Possible Bad coilpack?

Discussion in 'SN95 V6 Mustang Tech' started by tloughrin, May 1, 2011.


  1. tloughrin

    tloughrin Member

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    My Girlfriends 2000 3.8 is having a couple problems...
    It starts hard almost every time. It is getting about 9MPG... This car has been doing this since we bought it a year and a half ago. After doing some research it lead me to the coil pack. I tested the coil primary terminals and got 1 OHM of resistance, which is within specs according to my haynes manual. I tested the secondary terminals and was not able to get a reading, the tester stayed in OL. I will try with another tester with a higher range on monday.
    I have done the full tune up.
    She puts in the mid grade gas.
    I am out of ideas.

    A list of things done to the car
    New tires, which are properly inflated
    Spark plugs and wires
    Fuel filter
    Trans filter and fluid
    New Battery
    Air filter
    Pcv Valve
    Thermostat and coolant flush

    There is also a problem with the Heat, It wont work until the car has been driven for 15 mins or so. I was thinking mabey heater core but not sure.


    Any help would be much appreciated.:shrug:
  2. tloughrin

    tloughrin Member

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    Forgot to mention that i cleaned the MAF too, and yes i used the correct product.
  3. Skymarshal

    Skymarshal Member

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    Your coil pack should either work or not. Does it seem like all the cylinders are firing? Once the car starts, does it idle smoothly and accelerate normally? You can use an in-line plug tester to see if the coil pack is working.

    I don't know what to check next, but I would say your MPG offers some clues. I would check the engine's compression in each cylinder, and pull the plugs and see how they look. Look for fuel leaks between the tank and the engine, keeping in mind that gasoline evaporates quickly. Is your CEL on, and what are the codes?

    You can stop using mid-grade fuel, too. It does nothing for your engine, whether it's running properly or not.
  4. dtpoirot

    dtpoirot New Member

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    Hum... I don't know about the 'work/no work' state of the coil pack. Dang CEL is useless.

    I changed plugs on the '01 that I just picked up and found the previous owner had them gapped really tight.

    New plugs at 0.54" and the beast ran like crap - rough idle, no power - but it ran.

    New (stock spec) coil pack (installed in the store parking lot) and I could tell the difference as I pulled out into the street.

    ...my $0.02
  5. tloughrin

    tloughrin Member

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    Car seems to idle fine, no problem with acceleration.
    The plugs are good i just changed them and the plugs before them looked almost brand new. There are no lights on.
    What is the correct gap for the plugs? I believe i gaped them .52 but cant really remember.
    How do you check cylinder compression?
  6. tloughrin

    tloughrin Member

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    Could it be a bad 02 sensor? I thought a bad 02 will send a code.
  7. tinyb99v6

    tinyb99v6 New Member

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    for your issue w the gas mileage check your intake tubing and around the iat (intake air temp) sensor i had a loose sensor and BURNED through gas till i fixed it so from my expierience leaks in the intake air tubing can cause you to burn through gas
  8. tloughrin

    tloughrin Member

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    It is an after market cold air intake, everything is sealed and tight. Even before the CAI was installed the mileage was terrible. Since i put it on and did the tune up the gas mileage has improved, but not much.
  9. robb15033

    robb15033 Member

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    Your testing of the coil is complete. I have tested them the same way without a secondary reading showing up.
    My gut feeling also is the O2 sensors- Check the three very brittle tubes to the EGR & upper intake.
    Lastly, to help eliminating a lot of second guessing- Do a Seafoam treatment the correct way. One can in gas tank and one can pulled (sucked) up pcv or vacuum line into upper intake while car is running. Helpful tip*Drop a drinking straw down into can to make access easier for you.
    Please update, and good luck with it.
  10. tloughrin

    tloughrin Member

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    Would the 02 sensors make the mpg that bad? The tubes all seemed fine. I never did the seafoam treatment... I would be alittle nervous putting it in the pcv seeing as i never did it. Could this help the hard start and MPG?
  11. tloughrin

    tloughrin Member

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    I was reading some articles and they say "1/3 can in vacuum line and rest in gas". Is 1 can in each the correct amount?
  12. tloughrin

    tloughrin Member

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    Today i seafoamed the car. I put 1/3 in the pcv line, 1/3 in the oil and 1/3 in the gas tank. It did not give alot of smoke like i saw in videos that i watched, only while i was putting it in the pcv line. Th car runs the same as before. Did i not use enough? Another thing noticed is that a connector coming off the fuse box in the engine compartment is disconnected, the other end goes into the fire wall.
    Im not sure why it is disconnected...
  13. richardv6

    richardv6 New Member

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    hi
    just a thought but your saying it takes 15 mins to warm up maybe your themostat is stuck ?

    so maybe the car is not getting to temp its needs to run right so useing more fuel ???

    other ideas maybe leaky injectors ?
    and have you cleaned the throttle body my didnt start right up first time , but then i bought maf cleaner cleaned that and also used it to spray inside the thottle body now it starts first time ....

    just some ideas for you hope u get it sorted ...
  14. tloughrin

    tloughrin Member

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    The t-stat was my first thought to, so i changed it last year. no difference. I have cleaned the MAF but not the throttle body, i will try that.

    Thanks for the help to everyone who has posted
  15. robb15033

    robb15033 Member

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    In regards to the Seafoam- I usually put one full can into the gas tank. If I put it in the oil, I run it about a hundred miles then change the oil. Putting a drinking straw into the Seafoam can help get it sucked up into the intake easier through the pcv. If enough is getting sucked up through the engine should bog a little and definite smoke should be seen. If thats not helped it then i would be looking at plugs/ign coil. Air/Fuel/Spark is what is needed. The proper plugs too, not gadget plugs like E3 or Bosh. Our cars run best with copper or platinum Motorcraft, Autolite, or NGK spark plugs. A fuel filter is cheap and brown goopy **** can build up in there all of a sudden. Air filter should always be clean. Lastly EGR vacuum lines directly effect idle. O2 sensors produce bad gas mileage ect. but usually produce check engine lights.
    Hope thats helpful. Please update again.
  16. wmburns

    wmburns SN Certified Technician

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    It sure would help me to know what the DTC codes are. For example, if there is a cam related code, this could explain the poor gas mileage. There are 1000's of codes and they each have a story to tell. Don't guess.

    As for the heater not working, how did you purge the air from the motor? The V6 is difficult to purge and unless all of the air is removed, there will be problems. Delayed warm up is a symptom of air trapped in the cross over.
  17. tloughrin

    tloughrin Member

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    wmburns: it is not giving any codes. The mechanic is the one who flushed the system so i don't know what he did.

    robb15033:I wwill change the fuel filter again and see if that helps and check my plugs.
  18. carstuff

    carstuff New Member

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    EGR valve and switch replacement usually clears up the idling and throttle response...
  19. tloughrin

    tloughrin Member

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    Well i did the math with this past tank of gas. I got 14.5 MPG, alot better than before. I guess the seafoam worked.:D

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