So I was driving all day today in the heat and I know our ecu's are sensitive and the rpms fluctuate, but today was the first time I saw my rpms go all the way up to around 4000rpms when I was at a complete stop at a light. Then a few minutes later, my rpms would drop to where the car sounded like crap almost wanting to stall at a light. It kinda felt like my car wanted to accelerate on its own when I was at a stop! Weird stuff. What was this?

 

It can happen once in a while, especially in the heat and standing still so that the hot air from the radiator get's into the intake... The sensor's give all that info to the ECU that will react... Stepping on the gas to try to correct it is usually the bad option.

Ow yeah, and since you're Berlina, they're the hottest as you well know, also under the bonnet, literally and figurally

 

What are you talking about? At no time should the engine ever rev to 4K RPMs without input from the driver.

My best guess would be a sticky throttle cable or maybe some sort of vaccuum issue, but I'm not sure.

It's definitely not "normal".

 

how "hot" was the weather?

 

^ He's in CA... so probably like 81.

 

No Check engine light? That sounds funny. Without any OBD2 diagnostics to help, here are the areas I would check out.

Idling is most affected by oxygen sensor reading and to a lesser extent throttle position and MAP sensor readings. You will need a voltmeter to read these signals. Or you can buy software that will display the sensor readings from the ECU on a laptop PC or palm/blackberry.

You might check for dirty, leaky fuel injectors, erratic fuel pressure due to bad regulator, or a malfunctioning idle air control valve.

 

can this be an expensive bill? around how much if it is one of these problems?

 

81 in california, more like 100.. I wish it was 81 here..

 

I meant it can happen that the revs suddenly go up or down to almost stalling when standing still with the engine running. Heat bog, ECU learning etc... That's what I was talking about.

When we're looking for another reason the revs went up that high, a sticky throttle cable would seem odd to me since the engine nicely went down to normal and suddenly went up again if I interprete correctly. Some sensor giving false info or the suggestions from snakeeater seems very good advice to start with

Was it the first time it did that? Did it happen again afterwards?

 

I havent had the problem since yesterday. Drove it today and it seemed fine now. This is weird