The cruise control on my 1993 945T works okay, I guess, but it surges, most noticeably on upgrades. I only use it on the interstate, so they are gradual upgrades, but still I get the surging. It holds speed well, but the tach will show an increase in revs, the boost gauge will get a little into the boost area, and I can feel a fairly abrupt acceleration, followed by deceleration, followed by acceleration.... you get the picture.

Is this normal? Or is it indicative of a problem with the cruise, or some other area?

I can only compare it to the cruise on my old '89 Mazda, which worked flawlessly.

Dear Inga,

Good p.m. and may this find you well. You might want to check the vacuum-powered cruise control actuator. This is mounted just behind the throttle spool (beside the intake manifold, towards the firewall). The actuate is black rubber, shaped like a cone, with the top cut-off. If it has a slight leak, the cruise control will not maintain a stable speed. The rubber can lose its resilience, and crack. If that's the case, there will be small vacuum leaks.

It is also possible, that your Idle Air Control Valve (IACV) needs to be cleaned. A dirty IACV can lead to rough idle. If the IACV fails, it will be hard to keep the engine running.

The IACV Is mounted (on non-turbo models) beside the intake manifold. It is an aluminum-color "can" with two hose connections at the front end (closest to the front of the engine) and an electrical connector (at the rear end, pointing towards the firewall). See the FAQs, under FEATURES, above, for the cleaning procedure.

Post back, if you run into problems.

Hope some of this helps.

Yours faithfully,

spook

Is your airconditioning switched on ?
This might cause a slight surging , while the pump switches on and off

Nope. A/C is switched off.

Not being in the car to really tell, you may want to check your vacuum lines for leaks,no leaks and all is probally fine, with leaks gas milage goes down and all sorts of little problems arise.
Hope that helps
Poolman

I have looked for vac leaks, but not been able to find any. Lately, the idle has gotten a little unsteady, but the cruise surging has been present since I got the car.

Fuel mileage is right around 22 mpg, with mostly highway driving. I was expecting more, as I typically drive with a light foot, but from what I hear, this is pretty normal for a 945T of this vintage.