I have a 94 hatch dx with 115,000 miles on it. It is only a daily commuter car. About two weeks ago I left my lights on and ran the battery dead. I jumped it from my wifes civic and rode for about 30 minutes and the car now starts up fine, but ever since then when I drive and then stop at a light, traffic, or just sit in the parking lot while it warms up, the engine revs up and down real fast. I dont have a tach so I cant tell how high, but it goes up and down for a minute, then idles normal, then it will do it again. What is the problem. Thanks for the help. By the way, when I baught the car, the guy put a larger b pipe on it, way to big for the 100hp it has. I can tell from where the stock is cut from the cat because of the bottleneck. but the b pipe is aftermarket and I will change that back to normal size soon. I wouldnt think that the b pipe would be the problem because it just starting happening after the battery went dead.

 

Are you sure you didn't overheat the car before you left the lights on? The idle going up and down like that is a typical symptom of a blown head gasket. Check your coolant level, hopefully it's still full. If not, then you might have a big problem. Also look for steam in your exhaust. If your coolant level is normal (keep checking if you keep driving) then I don't know what could be causing your problem. Try disconnecting the battery for a few minutes to reset the ecu maybe?

 

Make sure you didn't knock any vacuum lines off when you went to jump it. Last time my car was in limp mode it was doing weird things also so I reset the ecu and ran it for a couple of days and all was better.

 

The car doesnt overheat but I will check the fluid when I go to the car again. I will also check all the vacuum lines and also disconnect the battery to reset the ecu. Hopefully that will work. Thanks for your help.

 

check sensors near the thermostat. they have a tendency to cause silly things like that. IAC sensor too. thats a definite cause of up and down idle.

 

Could it be TPS sensor. My car does the same thing and my ecu is throwing the TPS and Map sensor code. If I unplug my TPS sensor then plug it back in it will run fine till I turn it off and start it back up

 

tps, iacv, throttle body - check all of those

 

Thanks, I will check those this weekend.

 

check ur thermostat and also ur pcv valve =] i had the same problem...but i think it was also my IACV as stated above...i changed both IACV and PCV valve...its not that big of a deal...its typical on hondas from what i've seen =]

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PabloDiablo &raquo;</TD></TR><TR><TD CLASS="quote">Are you sure you didn't overheat the car before you left the lights on? The idle going up and down like that is a typical symptom of a blown head gasket. Check your coolant level, hopefully it's still full. If not, then you might have a big problem. Also look for steam in your exhaust. If your coolant level is normal (keep checking if you keep driving) then I don't know what could be causing your problem. Try disconnecting the battery for a few minutes to reset the ecu maybe?</TD></TR></TABLE>

not even close. please dont answer if u have no clue what your talking about. If he was going to have a headgasket problem 99.9% sure his car would be overheating and he didnt mention a thing about his car over heating. So to you my friend.

Now to the real question. The irratic idle seems to be very nitorious on honda's. several things that you can do to fix it.
1.Run a CEL scan on your car and look for codes. the CEL doesnt have to come on to be throwing a code.
2. Before you start your car. make sure its cooled down. Remove your radiator cap and start the car. and let the car get warm while the radiator cap is off. pour in coolant as its warming up. it will start to bubble up (air coming out of the system) keep doing this til the coolant doesnt drop any more. and your cooling system is bleed.
3. Check your IACV. its on the backside of the intake manifold just to the right of the TPS sensor on the back of the throttle body. there should be 2 coolant lines going to it. Remove that with a 12 mm wrench. and check the screen on the IACV make sure its clean and that there isnt any debrea in the screen. if it needs to be cleaned. clean it with some carb cleaner or some Brake cleaner.

I hope this helps you.

 

i had the same problem, however, my battery was never killed. turns out the a/c clutch wasnt responding correctly and was turning on and off over and over. but i dont think that could be your problem. then again, if nobody elses ideas work, check that. hope i helped and good luck

 

Well my civic is doing the same thing , no dead battery for me but i just notice it about a month ago.....I got my helms manual
erratically iddle :
Check :
1.vacuum leakage
2.leaking egr valve
3.air filter clogeed &lt;~~~~ I think thats whats wong with mine changed mine 4 months ago.
4.fuel pump not delivering enough fuel to injectors
5.Leaking headgasket
6timing belt and/or pullys worn
7.camshaft lobes worn


I have to check all of this to this weekend, i will post my findings

Sorry jdmlifestyle but , pablo diablo maybe right according to helms manual

 

I have the same problem after I swapped my head, intake and exhaust manifolds, cam, and TB. It could be a # of variables for me. If I turn my idle up to around 1000-1100 (on the in car tach), the problem goes away. It's never so bad I can't drive, although it seems if I get on the motor real hard and then bring it down fast, the idle dips real low, then fluctuates alot. I won't trust it to udle, unless it's warming up. The problem isn't there when the motor is cold. My battery never died although I did notice at a stop light one time, I had my radio turned up (100w 10 in sub) and the idle would drop low when the bass would hit. It never happened before. Maybe it's an alternater problem? Hope some of my problems helped. You are not alone.