I saw some random post about 'the dreaded honda surge' but i dont know if that is or is not the same thing.

Have a 1994 Honda Accord EX - its the 145hp 4cyl, whether its F22 or F23 I forget but the stock engine. Automatic, about 240,000 miles on it. Had to sit for a year because of a water pump leaking like a sieve.

The car that i'm about to do the timing belt on, we had to start it and move it to where it's now parked and jackstanded up but when we start it it had sat a year... I dont remember if it did or didnt do this before. (i didnt drive the car, it was girlfriends car) But at idle in neutral the RPM would want to go low then high then low then high... like normal 800rpm or whatever for 3-4 seconds, then like 1300rpm for 3-4 seconds, then back down, then back up endlessly. Once the throttle is depressed it seems okay, can lightly press it to raise rpm and it doesn't surge, once it was moving forward in gear it seemed okay. (we didn't move it very far and had no battery in it and no current tabs so no room for a test drive)

Any suggestions what might be causing this? I'm not going to worry about it until after the timing belt/water pump is done (because that determines if were even keeping the car honestly) but if there's anything I need to look at while it's off (broken sensors or other problems) that's why i'm asking now...

 

Check this out:
https://www.hondaaccordforum.com/for...e-speed-38734/

That talks about a few things that can cause the idle to surge.
- vacuum leaks
- air pockets in the cooling system
- physical stop screw for the throttle plate should never be used to adjust idle

Since the car sat for awhile, I would add cleaning the IACV & FITV because they might just be dirty & sticking.

 

Thanks for the heads up... so the only thing that needs to happen during my timing belt/water pump change is just to try and not have air pockets in the cooling system. (which i'm not sure how i'll do that but i'm open to suggestions :) ) I mean I have to drain the coolant, flush things, and then refill anyways so if that doesn't self fix it, I can wait til TB/WP is done before I come back to troubleshooting or figuring out the wandering idle speed.

If I dont see any other followup posts (i'll be slowly fiddling with the TB/WP for a few days) i'll come back to this problem and post again if it's still doing it and I need pointers. (or/and in that thread)

 

There's a bleed valve on the thermostat housing (follow the lower radiator hose to the T-stat under the throttle body). T-stat housing is where air likes to hang out, so if you don't bleed out the air it can cause problems. Non-Honda guys don't always know that air pockets can confuse the idle-control system.

Another way for air pockets to form is a bad seal at the radiator cap. Coolant moves to the overflow reservoir and the bad seal allows the radiator to suck air rather than sucking coolant back in when it cools down.

The FITV (fast-idle thermo valve) is under the throttle body, and it has a small coolant hose. Rinse that out, because old antifreeze might make a gooey gel that can do strange things to the idle. If the FITV doesn't get a good circulation of antifreeze, the erratic temperature causes the idle to surge.

If the car sits for a year with a leaky waterpump, I'm just guessing about air pockets and gel/goo in the cooling system. The waterpump job is the ideal opportunity for you to clean that out. Then cross your fingers and hope that fixes the idle.

 

Do I have to stick to any special procedures when refilling coolant into the system to avoid air pockets getting stuck?

 

Other than being aware of the bleed valve at the thermostat, I guess the rest are common sense.

Set the heater temperature all the way to hot so coolant will circulate through the heater core sweeping air bubbles away.

I don't remember if 94 has an oil cooler sandwiched between the block & oilfilter. If so, make sure those hoses (and all other "small" coolant hoses) are OK and not kinked or plugged.

Make sure the thermostat is the right way around and right-side-up. The little rattle-pin vent goes at the top. I'm pretty sure the housing is made so the T-stat physically won't go in backwards.

When the engine is running, the 2 places where air will collect are at the thermostat & at the radiator cap. Use the bleed screw at the T-stat to remove air, and open the radiator cap (when cool) to top up the antifreeze.