Why does the engine rev up and down... [Archive] - The Acura Legend & Acura RL Forum

: Why does the engine rev up and down...

01-13-04, 01:43 PM
and up and down sometimes when I put my car into park? This is getting really annoying and I want it to stop soon. You can even feel when the engine is acting up when you have it in gear at a stop. It will really want to go and I have to hold onto the brake firmer than normal. When I do throw it into park at these moments it does the up and down idle thing again (700rpm up to 1600rpm and then back to 700 rpm and so on and so on). Is there anything that I need to replace to remedy this prob?:(

01-13-04, 01:47 PM
RPMS surging between 700 to 1500 means that most likely you have air in your system. That air needs to be bled.

Search on this forum on how to bleed air from the system.

IN the morning when you first start the car, the RPMs will be high (1500) as the car warms up but gradually the rpms should falling down as the car heats up. This is normal.

01-13-04, 01:55 PM
yup, what he said...

Replace your thermostat, flush and refill your coolant according to instructions. You'll be amazed... surging will stop and idle will smooth out, even when cold.

01-13-04, 04:11 PM
Originally posted by drmosh
yup, what he said...

Replace your thermostat, flush and refill your coolant according to instructions. You'll be amazed... surging will stop and idle will smooth out, even when cold.
did all of that last month and it didn't work for me. I had to replace my fast idle valve. :werd:

01-13-04, 04:42 PM
make sure you fill with coolant all the way up, and the overflow tank. could be fast idle valve, but most likely it is air related.

thing is, once you bleed it, you need to find the leak........

02-24-04, 08:27 AM
Hey midwestlegend,

Did you ever resolve this problem? What fixed it? Please tell me! :)

My 92 Legend has suddenly developed the identical symptoms, so I'm hoping whatever your problem was will be my problem.

I guess I should make sure there is no air in the cooling system, then go from there, but your description is so exactly what my car is doing that I thought I'd ask...


Pass You By
02-24-04, 08:52 AM
Absolutly right, air in the system. Before I got my water pump and timing belt, mine did the same thing and now it's smooth.

02-24-04, 09:28 AM
yeah mine does the same thing and was wondering what the problem was also...even after the engine is warm and everything if i put it in park sometimes it will do it too...jw how to fix this...thx

04-29-04, 01:09 AM
I got the exact same problem now... it goes all sorts of crazy, but only in really low rpms, it'll become possessed and try to rev more when i'm braking so gotta brake harder, and in park and neutral... that's just insane, it will jump up and down constantly till i turn it off or shift in gear.

dealership told me idle control valve. i dont believe them b/c after some research sounded like it may be air in the coolant system.

however, now mine has gone one notch above that.... when it is doing those problems, the temperature gauge will go up until it's almost in the red, then looks like fan kicks in and will go to normal and be fine.

any consensus on what these problems are or what people have done to get them resolved b/c i know i'm not the only one with this.

dont wanna shell out a couple of hundred dollars first for the control valve only to find out thats not the problem

thanks to acura of augusta too for telling me to check that other stuff out before buying the part from them b/c it could very well be something else than the idle valve.

need input fast, trying to get resolved asap b/c i have a trip coming up.


04-29-04, 05:43 AM
I had the same problem, what i did was replace the spark plugs, and then i replaced 1 coil that was bad... it hasn't messed up since. I hated that problem... if you need a coil then send me a PM i have 3 that are in excellent shape, and i wont sell them for as much as the dealership does. they run about 100 bucks each at the dealer... make offer if you're interested...

04-29-04, 06:27 AM
what you have to do in order to check your coils :

1. turn your engine on.
2. if it is reving up and down, then unplug one coil at a time, if it stops revin up and down then you have the one that's messed up.
3. if you dont have the right one, then plug it back in and continue with the next one.
4. repeat procedure until finding the bad coil. (there are 6)

04-29-04, 10:31 AM
i also had a problem with one of my coils, but caused more 'revving down' than up. also - that wouldn't explain the thermostat issue.

a little air in the coolant system will cause idle variations before you see it on the thermostat. when you start seeing your needle climbing then dropping back down, then it's probably a pretty good amount of air - certainly enough to notice that your coolant level is low when you look.

my opinion is that an easy test is to simply top off your coolant (even if it's just water) while idling after a cold start to burp the air out. if the idle is steady then you got yourself a leak somewhere. if not, then it's something else. but whatever that 'something else' is has to explain the temp problem too, not just the idle.