Bad idle, rough turn on and off, need some advice
Page 1 of 2 12 LastLast
Results 1 to 15 of 18

This is a discussion on Bad idle, rough turn on and off, need some advice within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hi everyone. I'm new to the forum, hoping I can get some ideas of whats up with the WRX. I ...

  1. #1
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10

    Bad idle, rough turn on and off, need some advice

    Hi everyone. I'm new to the forum, hoping I can get some ideas of whats up with the WRX. I have an 04, gutted stock UP, 3rd cat delete, Cobb stg1 93 octane. Last weekend I put on a BPM turbo inlet, and now when I start the car up, it kinda lurches/jerks. Then it idles really rough, kinda feels more than sounds like a grinding and theres a noticable shake in the hood. It is not the normal boxer shake. Sometimes it goes away and it will idle fine. As soon as I start moving it runs better, builds boost fine, revs to redline, all that. When I turn the car off, it REALLY lurches/jerks. When Im driving along I kinda hear a rattling sound, but I dont think Im knocking/detonating at all. No CELs at all, checked with the AP too. Im really thinking vaccum leak, but it looks like everything is connected on the inlet. Im worried that I am leaking somewhere and running lean, but no CELs is making me second guess myself. Anyone have any ideas of why the turn on/turn off is so rough? How do I search for the leak? Any help would be great.

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Registered User
    Join Date
    Mar 2005
    Location
    Turlock CA
    Posts
    7
    This may not be related, but I am having similar problems with my 04 STi. I have headers, up-pipe, vf34, catless downpipe and full exhaust. I have been running like this for a few weeks(ecuteck reflash is set for 6/19/06). As of last Sunday it would idle irradically and die sometimes after coming to a full stop. I took it to a dealer and the mechanic told me it was running very very rich. He said the air/fuel ratio sensor in the headers was reading a high oxygen content and adding fuel since it thinks the car is running lean. He suspected I had exhaust leak in the headers.

    I replaced all the gaskets and did find a crack in the headers and had it welded. But he car is still idling rough, not as bad as before though. I can almost smell fuel out my exhaust and it backfires alot when ever I let out the accelerator.

    Are you sure you're not running rich?

  4. #3
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    I dont think I'm running rich, there isnt any odd smells, and it hasnt been dying. I went through today andchecked and rechecked all my hose connections to the turbo inlet hose and it seemed to help a little. I cleaned the MAF too, and I had the engine idling for awhile while I cleaned the inside of the car and it sounded better. When I drove around for a bit, it kinda came back. Im 99% sure I fixed any leaks. The engine is visibly shaking/vibrating at idle, way more than usual. The next thing I am thinking is the silencer delete is messing with the airflow somehow and making the idle bad. I'm going to put the intake silencer back on ASAP and see what happens. I think I am strecthing for ideas though. The car still pulls hard, seems to run ok, builds boost fine. Also, Im thinking a motor mount could be broken or loose? Can this happen on a WRX? Still no CEL's. I guess I need to keep hunting.

  5. #4
    Registered User
    Join Date
    Jun 2006
    Location
    stewartstown, pa
    Posts
    2

    Question

    Quote Originally Posted by shaolin_racer
    This may not be related, but I am having similar problems with my 04 STi. I have headers, up-pipe, vf34, catless downpipe and full exhaust. I have been running like this for a few weeks(ecuteck reflash is set for 6/19/06). As of last Sunday it would idle irradically and die sometimes after coming to a full stop. I took it to a dealer and the mechanic told me it was running very very rich. He said the air/fuel ratio sensor in the headers was reading a high oxygen content and adding fuel since it thinks the car is running lean. He suspected I had exhaust leak in the headers.

    I replaced all the gaskets and did find a crack in the headers and had it welded. But he car is still idling rough, not as bad as before though. I can almost smell fuel out my exhaust and it backfires alot when ever I let out the accelerator.

    Are you sure you're not running rich?
    hey i also have an 04 sti, and it runs rich too, it will run great when your past 1/8 throttle. but sometimes during crusing or coming to a stop or low speed driving it will carry on like a stuck pig, i thought the o2 sensor(s) was going bad, but sometimes i do notice a odd sounding exaust note. is this a common problem to sti's, i bought mine when they first came to the us.
    but lately its been running better. maybe because carbon in the exaust has clogged up
    the hole? if thats the problem.
    oh well it's good excuse to get a set of headers
    also the car is stock, except vf34

  6. #5
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    Quote Originally Posted by jennab7707
    hey i also have an 04 sti, and it runs rich too, it will run great when your past 1/8 throttle. but sometimes during crusing or coming to a stop or low speed driving it will carry on like a stuck pig, i thought the o2 sensor(s) was going bad, but sometimes i do notice a odd sounding exaust note. is this a common problem to sti's, i bought mine when they first came to the us.
    but lately its been running better. maybe because carbon in the exaust has clogged up
    the hole? if thats the problem.
    oh well it's good excuse to get a set of headers
    also the car is stock, except vf34
    If you were running rich or the O2 sensor was borked, wouldnt you get a CEL though? I thought thats the point of having CEL's and such. I'm now thinking more and more that I have something loose or broken under the hood, today I was hearing a clank clank sound that kinda went with the rough idle, and it comes and goes seemingly randomly. I think I need to get under there and see whats up, but Im also gonna get an EGT gauge to make sure Im not doing some unseen harm.

  7. #6
    Boba Fett BrianH's Avatar
    Join Date
    Oct 2003
    Location
    Way up high.
    Posts
    17,924
    Did you unhook your TGV's at all recently?

  8. #7
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    Quote Originally Posted by BrianH
    Did you unhook your TGV's at all recently?

    Nope, everything was running good until I changed the stock turbo inlet. Mods are Cobb Stg1, 3rd cat delete, gutted stock uppipe, Stromung muffler. I also changed the trans fluid at the same time, and I had the car off the ground for a long time, and I think I might have started it up when it was up, and my thinking is that may have loosened/broken something and its making the engine shake and such.

  9. #8
    Moderator GV27's Avatar
    Join Date
    Jun 2002
    Location
    Green Mountain, Colorado
    Posts
    5,585
    I Support ClubWRX
    I'd be willing to bet you have a vacuum leak in the intake. Idle problems are the classic symptom, and since this was triggered by intake work. I'd guess maybe one of those connections for the inlet is not sealed well, or you left a vacuum hose lose or something.
    "Inasmuch as ye have done it to one of the least of these my brethren, ye have done it to me." -Jesus

    1990 Alfa Romeo Spider Veloce
    1992 Toyota 4Runner SR5 3.Slow
    1993 Honda CBR600F2
    2002 WRX SportWagon *sold*

  10. #9
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    1 of 2 things:
    Either a vacuum leak or the Cobb AP does not like you new inlet. Try swapping to the base map and see what happens with the idle. This may help you pinpoint the issue. Alternatively, if you can lay your hands on one of those leak detectors that use sound amplification for identification, this will also help to identify if you have any vacuum leaks. Have you noticed if your boost has been affected since you put the new inlet on? Idle manifold pressure is usually a dead giveway with a vacuum leak.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

  11. #10
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    I was thinking of changing back to base map on AP, I will try that. How else can I check for a vaccum leak? Can I blow some cigarette smoke near the inlet when its running as a cheapy way? I guess there still could be a leak, I checked everything but I certainly could have missed something. Boost levels are the same as previous, vaccum I'm not sure. What is the normal idle vaccum reading on the stock boost gauge? I'm hooked up the AP when I was idling and it was about -8ish psi, when I hit the brake it changed, but otherwise seems steady. I dont remember what it was before the inlet. Could it have something to do with the silencer delete, and the stock airbox taking air from the big hole in the fender wall? I was thinking of putting that back on and checking too.

  12. #11
    Moderator GV27's Avatar
    Join Date
    Jun 2002
    Location
    Green Mountain, Colorado
    Posts
    5,585
    I Support ClubWRX
    It'll be downstream from your air-flow sensor, so no - it's not your silencer delete.
    "Inasmuch as ye have done it to one of the least of these my brethren, ye have done it to me." -Jesus

    1990 Alfa Romeo Spider Veloce
    1992 Toyota 4Runner SR5 3.Slow
    1993 Honda CBR600F2
    2002 WRX SportWagon *sold*

  13. #12
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    So I need to isolate the leak between the MAF and the turbo. That doesnt seem to bad acutally, Ill just have to break out the hunting skills. I'm assuming this could be a pretty small leak, like a pinhole somewhere? There is no audible noise coming from the pipe, so it could be quite small right? How do I seal it up when I find it, can I use silicone or something like that? The inlet is silicone of some kind.

  14. #13
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    If you find the leak, your best bet is to replace the tubing. Chemical pathching is not a good idea for something under negative pressure...you shouldn't risk anything being sucked into a place it doesn't belong.
    I agree that it wasn't your silencer/resonator deletion...it has to be downstream of the MAF sensor or something related to the ECU.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

  15. #14
    Registered User
    Join Date
    Mar 2005
    Location
    Turlock CA
    Posts
    7
    I am 80% sure it is your turbo inlet. Out of desperation the night before I had the car tuned, I put back on the original filter my short ram intake came with. The weekend before I had just swapped filters with another one I had cleaned earlier. Instead of cleaning the filter it came with(didn't want to wait for it to dry). The original filter seems more restrictive than the newer one I had put on. Once I changed the filter back, the car idled just find and didnt hesitate anymore. And after being reflashed, it now runs very smooth.

    And I did spend the better half of my weeked looking for leaks through out my intake and exhaust system.

  16. #15
    Registered User
    Join Date
    Jun 2006
    Location
    Chicago
    Posts
    10
    Quote Originally Posted by shaolin_racer
    I am 80% sure it is your turbo inlet. Out of desperation the night before I had the car tuned, I put back on the original filter my short ram intake came with. The weekend before I had just swapped filters with another one I had cleaned earlier. Instead of cleaning the filter it came with(didn't want to wait for it to dry). The original filter seems more restrictive than the newer one I had put on. Once I changed the filter back, the car idled just find and didnt hesitate anymore. And after being reflashed, it now runs very smooth.

    And I did spend the better half of my weeked looking for leaks through out my intake and exhaust system.
    So you didn't have a leak in the inlet, it was just the filter? Could that be related to your aftermarket intake though too? I have the stock airbox, stock paper filter on there, just removed the silencer to hear the cool noise. Looks like maybe Ill have to buy a new inlet if this one leaks.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •