Point2Point

I came back from three weeks of travel and found my battery completely dead. After getting a jump and using my car as usual over the past few days, I noticed that it had completely lost its cold start high idle. Now when I start it up in the morning it just sits at the normal idle rpm. What happened?

izzy63

It's probably cus of the weather, I don't have the cold idle anymore since I brought my car down to LA from Canada.

Overspooled

same here man. I think it's due to the weather! I do get some cold starts once in a while but not many! In winter it's a different story

chrisridebike8

Your oil temp has to be below 90F degrees I think. And you car can't have been started within a couple hours. In the winter, I get 2 cold starts a day! In the summer, I only get it if I let the car sit for a couple days and get below 90 degrees in my garage.

jmueller

Same here. Mine won't even do high idle at 95 degrees.

abcut973

Summer weather !
Unless you have a vented hood just pop yours up every time you go back home to help with cooling. That is what I do every night and I get my nice cold start every morning. During winter i don't need to do that

Point2Point

Thanks for the info. Nothing to do with the flat battery then.

papashango

Hmm after reading this thread I became more cognizant of my cold starts and this morning I noticed it didn't do the high rev thing. Usually it starts just above 2000 RPM and slowly goes down. This morning it started at just over 1000 and didn't go down or anything, but I did notice that the oil temperature on the AMG screen seemed a little higher than normal.

It's weird though the car has been parked in the underground garage all summer and ever time (as far as I know) it did the high idle cold start and today as winters are approaching near and it's cooler outside, it didn't do the cold start. Perhaps they have cranked up the heat in the parkade, not sure. I did also notice the room temperature that the car showed was 27 degree Celsius, which is usually around 20-24. So perhaps it the oil was indeed already hot enough and it didn't need the cold start?

Either way, it seems like it's nothing to worry about right?

Critter

2000RPM is crazy fast for startup
1200-1300 max
10-20 seconds then normal idle 700 + or -
The guys are correct there is no need for high idle when the car is warm. In warm climate the engine coolant never drops off when in Alabama the temp would still show bars the next morning.

papashango

Well don't quote me on the exact RPM I guess, I've never really paid too much attention. All I know is that it's quite high when I start up and after about 10-15 seconds I hear the vaccum like sound and it falls down. That is until today it started and it stayed at just above the 1 mark on the guage.

papashango

Okay so I decided to pay proper attention to the RPM after work today. I park at an underground parkade at work and when the car started the temperature was at 35C and jumped to 40C almost right away. The RPM was just over 500...so around 700 area. When it's a cold start it's most definitely over 1000, but I guess like a poster above said the temperature would have to be lower than 32C or 90F.

jvanbrecht

This is the secondary air injection system. It is an emissions component designed to heat of the cats faster to operating temperature, amongst other emission functions.

The pump sits behind the bumper, driver side. During summer, it kicks in randomly as a test to make sure it is operational. In winter, it will kick in everytime you start you car if it has been sitting for over an hour or 2 (obviously depends on how cold it gets in winter).

All this does is pump additional air into the combustion chamber rather than letting the engine draw air in naturally while stationary.

roadtalontsi

close but not exactly. It pumps extra oxygen to the cats since the engine runs overly rich during cold starts and needs extra oxygen to work properly in that condition. The air is pumped directly into the exhaust not into the combustion chamber.