Car Q: High idle on startup. Sometimes. Normal? (Paging Dr. Rick!)

On cold starts, my car sometimes idles high - 1500 rpm or so. Otherwise it will idle at the normal 650-750. The high idle seems to happen about 30-40% of the time. What’s strange, however, is this is a new vehicle and this started almost from day one. Is this normal? Could this have something to do with outside temperatures?

FWIW - '09 VW Jetta, 2.5L (gasoline) engine.

IANAM, but this sounds normal to me. Engines nowadays have some sort of analog to the old fashioned choke. This means on cold days the car’s computer tells the engine to inject more fuel (enrich the fuel/air mixture) which increases the idle until the engine decides it’s warm enough to run without enrichment. Again, I will admit to limited knowledge on things automotive. Rick or Gary will show up soon I’m sure. I love those guys.

totally standard, on cold days your car will run a bit faster to warm up the engine quicker. if its to cold you run the risk of stalling the engine under what would otherwise be normal driving conditions.

It is normal for cold idle speed to be higher than warmed-up idle speed. My info doesn’t have the specs for your car, but the figures you mention are within the range I typically see for various vehicles. Ambient temperature could certainly be a factor.

What happens with cold starts the other 60-70% of the time? Is the idle speed around 700 then, or is it somewhere between that and 1500? If it’s the latter, and if the cold idle speed is somewhat proportionate to the outside temp (higher when colder), that’s exactly what I would expect.

It seems to me the rpms are either 1500 or 650-750. However, I have not monitored the rpms when they’re lower than 1500 to see if they’re above the 650-750 range.

I first assumed this was an outside temp thing. But, if this were the case, I would assume the rpms would be high every morning I start the car as I’m in the Chicago area and it’s winter. Do you have a guess as to what the outside temps would be to make it rev high?

Not really, but just for illustration let’s say that at 30’ or below maybe the cold idle would be 1500, at 50’ maybe 1200, at 70’ maybe 900. Somtething like this would strike me as a plausible design. If it’s 1500 one day at 30’, but 700 the next day at 30’, something is wrong. In order to intelligently evaluate whether or not you have a problem we’d need to know both the actual RPM AND the temperature at the time. “Winter” is too vague - it’s winter here in Kansas City and in the space of a week we’ve had temps of 20’ and temps of 65’.

OK, I checked it out this morning and the rpms are varied. It was 22F, and the rpm was about 950. The engine noise sounded similar to the low idle of 650-750, so I never noticed it before. I only notice when it gets up to 1500 or so, and that probably happens when it gets real cold, like < 0F.

Thanks all!

Probably completely normal.
Here is the deal, the faster the car maker can get the oxygen sensor hot, and the catalytic converter up to temp and functioning, the less pollution the car produces.
My 05 Volvo idles at 1500 for about 20 seconds before the idle drops to normal. In conversation I had with an emissions engineer about the fuel injection system on my car, I was told that about 90% of the pollution out of the tailpipe in a 20 minute drive is in the first 30 seconds or so. :eek:

You might want to check your owner’s manual and see it mentions this.