Please no use the search function replys I have used it and google literally millions of times I have done every suggestion on any thread I have ever read with no results to helping my issue. I tried to be as detailed as possible please someone help me out.

Car Info:
2000 Civic EX EJ8 D16Y8 5 speed manual completely stock motor

Not sure what real mileage on car is they were rollback according to Carfax in 2011 car was reported of having 145k miles. I bought the car in 2013 and odometer read 135k fast-forward a year now reads 147k so I have personally put 13k on it. I know the transmission is not original to the car due to the VIN plate on the trans does not match VIN on car.

I have no misfires on any cylinders the car accelerates fine normal power for a D16 no hesitation nothing out of normal.

Car idles low dipping all the time to 450-500 causing the car to shake and you can see it trys to shoot back up for a good 2 secs but just can't and stays low idle shaking the whole car.

For the life of me I cannot find the problem to my on going idle problem. As for most people when cold idle is completely fine no issues at all and as it gets to operating temp all hell breaks loose. Also to note the car seems to always run better at night time when the air is cooler. And there is no CEL on and yes CEL does work. What more could it be that I haven't already done?

Things I have already done:

-Cleaned IACV
-Clean Throttle body
-Checked Ignition Timing
-Checked "ALL" hoses for leaks (which to my knowledge wouldnt make sense anyways sense more air introduced to the engine would cause high idle/surging idle which I DO NOT HAVE)
-Changed Brake Booster and Brake Booster hose (idle goes really bananas when brakes are also depressed at idle based off testing thats what I concluded too but no help)
-Changed Spark Plugs
-Changed Wires
-Compression test done all cylinders were 165
-Seafoamed
-Changed PCV Valve and hose (the hoses was so worn it would collapse on itself (or pitching itself if you will) from the Vacuum.
-Adjusted Idle Screw(The right way right out of the Haynes, I only write this cause I just read so many threads of people doing it wrong and just want to clarify I did it to spec right out the Haynes)
-Throttle cable is fine
-Butterfly plate shuts properly and no gunk blocking it (cleaned it)
-Bleed Coolant
-Checked all nuts to make sure nothing was loose(Intake manifold nuts, throttle body, IACV, etc.)
-Clean Fuel Injectors (just your typical STP **** I know these things have there hits and miss but just throwing it out there cause I did try it)

Really from what I can think of the only thing I haven't done yet is:

-Test TPS sensor (don't have multimeter)
-Changed or test Primary o2 sensor (from what I read these things just can be clunky and a lot of times no CEL goes since they still are technically working but not as well as they should be)
-New Ecu

Anything else I'm missing and info is much appreciated the annoyance low idle and occasional stalls are just so frustrating.

 

Bump.

Really no answers?

 

Have you looked at your motor mounts?

 

Honestly didn't think of them as a factor when you say check them do you mean as in if they are lose? How would that contribute to a low idle?

 

Where is your idle usually at?

 

^^^

 

You said you checked timing, I assume you did with a timing light? did you check the mechanical timing of the engine at tdc?


Does the idle raise up and down as you put a load on the motor or the electrical system?

 

I checked with timing light correct. I have not checked mechanical timing a first time hearing so of it. I searched it up and found a thread that shows hows to do it with the Haynes. I will check it tomorrow would you mind explaining to me though how that works and why its important that the crank pulley and TDC line up/ how it would contribute with my low idle problem?Would much appreciate it I just like to know the knowledge behind it thanks for the suggestion and any others you have in mind if that isn't the case?

It will raise up but then it will try to settle but settles low for instance if I can remember correctly with A/C on idle should be 870 the car will shoot up to 870 right when I turn A/C on but then it will settle but drops/settles at i wanna say 750-800ish. Same with when I turn on headlights it will at first raise to what its suppose to idle at but then it will settle at a lower idle than what it should be idling at. Hope that makes sense

Edit: Is this what people mean when they are off by a tooth? I always thought they were talking about ignition timing (with timing light)

 

If your mechanical timing is off then it throws off the electrical timing


If the motor is advanced a degree it could be your problem.


If the idle is raising up and down then your iacv is working the way it should.


do you have a fitv? its under your throttle body if you have one.


Adjusting the air bleed stop screw on your throttle body has no affect on raising the idle?

 

I do not have a FITV.

And as far as the idle screw when I disconnect the connector adjust screw to spec and then plug it back in its idles awesome! But once I restart the car its like the car takes none of that new info anymore and the idle goes right back to ****.

 

Try removing the IACV plug and check the voltage on both female connections on the plug. They should be around 12V when the key is turned to the auxiliary position. It sounds like you have a wiring problem which is causing the IACV to drop voltage and therefore not open completely to idle at 750. If it doesn't read 12V on both of them with the neutral grounded to the frame, trace the wiring.

 

This could be very possible as well as the wiring harness itself looks like a hack job from previous owners. I had to personally solder the IAT wires as they were completely disconnected underneath a bunch of electrical tape.

I'll try to call a few buddies to see if they have a multimeter I can borrow or else I'll just buy a cheap one and test this, thanks for the suggestion!

 

Yeah it kinda sounded like it the way you described how when you loaded the electrical system it changed the idle. Definately check that out because if the IACV isn't working the car will idle so low that it's just on the edge of stalling. Multimeters are pretty cheap and if you plan on doing a bit of work to your car I would definately recommend it, even cheap ones still do the job. Let me know if that was the problem tho

 

Quick question while I have you hear I noticed that when I disconnect the IACV connector the idle does not change but when I did the adjustments and plug the connector back in the idle changes thoughts on this?

 

Yeah before you plug in the IAC again shut down the car, it messes with the ecu and it wants to open the idle up because it thinks there is not enough air flow to the engine while idling, so it will typically makes the idle bounce about a 3-400rpm bounce from where it normally idles. It's kinda weird that way but that just means that your iac is working which is a good thing because they're 400$ new!! The IAC is connected to the ecu which will supply a certain voltage to the IAC if that voltage from the harness is insufficient it will idle lower than it should such as in your case.

 

Okay thats what I figured and I usually do turn the car off and then plug it in as the Haynes says but one day I was experimenting with that cause from what I read the idle should drop significantly once the connector is pulled by mine doesn't change at all. And if its lower voltage does that just mean the smaller the valve opens? And the higher the voltage the more the valve opens?

 

Not the valves on the engine, the iac is a bypass valve which lets air bypass the throttle body so that the engine will idle and still have enough air to supply the engine with the throttle closed. So if you have low voltage getting to the iac the valve inside the iac will not open as far so there will not be as much air making it past the throttle body so the engine will idle with a lower rpm.

 

Sorry I totally misread that you are right

 

Hahaha no worries man it was a good laugh anyways thanks for confirming that, just like make sure my facts are all right so I myself don't go spreading wrong information to someone else

 

No problem man If you have any more questions feel free to ask 👍 let me know if that helped too 😊

 

I will do for sure! Thanks again for the suggestions nice to have some lead as to what to check instead of just throwing parts at it

 

Before concluding anything, I suggest you try this first (if you haven't):





What's stated there is obviously the factory setting (450±50 RPM). If you have extra loads during your daily drive that aren't stock, disregard that base setting. You have to do it the reverse way. During step 10, make sure the idle speed is 860 RPM (max of 810±50). It doesn't matter if its more than 450±50 RPM when the IACV is disconnected (step 5).

My idle issues were resolved by doing this. Make sure that during step 8-10, you introduce all possible loads like full fan speed, radiator fan, condenser fan, AC, headlights, rear defogger, fog lights, accessories, aftermarket gauge lights, aftermarket stereo, aftermarket speakers in full volume, etc...

If it's low, that means 450±50 RPM base speed is not enough. By "low", that means whatever RPM is still causing vibration during full load condition at idle.

But what if the vibration only goes away on an RPM considered too high for idling? Your issue could be caused by several factors. Bad engine mount is likely one. 450-500 RPM does not make a car vibrate (mine does not during step 5). So that means getting new mounts and adjusting the idle speed may fix a combination of issues you are getting, which is vibration and low idle speed.

 

This is wrong

12v on one side the other is the signal ground from the ecu

The iacv is a stepper motor works off pwm.

 

Both sides should read approximately 12, read the Hanes it tells you how to check it.

 

Im pretty sure it means to probe both terminals with a meter.

That would show 12v