Car stumbles a little during brisk acceleration

[bmw1racer]

For the past couple of weeks, I've noticed that when I accelerate briskly (not hard) the car stumbles a little like it's got a misfire or something isn't engaging mechanically.

If I rev the car rather hard when parked I don't notice any misfiring in a coil or spark plug and if I'm accelerating gently, I don't feel any stumbling at all.

Drivetrain problem? Differential?

Any ideas?

[BronkaidBrah]

Auto or manual transmission? Can you create a log ? Does your dsc light flash at any time during this issue?

[RonnieRobotPants]

I get this as well but generally only in 6th (6mt) when overtaking. I usually have to drop to 5th for it not to do this.

[bmw1racer]

Originally Posted by BronkaidBrah

Auto or manual transmission? Can you create a log ? Does your dsc light flash at any time during this issue?

Manual tranny. DSC light doesn't come on or blink.

Seems to typically stumble when I go from 2nd to 3rd gears. It's just momentary, as if a plug misfires.

Um, How do I create a log?

[BronkaidBrah]

Originally Posted by bmw1racer

Um, How do I create a log?

Most of us go through MHD or jb4 , you can use a more advanced scanner like an nt510 too to record data but without any of these your pretty shit out of luck to figure it out this way. Also pretty invaluable to have to read stored and pending codes that may relate to your issue. Pull your plugs and look for anything abnormal, there's a laundry list of things that can cause this. failing fuel pump, clogged or leaking injectors, failing coils, fouled plugs the list goes on and on

[ShocknAwe]

Not sure how to log on the N52.

What's the mileage on the following?

Plugs
Coils
O2 sensors
Fuel pump

Other than that, is it a hesitation or a surge? And what happens with the revs if you push it through? Do they spin up freely with no speed increase or hang?

Any exhaust detonation during these events?

Any shadow codes?

[bmw1racer]

Originally Posted by ShocknAwe

Not sure how to log on the N52.

What's the mileage on the following?

Plugs
Coils
O2 sensors
Fuel pump

36K miles. I did have coil #2 and plug replaced at 33K miles.

Other than that, is it a hesitation or a surge? And what happens with the revs if you push it through? Do they spin up freely with no speed increase or hang?

It's a hesitation, like a misfire (IMO) when going up the revs. After that, the revs are OK.

Any exhaust detonation during these events?

None that I'm aware of.

Any shadow codes?

Haven't seen any.

I did remember that I had an app (https://play.google.com/store/apps/d...rscanner&hl=en) with an ODBII bluetooth dongle... I ran the app and it reported no Diagnostic Trouble Codes.

I guess I'll have to take it to my mechanic and have him look at it.

[ShocknAwe]

Originally Posted by bmw1racer

36K miles. I did have coil #2 and plug replaced at 33K miles.


It's a hesitation, like a misfire (IMO) when going up the revs. After that, the revs are OK.


None that I'm aware of.


Haven't seen any.

I did remember that I had an app (https://play.google.com/store/apps/d...rscanner&hl=en) with an ODBII bluetooth dongle... I ran the app and it reported no Diagnostic Trouble Codes.

I guess I'll have to take it to my mechanic and have him look at it.

Hard to say then since there's no codes. I'd try pulling the plugs and looking for soot/oil

[bmw1racer]

Originally Posted by ShocknAwe

Hard to say then since there's no codes. I'd try pulling the plugs and looking for soot/oil

If I get the chance, I'll try to pull the plugs this weekend.

Now that I think about it, I don't sense/feel that hesitation when I'm not moving and revving the engine, only when I'm in motion... Seems like the drivetrain, maybe the differential?

I remember the diff on my E36 failed and I had it replaced. I don't remember the mileage on it.

[bmw1racer]

I pulled each of the plugs and checked them out. What a pain in the ass it was, having to remove all of that extraneous crap to get to them. Not to mention that brace from the shock tower getting in the way. Now I've gotta lie down and rest my back.

All of the plugs pretty much look like this one, which I think is OK:

[fast1eddy]

The plugs themselves look really good but what's the gap ? Looks too big from the pic.

[bmw1racer]

Originally Posted by fast1eddy

The plugs themselves look really good but what's the gap ? Looks too big from the pic.

Ugh, I didn't think to check. What should the gap be?

If the gap is too big and/or there's a bad coil, wouldn't I have gotten an error code?

[fast1eddy]

Originally Posted by bmw1racer

Ugh, I didn't think to check. What should the gap be?

If the gap is too big and/or there's a bad coil, wouldn't I have gotten an error code?

0.022". No misfire codes ?

[bmw1racer]

Originally Posted by fast1eddy

0.022". No misfire codes ?

0.022"?? When I Googled for that info, I got 0.043"

I've been checking almost every day... No codes at all.

[fast1eddy]

Originally Posted by bmw1racer

0.022"?? When I Googled for that info, I got 0.043"

I've been checking almost every day... No codes at all.

I'm not sure what plugs you have from the pic https://bmwsparkplugs.com/products/n...er-spark-plugs

[bmw1racer]

Originally Posted by fast1eddy

I'm not sure what plugs you have from the pic https://bmwsparkplugs.com/products/n...er-spark-plugs

The plugs I have are NGK LZFR6AP11GS and that matches what RealOEM.com indicates.

Can't seem to find a consensus on the plug gap for an N52 engine: 0.020", 0.022", 0.040", 0.043"...

[WDE82]

Originally Posted by fast1eddy

I'm not sure what plugs you have from the pic https://bmwsparkplugs.com/products/n...er-spark-plugs

He has a 128i N52. That is a N54 plug and spec.

Originally Posted by bmw1racer

The plugs I have are NGK LZFR6AP11GS and that matches what RealOEM.com indicates.

Can't seem to find a consensus on the plug gap for an N52 engine: 0.020", 0.022", 0.040", 0.043"...

Guys, the gap grows during the plug's life.

The spec for the N51/52 NGK LZFR6AP11GS is 0.043". That is only measurable when they're brand spankin' new.

Those plugs look fine and if <75K miles, they're definitely still ok. It's a waste of time to check on them unless you're experiencing issues. And if you are, then you'd best just buy 6 new ones because getting the old ones out just to put them back in is silly for the effort.

Your problem sounds like my E46 felt when I had a bad coil. It wouldn't set a misfire code unless I drove the shit out of it. On the street I thought the transmission was slipping. It was just a coil.

I'd probably just get a whole new set of coils and spark plugs and end the issue once and for all. If you're hesitant to do that, then drive the car really hard until it sets a code.

[olds350]

If I was a betting man, I'd say coils. I had the same thing happen to the 128 I was buying a few years ago. This random stumble won't throw a code. Go with the delphi coils, the bosch are being dropped by BMW. Change all 6. These are known to start failing around 30k and act just like you're describing, random stumble under modest acceleration...

[bmw1racer]

Originally Posted by olds350

If I was a betting man, I'd say coils. I had the same thing happen to the 128 I was buying a few years ago. This random stumble won't throw a code. Go with the delphi coils, the bosch are being dropped by BMW. Change all 6. These are known to start failing around 30k and act just like you're describing, random stumble under modest acceleration...

Yup, I'm going to replace the coils and the plugs.

Delphi coils and NGK plugs from FCP Euro... $215.

[bmw1racer]

My coils and plugs haven't been delivered yet, but when I drove the car today, it stumbled a lot and I got a Check Engine light. It went away after driving a little more. I ran the ODBII scanner as soon as I got home.

The ODBII report:
============1==============
29CD
Raw code: 29CD
ECU: Engine control unit
Status: Pending fault present, Validated fault has been present during this drive cycle


Engine Control Unit??

Uh oh.

Is it possible that it isn't the coils/plugs at all? Or is this fault code a result of failing coils/plugs?

[WDE82]

Originally Posted by bmw1racer

My coils and plugs haven't been delivered yet, but when I drove the car today, it stumbled a lot and I got a Check Engine light. It went away after driving a little more. I ran the ODBII scanner as soon as I got home.

The ODBII report:
============1==============
29CD
Raw code: 29CD
ECU: Engine control unit
Status: Pending fault present, Validated fault has been present during this drive cycle


Engine Control Unit??

Uh oh.

Is it possible that it isn't the coils/plugs at all? Or is this fault code a result of failing coils/plugs?

I'm pretty sure 29CD is misfire cylinder 1. So no worries here. We pretty much already knew you had a miss.

I would swap the coil from cylinder 1 with another coil and see if it follows. I'm pretty sure cylinder 1 is the farthest forward but you can swap 1 and 6 and you'll know you've swapped it. If you get a new code for cylinder 6 then you definitely know coils are the issue.

On the other hand you've already bought the coils so may not be worth the effort.

[bmw1racer]

Originally Posted by WDE82

I'm pretty sure 29CD is misfire cylinder 1. So no worries here. We pretty much already knew you had a miss.

I would swap the coil from cylinder 1 with another coil and see if it follows. I'm pretty sure cylinder 1 is the farthest forward but you can swap 1 and 6 and you'll know you've swapped it. If you get a new code for cylinder 6 then you definitely know coils are the issue.

On the other hand you've already bought the coils so may not be worth the effort.

Yeah, since I'll have everything taken apart, I might as well just replace everything.

Thanks for the support... It's really appreciated.