I just finished analyzing my $935 bill for my 100,000 mile service and the dealer's attempt to correct the hunting idle. The dealer thinks I "may" need another new throttle module. The last owner did this in 2003.

The specific things the dealer did to try to correct the problem this time was to replace the IAT sensor (intake air temp sensor), the ECT sensor and thermostat (coolant temp sensor), and performed a bunch of software upgrades...(....and unlike Microsoft...volvo charges for the software upgrades.....but I'd be happy if it fixed the problem.)

I'm just looking for a little advice here in case anyone out there can tell from my symptoms if its really the throttle module....or something else.

The car starts fine, and DOES NOT HUNT until it warms up. The hunting at idle increases in variation as the engine warms up, reaching a peak of 500 to 1000 rpm. Looks like it is going to stall as the rpm drops, but then the engine increases its rpm to 1000 then drops and the cycle contines. No hunting at all when it first starts when cold. Other than the idle issue, the car runs very smoothly....there is no variation at driving speeds. The performace is great, it doesn't burn any appreciable oil, the gas mileage is great. The car is a 5 speed, so the reduction in idle speed is not a serious safety issue. The car has only stalled once due to the hunting idle.

Does anybody have any thoughts on what to do next?

It certainly sounds like a faulty electronic throttle module (ETM) might be the culprit. But without any trouble codes to read from the computer, who's to say? In all cases that I'm aware of where the ETM was failing, there was a check engine light and there were OBDII codes present that pointed to this component. Mine did not have a hunting idle, but did throw a code and set off the dash light. It was replaced under warranty at 48,500 miles -- *after* the dealer replaced a bunch of other components and then *I* bought a code reader and *told them what to fix.* Can you guess how I feel about dealer mechanics' diagnostics skills??? (That was Red Bank Volvo, in NJ -- they deserve every plug that I can give them!)

In any case, the fact that your car doesn't act up until it comes off of the cold-engine enrichment system suggests that there might be a vacuum leak somewhere. I'd go looking around for popped vacuum lines, and may even try spritzing some throttle body cleaner around those lines and around any intake gaskets or seams in the intake tract. If spraying around any particular area changes the idle speed or quality, that might indicate a vacuum leak at that spot. Hopefully, this will only require a few dollars worth of new vacuum hose.

Good luck.

--
Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html

The most common problem for '99 to '02 Volvos that cause that is indeed an ETM. Volvo now admits that cleaning it is a waste of time. Even IF it helps temporarily, the problem usually returns soon afterwords and is usually an internal electronic problem. A bad MAF sensor might also cause that, as will a vacuum leak which should have been obvious to an experienced tech.
You can always request that either another tech diagnose your problem at that dealership or go to another dealer but you will pay for more diagnostic labor elsewhere.