Hi all, new to this forum....I have a problem with my girls 90 accord and cant figure it out for the life of me! It wont pass smog because the idle fluctuates from 1500RPM down to about 1000RPM over and over every like 4 seconds, i have replaced the IAC valve with 3 different ones (one that worked fine on another honda) I have replaced the fast idle control valve also, Im at a loss! please help! thanks in advance, James

 

If there is no check engine lights on it could be a few different things.... it may be as simple as cleaning out the throttle body, the temp sensor can also make it a little irradic....and I'm sure there are one or two other fairly easy things to check but I'm to hung over right now to remember what they are so I'll let someone else drop you an answer in a bit.... *L*

 

Hey thanks, yeah ive been searching like a madman on this forum for anything on the subject...havnt had a whole lot of luck. There is no check engine light. I appreciate any help i can get! Where is the temp sensor? Ok I just got a bunch of info, sounds like a vacuum leak somewhere.....i'll give that some effort.

 

Look for vacuum leaks.
Bleed air out from cooling system - bleed screw on thermostat housing.
Look again for vacuum leaks.

Search the DIY board here for 'FITV'
- fast-idle thermo valve is underneath throttlebody & the plunger inside can get loose & cause a surging idle.

 

Really ?? MM all you got to do is head to our DIY section, there is a post titled ( SURGING IDLE ? ) Go chk it out

 

Ok i cleaned the FITV, reset the computer....still surging idle, so i went to the junkyard, pulled another FITV, another IACV, replaced them reset the computer....still surging. I searched and searched for a vacuum leak, i found one, the brake booster...so i plugged the hose, reset the computer, still 2K to 1K idle...any other suggestions? Im about to bring this car to the junkyard and give up on it. thanks in advance, James oh yeah cleaned out the throttle body too.

 

i have a friend who owns a prelude that would do the same thing... his timing belt ended being off and he replaced it and now it sounds like normal

 

Ok That might be what i'll do next, ive been fighting this car for months, almost new from the head up..thanks

 

it is not the timing belt issue.......

remov ethe top cover of the fast idle valve, 3 phillip screws, get a regular screwdriver and turn in the inner valve ,, if it is ok or it still the idle surges.. than remove the top cover of the air boost valve and chk to see if the rubber diaphram leaks

 

Ok will do, however i just replaced both of those parts yesterday....but the parts were used so who knows......thanks