[MasonP95]

I’ve seen this topic on the E90 forums so I apologize in advance if it has a thread here.
My 2012 335I 118000Km has recently been pulsing while Accelerating, it feels like I got off the gas for a split second then goes back to accelerating to no gas etc when lightly speeding up to highway speeds it’s very noticeable from 60-80Km/h it doesn’t do this under hard acceleration. Car is FBO and Stage 2 bootmod3 but this issue has only occurred recently mods have been done for awhile. It still does it on stock map aswell. Anyone experience this or know probable causes?

[Desertnate]

I have a '16 435 with the N55 and 54K miles. Just took it for a 800+ mile road trip this weekend and didn't experience anything like what you describe.

I've taken it on several trips like that of the same length recently which would have given me a chance to have felt/experienced some form of surging, but I didn't notice any.

I can't offer any help with the diagnosis, but can provide a data point of my N55 not doing what you're experiencing.

[b58boi]

I have a 16 340i and am experiencing exactly what you are describing. But for me it doesn't happen every time but often enough that I noticed it being an issue. Very interested to hear from people that have had the issue and found fixes. Car is stock with 62k miles.

[Desertnate]

Just thinking out loud...

Do the RPM's fluctuate enough to see it on the tac? I'd think the needle would flutter a bit if the engine was cutting out even for a brief second.

Could it be transmission rather than engine? The above poster with a B58 appears to be seeing the same conditions as the OP with an N55, so it could be something else which causes the sensation. Along those lines, are both cars automatic?

Just trying to find some commonality.

[ChuckP49]

My 2016 F36 does that occasionally, but only when the AC is on. I thought it may be the compressor or the compressor clutch.
The fluctuation can be heard and felt but doesn't show up on the tach.
Mine is an automatic, with a MHD stage 2+ tune.

[thejeremyman9]

Originally Posted by MasonP95

I’ve seen this topic on the E90 forums so I apologize in advance if it has a thread here.
My 2012 335I 118000Km has recently been pulsing while Accelerating, it feels like I got off the gas for a split second then goes back to accelerating to no gas etc when lightly speeding up to highway speeds it’s very noticeable from 60-80Km/h it doesn’t do this under hard acceleration. Car is FBO and Stage 2 bootmod3 but this issue has only occurred recently mods have been done for awhile. It still does it on stock map aswell. Anyone experience this or know probable causes?

Best bet is capture a log when it is occurring and see if anything stands out, if you have no codes.

[b58boi]

Originally Posted by Desertnate

Just thinking out loud...

Do the RPM's fluctuate enough to see it on the tac? I'd think the needle would flutter a bit if the engine was cutting out even for a brief second.

Could it be transmission rather than engine? The above poster with a B58 appears to be seeing the same conditions as the OP with an N55, so it could be something else which causes the sensation. Along those lines, are both cars automatic?

Just trying to find some commonality.

No I don’t notice the RPM fluctuate at all. I don’t think it’s the transmission based on all the research I did with people having similar problems. I had thought it might’ve been my tires at first or just the road surface but the pulsing stops every time I let off the gas. Can’t be a coincidence I just happen to hit rough pavement right when I get on gas.

[b58boi]

Originally Posted by ChuckP49

My 2016 F36 does that occasionally, but only when the AC is on. I thought it may be the compressor or the compressor clutch.
The fluctuation can be heard and felt but doesn't show up on the tach.
Mine is an automatic, with a MHD stage 2+ tune.

How long have you had this issue? I’m genuinely hoping that a CEL pops up and gives me a code so I know what I’m looking for at this point but I don’t have any codes.

[ChuckP49]

I first noticed the fluctuation late in the past summer, when the AC was working hard. No codes or CELs, had them checked last month. Car has 77,000 miles, original belt and compressor.

[b58boi]

Originally Posted by ChuckP49

I first noticed the fluctuation late in the past summer, when the AC was working hard. No codes or CELs, had them checked last month. Car has 77,000 miles, original belt and compressor.

I’m having my Indy shop go over the car and see if they can find anything. I just had my spark plugs replaced so they think it might be one of the fuel pumps. So strange it doesn’t give any codes seeing there’s a billion sensor in these cars nowadays.

[Vreihen]

I have a 2013 335xi with 85k and started to notice this exact thing happen two summers ago. I've felt it only a handful of times since. Most recently last week.

It always happens while I'm cruising 65 on the freeway and feels like a quick pause, and can feel it in the pedal as well.

[Wires]

My 2008 335 had that. When I had it in for the HPFP recall, they swapped a bunch of injectors, and then it was fine.

Sounds like a lean surge which usually points to a injector / fuel pump issue.

[b58boi]

Originally Posted by Vreihen

I have a 2013 335xi with 85k and started to notice this exact thing happen two summers ago. I've felt it only a handful of times since. Most recently last week.

It always happens while I'm cruising 65 on the freeway and feels like a quick pause, and can feel it in the pedal as well.

If I didn't pay full attention to everything I felt through the car I don't think I would've noticed it. I think most people driving with music on and just going about their drive would never notice it. They might just register as road imperfections.

[b58boi]

Originally Posted by Wires

My 2008 335 had that. When I had it in for the HPFP recall, they swapped a bunch of injectors, and then it was fine.

Sounds like a lean surge which usually points to a injector / fuel pump issue.

It was a huge issue with the N54 cars from the research that I did.

[Wires]

Originally Posted by b58boi

It was a huge issue with the N54 cars from the research that I did.

Mine was a n54, and yeh, it was a known technical service bulletin. Thinking about it, I got the issue right after the injector/HPFP was replaced for a short while. Could have been due to it learning fuel trim values.

[b58boi]

Originally Posted by Wires

Mine was a n54, and yeh, it was a known technical service bulletin. Thinking about it, I got the issue right after the injector/HPFP was replaced for a short while. Could have been due to it learning fuel trim values.

I did also get my cats replaced. IDK if that would have anything to do with it. Maybe the cats need to broken in to flow properly? Cant' imagine that being more than 50 miles though.

[thejeremyman9]

So where's a datalog of the issue occurring?

[whoismorggan]

It could be your TMAP sensor located on your charge pipe. Mine got damaged when the OEM charge pipe blew up and I've experienced the same symptoms you're describing.

[b58boi]

Originally Posted by hellyesmorgan

It could be your TMAP sensor located on your charge pipe. Mine got damaged when the OEM charge pipe blew up and I've experienced the same symptoms you're describing.

Did you get a CEL for it? Also sorry for my ignorance but is the TMAP sensor the same as the MAP sensor?

[whoismorggan]

Originally Posted by b58boi

Did you get a CEL for it? Also sorry for my ignorance but is the TMAP sensor the same as the MAP sensor?

I've seen it called both MAP and TMAP. It's Manifold Absolute Pressure. No CEL

[b58boi]

Originally Posted by hellyesmorgan

I've seen it called both MAP and TMAP. It's Manifold Absolute Pressure. No CEL

Gotcha. With all the sensors in these cars I am now reluctant to change anything unless a code or CEL pops up for it. The issue doesn’t bother me enough and doesn’t happen frequent enough for me to trial and error all these fixes.

[F10_Shon]

Has anyone found a solution for this problem yet? I noticed in another forum with the same issue, the guy took it to the shop and they updated his software. He said that solved the issue.