CEL flashing, bad idle, severe misfire, P0302 P0316, compression test results

Discussion in 'SN95 4.6L Mustang Tech' started by evolucion311, Aug 19, 2011.


  1. wmburns

    wmburns SN Certified Technician

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    Why is your fuel pressure SOOOO high?????

    Should be a reasonablly steady 38-42 PSI. Especially since this is the intake (delta) referenced fuel pressure.

    I have never heard an IAC make a noise like that before. Especially since it is coming from from the timing chain area.

    Check out:
    Start up Rattling - Ford Mustang Forums
  2. Rick 91GT

    Rick 91GT SN Certified Technician Site Sponsor

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    In the video at 1812rpm your showing 42 degrees of timing???

    Ive had a IAC make that noise on a 4.6 2003 Explorer when it was bad, took me forever to track it down. Typically only heard at idle and when coming off the gas, you will hear it through the intake track.
  3. evolucion311

    evolucion311 Member

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    OK so I've got the valve cover off of the passenger side. What am I looking for? Can I tell if I have a bad valve by looking at it from the top without removing the cylinder head?

    How to check for bad valve springs, lifter/rocker?
  4. wmburns

    wmburns SN Certified Technician

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    Post pictures of the cam lobes. What you are looking for is evidence of over heating. Excessive blueing or rough/worn contact surfaces. Pay special attention to the roller follower on #2.

    See if you can get a picture of the timing chain adjusters. What you are looking for is wear through of the shoe. Excessive slack of the timing chain is another give away.
  5. evolucion311

    evolucion311 Member

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    I am in the garage at the moment... will post a video shortly. I assume I'll have to remove the timing cover to examine it? I don't have a pulley puller and will have to run to the store to rent one if so. Can I get away with testing the timing chain with only the passenger valve cover exposed? My preliminary examination of the cam shows normal/smooth wear and no black sludge or scoring. I'll have a video up soon.... gimme 5 minutes.
  6. wmburns

    wmburns SN Certified Technician

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    Don't have to remove the timing cover to see the shoe. Look down from above. Maybe hard to see but you should be able to tell if the shoe has worn all the way through.

    Obviously if you are willing to remove the timing cover, this offers the absolute best access for inspection. If it were me, I would hold up until there was more to go on.
  7. evolucion311

    evolucion311 Member

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  8. evolucion311

    evolucion311 Member

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    Hey.... anyone around? I've had my valve cover off for a few hours and am not sure what to do next. :shrug:
  9. Rick 91GT

    Rick 91GT SN Certified Technician Site Sponsor

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    If you burnt a valve you wont see it from the top unless you did a lot of damage. A leakdown test would be a good way to find an issue..

    To check springs you could use a spring install tool to make sure they all move, look to see if anything looks collapse....I don't think its a valvetrain issue personally.
  10. evolucion311

    evolucion311 Member

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    OK so here's the deal. I'm sick of this problem and I don't stealerships for a ****ing second.

    If you can correctly diagnose the car from afar I will offer you a $100 cash reward to be paid after fix is confirmed.

    I will do whatever diagnostics are required and can be performed.

    Update: I checked the vacuum lines from the FRPS and the lines are solid, no cracks. I rented a vacuum pump and put it on the EGR. After pumping up the EGR with about 25" of vacuum I heard a click and the level of vacuum falls slowly. I should mention that the vacuum pump tube does not perfectly fit the EGR tube and I had to wrap the EGR nipple with some tape to thicken up the connection between the tube and nipple.... a connection I doubt was perfect.

    So, gentlemen, make some free money. Help me fix my car. Everybody wins.
  11. wmburns

    wmburns SN Certified Technician

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    Ok, I have crossed checked some of your results from my 2003 GT. The advance #'s look OK. The coolant temperature looks high (214) but isn't likely the problem. The MAF #'s look reasonable.

    Disconnecting the EGR vacuum line did not improve results, so this tends to rule out excessive EGR as a possible cause (which is a shame as they say on CSI, "he looked good for it").

    Note the usual way to test an EGR value is to attach the vacuum pump and run the motor. Slowly apply vacuum. Once the motor begins to run like crap, this confirms the EGR valve is opening. Release the vacuum and the motor runs normal. This confirms the EGR value is closing. Repeat the EGR test using this method.

    Does your scanner access the DPFE flow PID?

    The LTFT are not jumping all over the place which is odd given the fuel pressure. Also given the FP, the LTFT value are POSITIVE. Which also seems wrong. Should be negative given the FP.

    The fuel pressure goes down to about 50 PSI as the motor revs. But is still too high.

    On my car, I tried disconnecting the FP electrical connector and the fuel pressure jumped to 88 PSI. I also tried disconnecting the Fuel pressure intake reference line. As expected the FP remained in the 38-40 PSI range but the motor bogged (delta FP is too high).

    Here's my working theroy. I believe there is a possibility more than one thing going on here.

    The LTFT are too static. In a well working car, LTFT change more than they do on your car. That tells me the O2 sensors are contaminated. Once contaminated the O2 sensors react too slow. This is not unreasonable given the car's mileage and low compression.

    The level of contaminated hasn't reached the level to throw a DTC code. Since both O2 sensors are behaiving about the same, replace both.

    I would like to cross check the fuel pressure with an external gauge. Confirm that the vacuum reference line is indexing the FP as it should. I'm not yet sure that the FP sensor has a problem, but as Ronald Reagan said, "trust but verify".

    The theory I'm working on is the actual AF ratio is wrong. This is bogging down the motor at low RPM. The amount of error decreases as RPM's go up.

    I'm a test and then replace sort of guy. So expect more tests, and less parts changing.
  12. evolucion311

    evolucion311 Member

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    Hey burns.... I was just out under the hood and disconnected the fuel rail pressure sensor. I applied a vacuum pump to it and it held 25" of vacuum without budging.

    Should a FRPS hold a vacuum?

    I also just confirmed that the DPFE vacuum lines are connected and free of cracks or tears.

    I studied economics in college.... people respond to incentives. I'm really looking forward to giving away $100 to one of you guys :D
  13. hotcobra03

    hotcobra03 Active Member

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    my guess is the wheel for crank sensor...keep pulling it apart


    you say you checked for vacuum leaks..what about vacuum restrictions


    reading your mod list...a wobbling lower pulley will cause po316..
  14. evolucion311

    evolucion311 Member

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    I loosened and then re torqued the crank pulley without effect. I think it's weird that the high quality Steeda crank pulley would throw me a code like this. I am inclined to agree with you that it may be the crank wheel behind the timing cover. I'd much rather pull a timing cover than a cylinder head so I'll try that first. I'll pull the timing cover this morning.

    Anything I should be looking for specifically that would indicate a bad crank wheel sensor?

    And about vacuum restrictions... how would I check for such a thing?
  15. hotcobra03

    hotcobra03 Active Member

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    i take the complete vacuum harness off...than blow and suck thru line..it should feel clear both ways..just like a straw...being these hoses are tiny ive found restrictions on mine with evap hose..

    i also would recheck engine harness by its self..when doing so check other pins in connector...could be shorted with another wire that wont show on test,,when you checked before from coil to pcm you checked to see if it had a break...0 said its connected but doesnt tell you its touching another wire..

    pull cover and take pic of engine and back of cover before you do anything else..its hard for us to help already without hands on like you...work slow and try not to disturb stuff before looking at it for awhile

    i havent listened to vid but wmburns is the man and he said noise is in front to him...as code 316 states..

    wheel could be bent on the tooth that triggers cyl 2...
  16. evolucion311

    evolucion311 Member

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    Alright well I've got the timing cover removed. What specifically would I be looking for if I had a bad crank position sensor wheel? or timing chains/gears?
  17. Rick 91GT

    Rick 91GT SN Certified Technician Site Sponsor

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    Bent teeth, missing teeth or cracks...
  18. Rick 91GT

    Rick 91GT SN Certified Technician Site Sponsor

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    How do the guides look? Any slop in the chains? Any debris or marks on the timing cover?
  19. evolucion311

    evolucion311 Member

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    I will make and post a video in about 5 minutes.... I need a beer after pulling that timing cover :)
  20. evolucion311

    evolucion311 Member

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    Rick 91 GT: I pulled the cover and lo and behold the passenger side chain has some slop in it. Video is inbound... YouTube is processing it right now.

    TIMING CHAIN SLOP VIDEO

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