2006 GT with a hesitation

46addict

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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.

There is more than one vacuum line to check. The brake booster line I believe tees into the fuel pressure rail sensor on the driver's side. Then there is one going from the passenger side valve cover to the intake tube if you left the stock PCV system alone.

Looks like you've already replaced the FRPS so I'm sure you got a chance to inspect that vacuum line, but it won't hurt to check the other areas. And I've been told it's good practice to replace the coil boots ($5 each) each time you change the plugs. The coils inside them go bad over time and when I was chasing a misfire/surging issue, changing these fixed the problem.
 
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bujeezus

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Had all of the plug boots off and checked for carbon tracks and put new silicone grease on them, all were good.

Hate to keep harping on this but a visual inspection is not enough. The material wears out and they stop doing their job. $40 isn't that much and they need to be changed any way.
 

rickf

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Hate to keep harping on this but a visual inspection is not enough. The material wears out and they stop doing their job. $40 isn't that much and they need to be changed any way.

Yes I understand but if a boot is bad I would have misfires, The only thing the boot does is insulate the spark from the head so it is either going to insulate or not and if not it will misfire. I am not showing any misfires in the history for the last several drive cycles.

I don't want to spend 40 bucks for boots if I am going to have to spend a couple hundred for new coils which would come with new boots and then I have wasted the 40 bucks.
I just want to be sure before throwing any more parts at this thing. I have already replaced several parts with absolutely no change. The rest of the parts are pretty pricey so I want to be sure before dropping the cash.
There is only one VACUUM line which does "T" off to the pressure sensor and the brake booster. The line from the valve cover to the intake is a vent line. I have sprayed the entire top of the engine, lines included while watching the fuel trims and not so much as a blip.

Here is another clue I have forgotten to mention, fifth gear running at 1100-1200 rpm at very light load it will surge, surge, surge, surge. About every 1-2 seconds. This is where we saw the knock sensor reading. Something is commanding a change in state every second or so at that throttle setting. I am sure this is related to the hesitation because it did not do this before the hesitation issue. It will do this surge in other gears but it is harder to replicate due to the lower gearing and trying to hold a steady speed.
 

bujeezus

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Ah, point taken. Past experience has taught me that when I know I'm right, I'm usually dead wrong. Lol!
 

SVT Rider

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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.
The more I read about your symptoms, it doesn't sound like oil pressure would be the cause.

My theory was that if there was slack in the chain, you could experience a hesitation-like feel due to the cam timing being thrown off between acceleration and deceleration. In addition the low oil pressure might be enough to create more friction on the bearings making the engine feel sluggish, but at this point I would say put this in your todo checklist once you get the hesitation issue figured out.

It does sound like a vacuum leak. I had a vacuum leak on the back side of my intake manifold last year. It was located on the passenger side where the IMRC shaft ran into the back of the plastic intake plenum. It got so bad I could audibly hear it hissing.
 

46addict

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I just want to be sure before throwing any more parts at this thing. I have already replaced several parts with absolutely no change. The rest of the parts are pretty pricey so I want to be sure before dropping the cash.
There is only one VACUUM line which does "T" off to the pressure sensor and the brake booster.

Test health of injectors and o-rings?
 

rickf

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People keep saying vacuum leaks but would that be the case with my fuel trims being as close to perfect as you can get? STFT at -3 to +3 and LTFT at 0 to +2. Any vacuum leak would give high LTFT. Correct me if I am wrong.

I am still thinking about fuel pressure but is there a way to determine if it is the pump or the module? I am thinking if it is the pump then the module would not be able to vary the pressure up to 40 as needed. But I cannot get anywhere near the 70 on the high side of the specs, I am actually a bit below the low side of the specs. The pressure varies so the module is changing the pump speed but it is not getting up to the specified pressure.
So here is my question, why is the module not running the pump harder to try to bring the pressure up into the midrange of the specification? See my dilemma here? Pump or module? They are both expensive and I don't want to replace both.
 

rickf

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Where would I get the injectors checked and be able to get it done fairly quickly, this is my daily driver right now. Pulled the pump and found no issues, it is the latest pump so the recall should not pertain.
 

deebo05

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if your fuel pressure is 28 psi idle and 40 psi wot that is normal, unless you have boost. without boost you wont see 70psi.

what does fuel pressure do when the hesitation occurs?
 
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rickf

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The best I can tell it blips up in pressure just a hair in response to the hesitation. I am guessing that the hesitation causes a drop in vacuum which raises the pressure, as it should. I have never seen it drop out. The pressure seems to be reacting as it should, I was just concerned about the actual pressure readings themselves since the Ford specs are 35-70 lbs.. So now I move on to other ideas. I had pulled the pump to check the intake filter on the bottom of the pump since the original problem was a clogged fuel filter. There was no dirt coming out of the outlet of the filter even with banging it on the bench though so I doubt any got through to the injectors. It ran fine for a couple weeks after the filter change. This feels electronic because the hotter the engine gets the worse the problem gets and it is not the engine temp, it is the engine bay temp. There have been a coupe times where it felt like it shut off for a split second, not a miss but a shut down. No codes and no backfire so it had to shut off fuel and spark. I have not been able to catch that even on a graph yet though.
 

rickf

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Ok, Replaced the throttle body with a new Ford performance replacement and same problem. I figured this would cover the throttle plate gears and motor as some suggested and also the TPS as many suggested. NO CHANGE! So far I have a new Ford Mass air sensor, a New Ford complete throttle body, New Ford spark plugs, New Ford Fuel rail pressure sensor, New Ford fuel filter (twice), Pulled fuel pump from tank and checked intake filter. Checked all the coil boots for carbon tracking but in addition to that there is no history of misfires at all. The fuel trims are right around zero for both long term and short term.
Beyond the aggravating part this is also getting damn expensive. I can't find anyone who has had this problem who posted a solution, several threads about the problem but no solutions! What did they do? Scrap the cars!

Has anyone ever had their ECM get corrupted? I have called and or e-mailed all of the companies the make or sell tuners to see what they say, Most did not answer e-mails and the ones that answered the phone calls................. Lets just say that the answers given were hard to believe that they came from people that advertise that they build and race Mustangs!!!!!

Totally frustrated and sorry I ever bought this car.
 

rickf

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Well, it just got better. I decided to pull the plugs and check the condition even though they are new and saw that the never seize had melted and ran down the plug so I figured that may have been causing a problem. Cleaned up all the plugs and checked all the coils for tracks and put it all back together and started it up and WTF!!!!! It was only running barely on one or two cylinders! if I tried to give it gas it just died and now it will not start at all. It might start if I hold the gas all the way down and keep it at about 3/4 throttle once it starts but it is only running on a couple cylinders. no codes! Now when I try it only fires on one cylinder and will not start. Fuel pressure is 40 lbs. What is it with this car!? I am at my wits end, I need transportation. The only thing I can think of now is timing chains even though they made no noise at all.
 

Phil1098

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If it is only running on one or two cylinders you should have six or seven wet gas soaked plugs if the problem is spark. If you pull all the plugs and they are all clean and dry then it's a fuel issue. I would crank it up and as soon as it runs for a couple minutes, pull the plugs and see.
 

skwerl

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Plug gaps correct?

Also if the fuel pump seems marginal then you can do Jeremy's wiring upgrade which will reduce fuel pump duty cycles by about 10-12%. It's a common and inexpensive mod for guys adding boost, before they go nuts and start upgrading fuel pumps. It's been several years but I think I paid $35.
 

deebo05

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if it was running before you pulled the plugs then its your plugs now. just because plugs are new dont mean anything.

what plugs are you running?

your getting knock sensor activity on one bank, I would do some more data logging before just guessing and throwing parts at it...watch stft when the hesitation occurs...also watch cam timing on that bank.
 

rickf

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Deebo05, I think you are right on the plugs. It was running fine with nothing more than the hesitation before I pulled the plugs and cleaned them with carb cleaner and blew them out. It is possible they did not like the carb cleaner. They are the stock Ford Motorcraft latest style plugs. I am going to replace them today and put in new ones with no neverseize on them and see what happens. I am just going to get whatever plugs I can get at Autozone for now just to see if the plugs are the issue.

I do not have the ability to see the cam timing with the scanners I have. I have a higher end actron and also using Torque Pro for Android. I can't justify buying anything higher end for one car diagnosis. I do not see the cam timing in the pid list, I am guessing it is a proprietary scan?
 

rickf

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Put new Auotolite plugs in it and it runs good, Once the relearn went through the hesitation came back. I am convinced it is in the PCM. I did a couple of WOT runs and it comes right back to a smooth idle so I don't think the VCT solenoids are acting up. The only other mechanical part I can think of is the charge motion control plates, I don't think it is that since this hesitation feels like a timed event more than a load controlled event. If I start out easy in first and hold first it will happen in first but if I start out in first and shift quickly into second the hesitation hits in second at about the same time frame. It is always about 4-5 seconds after starting out. It feels like an air bubble in the fuel but I have watched the pressures and fuel trims until I am blue in the face and they are not changing to show any fuel related issue. It has to be electronic but no codes, that is the part that is driving me crazy!
 

Gh0stRep0rt

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Put new Auotolite plugs in it and it runs good, Once the relearn went through the hesitation came back. I am convinced it is in the PCM. I did a couple of WOT runs and it comes right back to a smooth idle so I don't think the VCT solenoids are acting up. The only other mechanical part I can think of is the charge motion control plates, I don't think it is that since this hesitation feels like a timed event more than a load controlled event. If I start out easy in first and hold first it will happen in first but if I start out in first and shift quickly into second the hesitation hits in second at about the same time frame. It is always about 4-5 seconds after starting out. It feels like an air bubble in the fuel but I have watched the pressures and fuel trims until I am blue in the face and they are not changing to show any fuel related issue. It has to be electronic but no codes, that is the part that is driving me crazy!
I know is a late reply, but did you end up checking the charge motion plate?..
Also did you check the connection of it to see if its dirty.
Is the alternator working fine?
I hope you found the problem and got it fix



Sent from my SM-G925T using Tapatalk
 

rickf

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Nope, still have the problem. Just got done changing the filters in the injectors. It runs fairly well until it gets done with the relearn and then we are back to the hesitation so it is in the electronics somewhere. I am out of ideas. I am most likely going to sell it. Now the bank two convertor is going bad. It set a code once and I can see it on the scanner, the downstream O2 sensor is way too active. I have sunk far too much money into this car for absolutely zero return. I have thought about the Charge motion plates but what am I going to do? Replace them, eliminate them? Either one takes substantially more money and I really don't think it is them. Then what next? Timing components, Might as well replace all of it at 90,000. another 400.00 down the tubes. lifters and cam followers, could be them. Nobody that has had this problem has EVER posted a solution. I really thought I was going to be the one to do it but I guess I am going to be like the rest of them, At least I gave it my best shot and documented everything I did and why.

I did not check the alternator yet mainly because this problem is far too consistent. When I start out from a light I can count to three and bang, there it is. Every time. I can start out in second gear and the same thing, three-four seconds the car shuts off for a couple miliseconds. It is like the key is turned of. It has happened at higher speeds also.
 

Tbone

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Is by chance your passenger side floor wet? If the cabin filter area gets plugged water builds up and drips over the sjb, causing all sorts of problems. Like pull up the carpet and check.
 

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