crxguy406

The problem in a nutshell: After sitting outside on a hot day, but before reaching normal operating temperature, revving up and then letting off the throttle causes the idle to take an initial quick dip to just below 500rpm where it will barely recover, or sometimes just flat out stall. Once it recovers it idles perfectly normal until I do it again, or until the engine warms up and the problem goes away.

I've cleaned the IACV, tested ok the brake booster, replaced new all the vacuum hoses to eliminate any potential vacuum leaks, and tried setting the idle screw slightly higher.

Extremely frustrating glitch, and I'm out of ideas on what else to try checking or replacing, any help would be appreciated.

sstupid

I had this with my 1991 Civic for 3 years. Unfortunately, I never figured it out. I have an '88, now and it doesn't do it. Well, it does it when the A/C kicks on, but I doubt I can fix that.

crxguy406

Tried replacing the alternator, ecu, iacv and main relay. No change in the problem.

Ideas? Anyone? This random replacement of parts is getting expensive.

crxguy406

Just replaced the ELD, and the throttle dashpot. Still no dice.

Can anyone explain what the tandem solenoid and dashpot assembly does? I know it has something to do with fuel efficiency and emissions, but does it affect idle? Is there a procedure to test it? I'm shooting in the dark here.

cjwang2

I've had the same problem for about a year now, but the car never stalled. I will be driving, put it in neutral as I come to a stop, then the idle will drop below to 500 rpms, sometimes a little below, then recover immediately to around 850. I too replaced the IACV, alternator, battery, did a vacuum leak test, and nothing solved my problem. So far, I am just living with it. Would be interested to see if anyone was able to provide a fix.

sstupid

Sounds like you are describing the MAP sensor.

crxguy406

I'm referring to the second dashpot in this picture, the one that would be closest to the firewall in the engine bay. It is linked by vacuum hose to the "tandem valve" (whatever that does) which in turn plugs into the engine harness.

ax77

did you ever figure this out? I have the same problem

crxguy406

Unfortunately not really. As the season has gone from extremely hot to just warm out, the problem has mostly gone away. (Only happens after my car has been parked in the sun outside at work and it's at least in the 90's.)

I'm guessing it will just come back next summer.