Surging idle ONLY during cold start

[im4darush]

Car starts and goes to about 2000 at first. It then gradually begins to drop as it should. Once it gets to about 1000 , the idle drops off and begins to surge. It does this about 3-4 times between 600-1500 and then settles in at a steady 850 or so. After this the idle is rock solid. All starts when the car is warm are fine...the idle does not surge and it idles very smooth and steady.

So can this be IAC, TPS related or does this sound more like a chip issue. Oh...it started doing this in cooler air.

 

[GSX-PKV]

That sounds like what is normal for a a stock chip in cooler weather.

 

[im4darush]

Really? I've had a few buicks in my time and I don't think I remember them surging. Steady higher idle is fine until they settle down, but up and down surging?????

 

[groumoutis]

Scanmaster readings?

 

[im4darush]

No can do. Scan master not currently on hand. I can say that TPS is at .45

Everything else is a mystery.........LOL

 

[salvageV6]

.45 TPS can easily become .46TPS at cold temps. with higher alternator voltage.

I'd reset it to .43 or so and make sure the IACV is clean and set properly at the same time.

If that doesn't help it's the chip.

Most aftermarkets now have cold temp. idle and startup under control.

The stock chip sucked in real real cold temps. under 20 degrees F., so did Kenne Bell's and Red's.

 

[Turbo Loyd]

Try setting the base idle within 100 rpm of you chip's idle speed. The IAC is slow and tends to overshoot the idle speed desired causing the surging. Then reset the TPS as you will probably raise it a bit.

Hope that helps

 

[GSX-PKV]

When my car was new and stock, in cold or cool weather, it would start and then the idle would go up and down like that. I don't know if your car has a stock chip, but if so, I think that's a lean chip at startup and when cold, the car likes it rich.

 

[GullsGN]

It is normal.