I drive a 99 civic 1.6 vtec SIR Coupe. The car jumps when driving slowly first to second gear. When I go over 2k rpm the car drives fine but coming off the throttle in low revs and the car hops a little. Its like an on/off switch attached to the throttle. Thats the best way of describing it I was told it was an idle control valve issue so replaced it When replaced, the car immediately idled at 2k rpm and revved up to 3.5k rpm occasionally. The original problems still remain but when I drive for a bit of time, the ECU appears to reset and the revs drop to 700rpm and all problems disappear. Is this something I did when fitting the new idle control valve or doI need to adjust something? Any advice greatly received as this is annoying as hell.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Docher &raquo;</TD></TR><TR><TD CLASS="quote">I drive a 99 civic 1.6 vtec SIR Coupe. The car jumps when driving slowly first to second gear. When I go over 2k rpm the car drives fine but coming off the throttle in low revs and the car hops a little. Its like an on/off switch attached to the throttle. .</TD></TR></TABLE>

I'm not 100% sure but I don't think the IACV does anything but make the motor idle steadily. In other words, it's not doing anything when you are driving/accelerating, I think. It sounds like it may be something else...

 

2000 rpm is definitely the point where theres an issue anyway. The engine management light is on aswell which makes me think theres an air leak in the exhaust maybe. I cant get Honda to take a look because they wont touch it when the cat has been removed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Docher &raquo;</TD></TR><TR><TD CLASS="quote"> The engine management light is on aswell which makes me think theres an air leak in the exhaust maybe. I cant get Honda to take a look because they wont touch it when the cat has been removed.</TD></TR></TABLE>

Your engine management light (or CEL) is on probably because the cat is missing. OBDII systems don't like that.

 

To be fair, the de-cat pipe was on the car when I bought it 6 weeks ago. Theres a manifold back, 3inch twin exit manifold back powerflow exhaust system on the car.Is there much of a power increase in the de-cat pipe or would ye recomment just putting the cat back on, to sort out the issues Im having?? Thanks for gettin back to me...

 

My car does the EXACT same thing when its cold. My IAC is a piece of junk. It sticks open, which does exactly what your car is doing. High idle, touchy throttle at/below 2k rpm, it stutters when in gear at 2000 rpm(feels like a rev limiter). Go any higher on the rev range and it drives fine. You most likely have an "idle control circuit malfunction" code in the ECU. I can shut the key off, restart, and she's OK. I'm glad I'm not the only person this happens to. My Honda technician co-workers have told me it's a relatively common problem for the 99-00 Si (or SiR if you are in Canada)

 

I have that problem with my b16a in my hatch...but for me itds more like 1500 rpm... pulsates at 1500, anything above it drives fine...i cant figure it out

 

I was told to check the connections at the IAC, clean , replace IAC if cleaning is no good. I dont want a cheap AutoZone knock off, and I dont have the money for a 180$ dealer part. So, I just take mine off and blast it with Cyclo carb cleaner, which seems to unstick it for a while.

 

Lads I just replaced the original Idle Control valve, it cost me 290euro and had to be shipped from Japan. This problem doesnt go away on shutoff....it seems to decide for itself when the ecu resets. The issue that you mention with the ECU fault may well be where im going wrong.

 

Try blasting out the IAC port on the back of the manifold without the IAC in place. Could be plugged with crap.

 

When you say blast the port, do you mean run the car without it attached or do you mean blast it with cleaner?.....To be fair I didnt check the port when I fit the new control valve so I'll try that.

 

I have the same issue .. i thought it was the iac but then my friend un plugged my map sensor and the car idled fine ... i think it is ur ECU or your map sensor.
I have an unchipped p28 running my B16A in my EG and i got mad idle surge it goes from 1K to 2K when idling but when i drive its perfectly fine .. im still trying to work the bugs out .. thought it was vaccuum but used starting fluid and it didnt bog at all.

I'd say check your map sensor because theres a vacuum line on it asnd a plug and if u unplug it and the car idles fine there ya go!

 

had the same prob with my gsr swapped rex. it was a 98 jdm engine, and i replaced all kinds of stuff and the problem never went away. it was hard to start, and idle surged just a little bit and had no power untill it warmed up. one of my friends said to change the coolant temp sensor that has the 2 wire plug on it cus it sends a signal that helps the ecu determine how much fuel to deliver based on engine temp, and all of the other readings of corse. my car never threw a code for anything, but i replaced it, and the problem went away.

 

DISCONNECT THE COOLANT LINES ON THE IDLE AIR CONTROL VALVE.RUN THEM TOGETHER AND SEE IF THIS WILL FIX THE PROBLEM. ONE OF THE PROBLEMS THAT IT SOUNDS LIKE IS THERE IS AIR IN THE COOLANT AND WEN THE MOTOR IS RUNNING AIR PASSES THROUGH THE IAC AND CAUSES THE SURGING

 

There has been an on/off airlock in the rad that comes and goes. Ive ordered a new stainless steel rad on ebay.You may well be right as the heating blasts out cold air instead of hot at times. Would this not make the car idle differently all the time if it is trapped air in the coolant?....cos the issue is at exactly 1800-2000rpm constantly and then the engine heats up and the idle drops to 700rpm...

 

it is possible. Air hitting the coolant temp sensor may throw it off.

 

my car doesnt like to warm up very much either even after driving it for 30mins.....it surging at about 1500 rpm still somewhat warm than kinda goes away but still it there..... coolant temp sensor???