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Old 09-19-2014, 10:32 AM   #1
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Default Engine hesitating under acceleration

So I lately been noticing that my 2001 screw 5.4 hesitates while I accelerate. The hesitation is getting worse. The truck has 162k miles. I already changed the spark plugs with motorcrafts 3k ago, cleaned TB, cleaned MAF, cleaned IAC, changed oil and filter, cleaned air filter, changed the transmission fluid(drop the pan and new filter). I also changed the fuel filter and checked the fuel pressure at the rail which it was 30 at idle. If I rev the truck the fuel pressure goes up to 32.

The truck had a passenger side exhaust leak and it was the gasket. I replaced the gasket and it is not leaking anymore. I used to hear the ticking noise from it and now is gone. I don't hear any vacuum leaks.

It almost sounds like the exhaust is leaking but I don't hear the ticking anymore. I haven't checked the driver's side manifold for a leak. I have no SES light or codes. While i'm driving if I put it on neutral and I rev the engine up it doesn't hesitate or vibrate. It only happens on gear while accelerating. I can feel a slight hesitation at idle.

I was thinking it was the fuel pump going bad because it kinda feels like that but the fuel pressure seems fine according to the book.

Any suggestions on what else to check? I have been told that I should replace the coils but i'm not sure if the coils while do that under acceleration without giving me a ses code. Thanks.
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Old 09-19-2014, 11:45 AM   #2
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Quote:
Originally Posted by jayta98 View Post
So I lately been noticing that my 2001 screw 5.4 hesitates while I accelerate. The hesitation is getting worse. The truck has 162k miles. I already changed the spark plugs with motorcrafts 3k ago, cleaned TB, cleaned MAF, cleaned IAC, changed oil and filter, cleaned air filter, changed the transmission fluid(drop the pan and new filter). I also changed the fuel filter and checked the fuel pressure at the rail which it was 30 at idle. If I rev the truck the fuel pressure goes up to 32.

The truck had a passenger side exhaust leak and it was the gasket. I replaced the gasket and it is not leaking anymore. I used to hear the ticking noise from it and now is gone. I don't hear any vacuum leaks.

It almost sounds like the exhaust is leaking but I don't hear the ticking anymore. I haven't checked the driver's side manifold for a leak. I have no SES light or codes. While i'm driving if I put it on neutral and I rev the engine up it doesn't hesitate or vibrate. It only happens on gear while accelerating. I can feel a slight hesitation at idle.

I was thinking it was the fuel pump going bad because it kinda feels like that but the fuel pressure seems fine according to the book.

Any suggestions on what else to check? I have been told that I should replace the coils but i'm not sure if the coils while do that under acceleration without giving me a ses code. Thanks.
Yes, one of the coils could be going bad. Still firing but loosing spark. Had this happen to me. Eventually it will throw a code. You can try removing one coil connector at a time, but it may still prove difficult to find. or swap one coil out at a time until you get results.
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Old 09-19-2014, 12:06 PM   #3
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It doesn't make a difference if I swap a coil because I don't a code for any of coils. I been holding off on buying the coils but I think im going to go ahead and buy them new. Motocrafts or visteons only.

I called ford and they charge $100 for an specific issue diagnostic.
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Old 09-19-2014, 12:09 PM   #4
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Change coils. Problem will be solved
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Old 09-19-2014, 08:42 PM   #5
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I agree. It's the coils
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Old 09-20-2014, 07:01 PM   #6
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I had this problem! I took it to my friend who is a Ford Truck mechanic and he replaced the coils. My engine is the 4.2 Liter V6. He told me this is a common problem. When it rained and there was high humidity the engine would cut out on acceleration.

I agree with the coil hypothesis. Look at them and determine if they are cracked.
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Old 09-21-2014, 12:55 AM   #7
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So no CEL ? COP system, -do you have a android phone?

What happens when you floor it? Does it smooth out or still misfire ?
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Old 09-21-2014, 07:39 PM   #8
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So no CEL ? COP system, -do you have a android phone?

What happens when you floor it? Does it smooth out or still misfire ?
I do have android. I have a obd2 scanner and no codes. I feel a slight miss at idle but it doesn't necessary means it is a misfire. If i floor it I don't feel a misfire. If I slowly give gas(normal driving) I do feel a slight hesitation but I mostly hear it on the exhaust. If i shift to neutral while the truck is in motion and i give it gas I don't feel it or hear it in the exhaust. Same thing if I am at idle at home, if i rev it up I don't hear it or feel it.

I don't have a passenger side exhaust manifold leak anymore. I checked around the exhaust and no leaks. I did hear a pop noise at idle from the air filter like it is missing but I only hear it on the air filter(KN). I have a video of the noise on another post that so far nobody i know ever heard that noise. I'm going to check the driver's side manifold but I don't hear any ticking noise.

I pulled out the intake today and checked all the vacuum hoses and they are fine. I cleaned TB, IAC, MAF, IAT and EGR valve. I sprayed carb cleaner around the intake area to check for a gasket leak but no change in the idle. I also pulled all the plugs out again and rechecked them for gap and appearance. The gap was fine in all of them. I didn't noticed any cracks on them.

I mean the truck is not running horrible but it didn't do this when I got it 4 months ago. I might just keep driving it until it gets worse. I am thinking it could be the coils (but is not missing when I floor it), cats maybe getting clogged or maybe the tranny? I did change 8 quarts of trans fluid in two stages plus a new filter since I got it. The tranny was shifting hard between 2nd and 3rd and I after I change the fluid it shifts normal.

I might take it to ford for diagnostics since I don't have live data scanner.

Any other suggestions you can think of Jbrew?
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Old 09-21-2014, 07:49 PM   #9
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I did forgot to mention that i did checked the resistance in all the COP's. Not that it means anything as I have read checking the resistance might not mean anything unless the unit is a complete fail but this the results i got. All the COPs look like the originals(or at least motorcrafts) except #5

cyl primary / secondary (K/ohms)
#1 1.9-2.0 /5.55 K
#2 1.4 /5.58 K
#3 1.4 /5.55 K
#4 1.5 /5.6 K
#5 1.6 /5.56 K
#6 0.9 /5.5 K
#7 1.5 /5.5 K
#8 1.6 /5.47 K
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Old 09-21-2014, 08:14 PM   #10
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Resistance/ohms don't tell yuh squat unless they are completely fried. Unfortunately, COP system coils don't go out that way. They slowly burn turns in the wire, copper windings (turns) like say you would find in a transformer. Windings are spooled together for the most part (not all, -step tf) so resistance tests are going to point a low grade misfire.

Any kind of hesitation is a misfire. The cause can be different. What guys are doing now to narrow it down is retrieving live data via Android phone and the Torque or Torque pro app. It was a $5 download on line, not sure now.

That will show you live cylinder info, so when it's missing, you'll see where. Doesn't mean it's a coil necessarily, but it will narrow down quite a bit. The misfire monitor itself won't pick it up until the count is high enough. Which doesn't help most of the time...
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