Close

User Tag List

Results 1 to 14 of 14
  1. #1
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    TPS reading/relearn

    I am fighting poor acceleration and a horrible misfire at low throttle position with the 02 SC2. Compression is 210 across all cylinders. I have taken the intake manifold off and completely cleaned it and injectors, replaced MAP, TPS, IAT, ICM, coils, wires, and plugs. CTS was done not too long ago. I also ripped the exhaust manifold off and broke the precat out seeing if that would help. I have data logged it with HP Tuners and my LTFT were pegged -23 and STFT were ranging from -15 to -50. I reset the pcm and brought the fuel trims back to 0, but as soon as closed loop hit, STFT just kept going to -20. I decided to replace the fuel filter again since I have heard anything other than oem and Wix won't work right. Put a wix on and fuel trims were very promising. Went and drove it, and the misfire was still present.

    I then starting wondering about the TPS again because it reads 0% with no throttle. I thought the TPS was absolute over relative, so it started raising concern. The problem I have seems to be based on the throttle position. Once I hit roughly 13-14% throttle, the miss happens. It is a full on, engine dies, miss. There is something about that spot, which falls right about where normal cruising is and car always wants to die when taking off and change gears. So is the TPS supposed to read 0% closed (I find very odd)? If not, is there a way to relearn TPS position?
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  2. #2

    Join Date
    Nov 2007
    Location
    Nova Scotia
    Posts
    2,057
    Post Thanks / Like
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Yes the tps should read 0% . approx 1.35v when at rest
    87 Fiero: Long term project.
    00 sl2: cheap DD pls no mods.
    01 sc2: high comp build round 2.
    08 lmm: aux tank, custom alum tonneau, aux oil cooler, aux filters, plow
    18 Acadia: Family hauler.

  3. #3
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    First car I have logged that does that.

    Well starting to believe the pcm is bad. I logged it again and saw my STFT go to -50 once I hit 13.5% throttle and stayed until about 20% throttle. If I eased off throttle and dropped below 13%, still read about -50% STFT. Once I completely dropped throttle and opened back just below 13%, fuel trims were fine. Where the cursor is, is the point where I dropped throttle. Before that, -50% STFT. After it, max of 5% STFT. All at the same throttle below 13%.

    saturn cruise-1.jpg
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  4. #4
    SMGordon1259's Avatar
    Join Date
    Sep 2017
    Location
    Yakima, Washington
    Posts
    112
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ok have you cleaned the area under the PCM? If you dare remove the coils and clean the area under the pcm and on the mount point. i would also clean/ wire brush the bolts. sometimes when it is dirty/ rusty ground becomes intermittent. just a thought
    2002 Saturn SC1, Metallic Orange , L24 1.9 , 204,170 miles

  5. #5
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You mean the icm. It has already been dealt with. Cleaned it a year ago when I did the clutch, did again just recently when I put new icm and coils on.

    I think I should be able to use my HP Tuners cable to reflash the pcm. I'm on TDS and TIS2web, so it is a cheap option to try. I am hoping to have a spare pcm on hand to also flash and swap if needed.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  6. #6

    Join Date
    Jun 2009
    Location
    Hammond , Louisiana
    Posts
    1,471
    Post Thanks / Like
    Blog Entries
    2
    Mentioned
    7 Post(s)
    Tagged
    0 Thread(s)
    flashing the stock PCM? what is this?

  7. #7
    6S Moderator S.Bretz's Avatar
    Join Date
    Apr 2004
    Location
    Lutz, Fl
    Posts
    15,510
    Post Thanks / Like
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)
    -50% is wicked low. It shouldn't be pulling anything under -25% max. If it is pulling that much fuel to make the o2 sensor happy then i would suspect you have a leaking injector, a spark misfire on a cylinder or two (dead coil pack maybe?) or a bad o2 sensor.


    Easy thing to check and a common mistake is the plug wire order on the coil packs. When looking at the coil towers from the front of the car the order should be from left to right: 4-1-2-3. I have seen some weird under load misfires from the wire being in the 1-4-2-3 order. Since it is a waste spark system and 1/4 plugs both arch every time the coil pack fires. It will run like a top at idle but act like a turd under load.
    Last edited by S.Bretz; 07-05-2019 at 06:01 PM.
    -6S Resident Mechanical Forensics member #001.
    1995 SC2 Turbo 3.6L DOHC, 6sp manual, Ford 8.8 rearend running on MS3x.
    1998 F-250 5.4L triton...stock.

  8. #8
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, I've replaced damn near everything aside from injectors and pcm. I leaned away from injectors due to how it ran at times. If I can find all my shit, I'm building an injector testing station. The car ran fine before this, but steadily got worse over time. Now it's the same for past couple months. I didn't replace the o2 till last week since the response from it was great, but decided to toss in a new one if it somehow was giving a false reading.

    I also reprogrammed the pcm, and no change in this problem.
    Last edited by saturnspeed_12; 07-06-2019 at 03:47 PM.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  9. #9
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Well tested injectors for leaks. None. Flowbenched injectors. Perfect. Ultrasonically cleaned them anyways. Just checked exhaust backpressure, 0-0.5psi of pressure. Despite no other issues showing, perfect compression check, I think I only have one last thing it could be. Timing. Chain has to be loose.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  10. #10
    6S Moderator S.Bretz's Avatar
    Join Date
    Apr 2004
    Location
    Lutz, Fl
    Posts
    15,510
    Post Thanks / Like
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)
    You can remove the knock sensor from the engine and then wrap wire around the threads and then ground it to the engine. This will keep any noise out of the sensor so the PCM will not pull timing.
    A LONG time ago when I first started as a tech at saturn one of the senior techs did this to his 94 SW2 because it would pick up on false knock and pull timing. He just left the sensor hanging under the intake manifold off the harness and used a wire that had an alligator clip on one end and clipped it to the engine block to ground it out.
    -6S Resident Mechanical Forensics member #001.
    1995 SC2 Turbo 3.6L DOHC, 6sp manual, Ford 8.8 rearend running on MS3x.
    1998 F-250 5.4L triton...stock.

  11. #11
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    20190713_190837.jpg

    Chain has about 1/2"-3/4" of slack. I pushed the chain down and heard the tensioner puke. Now I don't think I will be able to drive it into the garage since it is now too slack.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  12. #12
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    New timing on, and fuel trims acted strange. Still wanted to go to -50, but after driving more, they looked normal. Fully warmed up before driving, and took a while till fuel trims came down. Engine finally felt like it had a bit of power. And yet, it still has the hiccup around 15-16% throttle. If I push throttle quick, it is violent. If I push really easy to get to that range, don't notice anything. So it really seems it is something with the pcm and tps.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

  13. #13
    Approved Vendor ZombieSatty's Avatar
    Join Date
    Feb 2007
    Location
    Omaha, NE
    Posts
    6,529
    Post Thanks / Like
    Blog Entries
    2
    Mentioned
    13 Post(s)
    Tagged
    0 Thread(s)
    Have you relearned the pcm?
    It's not my fault, blame the radiation.

  14. #14
    saturnspeed_12's Avatar
    Join Date
    Nov 2005
    Location
    Urbana, OH
    Posts
    3,012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, and I am debating about doing the neutral knock sensor Sam said. But I was able to datalog more today and found the car runs perfect in open loop. As soon as it hits closed loop, it has the issue. Light throttle cruise also has high negative fuel trim with engine temp from 140-160 degrees. Before and after that, they are perfect.

    I think now this is a log for everything I try if anyone ever has this happen to them. My next move is disconnecting the tps and driving. I know the tps itself isn't the issue, but trying to see if it will trick the pcm.
    Ian---The Fat Ass

    1995 SL2-High compression engine FOR SALE
    2010 Chevy Cobalt SS- tuned with plenty of goodness
    2002 SC2-New daily
    2017 Kawasaki Ninja 650 KRT- got a stupid deal
    2003 Ford Taurus SES- free daily beater

Posting Permissions

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