Hollow Cat 928S?

[Hkp7]

I have had a cold high idle problem for a few months now that I cant seem to solve. I have replaced all temp sensors, repaired any vacuum leaks I could find, replaced air flow meter, repaired all ground connections, replaced 02 sensor, and still when the engine is cold it runs a high idle around 1300 to 1500. I let it get to operating temp, even drive it and it still idles high and surges. When I shut the car off, let it sit for around 20 to 30 min, it starts up and runs around 300rpm. with less surge only on decel from 60 to 50mph. I noticed that my cat is hollowed out and have a new one on the way. Until I try to replace it I am wondering what input anyone can give me on hollow cats. It is an 84S Us model. I thought about how a hollow cat would pass more oxygen by the 02 sensor due to more flow and the fact that the cat is not there to keep the 02 hot. Thanks.

[Danglerb]

My guess, no real effect from the hollow cat. People take a metal rod and bash them out and all it does is increase hp a tiny amount and stink up the air.

High idle speed is too much air getting in. Have you tried turning down the idle adjustment?

[Hkp7]

Idle screw is all the way in. Thing is the problem is intermittant, only at cold start. Will timing effect idle speed in cold, does the time temp switch attempt to advance or retard timing in the cold and then maybe fighting an ignition or timing problem?

[Hkp7]

I was going over the car once again today and remembered someone telling me to check the auxillary air regulator. At that time, I cleaned out the regulator with carb cleaner and it made no difference although a lot of oil came out of it. Well today I removed the regulator and checked it with a meter, book says 40-75 ohms and mine read .01 or basically shorted. Ordered one today. Also my air flow meter checked out on all resistance tests except one. I bought a used air flow meter and installed it without checking the resistance. All resistance tests were way out of range telling me the meter is shot. I plan to replace that when I win the lottery, I guess they are around 300.00 or so for a rebuilt one. But good call on the high idle being caused by air. I was puzzeled because I had no vacuum leaks. Thanks and I will update when parts are replaced.

[SolReaver]

Vac leak? are all the sensors well connected? Grounds?

[morriss]

Oh yeah! Between this thread and harborman's maybe all of us with cold start issues will find what we are looking for.

[Normy]

One thing that I've noticed with my car: the throttle cable is a little sticky.

When I start it up, it usually idles at 1100 rpm, so I sneak my toe under the pedal and gently lift upward....now the idle drops right down to 750 or so. I've checked and all the connections appear tight, so I guess the cable itself either needs to be replaced or cleaned. Try this and see what happens on your car. I wonder how many idle problems are actually cable-related....

[Note: If you lift up too much....your pedal will separate from the cable. The cable has a ball on the end; just push it back into the round pit on the pedal it normally sits in]

N

[Fabio421]

Before you replace the AFM be sure to check out the serial number break. There were two batches for your car and they test out at different Ohm values.

Regarding the auxilliary air valve. You can drill out the rivets and take them apart. Theres not much to them. Its just a bi-metalic strip that bends when it gets warm and rotates a little wheel with an odd shaped opening. This allows more or less air to bypass. The metalic strip is heated by a little heating element. You probably could just solder the wire back on and be good to go. If you've already ordered one then just replace it I suppose but maybe this post will help someone else in the future.