No surge when cold and at idle. However, when engine is warmed up after highway driving, it surges a bit at idle. I don't notice any issues when driving. Ay suggestions? Thanks and Regards!

 

Google "Honda Idle troubleshooting" and find out how to clean your IACV, or further diagnose.

 

I will add: the idle, when cold, is controlled by a manual mechanism called the Fast Idle Throttle Valve (FITV??) and...when it warms up, the idle is controlled by the Idle Air Control Valve(??) (IACV). :D

 

^ this.

It sounds like your Cold Fast Idle Valve is not closing when coolant warms up.

Both full of useful info on the subject:

 

Thanks folks! Great help and now I've got a lead. Those films are awesome, silkypillows. I'll follow up when I figure out what's up.

 

If you've done anything with the coolant hoses bleed the coolant

 

I took off the IACV today ( I found out the '91 1.5L has no FITV )
I cleaned it out really good with brake cleaner and got a good bit of gunk out of it. Put it back on and ran the engine through 2 fan cycles with the radiator cap off to bleed the coolant. A substantial amount of bubbles came out. Did that until it stablilized and got no more bubbles.
It runs much better, but still surges just a little bit at idle. Especially after gunning it, where it then stabilizes after about 10 seconds. Perhaps I didn't get the IACV completely cleaned, or there's a bit more air still in the coolant? I can live with it for now, with my eye on maybe getting a new IACV. Not sure if dirty injectors would cause rhythmic surging? Thinking of putting some Seafoam in the fuel...
Thanks.

 

Did you crack the bleed valve its where the top radiatior hose enters the engine side its a 12mm

 

Thanks. I just went out and cracked it, ran her for a few. Got some small bubbles but that was it.
It runs pretty good at regular idle, around 600rpm or so. The surge is more pronounced when I hold the acceleration at around the 1000-1200rpm range or so.

 

if you have no fitv then pull the throttle body off and clean the **** out of it... i dont have an fitv either and had a surging idle about 4 days ago cleaned the iacv an throttle body along with bleeding the coolant and it went away leaving me with a high idle due to a bent throttle cable bracket... I literally just solved my idle problems today

 

Thanks. I'll do that. What do you suggest to clean the injectors with when I get it off of there? I ordered a PCV today ($4) on the off chance that might help.
Congrats on getting yours fixed.

 

I've had good luck with seafoam in mine put it in the tank down the throttle and in the oil then change oil in a couple hundred miles

 

Silkypillows, Nice find!!!

 

I changed the PCV. The old one, with 191K was essentially a carbonized plug. It seems to have made a difference. It's an easy repair and only a few dollars. I still get a very slight surge, but it's intermittent. I put in some Sea Foam today, in the gas tank. Haven't had time to "deep clean" the TB.