Hi everybody - I'm new to this board, but I'm pretty experienced with fixing my owm vehicles (as the name suggests).

I've got a problem with my 91 honda accord lx (150k, slow commuter on 15' ex rims, seems to move faster than ex models) that someone out there probably has run into before. The warm idle speed alternates between 1400rpm and 1100rpm continuously. This is totally related to the vacuum device in the intake tube that feeds into the third vacuum port on the intake manifold (closest to the cabin).

I eventually got pissed, ripped out that factory-crap intake, and stopped up the vacuum line (right after passing emissions). The problem is erratic, which frustrates me more.

Please help. As a reward, I will post a photo of may redneck $6 cai that I would guess flows almost as well as the $250 variety.

PS From an engineering standpoint, I would like to see a convincing arguement that 1 cai is better than another.

Thanks much!!!

 

this could be 2 things ...

a cracked PCV valve

or

a busted fast idle thermo valve

both give off the exact same thing you're describing right now.

 

:werd: I was going to say the same thing but you beat me to it. Double check all the vacuum hoses, as after 13 years they tend to get brittle and crack.

Welcome aboard.

 

Thanks for the response, Eklypse39. Please tell me about the fast idle thermo valve. Where is this dude located?

I might have suspected the pcv valve, but I recently replaced it in my desperate attempt to pass emissions.

I have a mechanic friend who was suggesting the EGR valve. I do know that my NOx is way high (barely, barely passing) which also suggests that the EGR is dead.

 

a jammed or broken EGR valve will also cause weak idles at stops. your car will feel like it will die while the rpms stumble all the way down to 200.

i am not too sure where the fast idle valve though. i went through the same problem you did back in November. i cleaned the egr valve, replaced the pvc valve, and looked for vac leaks ... nothing worked. i sucked it up and brought the car into the dealer.