Stock '83 with 305 and Rochester.
This has been going on for many months.
When I slow to a stop at a light, idle sometimes dips to under 500, then recovers to a more-normal 500 to 600 [depending on outside temp, full moon or crescent moon, etc.] in a few seconds.

What do I need to look at? The weather will be cooperative in the next few days.

Thanks,

Seth

 

try checking the o2 sensor. i used to stall at lights the rpms would drop way below 500 and then stall. only way to recover was drop it in neutral and gas it a little or push in the clutch and hold the gas in. it was a fun juggling act of brake gas and clutch but i worked it. after getting sick of seeing the voltage drops, stalling, etc i trouble shot a bunch of things and found that my o2 sensor was not working correctly. try checking yours it should be on the drivers side header, my wires were a little messed up so just take a look and be careful taking it off, they are on there good.

 

Try disconnecting the EGR? Valve or solenoid could be sticking. Wasn't it buzzing on you recently?

You may also want to run it with the dwell meter hooked up to see what the ECM is commanding when it occurs. Whether it's responding to a temporary rich or lean condition. Think simple: PCV valve good? Charging system OK?

Mike

 

Thank you.
And, by the way, why is that pesky computer-controlled EGR thingie buzzing?
Think about it. The buzz is far from new, but it only reappeared when I got the TPS back to an adjusted state. It may or maynot buzz while driving. No clue.
PCV is new.
Also, how do I keep the TPS from wandering out of adjustment? I do not want to put that horrible plug back.

Seth

 

The EGR solenoid is pulse width modulated. The solenoid opens and closes the vacuum path for the EGR many times a second. The ECM varies the time its open and closed to vary how must exhaust gas the EGR lets pass through it. The EGR solenoid should be pretty quiet. I'd make a junkyard run and pick of a few spares to try out.

You should put that plug back in to keep the TPS adjustment screw from moving. What I did was drill a hole in the plug and filled it with RTV sealer so it could be easily removed with a small screw if needed.

 

So, what you have revealed, is good news. A properly-working computer does pulse the valve. The problem is simply the noise. The junkyards here are, quite frankly, junk. I will pull the valve and try to figure out why it is too loud.
The little TPS screw plug might still be in the rebuild-kit box. If the plug is wide enough, I can take a phono cartridge mounting bolt and nut, and install in the plug as a pull. Yes, I still listen to records, as they can and do sound WONDERFUL on a decent system.

Seth