The Problem: About a year ago, my '96 Camry (141,000 miles) would stall - only when warm, only when approaching a stop light or stop sign, and only after being driven at least 7 miles. RPMs would fluctuate between 250 and 750 RPM; throwing the transmission into Neutral and tapping the gas pedal would help to avoid a stall. If it did stall, cranking the car could usually revive the engine.
In the past, this only happened about once a month. Didn't bother me that much. Lately, though, it had begun to stall on any trip longer than 7 miles. My commute to work is only 3 miles; so, I took my time trying to figure it out.
The Solution: My EGR Vacuum Modulator needed replacing.
What I Had Tried Before: o replacing intake air hose (it was cracked and needed replacing anyway; $90 at the dealership) o replaced stuck PCV valve (I forget how much) o changed spark plugs (they were clean; no sign of soot); done myself o changed leaking distributor O-ring (mechanic did this; about $90 for the labor) o tried Tri-Flow Teflon in IAC valve; done myself o cleaned throttle plate with throttle plate cleaner and a toothbrush; done myself o disassembled and cleaned throttle body (with throttle plate cleaner and a can of compressed air); done myself o disassembled and cleaned idle air control valve (and stripped a Pozidrive screw; thank goodness for the Dremel screw extraction method!); done myself o changed transmission fluid (thinking it was a stuck shift solenoid); done myself o changed coolant sensor ($12 at Autozone); done myself. (Haynes said to measure the voltage across it; should be 5V. I measured 10V, so thought this was bad. Guess I was wrong. o steam-cleaned the inside of the engine by squirting distilled water into the intake manifold while the engine was running. o removed and cleaned EGR valve; done myself (had to remove the nut at the engine; blowtorch method loosened the valve from the pipe)
What Worked: Disconnected my EGR valve, and placed a 3-inch nail in the vacuum line. Car didn't stall anymore, but I didn't want to risk the higher engine temperature, and I wasn't too comfortable with the knowledge I'd fail a smog check. Worked when I had absolutely no choice though (stalling like crazy on a city street; pulled over, put the nail in, no problem).
Now that I knew it was the EGR system, I had to narrow it down to: EGR valve, EGR modulator, vacuum switching valve, or some leaking vacuum line.
I took out the EGR valve, and cleaned it (twice) with throttle plate cleaner. It didn't hold vacuum very well (vacuum pump had it losing pressure slowly), but at least it would spring back to the CLOSED position fairly quickly.
Took a chance: borrowed the EGR modulator from my wife's '99 Camry (some research showed the parts are interchangeable), then drove around with that in my '96 Camry. 30 mile trip; no stall.
Notes: My mechanic said they would charge $85 just to LOOK at the problem. That got me motivated to disassemble the throttle body and IAC valve (which the mechanic said was a usual problem with these Camrys). Ordinarily I wouldn't do that.
Posting here, in the hope this will be of use to someone.
Michael
-- Wireless network setup, computer upgrades and repair.