This is on my 91 LX five speed. After fixing the bum coil and driving this thing around a little, I havenoticed a cute little problem. After it warms up, when coming to a stop it want to stall - pretty much every time. It's in the last 100' or so, as you push the clutch in and shift to neutral. It's quiet anyway, so I usually don't notice until the dash lights come on. It restarts immediately. After it warms up,the idlehas trouble recovering if you rev it a little. The idle seems to want to dip lower than normal beforeit stabilizes at 700. My theory is that this dip is what causes the stall on the road, though I don't know what's causing the idle speed to dip.

I tried adjusting the idle speed, but it didn't seem to affect the problem at all, good or bad. What should I check next? Tomorrow I plan to remove the IAC valve and clean it. This car did sit for awhile before I resurrected it.

 

Sounds like you're on the right track, cleaning the screen of the IAC is a good idea. I always use Berrymans B-12 carb cleaner.
Quick check of the IAC; unplug it and the idle should drop about 200 RPM
I hope you didn't adjust the idle with the throttle cable, because the TPS will cause the timing to advance and can take the IAC out of operation.
In the pic below there is a Grey coated screw at the 11'O' clock of the throttle body, that is the air idle adjust screw.
if you scrub out the throttle plate area, use someone elses toothbrush, never metal brushes.

 

Here's a quick update. I cleaned the throttle body and IAC. There was some fluff on the IAC, but it made no difference. I've also adjusted the valves, checked the base timing (correct), removed and cleaned the EGR valve, and tested the EGR valve. It holds vacuum, the pintle moves freely, and it stalls the car when vacuum is applied. It looked quite clean inside the EGR ports on the manifold.

I noticed that the problem occurs when braking from more than 20 MPH. I doesn't matter if I use the service brakes or handbrake. If I brake slowly enough, it doesn't seem to be as bad - or does not occur at all. If I brake normally, I can watch the RPM's drop until the idle gets rough and it just quits. It restarts immediately with the starter or if I pop the clutch while rolling. It is 100% repeatable. I'm beginning to think fuel system, because the problem only manifests itself while rolling. Maybe the fuel is sloshing funny or the pickup is clogged. I have an EFI fuel pressure gauge. Are there any suggestions how to build an adapter from the Honda fuel rail to 5/16 FI line (which plugs neatly into my gauge)

 

Well the EGR is not in the picture when at idle RPM.
What happened when you unplugged the IAC at idle?
Is there a little bit of slack in the throttle cable?
You have checked for vacum leaks? [spray around with carb cleaner to see if idle changes]

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In my Haynes manual, there is a procedure to diagnose engine problems by checking engine vacuum with a gauge.

Its not great for pinpointing a problem, but it might lead you in the right direction.

 

I have not been able to do a thorough check for vacuum yet, but it's a strong possiblility. I was concerned that the egr might be stuck open slightly - but it wasn't. The throttle cable has a slight amount of slack. I adjusted the idle the other day with the grey coated plug, per the Haynes manual. The idle falls with the IAC valve plug removed, and jumps up with it plugged in. So that seems to be ok. They seem quite expensive - I hope it's because they're well made and not prone tofail!

I will do the spot spray test for vacuum leak and report back.

I continue to be amazed by the lack of abnormal wear or crud buildup in/on this motor. As soon as the problem is sorted this car is going to cut my fuel bills in half! Right now I drive one of the few US motors that comes close to matchingHonda's longevity - the stout (but thirsty) Ford 300 straight six.

 

Well, I checked for vacuum leaks and found none. However, while waiting and looking for a fuel pressure adapter, I changed the fuel filter and foundsome rusty bits and sedimentwhen I drained the old filter. I decided to drain the fuel tank and open it up for a look. It seems like I'm getting some sort of restriction or slosh effect because it's stalling after a stop or when I back up. I put a spare hose on the return side of the regulator to pump the tank out - it works pretty quick if you've never tried it! Anyway, at about 1/4 tank I noticed the return stream going into the gas can changed. It became very intermittent and weak. The idle was ok, but I noticed some variation that seemed to correspond to the intermittent return stream. When I blipped the throttle, there was a nasty hesitation. Darkness is upon me (no shop lights yet - I do a lot of work outdoors) so I put the rear end on jackstands and left it for another day. Looks like I'll be dropping the tank to look for a restriction, and probably replace the pump while I'm there.

 

Pull the vacum line off the FPR and see if there is raw gas in it?

 

I looked already. No gas in the FPR vacuum line.Everything seems to point to an ailing fuel pump or a huge blob of crud on/around the pickup, so I'll report back when I find out what's in the tank. I'm excited about getting this thing on the road - it will help when daylight savings kicks in.

 

Tank's out. It looks like rust contamination is the problem. There is a lot of rust on the fuel pump body, and I can see lots of orange in the tank. It looks like the pickup is mostly clogged. It appears that the tank was a little less than half full when parked, and there's a perfect borter of rust/no rust. I got a pump and pickup already, and I'm going toreplace the tank while it's out.