Strange Acceleration Hesitation

[Leigh_bullitt]

Nothing to do with lugging
This person has the same issue..

https://www.mustang6g.com/forums/threads/5-0-acceleration-catch-slight-jerk-hesitation.36979/

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[KingKona]

Nothing to do with lugging
This person has the same issue..

https://www.mustang6g.com/forums/threads/5-0-acceleration-catch-slight-jerk-hesitation.36979/

OMG dude.....you're so obsessively desperate. You literally went back 9 freakin' years to support your perceived issue.

Seriously dude.......just stop it.

 

[Leigh_bullitt]

Hahahaha
Yeh it was a long time ago.

 

[NGOT8R]

This is one instance where I feel very confident that lugging the engine is the issue. A member on here came to my house a couple of months ago and asked me to have a look at his car that was making a clunking noise. He thought he was having tranny and clutch issues. Turned out, he was just upshifting too early. He asked me to drive his car and I was able to demonstrate for him, what was occurring. Right afterward, I took him for a ride in my car and deliberately upshifted early to show him that the problem could be replicated in any car.

 

[TonyT930]

Hi All
First and Foremost Happy new year.

So I have a 2020 Bullitt and some strange hesitation has started to happen and I’ve found other people with the same problem but no solution yet.

The Problem
So imagine I’m cruising in 5th at say 50-60mph and I take my foot off the gas. As I reapply their is this sudden jerk or hesitation that happens. Almost like power goes flat for less than a second. If I’m in lower gears it’s not noticeable. Only when cruising.

it seems a bit intermittent too. I notice the car doesn’t run quite as well at lower rpm’s when this happens it can feel a little jerky when driving in traffic etc.

But then it will go as smooth as silk and run great again.
Any ideas ?.

changed spark plugs
Car has 30,000 miles from new

it has a tune but I this is confirmed to happen when returned to stock as well.
Always use shell or BP 98 fuel ( 93 US ).

any help would be appreciated.
Cheers

I have the feeling it's the tune.

 

[RazzaRossa]

You're lugging the motor. 5th is an overdrive gear in a manual. 6th would be even worse. Row them gears boy!

 

[xcm77]

'20 Bullitt owner, 100% stock.

What you're describing sounds to me like lack of power in the low rpm range in 6th. Repeat the test in 5th (also overdrive like 6th) at the same speed and see of it behaves any different. It should btw.

 

[Hack]

My first thought was possible wear/defect on the electronic throttle position sensor where small input changes at light throttle aren't being read correctly. But I do agree with others that if you are trying to accelerate, the engine RPMs should be 2,500 or above. If the engine is turning less than 2,000 RPM and you try to accelerate, that isn't good for the engine to do (lugging). You will hear a rumbling noise if you lug the engine. That noise is from the piston skirts hammering against the cylinder walls. Of course in first gear you are going to do this sometimes (accelerate from low RPM), but you should never do it in higher gears.

 

[JetGray_Mach1]

Its normal, the car does not like low rpms. If I get a little yerk I know I was too low of an RPM. Also errors happen, there is tons of sensors and ECU working together a little random jerk is no big deal (sometimes the tune will do it too). What IS a big deal is if your car is misfiring or jerking violently as the rpms climb. Just enjoy the car, send the beast to 7K rpm the way she wants to be driven.

 

[ice445]

My first thought was possible wear/defect on the electronic throttle position sensor where small input changes at light throttle aren't being read correctly. But I do agree with others that if you are trying to accelerate, the engine RPMs should be 2,500 or above. If the engine is turning less than 2,000 RPM and you try to accelerate, that isn't good for the engine to do (lugging). You will hear a rumbling noise if you lug the engine. That noise is from the piston skirts hammering against the cylinder walls. Of course in first gear you are going to do this sometimes (accelerate from low RPM), but you should never do it in higher gears.

Yeah, I think something is wrong. Lugging these engines requires you to actually try to do so. As long as you feed in the load slowly, it has no issue. The A10 cars are always trying to run the highest gear they can. My M6 car can climb pretty much any mountain pass around here, at least interstate ones with somewhat reasonable grades in 6th gear with maybe 25% throttle max. Nary a complaint to be found. It's actually amusing to me how little it cares. Now if you're trying to do a full throttle passing maneuver in 6th, that's obviously suboptimal.

 

[Leigh_bullitt]

Fixed this problem by the way.
On the other forum was quite a few cars with the same issue.
They recommended a crank relearn which didn’t help.

I ended up re gapping the plugs from 0,52 to 0,40.
Whether it was the real reason I don’t know but the engine is now much more responsive.

 

[SheepDog]

I find it strange that people in Europe us commas to denote a decimal place

 

[Leigh_bullitt]

Hi All
Gapping the plugs didn’t solve this issue and the problem came back.
However…..try this
With the engine off unplug the IMRC solenoids and this will leave them in the open position.
now take the car for a spin and tell that the problem has gone .
You will get some other symptoms like some surging because the ecu isn’t expecting so much air in the lower rpm’s but I’m 100% the IMRC runners are the suspects for this issue.

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