1. Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;)

Rough idle, bogging, hesitation narrowed down to fuel issue

Posted by bmxunderground, Jan 24, 2009

Please Support JNZ Tuning
Please Support STM Tuned
  1. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    I'm looking to see if I have covered all the ground I need to before continuing my repair of this 95' 420a N/T. I purchased this car from an old tuner friend for $100 dollars as he's moved to Germany. After three days of diagnosis outside in 10degree temperatures I cured the cars first problem of NO START. running through a battery of tests lead me to find a lack of fuel pressure which turned out to be worn out O ring on the fuel pump housing allowing the fuel to "fountain" back into the tank without making it to the rail. Just figured I'd put that out there for those collecting information on random problems to check for. Now back to my current issue.

    The car starts and runs but the symptoms are as follows:

    -loping idle
    -hesitation when the gas pedal is pushed followed by poor "no balls" acceleration after hesitation passes.
    -A/F gauge registers lean during hesitation
    -intake backfire

    Things tested today (or replaced during N0 START condition)

    -spark plugs
    -wires
    -coil pack
    -cam angle sensor
    -ecu
    -fuel pump
    -fuel filter
    -battery
    -ASD/MFI relay

    After flushing the fuel filter, the liquid coming out looked more like Amber Bach than gasoline so my first step in the morning is to remove the injectors and install 4 low mileage injectors I have in a box to see if it was severely clogged injectors. In case this doesn't solve the problem I wanted to hear some of your opinions. In line for checking are: Map sensor, IAC, TPS, and Crank angle sensor. Your input would be much appreciated. If I left anything out its because I'm frozen and tired, thank you.
     
  2. Locke

    Locke N/T DSM Wiseman

    2,683
    12
    Joined Jan 1, 2005
    Houston, Texas
    What is your fuel pressure? It should be near 50psi.

    Check your cam timing, and check that the engine's wiring harness has not melted against the EGR pipe.
     

    888  0

    1999 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  3. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    already checked the wiring harness, forgot to post that. Going to grab a fuel pressure gauge today as I was a little too busy to get back into the project today. I'll drop the info shortly.
     
  4. tunerinms

    tunerinms Probationary Member

    11
    0
    Joined Jan 19, 2009
    Jackson, Mississippi
    where is the fuel filter located?
     
  5. tunerinms

    tunerinms Probationary Member

    11
    0
    Joined Jan 19, 2009
    Jackson, Mississippi
    nevermind i figured it out
     
  6. xD BILLZx

    xD BILLZx Probationary Member

    1
    0
    Joined Apr 4, 2008
    Merriam, Kansas
    have you checked the I.A.C on the intake
     

    221  0

    1995 Mitsubishi Eclipse N/T
    · 2G DSM
    Loading...
  7. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    My car has been covered in ICE from this storm passing through KY, IN and OH. looks like I'm going to have to work this into the weekend. In the mean time, I'm going to search for the testing methods of the I.A.C. and other sensors listed above. By all means feel free to post the link here while I hunt for myself, if you have it in memory already.

    :::My fuel filter, on firewall, below battery tray, in case someone still needed that.
     
  8. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    replaced I.A.C and TPS as well as flow tested injectors, all checked out. More noted issues on testdrive today.

    -Complete lean out upon ANY hard pressure on the accelerator and the expected bog down as a result.

    -No CEL light at all when there clearly should be some sort of response.


    Weather is warm now so I'm back in business in case some wondered why there was a small vacation between last post.
     
  9. shorty10011010

    shorty10011010 Proven Member

    31
    0
    Joined Apr 14, 2008
    Silver Springs, Florida
    Have you tried the crank angle sensor? All your symptoms equal that or as you say a fuel issue.
     

    272  0

    1998 Mitsubishi Eclipse GST
    manual · 2G DSM
    Loading...
  10. LD25Delta9

    LD25Delta9 Proven Member

    606
    13
    Joined Feb 12, 2008
    Ft. Wayne, Indiana
    No, it doesn't. Make sure you know they way our system runs before you post about it. The CAS controls spark. Along with the all the other sensors, it helps to control fuel. If his CAS was shot, the car wouldn't even start. And thanks for repeating the OP's problem. He already know's what it is: Fuel. :banghead:

    To the OP: If you replaced your pump disregard this, however if not, I would almost bet that it's your pump, with the way it leans out during a load. And I believe I am right when I say that there is no sensor that the ecu would read if the pump were shot. So that's probably why you're not throwing any CEL. Correct me if I'm wrong Locke. If you didn't replace it, like Locke asked: What's your fuel pressure? That'll tell you if it may be a funny sensor or your fuel lines. If you've got good pressure, it's not your lines. Make sure you get a reading under load with a friend hittin the gas. And if you can try and post a link to a video with quality audio so we can hear how bad the lope is.:thumb:
     

    753  0

    1997 Eagle Talon N/T
    manual · 2G DSM
    Loading...
  11. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    The fuel pump is new, not to say it couldn't be faulty but yes, new. I'm going to borrow a video camera today. I'll try to get the fuel pressure gauge as well. Then I'll upload the video for you guys.
     
  12. rstare

    rstare Proven Member

    777
    6
    Joined Jun 9, 2008
    Winthrop Harbor, Illinois
    '95's are known to have the ecu's fail go out and cause all kinds of weird stuff.
    In your first post you mentioned an A/F gauge; what does it read? (Give us multiple areas, like idle and high throttle under load, etc.)
    Do you have a datalogger of any sort?
     

    951  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  13. Locke

    Locke N/T DSM Wiseman

    2,683
    12
    Joined Jan 1, 2005
    Houston, Texas
    That is correct - the ECU has no way of knowing what the fuel pressure, it can only assume that it is ~50psi as it should be. A failing pump, leaky fuel lines, or faulty regulator can cause you to go lean under load as well as many of the things that have been listed by others.
     

    888  0

    1999 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  14. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    I'll be back on in a few to add one more video and some more answers to your questions. Till then, here is the video from the front you can hear everything I believe, and theres a second video there too:

    YouTube - eclipse trouble 2
     
  15. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    ok, thanks to harbor freight, my 9.99 fuel pressure tester shows I have about 20psi to the rail and drops rapidly to zero. No leaks by the rail and none under the car. Anyone have any suggestions to add before I get into the search in a day or so?

    I'm wondering why the pressure would drop instead of hold, the car you see in my avatar runs at about 50psi and when turned off will maintain 40-50 for a while.

    let me know.
     
  16. Locke

    Locke N/T DSM Wiseman

    2,683
    12
    Joined Jan 1, 2005
    Houston, Texas
    If there is indeed no visible leak, I would suspect the pump's pressure valve or your regulator has failed.

    I believe the FPR on your 95 requires vacuum; pull the line and inspect for fuel. If there is fuel in the vacuum line, your FPR has failed and is both not regulating properly and relieving pressure into the intake stream.
     

    888  0

    1999 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  17. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    even before the car starts, the fuel pump should prime the system with upwards of 50psi correct? I have to prime the car about three times to get enough fuel to the rail. I'm going to check under the car tomorrow and see if any lines are crimped, then switch the pump with a spare walbro I have laying around to see what happens.

    If the FPR is bad could it just recycle the fuel back through the return?
     
  18. Locke

    Locke N/T DSM Wiseman

    2,683
    12
    Joined Jan 1, 2005
    Houston, Texas
    As you turn the key to the ON position before starting, the fuel pump will run for a couple of seconds to prime to full pressure of ~50psi.

    The usual way that a FPR would fail is when the diaphragm becomes damaged and leaks fuel past it, which would in the case of a vacuum regulator leak fuel into the vacuum line and to the intake. I am sure there are much less likely methods that it could fail, though.
     

    888  0

    1999 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  19. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    So I went back into the fuel tank and the 95 unit has the pump wedged into an O ring then pressed into a little hole. I put a second O ring on there and pressed the unit tight as I could back in and the fuel pressure bumped up from 20 to 40. looking better. Took the car for a drive and it started to dive on me again. Got back and found the alternator choke fuse busted (120amp WOW!) So now, before I continue on the fuel problem trail, I'm going to replace the alternator for an OEM known good replacment and I'll be back.
     
  20. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    fuel pressure looks to be holding at 45psi. Do you think I should continue to correct it until I see 50psi? If so I'll pick up a different fuel pump housing that uses a hose fitting instead of wedging the pump into rubber O ring configuration.
     
  21. Majikterror

    Majikterror Proven Member

    91
    0
    Joined Feb 18, 2003
    Oak Lawn, Illinois
    Did you end up resolving your issue? I'm having a similar one, and I'm curious.
     

    222  0

    1997 Mitsubishi Eclipse Spyder GST
    13.439 @ 106.700 · 2G DSM
    Loading...
  22. Locke

    Locke N/T DSM Wiseman

    2,683
    12
    Joined Jan 1, 2005
    Houston, Texas
    50psi would be target, though not everyone's car runs at that. 45 ought to be ok, as in the ECU can self-correct for the lack of pressure by increasing injector pulse-width. The real question is whether the pump in unable to pump adequate amounts of fuel, or if the regulator isn't keeping fuel pressure were it ought to be.

    Take a fuel pressure gauge and situate it to where you can see it while driving the vehicle. Put a load on the vehicle, such as accelerating up an on-ramp and see that the fuel pressure doesn't change more than 1-2 psi while accelerating. If the fuel pump can maintain pressure while you're under full load, you should be okay.
     

    888  0

    1999 Mitsubishi Eclipse N/T
    manual · 2G DSM
    Loading...
  23. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    When I had that car, I acutally just put in a second rubber oring I had around and it finally bumped up the pressure with a better seal.

    On my later model cars I simply clamp a piece of hose between the fuel pump and the pipe leading out. I did cut off the little bell shaped receiver portion that previously seated the rubber oring.
     
  24. bq509

    bq509 Proven Member

    42
    1
    Joined Jun 29, 2010
    Moses lake, Washington
    I'm having a similar problem. My car will randomly die at idle and under load in ONLY 4TH AND 5TH gear it "hiccups" or bogs and I can feel it jerk. Another problem that just popped up is sometimes it won't want to even idle at all by itself when I let it sit for a few days and I have to keep my foot on the gas. I also notice that my dash lights barely flicker when the car is idling (mind you the idle is very lopey like you explained and kind of rough)...I know I don't have came. im thinkin its either a fuel problem or alternator. Let me know if you have an answer!

    Whoops...I meant cams* LOL
     

    347  0

    1995 Mitsubishi Eclipse GSX
    15.186 @ 89.300 · 2G DSM
    Loading...
  25. bmxunderground

    bmxunderground Proven Member

    213
    3
    Joined Dec 11, 2007
    Bowling Green, Kentucky
    My problem in this thread was a leaking seal at the fuel pump. I was able to find it by using a fuel pressure tester. When my car was idling poorly, I could see fuel pressure drop very low. Start there.

    2nd car I drove after this ended up having a rusted fuel tank. The rust clogged not only the in tank filter, but the entire in line filter as well. This caused stalling, and hiccups at idle and also under load at highway speed.

    If you after checking your fuel system, you still don't find your problem. Post once more and I will try to point you to some good search options related to your issues. Be sure to include any CEL's you may have.
     

Share This Page

Support Vendors who Support the DSM Community
Archer Fabrication ECM Tuning ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications OHM Racing RixRacing RockAuto SouthBay Fuel Injectors STM Tuned Track Decals Track Sculptures VR Speed Factory