Very strange hesitation... can you help?

[BlueChappy]

So not that long ago, I ran the tank almost empty. I did not run out of fuel but I was within 6 miles. I have a 2005 Mustang GT and it’s slightly modified, so 6 miles is probably closer to 2-3 miles.

Anyway, since that day, I’ve been having a horrible stutter on acceleration. It happens at lower RPM’s, and slightly on straightaways, but really is accentuated after making a turn.

I did what I thought it was. I changed the fuel pump, fuel filter, and the fuel injectors. They are all now brand new, and the car is still stuttering especially around corners. My coil packs are less than a year old and I changed the plugs at that time as well.

I’m thinking it’s a fouled plug. But are there any other ideas what might be causing this? I don’t want to keep sinking money into things I don’t need. It would be easy if there were an engine light to get coffees from, but no light is present.

Any ideas?


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[teeje]

So not that long ago, I ran the tank almost empty. I did not run out of fuel but I was within 6 miles. I have a 2005 Mustang GT and it’s slightly modified, so 6 miles is probably closer to 2-3 miles.

Anyway, since that day, I’ve been having a horrible stutter on acceleration. It happens at lower RPM’s, and slightly on straightaways, but really is accentuated after making a turn.

I did what I thought it was. I changed the fuel pump, fuel filter, and the fuel injectors. They are all now brand new, and the car is still stuttering especially around corners. My coil packs are less than a year old and I changed the plugs at that time as well.

I’m thinking it’s a fouled plug. But are there any other ideas what might be causing this? I don’t want to keep sinking money into things I don’t need. It would be easy if there were an engine light to get coffees from, but no light is present.

Any ideas?


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Check the spark plugs. Hope they’re oem. If not, the new part number is sp547 or you can get autolite HT1s. Standard heat range. I run HT0s one step colder for boost. Autolite and ford appear to use the same exact manufacturer. They’re now one piece.


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[skwerl]

Sounds like the pump in the tank. Time to pull the back seat and pull the pump assembly out of the tank. Crud in the sock or else the sock is torn and crud in the fuel pickup.

 

[crjackson]

Sounds like the pump in the tank. Time to pull the back seat and pull the pump assembly out of the tank. Crud in the sock or else the sock is torn and crud in the fuel pickup.

I changed the fuel pump

According to OP’s post, he already did that. This would have been my internet guess of the day too...

 

[BlueChappy]

Sounds like the pump in the tank. Time to pull the back seat and pull the pump assembly out of the tank. Crud in the sock or else the sock is torn and crud in the fuel pickup.

Already changed the pump. I thought the same thing. The fuel pump, fuel filter, and the fuel injectors are all changed.


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[skwerl]

Maybe back flush the fuel line? Could even be done with compressed air.

 

[golkhl]

Fuel rail pressure sensor? Just a guess.

 

[07 Boss]

You know what has me baffled is why you say it does it in turns. If indeed it is the cause then it has to be fuel or fuel pick up related. I have a feeling you think it happens when you're turning because the load is light and your not on the throttle, low RPMs. I currently have a slight stutter/roughness to below a certain RPM and I know its probably a plug. I only feel/hear it when I'm below like 1800 RPM's which is basically never. My point being that it is RPM related as far as the visible symptoms and yes it happens more while making turns and sometimes on the straights depending on gear and load. Just gotta get the other car out the garage (waiting on brake lines) to go pull them. Mine are only a couple of months old but I've already had one failure.

Tell me more about this running low on fuel incident. Why exactly do you think this is related to your issues. Were you on it hard, did it run lean? Was there any knocking? I think pulling your plugs is the first step. They can tell you a lot about the way your engine is running. That used to be the way we did it back in the day. We didn't have codes to sort stuff out.

 

[BlueChappy]

No that makes a lot of sense about the low RPMs. Normally around corners, I keep it in second gear. So RPMs do get low.

The reason I thought it was a fuel issue and was related to me running very very low on gas, was because it started immediately after that. I thought it was picking up some junk from the bottom of the tank and sucking it in. I also thought since it was that, I might have burned out the pump. Especially since fuel is what keeps the pump cool. So I changed out the fuel pump and the fuel filter since I was there anyway. It kept going, so a week later I changed my fuel injectors. That was yesterday.

Fixing the car myself is fine, I just don’t want to keep sinking money into it.

I’m hoping that there’s a code on the computer but the engine light isn’t on. So I’m going to head to AutoZone and check to see if they can see a code. That might help out a lot if there is one. Any other thoughts are welcomed!!!

Thank you.


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[habu]

How is your oil level? I had something similar happen to me, stumped me too, changing filters..plugs..etc. Turned out the oil level was really low. Extremely stupid on my part but it sounds very similar to your description.

 

[BlueChappy]

How is your oil level? I had something similar happen to me, stumped me too, changing filters..plugs..etc. Turned out the oil level was really low. Extremely stupid on my part but it sounds very similar to your description.

Well, I haven’t checked that. I just changed it a month ago. But I’ll check.

What exactly happened to you?


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[Laga]

Check electrical connector to fuel pump and make sure it is secure. Then clean TB and MAF.

 

[habu]

Well, I haven’t checked that. I just changed it a month ago. But I’ll check.

What exactly happened to you?


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Same thing, hesitation at low speeds and especially when turning. Like turning left from a light, turning in a parking lot and all at low speeds. Once I had some RPM, it was fine. I babied it because the last thing I wanted to do is hurt anything so for about a year I chased ghosts. Turns out the oil level, in my case, was really low. Oil change and now months later problem is completely gone.

I am not at all suggesting that the other recommendations are bad, they are all things to check. In my instance I chased ghosts. What caught my eye is your comment about turning and that was exactly what I was seeing.

 

[BlueChappy]

Same thing, hesitation at low speeds and especially when turning. Like turning left from a light, turning in a parking lot and all at low speeds. Once I had some RPM, it was fine.

That’s exactly what was happening.

But let me tell you something... as soon as I saw your original post, I changed my oil. It was low. I also cleaned my cold air filter.

I drove it to the grocery store and had zero hesitation. I will take it out for a better test drive tomorrow. And will keep everyone updated.


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[habu]

Sweet, hope that solved your problem.

 

[Dino Dino Bambino]

Yup. If the oil level is low, there may be insufficient oil pressure at idle/low rpm to operate the VCT system.

 

[BlueChappy]

Yup. If the oil level is low, there may be insufficient oil pressure at idle/low rpm to operate the VCT system.

I wish I would have checked that first. It would have saved me some money. Oh well, at least I have a new fuel pump, filter, and injectors. I plan on riding around today a bit more to see if that was it. But now I have to find the oil leak. Always a project. [emoji23]


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[BlueChappy]

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[07 Boss]

Yup. If the oil level is low, there may be insufficient oil pressure at idle/low rpm to operate the VCT system.

True, I was just thinking to myself how was low oil going to make the engine stumble or hesitate.

But wouldn't that throw a code?

 

[BlueChappy]

True, I was just thinking to myself how was low oil going to make the engine stumble or hesitate.

But wouldn't that throw a code?

You would think. And I know Fords especially during those years was habitual in having codes on the computer but not throwing the check engine light on. So I checked yesterday at AutoZone and there was no codes on the computer either. But hey we’re driving!


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