I have a very complex problem and it has several symptoms which lead me to think there might be more than just one problem. I will try to be as clear as possible…
First off, I have a 1999 Honda Accord V6 3.0 VTEC, 2 doors automatic, and as far as I can tell nothing has been modified, everything it stock.
One symptom of the problem is if I step on the gas and it revs up to 5k RPM (I can tell the VTEC kicks in fine) but after I slow down the RPM will fluctuate from 900 to 1200 while the car is on idle.
Well, that was one, the other is, 90% of the time when I get off work for lunch (at around 1pm and I get to work at 8am) I will put the car on D (drive) and it will not respond for a second or two, and when it finally the car gets on gear it will get on gear hard, I mean, the car will literally give a small jump forward.
Yesterday, I decided to clean the engine, so I started to spray degreaser like I always do (is not my first time washing engines, I have done it several times without a problem) and finished up with pressure water, and when I started the car this morning it started to rev up, oscillating from 900 to 1200 RPM while on idle and while driving the car was more accelerated than normal, I could actually feel the breaks working harder when I tried to stop.
That sums up what’s happening to my car, I’m open for suggestions for probable causes.
Thanks.

 

Idle air control valve (IACV) can become dirty/grimy and not control idle speed well. Remove throttle body to access/clean IACV, throttle plate, and throttle body.

Too high idle will cause abrupt trans shifts into drive.

Worn/damaged motor mounts can cause lots of engine movement feedback through gas pedal during shifts and make things feel worse. Check motor mounts for damage.

good luck

 

Thanks for the feedback TexasHonda, I will clean the IACV, and the throttle plate and throttle body. I will post results after testing.

 

Ok, I manage to figure out where the IACV is, I removed it and clean it. when I put everything back together it became worse, now instead of just fluctuate RPM while idle it also fluctuates while on gear. I had my hand break and break peddle and put the car on "R" reverse and I could feel the car try to go revers hard and then soft, then hard and so on.

another thing, what I think is the IACV, seems to be a magnetic field control, if you see the image, I only removed and clean the black part.

If you wonder what is it that I clean, I cleaned the hole where the magnet goes and I also clean the 3 terminals to ensure a good connection.

lastly, I looked at the motor mounts and they seem fine, the black plastic seems solid with no cracks or signs to be worn off.

I'm about to go and buy the IACV and replace it, but I would like feed back.

I appreciate any help.

 

You removed the throttle positioning sensor (TPS). This provides ECM w/ throttle plate angle.

Suggest purchasing a shop manual for your car from automanualsource.com.

IACV is on bottom of throttle body and not accessible w/o removing throttle body.

You probably have TPS disengaged from throttle plate and ECM is getting false info.

good luck

 

Ok, after removing some hoses I ended up like this...



I removed the throttle body



Where the Throttle body mounts I found oil inside I guess that is not a good sign...



lastly I found the O-Ring or gasket damage where the throttle positioning sensor mounts, then again, I guess that is not a good sign.



I will continue to clean throttle plate and by that I guess this is it...

 

Oily intake manifold and throttle body suggests perhaps lots of blowby being pulled into air intake duct through PCV air intake.

Flow into PCV air intake is reverse flow and will only happen when engine vacuum is very low and blowby pressure high. This can happen due to non-functioniong (blocked PCV valve or hose) and/or worn engine w/ excess blowby. Some oil in intake is normal, but yours appears excessive.

You should be able to fabricate a replacement gasket for TPS from raw gasket material if you can't purchase one.

good luck

 

Well I clean everything I could and the oil in the intake manifold wasn't as bad as the picture may led you to think, it was a very thin layer of oil on the metal, but the flash made it look like a puddle of oil.




The IAC Valve was in very bad shape as suggested by TexasHonda...





I clean the IAC Valve, throttle plate and everything else...







I also check for plug hoses and they all seem fine.

After all this, the problem persist, I posted couple of videos on youtube, I hope they better explain the problem.


I thing I have to say is that after driving a few miles, the problem will go away, and it will only came back if I accelerate fast over 5000 RPM. Note: if I accelerate slowly the problem will not present itself. since I don't drive fast and I hardly every accelerate fast, this doesn't really bother me, but it bothers me knowing there is a problem.

on the other hand, I still have the problem of not going into gear after a cold start, this problem doesn't always happen either, it is only if I set it to D on a cold start, and again, it doesn't always happens (weird)

I just saw a video on youtube of a guy with a similar problem on a 1999 Civic, he change the ECU and problem fixed!, I started to wonder if it could be the same on my case, btw, do keyless door locks operate with the ECU or its a separate system? because my passenger door doesn't open.

 

The 2nd video has a sound like an intake air leak. An intake air leak is a frequent source of idle instability.

Good side, IACV is working. Idle control uses IACV to try to produce a stable idle. An air leak makes this impossible and results in "hunting" hi/lo idle you have experienced.

Is check engine light on? If yes, what codes are presented?

Good luck

 

No check engine light comes on, and last time I check for codes it gave me one for VTEC, I can't remember what the problem was but I had it fixed at a Honda shop, that was probably 4 months ago.
I just took the car for a spin and while driving I had no problems except for the car was too accelerated, I mean it wanted to keep moving forward and at stop lights the RPM indicated 1100 RPM. When I got back home and I put it on Park it RPM started to oscillate again just like on the video.

Where would I check for intake air leak??