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Discussion Starter #1
I've had my car for nearly 3 years now and this has been happening ever since I had the car. I'll be coming up to a stop, and when I push the clutch in and put it in neutral, the revs will drop below idle for a couple seconds and come back to normal. Only recently it's started to sometimes die on me. It only happens when the car is still warming up. The temp needle will get to normal level, and then idle weird, and then go away after a while. When it does die, it fires back up like normal, but the revs will drop back down and idle weird, then return to normal idle.

I'm thinking there's a vacuum leak somewhere, or possibly that I haven't changed the air filter in almost 3 years, but I'm wondering if there's anything else it could be.

Also, don't know if this matters, but when the funky idle goes away, my car always seemed to idle around 450-500rpm. I don't know if that's low or not, but maybe my idle is just set too low? I've never messed with the idle.
 

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Discussion Starter #3
I was thinking about doing that... Is that a common issue to cause the weird idle issue I'm having?
 

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Discussion Starter #5
Valve lash is already adjusted, I did it a couple weeks ago when I changed my belts. I'll clean out the IACV tomorrow. Is there anything else that could be a possible cause besides the IACV?
 

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Discussion Starter #7
I took the intake off when I did my clutch a couple nights ago, and the throttle body looked okay, but I'll take a closer look at it.
 

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Discussion Starter #8
So I took off my IACV to find that I have the filthiest IACV in California, the world, and the Universe. Lol gonna put it back on and see how it goes
 

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Discussion Starter #9
 

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Lol I've had worse. Another thought could be injectors. I'm having this issue too and it seems like she isn't getting fuel.

Do you surge at all?
 

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Discussion Starter #11
After cleaning my IACV, the car doesn't seem to drop idle as much, but it still drops idle sometimes in the same conditions as described in my first post.

The car doesn't have a surging idle at all, and never has since I've owned it. I mean, while it's still warming up, it'll drop idle a bit… then come back up. Almost as if the ECU is like testing to see if it's warm enough to idle lower lol. But it's always kinda done that ever since I had the car.
 

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Discussion Starter #12 (Edited)
My car still has the weird idle dropping. Did it to me today in traffic on the freeway. What else could be causing this? Could I possibly be looking at a vacuum leak?
 

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Well lets see. For the guys that might tell you to check the FITV, well your car doesnt have one.

As far as cleaning the IACV, it can only be cleaned for a bit (a day or a year, but it wont work forever). The plunger inside the IACV has a seal that is worn out due to dirt being introduced into the bore. That screen only stops BIG items from jumping into the intake manifold.

I would look at the TPS and MAP sensors for correct voltages at idle/etc. The older obd2 systems (pre-COP systems) are a bit too open for values on sensors. I would also check the o-ring for the MAP sensor. A little tiny nick can cause HUGE problems.

Sooo, here is what I would do:

-Quick check voltage output from the alternator (A/C output = bad diode bridge, low voltage output when going from high load to low load)
-Get a new o-ring for the MAP sensor
-Get a new IACV
-R/R IACV and bleed coolant, doing a quick HG check for possible seepy HG (can cause low speed idle issues)
-Get a hand vac pump and test the MAP sensor, change o-ring after test obviously
-Get a graphing multimeter and graph the TPS

From there, I would then check for fuel pressure, spark issues and mechanical connection issues (soft set or worn connectors).
 

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Compression?
Ignition Timing?
Engine Timing?
Air filter clean
IAC and FITV Clean.
Vacuum leaks tested with smoke machine?


Base Idle and FITV adjusted properly?
TPS adjusted properly?
Valve adjustment?

Cars dont fix and adjust themselves. Pre 2001 there's a lot of adjustments. that are part of regular routine maintenance.
 

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Discussion Starter #16
I would look at the TPS and MAP sensors for correct voltages at idle/etc. The older obd2 systems (pre-COP systems) are a bit too open for values on sensors. I would also check the o-ring for the MAP sensor. A little tiny nick can cause HUGE problems.

Sooo, here is what I would do:

-Quick check voltage output from the alternator (A/C output = bad diode bridge, low voltage output when going from high load to low load)
-Get a new o-ring for the MAP sensor
-Get a new IACV
-R/R IACV and bleed coolant, doing a quick HG check for possible seepy HG (can cause low speed idle issues)
-Get a hand vac pump and test the MAP sensor, change o-ring after test obviously
-Get a graphing multimeter and graph the TPS

From there, I would then check for fuel pressure, spark issues and mechanical connection issues (soft set or worn connectors).
It's funny that you mention checking the alternator voltage because I've been having this thing where my cluster backlights will flicker from dim and bright… Did I mention I've replaced my belts recently?? lol I've already retightened them all, except the timing belt. Haven't had enough time to take the covers off to get to it. But I'll check out the voltages, MAP o-ring, and bleed the coolant first, since those are easy for me to do.

Have you change your plugs?
I had dipping and lean idle with ac on. Turn out to be bad plugs. Now it idles smooth.
I don't really use A/C that much, only when it's like the middle of the day and I'm driving on the highway. Usually I'll just open the windows. But my plugs have been looking white lately… the electrodes looked okay, but it sort of bothered me that they were white. They don't even have 15,000 miles on them… then again, I have done 4 track days with them. Might be a good idea to change them anyways.

Compression?
Ignition Timing?
Engine Timing?
Air filter clean
IAC and FITV Clean.
Vacuum leaks tested with smoke machine?


Base Idle and FITV adjusted properly?
TPS adjusted properly?
Valve adjustment?

Cars dont fix and adjust themselves. Pre 2001 there's a lot of adjustments. that are part of regular routine maintenance.
From what I've been told and researched, my D16Y8 doesn't have a FITV, but the IACV has been cleaned. I admit, my air filter has never been changed since I've owned the car, so I might replace that with the spark plugs. I did a compression test 2 years ago and all was well, but wouldn't hurt to do another. I've honestly never touched the distributor or any ignition components (except changing the plugs like a couple years ago) since I've owned the car, but this idle issue has been going on since I've owned the car. Might be worth looking into. Valve adjustment is good, I did another one before heading to Willow Springs on June 28th. Engine timing was spot on when I did the timing belt. I haven't checked for vacuum leaks yet, I was thinking about doing that though.

So it seems my list is:
-new spark plugs
-new air filter
-check alternator output voltage
-check TPS and MAP voltages
-check o-ring on MAP (maybe replace?)
-check for vacuum leaks
-bleed coolant
-compression test
-check ignition timing
-tighten timing belt

I'll do all of these and get back to you guys with an update. Thanks for all the advice!
 

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well, I'd do all new cap, rotor, plugs, wires all at the same time with ngk and or OEM>

vacuum leaks on honda's do weird shit. Great place to start.

with a good scan tool with iac data can't really find leaks to easy. smoke is the best. water or carb clean works if it's bad.
 

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Discussion Starter #18
I'll add that to the list. Better safe than sorry, right?
 

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too, something like vacuum leaks, ignition timing, etc. all should be checked before throwing a tune-up and or filters. You can spend a lot of money not fixing the problem.

I've had idle issues. At one point I took my whole manifold off, cleaned it really good and replaced all seals and gaskets, thermal intake gasket, and the idle was great.

The thing is there's a few adjustments too. Get a FSM online and you can go throw all the proper adjustments.
 

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Discussion Starter #20
I have the service manual, I'll go through it when I do all the adjustments
 
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