Ok, folks, I have two issues going on with my 90 Accord LX, and I am not sure if they are related to each other. The car has 266K miles, and has an automatic tranny. I bought it about two months ago.
First: the car was running rough a while ago, hard to start, RPMs dipping low (below 500) when stopping at lights or stop signs, and sometimes completely stalling. I figured that I'd give it a tune up. Put in new cap/rotor, wires/plugs, battery, fuel filter, and PCV valve. Started up great and ran fine. Today on the way to work, I came up to a stop sign, and the RPMs dropped and it stalled again. It didn't stall right when I let off the gas pedal, in fact, it seems like the rpms dropped when the "clutch" engaged, if that makes sense. Right when I was about to completely stop. Checked all the vacuum hoses and all seems good.

Second: I have noticed that sometimes on occaision when I shift from either reverse or drive into park, there is a delay of about 2 to 3 seconds or so. And then the red "D" lights up on the dash. Sometimes it locks the tranny so I can't move it out of park. In the above stalling incident, I shifted into park to start the car, but it wouldn't start, I guess it thought it was still in drive?

I am guessing that for problem #1, some sort of sensor needs to be replaced somewhere, maybe?? I don't have a clue for problem #2

Any help is greatly appreciated. Thanx

 

Problem #1 ; with the engine at idle in park, unplug the IACV and see if the idle drops.
That will tell you if it is working. There is a screen on it that needs to be cleaned with carb cleaner,[2-12mm bolts hold it on the TB]also remove the air tube snorkle, open the throttle plate and use a toothbrush and carb cleaner to scrub out the ring of crud in the throttle body.

Problem #2; be sure the brake lights are working, and when you step on the brake you should hear the shift interlock solenoid under the console.
If you had a D4 light the TCM should have a code stored, jumper the Blue 2 pin connector at the top of the passenger side kick panel, turn on the key and watch for flashing lites.
From your description I would be suspect of the trans range switch under the console.
All those years of coffee and cola spills.

When was the last time the trans fluid was changed?

 

#1: You're idle air control valve on the back of the intake manifold may be clogged and may not let enough air through when the throttle plate is closed. Also there is an idle adjustment screw somewhere on the engine, normal RPMs when stopped at a red light is 750 +/- 50. When I had an AT, idle at a stop light tended to be around 1000.

#2: When I had an AT it was normal for it to take 2-3 second for it to shift into park or reverse, but he lights lit up right away. When you can't move the selector from park it makes me think that something is wrong with the switch on the brake pedal or the solenoid in the gear selector itself.

 

hondadude/finch: I will check & clean the IAC valve this weekend. Normally it does idle around 700 rpms or so, but will adjust if necessary. The brake lights work, and I do hear the shift interlock solenoid under the console clicking. That is, when the red "p" is illuminated on the instrument panel. I will check for codes, but should the D4 light be flashing, or the check engine light? As far as when the fluid was changed, I don't know any of the previous maintenance history, but when I checked the dipstick, the fluid was pretty cherry red, and had no burnt smell, so I am guessing it is somewhat fresh. It does shift (both up and down) rather rough, kinda jerky. But I attributed that to being 18 years old and 266K on it. Thanks for your help.

 

Some trans codes don't cause the D4 light to flash. So a check is in order.

good luck

 

Ok, I checked the IAC valve. The idle did drop when I unplugged it. When I pulled it off the IM the screen was pretty cruddy. Cleaned w/ carb cleaner. Took it for a test run, and it ran fine until I pulled in the driveway and then it stalled again. The RPMs are about 650 to 700 when idling in park. But when I am driving and come to a stop sign, it dips down to below 500. Should I adjust the idle up a little? Maybe up to around 800 or so?

Brake lights are fine. Checked for codes and none were present (no flashing CEL or D4).

[sm=headbang.gif]

 

Adjust idle w/ IACV electrical connector disconnected. Adjust to 600 +/- 50 rpm. Reconnect IACV, reset ECU to clear code, and idle should hold about 700-750 rpm even w/ added load; lights, AC, etc.

Ildle speed above is adjusted by opening/closing the air bleed screw on the top center of the throttle body where duct connects to throttle body. Do not adjust idle stop screw! This is factory set. Your problem could be someone adjusted this idle stop and has throttle plate too closed. This may show up when you attempt to adjust idle above.

good luck

 

I thinkthe mechanical stop for the throttle is supposed to allow it to go pretty much closed. Just enough so it doesnt wedge stuck closed. Also make sure the throttle cable goes slack so itDOES NOT hold it open AT ALL.

On newer Accords, you want to allow the ECU to re-learn the idle behavior, like this...
Reset the ECU.
Start the engine without touching the gas pedal.
Allow it to warm up completely without touching the gas pedal.
(I dont know what year that procedure started...)

 

I think these 2 issues are related, but don't HAVE to be. In addition to all of the recommendations above, check the resistance on the tranny solenoids. Your stalling at a stop problem sounds like something I had on an '89 Z24 Cavalier. The lock-up solenoid died leaving the tranny in lock-up mode and when I'd come to a stop, it would stall. A check for this would be if it feels like it's going to stall and doesn't if you throw it in neutral. ODB2 should pick this up, but there are many cases where codes aren't thrown that should have been.

 

Falkore24: Yes, when it feels like it is about to stall, and I put it in neutral, the RPMs come back up to normal (between 700-800 or so). What do I need to "check resistance" and, um, how do I do it? Will try finding codes again this week.