[j2dad5389]

When I cold start my car and drive off from first to second gear my car will jerk me back and forth in almost sort of a bucking motion. If I sit and let my car warm up for like 5 minutes it doesn't happen. Once car is warmed up and up to operating temp it's gone completely. This didn't happen until I put bm3 stage 2 on my car along with a catless DP. Any idea what it could be? Spark plugs?

[Throttlesteer14]

Check with 240Newbie. He apparently made the same modifications and is a sr. master tech.

On a serious note, you might monitor for a few days and see if it continues. Sometimes it takes a bit of time for the tune to settle in. It's also possible you have a slight exhaust leak from the dp install.

[Mason Hatcher]

No offense, but just a general observation: you guys who "modify" your cars, experience problems then wonder " what could it be?" crack me up

[j2dad5389]

Originally Posted by Mason Hatcher

No offense, but just a general observation: you guys who "modify" your cars, experience problems then wonder " what could it be?" crack me up

yeah no shit it's from the mods thanks for chiming in

[Mason Hatcher]

Originally Posted by j2dad5389

yeah no shit it's from the mods thanks for chiming in

Why, you're welcome

[Winemaker2]

Originally Posted by Mason Hatcher

Why, you're welcome

Unless you go with safe and sane mods, just like fireworks

[BimBimM2]

Originally Posted by Winemaker2

Unless you go with safe and sane mods, just like fireworks

I don't why but this comment made me laugh.

[BimBimM2]

Originally Posted by j2dad5389

When I cold start my car and drive off from first to second gear my car will jerk me back and forth in almost sort of a bucking motion. If I sit and let my car warm up for like 5 minutes it doesn't happen. Once car is warmed up and up to operating temp it's gone completely. This didn't happen until I put bm3 stage 2 on my car along with a catless DP. Any idea what it could be? Spark plugs?

Hey OP I am not clear, did you do anything with the spark plugs? Did you gap them? Put in new ones?

Also pull your logs. Reach out to BM3 with your logs; they are great with customer service and they can advise you.

[XutvJet]

This is a very normal thing. My M235 occasionally does this and has done it in stock and modded form since buying the car 4.5 years ago. It has nothing to do with the mods. It's a cold running engine issue with BMW's stock tuning. Unfortunately, there's no rhyme or reason to when it happens.

[BimBimM2]

Originally Posted by XutvJet

This is a very normal thing. My M235 occasionally does this and has done it in stock and modded form since buying the car 4.5 years ago. It has nothing to do with the mods. It's a cold running engine issue with BMW's stock tuning. Unfortunately, there's no rhyme or reason to when it happens.

Is this a transmission issue? You mention stock tuning; I am curious which tuning.

[XutvJet]

I have a 6mt. It's most prevalent in 1st. When it does happen, I simply clutch in, blip the throttle, and it figures itself out.

It did it when:

1) The car was completely stock. 1.5 years.

2) Dinan Sport. 6 months.

3) Dinan Sport and catted DP. 6 months.

4) Catted DP. 1 year.

5) Dinantronics Stage 1 and catted DP. 6 months.

6) Dinantronics Stage 2 and catted DP. 3 months.

7) Dinantronics Stage 2, catted DP, and charge pipe. 1 month.

In that order. It seems to happen once or twice a month.

I have 43k miles on the car and the stock spark plugs.

[j2dad5389]

Originally Posted by XutvJet

This is a very normal thing. My M235 occasionally does this and has done it in stock and modded form since buying the car 4.5 years ago. It has nothing to do with the mods. It's a cold running engine issue with BMW's stock tuning. Unfortunately, there's no rhyme or reason to when it happens.

Are you sure? I hope you're right. Like I said this never happened until I did the stage 2 + downpipe.

[j2dad5389]

Originally Posted by Throttlesteer14

Check with 240Newbie. He apparently made the same modifications and is a sr. master tech.

On a serious note, you might monitor for a few days and see if it continues. Sometimes it takes a bit of time for the tune to settle in. It's also possible you have a slight exhaust leak from the dp install.

Paging 240Newbie

[Dylan86]

Never had this happen on my '15 m235.. all it has is a JB4 for now, but have you tried flashing the stock map back and seeing if it's consistent? If so you can chalk to tune out of the equation for sure. How old are your plugs and if new did you gap them (and to what gap?).

D

[j2dad5389]

Originally Posted by Dylan86

Never had this happen on my '15 m235.. all it has is a JB4 for now, but have you tried flashing the stock map back and seeing if it's consistent? If so you can chalk to tune out of the equation for sure. How old are your plugs and if new did you gap them (and to what gap?).

D

Good idea, I'll try that. Spark plugs are still the same ones from when the car was built I'm guessing. I got mine off a lease at 18k miles. Currently sitting at 21.6k miles.

One thing I did do was move from Stage 2 (AGG) to regular stage 2 and I think it helped a little with the problem. I started my car this morning on cold start and drove away and it wasn't nearly as bad as my previous tune. One thing I did notice was the car kind've struggled going from 1st to second, but it didn't jolt my car or buck me as it had done before.

This only happens once too and then it's gone. Only on my first startup from 1st -> 2nd gear and then it's smooth from there on out. Wonder if it's just a matter of getting the car warmed up. My only concern is I'm not sure if I'm causing any sort of harm to my engine or transmission when this happens. I hope not

[Dylan86]

Originally Posted by j2dad5389

Good idea, i'll try that. One thing I did do was move from Stage 2 (AGG) to regular stage 2 and I think it helped a little with the problem. I started my car this morning on cold start and drove away and it wasn't nearly as bad as my previous tune. One thing I did notice was the car kind've struggled going from 1st to second, but it didn't jolt my car or buck me as it had done before.

Yea depending on engine hours etc the plugs could be a bit "gapped" open, from factory settings. Or if you installed new plugs, a lot forget that step also, which can create cold start and break ups when running on cold start parameters.

Worth a shot, it's free!

[XutvJet]

Originally Posted by j2dad5389

Are you sure? I hope you're right. Like I said this never happened until I did the stage 2 + downpipe.

How long have you owned the car? A few months?

8AT or 6MT?

I'm very sure this issue was there prior to any mods. My car is a 6MT. I can't offer any input if your car is an 8AT.

When my car does this, it will buck hilariously in 1st with absolutely no additional throttle input from me. It feels like I'm slightly stabbing the throttle or shift to 2nd. The fact that it only happens on a stone cold start and goes away with a simple clutch in and quick throttle blip tells me that this is a cold start tuning issue.

I don't have tune, just a piggyback. There is no manipulation of parameters when using little to no throttle. If it were an issue with plugs, it wouldn't make sense that the issue would be present on a cold start and low idle. Plug issues occur in higher load and RPM situations.

I put this weird issue up there with the other very random and common issues these cars can have including:

1) An occasional rough idle cold start and that makes the car feel like it's a push rod V8 with a very lumpy cam. I simply give it a few quick blips and it goes away. Done this since buying the car 4.5 years ago. This is a common issue noted numerous times of this forum. There is no fix.

2) Under seat subwoofers that occasionally don't turn on. A simple restart of the car fixes the issue. This is a common issue noted numerous times of this forum. There is no fix.

[morphomeman]

OP: Don't you know that God hates catless DPs?
He or she is exacting revenge for your messing with the planet for purely selfish reasons.
Maybe you should put a mask on the car.

[j2dad5389]

Originally Posted by morphomeman

OP: Don't you know that God hates catless DPs?
He or she is exacting revenge for your messing with the planet for purely selfish reasons.
Maybe you should put a mask on the car.