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Terix Terix is offline
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Posts: 41
Join Date: Apr 2018
Car: 2013 BMW 335i
Question Random warm start rough idle/no throttle response after PI intake manifold install - 09-01-2021, 03:08 PM


I've been having an issue that seems to have started after installing my PI aluminum intake manifold towards the beginning of the year.

Whenever performing a warm start, there's a ~20% chance that the engine will stumble and have rough/stumbling idle (sometimes it will stall). When this happens, there is no throttle response at all. The car starts perfectly whenever it's cold, but if I drive around, stop and turn off the car for a short period (like running into the store), and then try to start it again, the issue may happen. When it does start/idle fine (when warm), it still sounds like it struggles a little for the first second before idling fine. I want to note that there are no long cranks, the car cranks fine. It's only after the engine starts where there is a problem.

Initially, I thought it could be vapor lock. I'm running straight E85 and figured the lower boiling point could be playing a factor. When blending it with 93 octane though, nothing seems to change. I've noticed that opening the hood and letting the car vent for 10-20 minutes seems to help get it to start, though it may take a few tries still.

Until a couple days ago, no codes were ever thrown whenever this occurs. Though I can't be sure the following codes actually were caused by the issue, or if they may have been from a little earlier (though I do read and clear codes pretty frequently).


29D8 - Intake air temperature sensor, plausibility: Intake-air temperature too high (this one I've seen a decent amount while driving around)
387F - Power management, closed-circuit current violation (I've seen this one pretty frequently as well)
29D0 - Intake air temperature sensor, electrical: Short circuit to B+ (new from the other day)
29D2 - Intake air temperature sensor, electrical: Signal not plausible (new from the other day)

The recent codes related to the intake air temperature sensor are now steering me towards the MAF possibly starting to die. However, 29D8 started occurring right after installing the intake manifold, which has got me thinking of a different cause. The new intake manifold prevents the stock air box from being able to be installed. Without this, the air intake's body is making contact with the intake manifold's fuel rail and the filter is hovering over the intake manifold. I'm thinking that the heat coming off the aluminum intake manifold is essentially cooking the air intake/MAF.

That leads me to my next question. What are others doing about the inability to install the airbox to prevent all the excess heat affecting the air intake/MAF? I know heat shielding material/tape exists, but am not sure if that's my best option. Of course, I don't know if the issue is truly related to the heat or not. I'm just listing down my thoughts.

For added info, here are some parts I've replaced (thought not necessarily to fix this problem) that may be asked about:

Spark plugs: a week ago
6x Ignition Coils: September 2020
6x Fuel Injectors: August 2020
Stage 2 LPFP & PI Intake Manifold: End of January 2021
Battery: April 2021

Any feedback/recommendations are greatly appreciated.

2013 E93 N55 335i | AT (xHP Stage 3)
Pure Stage 2 | DV+ | Pure Inlet | JB4/MHD BEF
Phoenix Racing PI Intake Manifold w/ 750cc injectors | Fuel-It Stage 2 LPFP
BMS 7.5" FMIC + 3" J Pipe | BMS Intake
VRSF DP and CP | N20 TMAP Sensor
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