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ECM questions - please help

Discussion in 'Chevy Trucks' started by Kaboom352, Mar 17, 2004.

  1. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    Ok here is what I have... I have a 91 chevy cavalier 2.2 L . ( in know this is a truck board but I figured someone could help). The problem started 2 weeks ago with hard starting and spuddering at about 3000 RPM. I change the fuel filter check plugs and wires everything was fine. Its a beater so I just kept drivng it figureing it wasen't to bad. The other day I had a real hard time starting it (acted flooded) but after it was running it run good till 3000 RPM. Today I took off the air cleaner and such to check things out and it was dumping way more fuel than it needed. A steady streem at idle and what seemed like cup fulls reved out... I think it is the ECM. I called parts stores and they say the replacement does not come with the "chip" do I need the chip or can it be swaped out. The car is now broke down on the side of the road is an ecm swap something that can be done on the side of the road? Do I just plug in the new ECM and go or does it need to be programed and such... please help me out I need my beater...
     
  2. Mebes

    Mebes Senior Member
    Messages: 415

    This sounds like a restricted exhaust to me.
    It runs good and idles ok?
    Starts to loose power at 3000rpm correct?
    You said it looked like to much fuel was being delivered.
    Is this a throttle body injection system?
    (the injector sprays a stream of fuel that you can see into the throttle body)
    Does the fuel spray look smooth or does it look like there is air coming up out of the engine blowing up into the stream?
    Could also be a bad fuel regulator (to much pressure).
     
  3. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    Are the sprays from the 2 injectors perfectly round and even? If not then it's probably a bad injector. Do you have any error codes(check engine light on while engine was running)? It can be read without any special tools. A shop manual with tell you how to do it.
    I have never seen an ECM cause any problems like that. They always just die...Chuck
     
  4. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    update

    I went back to the car to try and get it running and it was dead. it would turn over but not fire up at all... this was a couple days ago. Today I went back to clean it out (I was going to get rid of it figureing that it wasen't worth fixing for me beacuse I am moving and not taking the car with me) and I started right up and ran fine... I don't have a clue what is going on...
     
  5. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    I really think it's in the fuel system. Might try some concentrated fuel injector cleaner in it...Chuck
     
  6. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    ...

    A couple days before it broke down I put a can of good fuel system cleaner in a half full tank. I think I am going to pull the injector and soak it in some cleaner. maybe replace it...
     
  7. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    There should be 2 injectors on it...Chuck
     
  8. Mebes

    Mebes Senior Member
    Messages: 415

    Re: update

    Why pull and soak the injector if it ran fine after a few days?
    Is it running beter now after a few days?
    Or is it back to its old 3000rpm trick again?
     
  9. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    yeah, it back to the same old tricks... but it is running. I starts hard and loses power at around 3000 RPM. tomorrow I am going to be pulling it apart...
     
  10. JMR

    JMR Senior Member
    Messages: 567

    Blind guess (NO DIAGNOSTICS) from your description, weak fuel pump. Fuel pressure is critical on F/I vehicles. Just because you have fuel at the injectors doesn't mean the fuel pressure is right. Remember there is no substitute for good diagnostics procedures.
     
  11. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    but would low fuel pressure cause it not to run at all for 2 day then start right back up... also it looks like it is getting to much fuel.
     
  12. Mebes

    Mebes Senior Member
    Messages: 415

    To much fuel and a loss of power above 3000 rpm.

    I would think that you could dump allot of fuel in at 3000 rpm without much effect. (if you had a stuck or leaking injector it would idle and start poor but when the rpms got up there it would clear up)

    Does it run perfect or is it marginal at idle?

    I am still thinking that is sounds like restricted exhaust to me.
    But that would not explain why you could not get it started.
    Usually restricted exhaust runs fine until you get on it and then you start to lose power.

    You could try disconnecting the exhaust before the catalytic converter and driving it around the block to see if thats your problem. (don't forget your ear plugs)

    Could also be valve timing but I think that your motor has the gear to gear setup not a timing belt.

    If you think that you are getting to much fuel you might want to invest in a fuel pressure tester.
    Most fuel injected cars have a tap on the fuel line under the hood (like a valve stem on a rim) that you hook a pressure tester up to read the fuel pressure, and they are prety cheap.

    Also there should be a fuel pressure regulator on the fuel line (under the hood) that is connected to a vacuum hose that (when vacuum is lost) raises the fuel pressure.
    Maybe the vacuum line fell off or is cracked causing to much fuel pressure.
    But remember that when your foot is to the floor this regulator looses vacuum anyway and cranks up the pressure (this would cause poor idling but clear up as the rpms increase)this is why I think that high fuel pressure is not the problem.
     
  13. Kaboom352

    Kaboom352 Junior Member
    from Florida
    Messages: 7

    ok I pulled the injector (it only has one) and I am going to soak it over night. I ran the car some more today and I am going to see if I can explain what is going on better.

    Ok the car starts hard turns over for 20 - 30 seconds sometimes it starts up after the 30 seconds without gas. if it doesn't I back off the key and turn it over again and it will usually start right up.

    when it is running it idles fine. When I give it about half throttle it revs up great no loss of power at all. at about 3/4 / full throttle it revs up then seems to misfire / loss of power / but not backfire. basically at full throttle it goes to a really ruff idle that seems like its going to die and I bet if I kept on it it would.

    the car does not have a catalytic converter so I don't think that the exhaust is restricted.

    one of the first things I was going to do was check the fuel pressure but the line does not have a tap on it...

    If I can get it to Autozone they do a code check on it for free. will the scan pick up fuel problems.

    something that I realized today. a while back I had a broken return line, and a not so good looking sending line off the pump. so I broke them off and cut away the bad and spliced them back together with rubber hose. could it be sucking air there after them pump. or leaking on top of the tank and I am not seeing it?

    thanks to everyone for the help so far....
     
  14. JMR

    JMR Senior Member
    Messages: 567

    The way you describe it I will once again call it lack of fuel pressure. Cycling the key runs the fuel pump for 3 seconds. Thus, builds enough fuel pressure to start vehicle. Lacks power, sluggish mushy. Again points to lack of fuel pressure. All of your symptoms point to fuel pressure.

    Check your repair, rubber fuel line splice, be sure you used fuel hose rated for the higher fuel pressures of fuel injection.It is not the same as conventional fuel hose. Check for &/or replace fuel filter. Your rubber splice would be a good place to check fuel pressure.

    No the codes, if any, probably won't point you to the fuel pump.

    Good luck, diagnose and test before you through parts at it. There is no substitute for good diagnostic procedures.

    FYI fuel pump specs are 9-13 psi running. Vehicle will most likely act the way you describe @ 6-8 psi fuel pressure.
     
    Last edited: Mar 27, 2004
  15. Mebes

    Mebes Senior Member
    Messages: 415

    I have a question about this loss of power.
    Does it only do this when you are driving down the road?
    Or will it do this in park also?(if so then maybe you have a non fuel related problem like a TPS)

    You need more fuel when you are under load like driving up a hill.
    So if you have a low fuel pressure problem then the rpms that bring on this problem would change with the driving conditions.(maybe it falls off at 3000 rpms on a flat road then say 2500 rpms when going up a hill and then maybe 3500 rpms going down a hill)that would be a good sign of low fuel pressure.

    You have an in tank pump correct?
    If so then no you would not be sucking air into the lines.

    Now if you had a fuel pump on the frame that had a repair in the suction line to the tank you could be sucking in air.
    The suction from the pump could also cause the rubber fuel line to collapse.

    Like JMR said don't throw parts at it.
    I'm just making suggestions on things to look at... You should always diagnose a part before replacing it.
     
  16. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    Get the diagnostics test on it... TPS (throttle position sensor), could be, easy to test, disconnect harness, attach analog ohm meter and have someone slowly push then release gas pedal. Should have nice smooth sweep of needle...Chuck