2006 GT with a hesitation

Discussion in '2005+ Mustang GT 4.6L Tech' started by rickf, Apr 28, 2017.

  1. rickf

    rickf forum member

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    I have a 2006 GT that has a hesitation. This all started after changing the fuel filter due to a different type of hesitation that was cured by the filter change. The filter appeared to be original with 95,000 on it. I also put in new plugs at the same time, these were also the originals. I took a 300 mile trip with no issues after that. The problems I have now seem to have started after a WOT hit up to 6,000 rpm and the hesitation is worse once the engine is hot. I have replaced the Mass air sensor, it was bad according to the data. I have also cleaned the throttle body with the correct cleaner, it was REALLY bad. I cannot see any data on scanners that is showing any issue. I just had a mechanic friend of mine ride with me with his latest scanner and all he could see was bank one knock sensor activity when it hesitated. This could be anything causing it to run lean and knock but there are no misfires, real time or history. I want to put a tuner on this car but I need to have it right before I do so. Fuel pressure has also been checked with pids at 39.5 and actual at 29.5 Vacuum removed from fuel rail pressure sensor results in pid and actual of 40 lbs. running. At first turn of key actual fuel pressure hits 50 and if I hit the key a second time without starting it will hit 55lbs.

    Any suggestions are very much appreciated. I am a retired master tech and this kind of thing aggravates me because I know I am overlooking something.
     
  2. Brandon08GT

    Brandon08GT forum member

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    Do you have any modifications to the car? How long have you had the car?
     
  3. bujeezus

    bujeezus forum member

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    Always check the simple stuff. I'd recheck the torque on your spark plugs. Did you change the boots too? It's recommended when you change plugs. Be careful with the new boots. Mine were a little too snug and when I installed them on the coils, they grabbed the spring and contact and kept them from coming into contact with the ends of the spark plugs.
     
  4. 46addict

    46addict 13726548

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    Look over all the vacuum hoses going to the intake manifold. Trace the hoses and check for cracks/leaks. It may be worth removing all injectors and getting them ultrasonic cleaned and looking over the o-rings since the car went 95k without a filter change.
     
  5. redfirepearlgt

    redfirepearlgt forum member

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    All great advice and further to that list:

    If the engine is leaning out and you are seeing knock, it may be because you have contaminated gasoline. Water in teh tank getting pulled up into hte fuel system when you go hard throttle would cause hesitation AND would cause the knock sensors to pull timing due ot the sudden drop in Octane within the A/F mixture. H2O (water) vaporizing will add oxygen to mix within the cylinder, the water will also displace what would have otherwise been Octane and thus a knock sensor would likely pick up on this and pull timing. May wish to add flushing the tank to the simple list.

    Of the more common things have not resolved anything try this next BUT! Not until you have exhausted the more common items mentioned plus gas contamination first.

    Out of curiosity does the car hesitate and miss throughout the entire RPM range once this problem crops up right after an initial WOT hit? Or is it only in a certain range like below 3000 at light throttle or only above 3000 at WOT throttle that it starts hesitating?

    Test the EGR valve out. If it is sticking open this will cause issues. BUT...AND I MEAN BUT! Check all of the above suggestions first and foremost.
     
    Last edited: Apr 28, 2017
  6. deebo05

    deebo05 forum member

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    no egr on the 3v.....also check the fuel crossover line between the rails
     
  7. redfirepearlgt

    redfirepearlgt forum member

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    Thanks for the correction. My bad. Thought EGR's were done away with after 2010. I remember the one on my 2002GT, and thought there must be one on the 2005 I had but that it was tucked away on the backside of the intake (like on a 1993 Z28 LT1 where it's on the back side of the intake and almost impossible to get to). Never mind then. One less thing to worry about.
     
  8. rickf

    rickf forum member

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    No modifications to the car, all stock. I have owned it and driven it regularly for over a year. Had all of the plug boots off and checked for carbon tracks and put new silicone grease on them, all were good. Only one vacuum line on the car and I have checked it end to end. the fuel trims show perfect so no vacuum leaks. I pulled the new fuel filter to check for fresh contaminates and it was perfectly clean, no water in it either. I get my gas from several places and all are high volume stations with good reputations. The problem is most apparent on low rpm light acceleration. I can feel it on moderate acceleration but on hard acceleration I do not feel it. I would guess it is still there though.

    Heat definitely makes it worse so I think it is electrical in nature. A sensor failing in range and not setting a code. A coil that is not misfiring but also not completely burning the charge. I just need the justification before throwing any more parts at it.
     
  9. redfirepearlgt

    redfirepearlgt forum member

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    Yip a tough one. Trims good, but still getting a knock sensor indication to pull timing during the hesitation...hmmmm. Any chance when it's doing this and you shut the car off and restart it, it drives normal again until you give it a good WOT pull? As I understood it you had no issue while driving until you laid into pretty good correct?

    If you haven't done this create the hesitation and then pull over and shut the car off. Restart it within 10-15 seconds and see if the hesitation goes away until you jump on it pretty hard again. And out of curiosity when the hesitation begins happening is there any unusual additional noises coming from the engine? I am simply trying to recreate a version of the same issue I had with my 2005 before go jumping to a suggestion on something that will be much more costly. If its what i think it might be, you may not get any CEL's at all but the car will miss and maybe even have a knocking sound while running after a quick rev up after it idles back down.
     
  10. ZGrand

    ZGrand forum member

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    Fuel pump?
     
  11. rickf

    rickf forum member

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    No, It does it all the time, fresh start or constant run. And it will do it without ever romping on it, that was just what started it.
    Zgrand, it certainly feels like a fuel pump issue and the pressures are on the low side of acceptable but they are consistent an do not dip with the hesitation. The other thing steering me from the pump is the heat related part of it, Definitely gets worse as the engine bay temps go up, NOT the actual engine temp. Note that, it gets worse as the temperature of the engine bay itself goes up in other words, as the sensors and components heat up around the engine. I am leaning towards a coil but I am not showing any misfires, even in history. Does anyone know if the 4.0 in a 2005 Escape uses the same coils? I have three brand new of them I could swap in.
     
  12. redfirepearlgt

    redfirepearlgt forum member

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    That's a good thing then. Trust me. I was trying to eliminate cam phasers which by your follow up description I would not factor in to the equation now. Been there....done that once. My problem would go away at first startup and then start exhibiting the symptom after a hard hit on the throttle when the engine speed returned to idle. Shutting the car off and restarting it would clear the issue and the car would idle fine until another hard throttle up. Cam Phasers ended up being the culprit in that case. Took about 2 weeks to isolate because there were no CEL's at all. Compression checked good, fuel pressure was good, cats were good, spark, etc.

    Your getting good direction here so I will bow out.
     
  13. rickf

    rickf forum member

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    One thing I have not really thought too much about are the VCT solenoids. What are the symptoms of them going bad? one thing I have noticed is that my idle hangs higher than stock on many occasions and takes a while to drop. I do not have any way to scan the VCT solenoids that I know of. I REALLY do not trust dealers! Before I retired I was in charge of a fleet of vehicles from cars to trucks and on occasion I had to send one in for warranty work and I came to find that the mechanics at the dealerships for the most part did not know as much as I did. Most were just out of trade school or Vo-tech school.
     
  14. JeremyH

    JeremyH 3V Fuel Guru

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    Check the spark plugs yet?

    If pressure is not correct the injectors may not deliver the correct amount of fuel. Also pressure is what keeps fuel from boiling in the lines when its hot. So since its more pronounced when hot you could be experiencing that. The fuel rail pressure sensor also has a temperature sensor. And when its hot the pcm actually raising delta pressure to prevent this. What is pressure doing exactly? You mentioned it was low?

    Also the car can start acting funny when the alternator starts acting up.
     
  15. SVT Rider

    SVT Rider Junior Member

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    How's the oil pressure? I highly recommend hooking up a oil pressure gauge to the oil sender port.

    The timing chain tensioners are known to fail with blown gaskets and that kills oil pressure. Also the OEM oil pump is known to have a back-plate that flexes under pressure.
     
  16. Gh0stRep0rt

    Gh0stRep0rt forum member

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    Have you check the plastic gears inside the throttle body on the driver side, thats how mine started with hesitation and the rpm jump high and after a while the teeths broke off...

    Sent from my SM-G925T using Tapatalk
     
  17. rickf

    rickf forum member

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    Actual pressure is 28lbs at idle and 40 lbs. at wide open throttle and if I disconnect the vacuum line at the pressure sensor. Plugs were just replaced with the correct Ford plugs. Pressure sensor was just replaced with a Ford part and there was no change in pressures at all. What kind of pressures do you want to see? I was thinking pump but wouldn't the module try to run the pump harder if it was not seeing the pressure it wanted?

    Wouldn't this show up on the throttle position sensor as a jump on the graph line?

    Where is the sender port? I will check it.
     
    Last edited by a moderator: Apr 30, 2017
  18. Gh0stRep0rt

    Gh0stRep0rt forum member

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    Idk...when it started going south for me it didnt show any sign that tps was having problem.

    Sent from my SM-G925T using Tapatalk
     
  19. SVT Rider

    SVT Rider Junior Member

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    It is located on the oil filter adapter. You can remove the "dummy" on/off OEM oil sensor from the port and thread a oil pressure guage in its place for a check. The computer's dash will likely complain, but you can get an accurate reading with the real guage. It best to check both at cold (should be ~70psi on first start) and then at hot after a drive cycle (28-30psi) with Motorcraft 5w-20 oil.

    If it is <25psi hot (mine was in the 17-18psi range), it is time to replace the tensioners and put in a new oil pump.
     
  20. rickf

    rickf forum member

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    Ok, BUT, good oil pressure aside how will this problem cause the symptoms I am having? My timing chains are dead silent so I don't think I have an issue with the tensioners but checking the oil pressure is easy enough.
     

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