Fuel Slight jerking ?? HELP

CrazyChick08 · Oct 11, 2020

2005 Mustang GT. 5 speed manual.
The problem I'm having is theres a slight jerking(that bucks a little constantly until I let off or go faster) only at steady throttle. No matter what speed I'm doing, there's a noticable jerking and it's worse when I'm at low rpms in low gears.
I changed out the spark plugs, the fuel filter and I've cleaned the MAF and throttle body. It does not throw any codes! The rpm sometimes stays at 1000rpm at idle and doesn't go down until driving it a little. It's driving me crazy. If anyone knows anything, let me know!
No mods, all stock besides exhaust and catalytic converters were removed 4 months ago

Dino Dino Bambino · Oct 12, 2020

Those sound like symptoms of a defective throttle position sensor. Have you pulled any codes?

cbxer55 · Oct 12, 2020

He said it does not throw any codes.

7991LXnSHO · Oct 12, 2020

Old school answer, especially for a manual transmission or if it happens with the torque converter is locked up. Check the drive line components for play. U joints are the first suspect, but the yokes or rear gears could also have play in them. a transmission or motor mount is also possible, but way down the list percentage wise.

CrazyChick08 · Oct 12, 2020

7991LXnSHO said:
Old school answer, especially for s manual transmission or if it happens with the torque converter is locked up. Check the drive line components for play. U joints are the first suspect, but the yokes or rear gears could also have play in them. a transmission or motor mount is also possible, but way down the list percentage wise.

Ok thanks. I'll do that first

Dino Dino Bambino · Oct 13, 2020

One thing you could try is resetting the throttle position as per the owner's manual. Turn the ignition to the ON position but don't start the engine. SLOWLY depress the gas pedal to the floor, hold for a second or two, and then slowly release. Repeat twice and then you should be good to go.

CrazyChick08 · Oct 13, 2020

Bullitt95 said:
One thing you could try is resetting the throttle position as per the owner's manual. Turn the ignition to the ON position but don't start the engine. SLOWLY depress the gas pedal to the floor, hold for a second or two, and then slowly release. Repeat twice and then you should be good to go.

Yeah, I've done it but it didn't change anything. I also notice a slight gurgling sound from the exhaust when it's idling too

7991LXnSHO · Oct 13, 2020

CrazyChick08 said:
Yeah, I've done it but it didn't change anything. I also notice a slight gurgling sound from the exhaust when it's idling too

That sound must be from the squirrels using mouthwash when they are not providing extra power. ;-)

The next steps I can think of involve scanning for codes and checking for ignition problems.

CrazyChick08 · Oct 13, 2020

7991LXnSHO said:
That sound must be from the squirrels using mouthwash when they are not providing extra power. ;-)

The next steps I can think of involve scanning for codes and checking for ignition problems.

There's no codes coming up at all. No engine light whatsoever

7991LXnSHO · Oct 14, 2020

I have no idea of your level of mechanical and diagnostic aptitude so I am going to ask for clarification.
Did you hook up a scan tool, not just seeing the check engine light is off? OBD 1 does not always set off the light with codes. I am not sure about this OBD2, but GM’s have been known to count intermittent misfires without setting off the dash light. VW on the other hand likes to make the dash pretty with all the check stuff lights.

CrazyChick08 · Oct 14, 2020

7991LXnSHO said:
I have no idea of your level of mechanical and diagnostic aptitude so I am going to ask for clarification.
Did you hook up a scan tool, not just seeing the check engine light is off? OBD 1 does not always set off the light with codes. I am not sure about this OBD2, but GM’s have been known to count intermittent misfires without setting off the dash light. VW on the other hand likes to make the dash pretty with all the check stuff lights.

I have put a scan tool in and did monitor the performance of the car. The only thing that struck out is when I went to see the drive cycle and it said under components: incomplete and misfire: incomplete

7991LXnSHO · Oct 14, 2020

That’s what I was hoping for. The good news is that a tune up (wires, plugs, check the coil or coils and other ignition components) is likely to fix the issue.

CrazyChick08 · Oct 14, 2020

7991LXnSHO said:
That’s what I was hoping for. The good news is that a tune up (wires, plugs, check the coil or coils and other ignition components) is likely to fix the issue.

I thought about that but wasn't sure. But another question is the PCV valve. Would that likely be the issue? I read where they can get stuck open. Plus there's oil inside the hose itself

7991LXnSHO · Oct 14, 2020

I have never heard of a malfunctioning PCV system causing misfire symptoms. Some oil in the PVC hose from the crank case vapors is not unusual. If in doubt, replace the valve to help with oil consumption. They are usually a small price item.

CrazyChick08 · Oct 14, 2020

7991LXnSHO said:
I have never heard of a malfunctioning PCV system causing misfire symptoms. Some oil in the PVC hose from the crank case vapors is not unusual. If in doubt, replace the valve to help with oil consumption. They are usually a small price item.

Ok thanks. The things I've read online said they could cause surging, which I have and misfire at idle which I'm sure also

racerraj · Oct 14, 2020

Does the engine run smooth, do you hear any misfire? Maybe try unplugging one coil pack at a time and make sure it the sound changes each time. If one cylinder doesn't change, that one is misfiring. Could be Plug (Which isn't likely since you changed them), coil pack, or fuel injector. Move the coil pack to another cylinder to see of the problem follows the coil pack. But I am guessing it is running smooth. As someone mentioned, ujoints can cause that feeling too. Maybe get up to speed, throw it in neutral, shut the motor off. If the jerking is still there then it would likely be driveline related - driveshaft, ujoints, bearings, and such.

CrazyChick08 · Oct 14, 2020

racerraj said:
Does the engine run smooth, do you hear any misfire? Maybe try unplugging one coil pack at a time and make sure it the sound changes each time. If one cylinder doesn't change, that one is misfiring. Could be Plug (Which isn't likely since you changed them), coil pack, or fuel injector. Move the coil pack to another cylinder to see of the problem follows the coil pack. But I am guessing it is running smooth. As someone mentioned, ujoints can cause that feeling too. Maybe get up to speed, throw it in neutral, shut the motor off. If the jerking is still there then it would likely be driveline related - driveshaft, ujoints, bearings, and such.

It doesn't idle smooth. The rpms stay at 1000 up until I start driving it a little. Theres a slight misfire at idle and when I'm in low gears(1st or 2nd) driving slow, theres definitely a noticable surging and hesitation until I go faster or get into a higher gear

Shuttleman83 · Oct 14, 2020

N/M noticed year of the car.

racerraj · Oct 14, 2020

High idle may be from a vacuum leak somewhere. Which can cause it to run lean and cause misfires. Can you hear a hiss under the hood around the engine area? Check all vacuum hoses.

CrazyChick08 · Oct 14, 2020

racerraj said:
High idle may be from a vacuum leak somewhere. Which can cause it to run lean and cause misfires. Can you hear a hiss under the hood around the engine area? Check all vacuum hoses.

I already did a vacuum leak test and couldn't find any. There is a hissing now that comes from the engine

Fuel Slight jerking ?? HELP

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