Engine sounds like its gonna die on cold starts

[mark248am]

So a few weeks ago I started to notice that my 380 was acting weird on morning cold starts. When I start the car the rpm stays really low and it starts sounding like its gonna choke and shut off. After 30 seconds or more the RPM starts going back up to settle normally. If I step on the gas to raise the RPM it chokes and sounds like its gonna die again. Once i also got an engine error after pressing the gas and the code was for an engine misfire but that code ended up clearing later.

I took it to the dealer and they changed the spark plugs, checked the catalytic converter and tried a few other things and they can't seem to figure out whats causing this behavior. It only happens during the morning cold starts.

Since they can't figure out the issue figured I'd ask you guys if you've had something similar happen before or know what this might be.

[Hangar 111]

Hi Mark.

Check: MAF sensor, function and wiring/connector; O2 sensors, function and wiring/connectors; battery voltage when cranking.

Don't touch the throttle at any point during start-up, or until it has cleared its misfire after 30 secs.

Dave

 

[mark248am]

thanks i'll pass it on to their mechanic

[mark248am]

So I took my car to service and I still think the problem is there. Can you guys watch the video below and tell me if that looks normal for a cold start? My memory is horrible so my cold starts might have always been like this but i don't think thats the case. Notice the big RPM drop right at the start? And then the engine sound after that before it settles.

 

 

[MrP_]

3 minutes ago, mark248am said:

So I took my car to service and I still think the problem is there. Can you guys watch the video below and tell me if that looks normal for a cold start? My memory is horrible so my cold starts might have always been like this but i don't think thats the case. Notice the big RPM drop right at the start? And then the engine sound after that before it settles.

 

 

Not a 380 but mine does not drop like that. Certainly not that I could notice to any level. I'd agree with you that it sounds like it's hunting, but then recovers 

[BatMobile]

Ditto mine doesn’t do that - it’s a 350 but even so that doesn’t sound normal.

[vd9]

Another 350 here - mine has never done anything like that, even with very cold (<0C frozen) starts. I would expect this to be related to either MAF or vacuum lines somewhere in the intake.

[Bibs]

This could be a fuel learning issue. Might be worth keying off, giving the car 30 mins to settle itself down and then disconnecting/reconnecting the battery to let it relearn. 

[Hangar 111]

ECU reset would be worthwhile next step I think.

Dave

[geartox]

indeed not normal for me.

 

[mark248am]

Is there a way to reset the ECU without disconnecting the battery?

[mark248am]

Ok disconnected the battery, waited a few seconds then reconnected it and started the car. it did the same thing again but went out for a short drive and came back and i'll start the car tomorrow morning and see if its still the same. A friend suggested it might be the coils? no idea what that is...

[MrP_]

25 minutes ago, mark248am said:

Ok disconnected the battery, waited a few seconds then reconnected it and started the car. it did the same thing again but went out for a short drive and came back and i'll start the car tomorrow morning and see if its still the same. A friend suggested it might be the coils? no idea what that is...

I’d leave it disconnected for a good 10-20 minutes if possible

[Maxi_z]

My 380 cup with the new engine do something similar when just started and cold

The first couple of throttle inputs in reverse it would bog and loose rpm but after that it just works normally

 

[mark248am]

4 hours ago, Maxi_z said:

My 380 cup with the new engine do something similar when just started and cold

The first couple of throttle inputs in reverse it would bog and loose rpm but after that it just works normally

 

Yeah, same here, not in reverse but sometimes after reversing and driving out of my parking slowly the car feels like its gonna choke and then recovers.

[mark248am]

Just a quick update, started my car this morning and it didn’t do the I’m about to die rpm drop! Looks like the ECU reset might have done the trick.

Hopefully it worked out and doesn’t come back again tomorrow.

[mark248am]

Another update, if this did turn out to be a fuel learning issue which is fixed now i might know what caused it.

When I was in Bahrain for a track day a few weeks ago the fuel station next to the track was out of 98 octane fuel which is what I normally fill with. So used 95 Octane. When I came back to Kuwait went back to 98. So I guess that might have triggered this.