Throttle Surge

1994 Honda Civic, 1.5L, 210,000 miles. Engine light came on recently.
Car would stall or idle at 200 rpm and surge at 1500-1700 rpm. I have
added fuel injector cleaner to gas and removed air cleaner and cleaned
intake and throttle plate with cleaner. This fixed the idle problem
but still have engine surge at 1500-1700 rpm. What sensor should I be
looking at replacing or how should I proceed from here?

 

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Low coolant will cause throttle surge. Try filling the reservoir to MAX
and see if the level drops next time it's cool. If so, fill to MAX again
until its stable. No tap water.

'Curly'

 

and don't just check the bottle - check the radiator directly. if
there's a leak or too much air, the bottle doesn't suck back correctly
and can be full, even when the radiator's empty. only open when cool.

 

wrote in 80g2000cwy.googlegroups.com:

Get the error code. It's still in memory even if the light's off now.
http://www.tegger.com/hondafaq/misc/3173_ICCR_E_14JAN03.pdf
See page 15. The "tool" is a bent paper clip.

Fluctuating idle is often due to a big air leak. First check your coolant
as suggested by Curly and jim beam. If the fluctuation is still there, you
need to check for suction at the lower port in the throttle body,
immediately ahead of the throttle plate (engine full warm). If there IS
suction, the Fast Idle Valve is stuck open.

 

Have you had the intake manifold off the engine? If so you may have
not sealed the gasket well allowing an air leak. That happened to my
90 prelude. I replaced the gasket and gooped it this time and it
solved the problem. Other possibility is vacume line leaks.
Good luck.

 

What was the code??? A P0505 idle control malfunction? It's likely
a bad IAC valve.
Chip