Strange cold start

L

LordLolzeye

Member
Hello,

I own an 30i, N52 / automatic transmision Z4. I believe it has a strange cold start but I might be wrong, symptoms described below (note this happens only for 15 seconds):
- When I start the car it feels like the car is trying to drive off on it's own (even if it's in P), when I put the transmission in drive mode i sense that the engine gives way more power than it normally should for the RPMs it has
- I can also feel that the engine is generating more boost for the brake booster (as a side note, I have changed the brake booster on my car (2019) and the previous owner changed it as well in the past (2015) - both cases -> the brake pedal turned hard then the booster exploded)
- There is no rough idling, the RPM's are slowly dropping to the idling point without any problem
- I removed the vanos solenoids and cleaned them about 6 months ago
- The spark plugs have about 5k km on them (installed them around 6 months ago)
- Probably doesn't matter, but oil is changed each 10k km or 1 year (whichever comes first)
- Engine sounds completly fine, the only difference being the sound EVAP makes (noticed it turns on only on cold starts).
- The valve cover was replaced about 4 months ago (I had a whining noise before)

Did anybody encounter something similar to this?

I was thinking of replacing the vanos solenoids as these sometimes do not throw errors and can cause misfires / rough idling at startup.
 
LordLolzeye said:
Hello,

I own an 30i, N52 / automatic transmision Z4. I believe it has a strange cold start but I might be wrong, symptoms described below (note this happens only for 15 seconds):
- When I start the car it feels like the car is trying to drive off on it's own (even if it's in P), when I put the transmission in drive mode i sense that the engine gives way more power than it normally should for the RPMs it has
- I can also feel that the engine is generating more boost for the brake booster (as a side note, I have changed the brake booster on my car (2019) and the previous owner changed it as well in the past (2015) - both cases -> the brake pedal turned hard then the booster exploded)
- There is no rough idling, the RPM's are slowly dropping to the idling point without any problem
- I removed the vanos solenoids and cleaned them about 6 months ago
- The spark plugs have about 5k km on them (installed them around 6 months ago)
- Probably doesn't matter, but oil is changed each 10k km or 1 year (whichever comes first)
- Engine sounds completly fine, the only difference being the sound EVAP makes (noticed it turns on only on cold starts).
- The valve cover was replaced about 4 months ago (I had a whining noise - boost leak)

Did anybody encounter something similar to this?

I was thinking of replacing the vanos solenoids as these sometimes do not throw errors and can cause misfires / rough idling at startup.
Click to expand...

Can you confirm the engine you have, you mention “boost leak” but your car’s normally aspirated & has no boost?
The other symptoms sound vague and not normal? :?
Rob
 
my bad, it's a 30i, I meant a vacuum leak* (also edited main post). I might be searching for a problem where there is none :D

+ edit: How can you tell if the vacuum pump generates too much vacuum?
 
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