Car bogging after catless downpipe install

[M5_Raz]

Hey all,

I recently got my catless downpipes installed and put about 700 miles on the car.

The problem is that whenever I accelerate hard and the rpms go past 5k, the car bogs, stutters, and won't go (sounds like 2 stepping). I am still on the stock tune with a check engine light throwing codes just for emissions.

Is this happening because I don't have a tune? I am thinking that there isn't enough fuel being sent to compensate for the increased air flow. Let me know what you think, thanks!

[Craze]

No

[chadillac2000]

The car is probably making more power with the catless pipes and your coils and/or spark plugs can't keep up. I'd throw a fresh set of spark plugs in and see if that helps. If you tune the car, you'll definitely want to install a fresh set of plugs anyways to avoid misfires.

[M5_Raz]

Originally Posted by chadillac2000

The car is probably making more power with the catless pipes and your coils and/or spark plugs can't keep up. I'd throw a fresh set of spark plugs in and see if that helps. If you tune the car, you'll definitely want to install a fresh set of plugs anyways to avoid misfires.

Hmm I had new spark plugs put in about 3k miles ago. I would think they're still good, even with catless. Do they have to be gapped differently? Or is that just with a tune?

[Spacecpe]

You probably messed up one of the O2 sensors during the install.. if you've done everything correctly and none of the O2 sensors are damaged it should drive the same.

[M5_Raz]

Originally Posted by Spacecpe

You probably messed up one of the O2 sensors during the install.. if you've done everything correctly and none of the O2 sensors are damaged it should drive the same.

That might be the case. I was lazy and didn't disconnect them when removing and they probably got too twisted. Question is, do I just buy all 4? Looks like it's $400 in total from FCP Euro.

[chadillac2000]

Originally Posted by M5_Raz

That might be the case. I was lazy and didn't disconnect them when removing and they probably got too twisted. Question is, do I just buy all 4? Looks like it's $400 in total from FCP Euro.

How did you not disconnect them during removal? The primary o2 sensors sandwich in the top heat shield, right?

Sounds like spark plugs are not the culprit if you just replaced them recently.

[M5_Raz]

Originally Posted by chadillac2000

How did you not disconnect them during removal? The primary o2 sensors sandwich in the top heat shield, right?

Sounds like spark plugs are not the culprit if you just replaced them recently.

I simply unscrewed them from the downpipes. I didn't disconnect them from the connector side (which twisted them a lot in both the removal and install).

In the video I watched the guy did the same and was fine. After reading some more, it sounds like these sensors are very fragile...

I bought all four of them with overnight shipping and will see if it fixes the problem.

[Craze]

Never do that, twisting the wires wrecks them

[M5_Raz]

Update: Installed all 4 new O2 sensors. Car runs smoother but still bogs intermittently after 4.5k rpms (same problem).

I have no idea what's wrong. Taking it to a performance BMW shop on Tuesday and will update again then.

Weird thing is that I'm not getting any codes other than increased emissions.

[TinCanSailor]

Are you using a factory air filter? If you are using a high flow filter with oil like K&N it could be dirty MAF's. Also, did you check to make sure the air intake tubes are lined up and sealed all the way around.

[M5_Raz]

Originally Posted by TinCanSailor

Are you using a factory air filter? If you are using a high flow filter with oil like K&N it could be dirty MAF's. Also, did you check to make sure the air intake tubes are lined up and sealed all the way around.

The air filters are stock. I didn't touch the air intake tubes, except for the small hoses connecting to the intake itself. Is that what you are referring to? (Attached picture)

I will take a look at it tomorrow during the day. Not having those sealed all the way around can cause something like this to happen? Thanks!

[bongshi4]

Originally Posted by M5_Raz

The air filters are stock. I didn't touch the air intake tubes, except for the small hoses connecting to the intake itself. Is that what you are referring to? (Attached picture)

I will take a look at it tomorrow during the day. Not having those sealed all the way around can cause something like this to happen? Thanks!

Those hoses are Positive Crankcase Ventilation hoses, the downstream of this hose is connected to the inlet of turbo charger intake.

I'm not so sure if this would cause the bogging of your car thou..

[M5_Raz]

Originally Posted by bongshi4

Those hoses are Positive Crankcase Ventilation hoses, the downstream of this hose is connected to the inlet of turbo charger intake.

I'm not so sure if this would cause the bogging of your car thou..

Yeah, I'm at a loss of what could be the problem. These hoses aren't sitting as tight as they could be since the plastic holders/connectors aren't in the best shape anymore. So maybe some air creeps in under heavy load?

Something in the fuel system could have crapped out at the same time, but there's no codes. Just the increased emission codes.

[TinCanSailor]

Those hose do become brittle and crack. An easy way to see if you have any pirated air entering the intake is to spray a little starter fluid around the intake tubes and pcv. hoses. It only takes a short burst and you'll hear the eng pickup a couple hundred rpms. I'd inspect the pcv hoses for sure if you moved them around.

[TinCanSailor]

Did you happen to notice if there was any oil build up or leaking around the pcv hose coupler?

[TinCanSailor]

Also, how many miles on the engine? Are you the original owner and if not do you know if the prev owner tuned the car?

[M5_Raz]

Originally Posted by TinCanSailor

Those hose do become brittle and crack. An easy way to see if you have any pirated air entering the intake is to spray a little starter fluid around the intake tubes and pcv. hoses. It only takes a short burst and you'll hear the eng pickup a couple hundred rpms. I'd inspect the pcv hoses for sure if you moved them around.

I'll definitely inspect them and see if they're cracked. If they are, could this be causing the bogging issue at high rpm?

There definitely was oil in the pcv hose coupler, is that bad?

32k miles on the car and more than likely had downpipes and a tune before.

[TinCanSailor]

Originally Posted by M5_Raz

I'll definitely inspect them and see if they're cracked. If they are, could this be causing the bogging issue at high rpm?

There definitely was oil in the pcv hose coupler, is that bad?

32k miles on the car and more than likely had downpipes and a tune before.

any time you get pirated/unmeasured air involved things are going to not go well. If the car had pipes and a tune previously then it could be coils. The reason I ask about the tune is if they left it tuned then you may need to go with a step or two colder plugs and gap them as the added air pressure could be preventing spark.

[M5_Raz]

Originally Posted by TinCanSailor

any time you get pirated/unmeasured air involved things are going to not go well. If the car had pipes and a tune previously then it could be coils. The reason I ask about the tune is if they left it tuned then you may need to go with a step or two colder plugs and gap them as the added air pressure could be preventing spark.

I'll have the shop look at the coils as well.

In regards to the car still being tuned, I don't believe so since it drives like stock and it has a check engine light from increased emissions.

[TinCanSailor]

If this ends up being an injector(s) issue; I don't have the TSB/notice but BMW extended the warranty on injectors to approx 120k miles.

[M5_Raz]

Originally Posted by TinCanSailor

If this ends up being an injector(s) issue; I don't have the TSB/notice but BMW extended the warranty on injectors to approx 120k miles.

Thanks a lot, I'll look into finding the exact tsb. It covers all years of the f10 M5?