Cruise control - car slows and then throttles to keep up

The cruise control on my recently acquired 2004 Golf acts funny. I'll turn it on, set it by pressing the speed control down button (I'm presuming it's the same to set as my '10 JSW). About 90% of the time, the car will slow down a bit, and eventually throttle itself up to keep up to speed. Checked this with the GPS app on my phone - I'll set at 64 or 65. It'll go down to 59 or 60 before it gives itself more throttle to try to get back to what I'd set (64 or 65).

The road I tried this on was relatively flat, although there were a few small inclines. RPMs were just over 2000 in 5th gear. Is this common or just a quirk on a Mark IV? This is my first Mark IV and second TDI. I also can't read the owners manual, because it's in French (car originally came from Canada).

Yea my 00 does exactly the same thing. It's almost as if the Ecu is unable to keep up.
It is aggravating. The way I look at it the car is older and it still works but if there was a fix and it wasn't that expensive I would go for it since I'm on the Highway Daly....

Time for a new MAF sensor. This is one of the early symptoms of a MAF starting to die. Easy DIY replacement.

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Schoust said:

Yea my 00 does exactly the same thing. It's almost as if the Ecu is unable to keep up.
It is aggravating. The way I look at it the car is older and it still works but if there was a fix and it wasn't that expensive I would go for it since I'm on the Highway Daly....

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n1das said:

Time for a new MAF sensor. This is one of the early symptoms of a MAF starting to die. Easy DIY replacement.

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Click to expand...

Glad I'm not the only one with this problem, but I hope you're right. Is the MAF expensive? I'm guessing it's a sensor that plugs into the intake post-filter?

I have a new MAF, and my car has been pretty good. But just recently it's been acting up again. Just as everyone else describes.

MAF is expensive enough, make sure that's what's bad.

FWIW, I changed out the battery earlier today. It was so bad, I couldn't crank it in the Autozone parking lot (yes, I know about Autozone parts, but I've had good luck with their batteries and warranty). Couldn't find a date code on the old one, but it's a VW OEM battery, so it makes me wonder if it's the original. Anyways, I didn't have this problem with cruise control, even at highway speeds.

My 04 was doing this exact thing and a new 02 sensor fixed it. What finally tipped me off is that it threw a 02 sensor code. It has to due with the EGR trim being off and causes the cruise to go wonky. You can try unplugging the EGR valve to see if it fixes it temporarily.