out completely. Link to comment Share on other sites More sharing options...
subikid90 Posted December 18, 2010 Share Posted December 18, 2010 I say fuel pump also. In 4th and 5th gear your motor is asking for a lot of fuel, then when you are at low rpms in 4th/5th gear it is even more gas needed to maintain speed. I would run to autozone and rent a fuel pressure gauge just to try and rule it out atleast. Knock sensor will throw a code, and you only have one just like baddog showed in the picture. You could always look down there, with a flashlight, and see if it looks cracked. How old is your diff oils? maybe they have broken down and become thicker...idk lol? -Subikid90 1997 Legacy GT 5spd & EJ251 w/EJ25D heads ~10.5CR 1998 Legacy GT Limited waiting for EJ22T hybrid swap Link to comment Share on other sites More sharing options...
SLegacy99 Posted December 18, 2010 Share Posted December 18, 2010 Has the coil pack been replaced? Link to comment Share on other sites More sharing options...
Stang70Fastback Posted December 18, 2010 Share Posted December 18, 2010 Could it be your MAF? Mine was all sorts of messed up and caused the car to randomly start bogging down/stall when I was driving, and in many months of having the issue before I finally tracked it down, the CEL never came on. Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 19, 2010 Author I Donated Share Posted December 19, 2010 thanks for the answers guys. so far i've been told -knock sensor -idle air control valve -rear end oil -fuel pump -mass air flow sensor lol. I know how to cheeck the fuel pump. does anyone know the psi spec for fuel pressure? I can do the rear end oil just fine i can clean the idle air control valve however, how can i test the mass air flow sensor without putting a new one in to see if the problem goes away? I don't have the money to throw random parts at it until its fixed. thanks for the pic baddog -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
subikid90 Posted December 19, 2010 Share Posted December 19, 2010 I would leave the MAf for last. As far as I know there is no easy way to test the MAF. I have heard if you unplug it while running and nothing changes then the MAF is probably shot. -Subikid90 1997 Legacy GT 5spd & EJ251 w/EJ25D heads ~10.5CR 1998 Legacy GT Limited waiting for EJ22T hybrid swap Link to comment Share on other sites More sharing options...
Stang70Fastback Posted December 19, 2010 Share Posted December 19, 2010 however, how can i test the mass air flow sensor without putting a new one in to see if the problem goes away? I don't have the money to throw random parts at it until its fixed I did a lot of plugging/unplugging and in the end the only way I was able to diagnose it was to swap it for an extra MAF my friend happened to have Link to comment Share on other sites More sharing options...
ehsnils Posted December 19, 2010 Share Posted December 19, 2010 Don't rule out the throttle position sensor either. But a good idea can be to start with cleaning the MAF. Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 20, 2010 Author I Donated Share Posted December 20, 2010 Didn't have time to start digging into things today. I'm off work tomorrow so if its not freezing cold outside I'll start tinkering with it. I'll keep posted on progress -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 20, 2010 Author I Donated Share Posted December 20, 2010 OK.... so far so good. With the help of Baddog, i was able to find the idle air control valve Cleaned it along with the mass air flow sensor. I drove it for about 10 miles and didn't have the problem yet. So far it seems to be good. We will see how it goes when I drive 20 miles to work tomorrow -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted December 20, 2010 Author I Donated Share Posted December 20, 2010 OK. I drove some more and its not fixed. I happened to catch it on video this time. I was in 4th gear when it did it this time. [ame=http://www.youtube.com/watch?v=9DzGjdMYYV8]YouTube - VIDEO0466.mp4[/ame] Watch from 1:50. at about 1:55 you will hear the engine bog down, then a second later see the camera shake from it kicking back in. You may have to turn up your speakers to hear it good. Here is the list of things I've done : grounding mod new upstream o2 sensor tune up (plugs / wires / fuel filter) clean iac valve clean maf checked for vacuum leaks -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
GNG_Kirby Posted December 23, 2010 Share Posted December 23, 2010 My bet is air intake related. if your MAF is dirty or clogged it won't respond as well to low imputs of acceleration. Same thing with my cold air. If my filter is dirty or wet (since its so low to the ground) the throttle body is open to bring in air, but its not bring it in. Thats where I'd start. Link to comment Share on other sites More sharing options...
GNG_Kirby Posted December 23, 2010 Share Posted December 23, 2010 ^Well scratch my previous idea. Didn't realize you have already cleaned it. Uhhm.. Idk what else to do. I'll let you know if I think of anything else. GL -Kirby Link to comment Share on other sites More sharing options...
GNG_Kirby Posted December 23, 2010 Share Posted December 23, 2010 ^^^^Also jealous of your RED LGT.. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted December 24, 2010 Share Posted December 24, 2010 Whatever you do, do not rule out the MAF entirely until you have tried an entirely different known-to-be-working unit in the vehicle. By all means, try other, cheaper/easier alternatives first, but do NOT rule it out entirely. I ruled the MAF out first thing with my problem (because I had just gotten an OBD-II reader, and in my n00bness I assumed that since it seemed to be reading fine, that it was definitely working fine) and the result was 6 months spent looking for other causes whenever I had spare time. Link to comment Share on other sites More sharing options...
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