This is an odd one. 1998 Accord EX 4 cylinder ULEV automatic. It has around 80K on the odometer. Runs pretty well normally, idle seems steady, no CELs. It doesn't stall in normal driving, when braking to a stop normally, or stopping with hard brake pressure.

However...

Put it in park, rev to 3K RPM, hold it there for 15s, take foot off gas, and it stalls when the RPM falls like a rock through the idle point. Turn the key and it starts right up.

Strange, right?

Recently it would also stall if put into neutral, glide to a halt (going uphill) or stop with parking brake, and then touch the brake pedal. But I have not been able to reproduce this mode of stalling in several days.

Recent work:

• Replaced starter motor (click, no turning over, intermittent)
• Replaced air intake hose (split at bellows)
• Rebuilt distributor (leaking oil at the inner seal slowly)
• Replaced distributor O-ring (wrong size used at rebuild, leaked a lot of oil)
• Cleaned off all the leaked oil.

The brake booster seems to be OK, the pedal moves up when it should, down when it should.
Probably the IAC is dirty, but it cannot be too bad because normally the idle is stable.
The problem may have been around before any of the work, it was definitely present after the distributor was rebuilt, and before the bad O-ring had made a mess. It was just chance that one of the first things I did after putting it all back together was rev it like that.

I took it to my mechanic to see if they could figure it out. They said it is the distributor, but I don't see how that could be, and the guy at the counter had no details. On the plus side, they didn't charge me for this diagnosis.

Suggestions?

 

Crickets, eh?

Well, it would help if somebody who has a similar car could repeat the experiment and report back with what the RPM actually do on a working car. That is, put it in park, rev to 3K for 15s (or more), foot off gas (quickly) but do not put it on the brake afterwards. Do the RPMs fall smoothly to the idle point, or does it overshoot and RPMs go down below idle (how far) and then back up?

Thanks.

 

3 years later and it is still like this, no worse, no better.

Recently had a problem with a P0108 code. It has not come back in now more than an hour of the car running. That's in another thread.

https://honda-tech.com/forums/honda-...ccord-3383168/

Anyway, since Torque Pro was still hooked up, the IAC was "sort of" checked. With the car stopped in Drive and idling, foot on the brake, gas pedal untouched, "Vacuum" read -21 in/Hg. Then the AC was turned on, and that rose to -18 in/Hg. Toggling the AC on/off would move the pressure back and forth between those values (with a little bit of variation in the measurement, like plus/minus around 0.2 in/Hg). So the IAC does open/close, but I don't know if that is the appropriate amount or if the speed at which it does it is fast enough. Perhaps not, because the RPM was a little lower when the AC was on then when it was off. At the moment I'm leaning towards "IAC restricted but not fully blocked" as the explanation.

 

Swapped the MAP sensor with a used one from a 1999 Accord in the junkyard. This resolved the problem described in this thread, and probably resolved the other one too. It was interesting that with the "new" MAP sensor in the first few tests of rev to 3K and release the gas pedal overshot the ~600 RPM idle but didn't quite stall. However, after that the RPM moved smoothly down to 600 with no overshoot.