91 CX idle erratic cuts out and in

[2canoe]

Tried searching for solution on these forms. My civic runs good exept after engine warms the idle goes up and then appears like cuts out and back in.RPM drops and starts cycle over and over. No failure codes. Engine has been changed (not recently used for acouple years) not sure if its a 1.5 or 1.6 Help please

[MrWrongsalive]

Make sure the antifreeze is full, (this is done by loosening the 12mm bleeder screw on the upper radiator hose water neck), be careful I've seen them break off after so many years, then you fill the radiator until only antifreeze and not air bubbles comes out of the bleeder screw, afterwards just close the screw and top off the reservior. Hondas rely quite a bit on coolant temperature for maintianing idle and setting the proper fuel curves. The computer may very well think the engine is operating at 500 degrees and is trying to compensate by adjusting the idle.
This ofcourse would be my first step in diagnosing the idle problem, there may be other causes. As far as cutting out goes it depends on how the car cuts out, does it sputter out or is it like someone just hit a switch and it dies abruptly?
GOOD LUCK

[2canoe]

Originally Posted by MrWrongsalive

Make sure the antifreeze is full, (this is done by loosening the 12mm bleeder screw on the upper radiator hose water neck), be careful I've seen them break off after so many years, then you fill the radiator until only antifreeze and not air bubbles comes out of the bleeder screw, afterwards just close the screw and top off the reservior. Hondas rely quite a bit on coolant temperature for maintianing idle and setting the proper fuel curves. The computer may very well think the engine is operating at 500 degrees and is trying to compensate by adjusting the idle.
This ofcourse would be my first step in diagnosing the idle problem, there may be other causes. As far as cutting out goes it depends on how the car cuts out, does it sputter out or is it like someone just hit a switch and it dies abruptly?
GOOD LUCK

That was the first thing I checked thanks, The symtom is asif it is shuts off for a split second revs higher than idle speed and like it misses for a one shot and starts the cycle again, It is more like a someone shut a kill switch on and off. I can be about 15 second between cycles,,First idles fast for 14 3/4 second die for 1/4 second and does it again. someme times it doesnt do this at all.

[FrodoGT]

My First suggestion is to check and see if you have any trouble codes from the ECU. Do this by pulling the carpet up on the passenger side in the footwell area. There is a small window in the center of the ECU that will blink if it is throwing a code. Let us know if you are getting any, they blink in a series with a short pause between each, just count the blinks.

You could very likely have a vacuum leak as well. The MAP sensor will cause a surging idle, however it will usually do it all the time, cold or hot. The main target I would focus on would be the EACV. this little bugger is what controls hot idle, and can get clogged and dirty. Do a little searching and youll find tons of info on how to remove and clean/inspect it. Also make sure the wiring to it hasnt come loose/broken/out of spec (when measured with a multimeter).

[2canoe]

Re: 91 CX idle erratic cuts out and in

--------------------------------------------------------------------------------

My First suggestion is to check and see if you have any trouble codes from the ECU. Do this by pulling the carpet up on the passenger side in the footwell area. There is a small window in the center of the ECU that will blink if it is throwing a code. Let us know if you are getting any, they blink in a series with a short pause between each, just count the blinks.

You could very likely have a vacuum leak as well. The MAP sensor will cause a surging idle, however it will usually do it all the time, cold or hot. The main target I would focus on would be the EACV. this little bugger is what controls hot idle, and can get clogged and dirty. Do a little searching and youll find tons of info on how to remove and clean/inspect it. Also make sure the wiring to it hasnt come loose/broken/out of spec (when measured with a multimeter).Quote
No blinks on the failure. I will see if I can find info on it and clean it etc.
thanks

[2canoe]

It was a serious vak leak. hose off, thanks to all