Throttle tip-in issue/stumble (3.0 5-speed)

[andrewwynn]

I have no problem with throttle response but my transmission doesn't grip until about 1000 rpm so if i stomp on it from zero it'll spin up to a really high torque range before grabbing and spin the wheels. It's not an enjoyable jerk. So i have to give it gentle throttle until about 1200 before I "hammer down".

The x5 throttle programming is such the first 30% of motion gives you maybe 10% throttle. Very very different than cable driven throttle and many people hate it there are ways to get that reprogrammed. I'm portioning this out to see if this is what your issue is. It may not be a problem at all with the car just the way it is made.

So: when driving very slow like 5-8 mph over rough terrain, the first 30% of throttle can be used to gently change speed then after 30%, the transfer is more linear.

0-0
10->4
20->7
30->10
40->20
50->35
60->50
70->70

It's not exacty that just an idea.

Light throttle does very little. If you sweep steady through the range it'll feel like there's a delay.

My car right now has a problem with light throttle i have to "start" at 25-30% when engine is cold or it stumbles so i tap the throttle quickly through the first 1/4 of the range. Unless you get you throttle reprogrammed to linear you might have to train around that limitation also

All speculation that might be there issue not saying for sure it is.

https://youtu.be/8NohVmaY134?si=EnGxMd54EbbPAull

See video. Throttle adaptation may be your issue but i thought i saw you addressed that.

[80stech]

I don't remember if you checked fuel pressure but bit it's not impossible that the vent for the regulator is hooked to manifold vacuum which could cause this exact problem. Long shot but just takes a minute to check.

[Masospaghetti]

Originally Posted by andrewwynn

I have no problem with throttle response but my transmission doesn't grip until about 1000 rpm so if i stomp on it from zero it'll spin up to a really high torque range before grabbing and spin the wheels. It's not an enjoyable jerk. So i have to give it gentle throttle until about 1200 before I "hammer down".

The x5 throttle programming is such the first 30% of motion gives you maybe 10% throttle. Very very different than cable driven throttle and many people hate it there are ways to get that reprogrammed. I'm portioning this out to see if this is what your issue is. It may not be a problem at all with the car just the way it is made.

So: when driving very slow like 5-8 mph over rough terrain, the first 30% of throttle can be used to gently change speed then after 30%, the transfer is more linear.

0-0
10->4
20->7
30->10
40->20
50->35
60->50
70->70

It's not exacty that just an idea.

Light throttle does very little. If you sweep steady through the range it'll feel like there's a delay.

My car right now has a problem with light throttle i have to "start" at 25-30% when engine is cold or it stumbles so i tap the throttle quickly through the first 1/4 of the range. Unless you get you throttle reprogrammed to linear you might have to train around that limitation also

All speculation that might be there issue not saying for sure it is.

https://youtu.be/8NohVmaY134?si=EnGxMd54EbbPAull

See video. Throttle adaptation may be your issue but i thought i saw you addressed that.

Thanks for this. I did reset adaptations using INPA but I'll try this method as well. I keep wondering if this is how the vehicle came from the factory but I have a hard time believing it. I've driven many makes and models over the years and never had this issue before.

[Masospaghetti]

Originally Posted by 80stech

I don't remember if you checked fuel pressure but bit it's not impossible that the vent for the regulator is hooked to manifold vacuum which could cause this exact problem. Long shot but just takes a minute to check.

Thanks. Yeah I did verify fuel pressure. 54 psi at the rail with the pump running, 48 psi when the pump stops.

[80stech]

Those pressures are good but the regulator vent hose being hooked to vacuum will lower the engine running pressure so it might be a good idea to have a quick look at that hose.

[Masospaghetti]

Originally Posted by 80stech

Those pressures are good but the regulator vent hose being hooked to vacuum will lower the engine running pressure so it might be a good idea to have a quick look at that hose.

Is this the small hose that connects to the air intake elbow? Or which hose are you referring to?


I just checked pressures with the engine running and did some deep throttle stabs (in neutral of course), the pressure does bounce a bit as low as 45 psi but quickly recovers, almost instantaneously.

[andrewwynn]

Yeah i think that might be your issue. On my wife's e 53, when the FPR was shot it woukd do that.

After replacing, WOT no load wouldn't move the needle half a psi.

https://youtube.com/shorts/AEjiWbrrP...SWKqNcv3Itf4xm
Before

https://youtube.com/shorts/ctQFEWT6ftU?feature=shared
After

[andrewwynn]

If you are getting 5 psi drop from WOT that's 10% less fuel when engine is demanding most. Can you look at your O₂ sensor real-time to see if at the same time you're getting strong lean burn? I would expect a stumble from 10% drop in fuel.

No misfire or knocks? What about rough running?

[Masospaghetti]

Originally Posted by andrewwynn

If you are getting 5 psi drop from WOT that's 10% less fuel when engine is demanding most. Can you look at your O₂ sensor real-time to see if at the same time you're getting strong lean burn? I would expect a stumble from 10% drop in fuel.

No misfire or knocks? What about rough running?

The pressure is stable under idle, it doesn't oscillate like that first vid. but it does drop more than the 2nd vid with deep throttle application. Looks like the FPR is inside of the filter in this vehicle?

Interesting you mention knock. The engine does seem to knock quite a bit at lower RPMs But overall it's pretty smooth. I assumed it was VANOs noise because the knock sensors were supposed to activate and prevent knock but now it makes me wonder.

[andrewwynn]

FPR is attached to filter. My case the failure was just the o-ring between the two.