d14a4 idle problem

[Ej9Is]

hi.
i have civic 98 ej9 d14a4 M/T with idle problem.
4 months ago i do IM swap to y8 and all was good, 1 months ago i start the car and the idle started acting weird.

the problem:
1) cold start 2000-2200 and drop to 1500
2) when the car is warm the idle is 900-1000
3) when i hit the gas and leaves the RPM drop to 900 up to 1200 and back to 900-1000 and sometime drop to 750 and back to 900-1000
4) when i turn the headlight/ac/open or close the windows/radiator fan come on, the RPM is up and humming sound coming from the starter area.......
5) when i fully close the idle screw the humming sound start too

things i've done:
1) remove and clean the TB and the IAC very good!
2) new oem TB and IAC gasket
3) TPS calibration 0.45v - 4.5v
4) check all vacuum line and all was ok
5) check one more IAC
6) new oem distributor rotor and cap
7) check the IAC function with battery, full open is ok but when i make him full close its seams its close to mutch and leave 10% open.
8) bleed air from the cooling system

all that not fix my problem...

Things I noticed today:
some little pops come from the exhaus and little psssss sound come from back of the IM (cylinder 1 area).
when i do the swap i cleane the old gasket very good and install new one but no oem.
gasket can be destroyed after 3 month?

what more i can do or need to check?

[saxophonias]

A similar problem with my d14a4 for the last months. After I accelerate full throttle for some time I notice that after that the car idles to 1000rpms and you have to wait for 1 minute or so to reach the normal 740rpm idle. If i overdo it reaching top speeds and accelerate again for some time when it comes to idle the idle is erratic and jumpy. 1300-1000-1300. I have cleaned everything but the problem insists. When i drive in low rpms and relaxed there is no problem at all.
Also the consumption has increased to 8.5 lt/100 which is too much considering the driving style. I estimate that it has to increased to 1.5-2lt more.
I am suspecting the following
RACV (rotary idle control valve)
Dizzy
tps
map
injectors (never cleaned)
The engine has 315.000km by now

[Acc3l3ratoR]

A similar problem with my d14a4 for the last months. After I accelerate full throttle for some time I notice that after that the car idles to 1000rpms and you have to wait for 1 minute or so to reach the normal 740rpm idle. If i overdo it reaching top speeds and accelerate again for some time when it comes to idle the idle is erratic and jumpy. 1300-1000-1300. I have cleaned everything but the problem insists. When i drive in low rpms and relaxed there is no problem at all.
Also the consumption has increased to 8.5 lt/100 which is too much considering the driving style. I estimate that it has to increased to 1.5-2lt more.
I am suspecting the following
RACV (rotary idle control valve)
Dizzy
tps
map
injectors (never cleaned)
The engine has 315.000km by now

I have almost the same problem as you ...bat the engine is a d15b 3 stage vtec...

[saxophonias]

I am still trying to figure out what is wrong. For the last 2 weeks it works ok. The difference is that I am using for this period of time 98ron gas and the weather is not so cold.
I should say that I have cleaned the TB and the racv twice. It worked better for some time but the problem wasn't eliminated.

[saxophonias]

I replaced the IACV with a new from ebay and it works ok. In the meanwhile I also replaced the dizzy with a new one (not oem).

[Dodo Bizar]

Good to hear it helped Polivias, was it the RACV type still?

[saxophonias]

Yes! RACV! We don't have IACV in d14s.
Still there must be some minor, yet irratiting, issues that i haven't figure out yet. I have replaced the RACV, the dizzy, the maf sensor, the O2 sensor. I have the stock fuel pump, stock ignition cables and stock injectors. What it does? I can feel a sudden loss in power when I am in 4000rpms with 4rth or 5th gear. In full throttle there is no problem. I cleaned the TB and i think it doesn't hesitate anymore in 4000rpms but in 2000-2500 rpms. Not always though and not so noticeable. I can realise it when I am 3rd gear in 2000 rpms and there is uphill. Any guess? The engine has 350K
Should I replace the injectors and the fuel pump?

[Dodo Bizar]

I am a bit at a loss for this power loss you experience. Though I have had similar issues in the past, especially with the B16B and a D16Y7 turbo I'd driven. I remember it felt like the complete O2 partial throttle feedback loop was at error. Whether it was mapping too far of (which is a thing for your untuned ECU perhaps... which you answered by the RACV being still there ) or actual sensor/cable failure I am trying to recollect... all I know these problems are long gone in all my cars for now. Actually the feeling my car gave was if on a straight level road and not moving my gas pedal feet at all, the car would be oscillating in surge with a period of like second(s). But much more annoying and noticeably than the normal correctly functioning lambda feedback loop (which I usually cannot sense, only see in datalogs). Trying to recollect, if it pops up again I'll post it here.

[saxophonias]

Some small update! I ordered some ignition cables as the oem ones were there for too long. As the mechanic was replacing them I saw that one of them was cracked. So i thought to my self " We found the culrprit" Sadly the aftermket ones didn't fit well and i could hear some inteference in the radio as well. So I got them back and installed another oem set I had, but I am afraid they are as old as my own, not broken though. So it runs better but not perfect. Could it be the worn ignition cables? I will try to find how expensive the oem ones are and maybe I will order them. Any suggestions for other ignition cables?

[Dodo Bizar]

Yeah very likely the culprit found. Got myself an aftermarket brand which runs perfect. Forgot the brand though... but from akr-performance I believe.