I have a 1999 honda accord that has a problem when it warms up, the engine revs up and down. Anyone know what the problem might be? Or how to fix it?

 

Probably a large vacuum leak.

 

you think it might be the throttle body? where would I start first to find if its a vaccuum leak?

 

Start with doing an advanced search in the Accord 90-02 section for "reving" or "roaming" and "idle"
Then read the FAQ guide that's mentioned in 99.9999% of those threads
Then perform said actions from FAQ guide
Then post back if you have problems

 

Mine does this too. It says that it usually happens due to having a non factory intake system.

 

Your idle shouldn't surge, hunt, bounce or rev up & down when using a non factory (aftermarket) intake if it is installed correctly. Also the ECU has to be reset after installing a larger free flowing intake. If it still doesn't idle properly after this there is another issue.

The surging idle condition is very well documented in the Honda community. It's usually a vacuum leak, dirty IACV or a FITV that is out of adjustment. The other causes are low coolant or air bubbles in the cooling system.

Check the FAQ's there is a lot of good maintenance information.

 

Are you pressing and releasing the throttle when this happens?

 

thats probably not the case, i hav an aftermarket intake and it works well..all u have to do is make sure there is nothing unconnected..my car would rev up n down due to the fact i had an extra inlet for a hose..so i covered it up and problem wuz solved..

 

y do u have to reset the ECU if u have an aftermarket intake? and how?

 

so this problem occurs on idle?, i use to have this problem, its ur IACV, u need to take it off and clean, also while ur at it clean the throttle body, it makes a difference in cleaning these two parts. after i completed the cleaning on my car the problem went away and havent had a problem since. Try it and good luck!

 

Resetting the ECU sets the short and long term fuel trims (STFT & LTFT) and other factory ignition and fuel multipliers to their default/starting points. And allows for the ECU to relearn all of these parameters with the new intake system.

Disconnect the battery (-) terminal for 60 seconds to reset your ECU. If you have a factory radio, make sure you have the activation code prior to disconnecting the battery.

 

What cleaner is best to use on cleaning the trottle body and IACV?

 

Carb or throttle body cleaner.

 

Well is there a certain brand because i have read that certain ones can clog / mess things up.

 

I used to have this problem too...bought carb cleaner and cleaned the egr valve, iacv, and the intake manifold. Smooth idle afterwards.

 

Just make sure to get one that says that it's O2 Sensor friendly.

 

alright! it makes sense...i will reset her tomorrow!

 

one that says it will not harm oxygen sensors, cat converters, and injectors, good luck!

 

oh and when ur done with IACV, let it air dry for about 15 minutes.

 

if that dont work bleed the coolant line to take out the air, its by the thermostat ok it looks just like the brake line one.

 

I have had this problem with several of my Honda's that I have owned. It is usually a vacuum leak, all I do is spray a little soapy water to find it.. or as was said earlier it more than likely your IACV, which is cheap and easy to replace.

 

Why would you want soapy water to possibly get in your system? I use only water to test for vacuum leaks.

 

ok the car when its cold doesn't rev up and down, but when it warms up then it starts to rev. This is all in park, then when you put into drive, the reving stops and it runs normal. Anyone know what the problem might be?

 

ok it could be ur stp sensor, its at the back side or the throttle body.

 

Out of curiosity, have you done anything that was suggested?