I have a Honda civic 1999 its automatic and I have a low idle. In park it idles at around 300-400 in drive it idles about 100 and shakes but once I've driven the car for like 30 mins it idles at about 300-400 in drive. And this is with no load. no ac, lights, defroster, wipers. But when I do turn on my AC it drops instantly to 100 or lower. I already cleaned the IACV using a thread on here. Cleaned throttle body, timing is where its suppose to be. Checked my cap and rotor and plugs there also good, there is no vacuum leak. I'm stumped not sure what else it can be. I'm thinking it may be my PCV valve and hose. Thanks for any input. The First pic is when its in drive at a stop light the second one is in park.

 

my car seems to that every now and then. it can be really annoying. bump for some more information on the topic.

 

turn the idle screw on your throttle body to let it idle higher. check for vacuum leaks.

 

Could be a Bad TPS sensor, could be sending wrong signal to ecu, check tps voltage should be about .5V at close throttle and 4.5V WOT
You'll have to troubleshoot

 

I found out I was throwing a p0172. system too rich(bank1) . So i will check my TPS and MAP sensors out tomorrow when I am off. ^^^Good luck to the OP of the thread with your low idle.^^^

 

Anyone? I changed the pcv hose and pcv valve. New spark plugs and wires. Still the same. dpt79606 was the check engine light on? mine isnt

 

i have the p1607 code already because it isnt the stock ecu. so my cel light is always on thats why it didnt occur to me to check the codes. autozone or pepboys can scan it for free if you dont have a scanner. im sure its an easy fix just a pain in the butt for sure.

 

I already checked with the scanner.. nothing.. I'm lost .. And I have to smog next week. How do u check ur tps and map sensor?

 

first mark is 500 rpm you re idling at 500 and 650 rpm on those pictures not 300 rpm

 

Back probe the tps sensor with a voltmeter
Should be .5v closed throttle and 4.5v wide open
As you open the throttle there should be a linear increase in voltage until its maxed out at 4.5v, if there is any spikes then the tps is bad

 

raverx3m the car still shakes like hell tho when its at the first line. Miguel613ekb18c is the car suppose to be on or just on the key on position? Thanks for the help

 

Yes key on(II)

 

By way have u checked for a vacuum leak?

 

yea I checked spraying carburator cleaner over the hoses and gasket.

 

The idle speed is controlled by three methods:

The cold idle value, which is located under the throttle plate. Late model engines may not have the cold idle valve. The valve consists of a air channel bypassing the throttle plate which is blocked once coolant heats up a wax element. When the engine is cold the cold idle valve will allow a lot of air to bypass the throttle plate, and the idle will be around 2000 rpm. As the coolant warms up the cold idle valve will slowly close, bringing the idle speed down.
The idle air control valve (IAC or EACV), which is located on the back of the intake manifold. The IAC valve is a solenoid which is controlled by the ECU using pulse width modulation. Thus the ECU can control how far the solenoid is open and how much air bypasses the throttle plate. There are limits, both upper and lower, to the amount of air which passes through the valve because the solenoid will only work from 20% to 80% duty cycle.
The throttle air bypass screw, which is located in the top of the throttle body. Unscrewing this will allow more air to bypass the throttle plate, and so will increase the idle speed. The purpose of the bypass screw is to adjust the amount of air going pass the throttle plate so that the IAC valve duty cycle is within the limits of what the ECU can control. The manual tells you how to adjust this screw by unplugging the IAC valve.

Looks like last resort it to replace iac valve

 

You can adjust the screw next to the throttle body plate. As long as your tps is within specs, it wont cause any problems or bring the CEL on.

 

Is there a test to check my IACV? I disconnected the connector that goes to the iacv and the rpms went up to about 1500 and I turned on my ac came down to about 1100 after a couple seconds dropped down but then went back up. Bad IACV?

 

you can ohm it out with a multimeter. should show 0.00 with a .05 variance. is the little screen on it dirty?

oh, my car was idling low because the FPR needed to be adjusted. good luck!

 

did you ever get it figured out?

 

I never figured it out...

 

Good news guys figured out my problem. I went out and bought some feeler gauges and I adjusted my valves and a couple intake valves and exhaust valves were really tight when the piston was at tdc. Now it idles like its suppose to.