RPM fluctuate if you try to hold it steady

[wwli]

Hello peeps,

Car has been resting for a few months but it's about time to bring it back. Before it's back on the road, I had this odd RPM fluctuation problem which I wasn't able to debug. The engine is a fully built Boosted B18c1.

Basically if you turn on the car, the car idles fine no problems what so ever for it sits at 1k(its set on the ecu to idle at 1k). With the car in neutral, and you press the gas to say hold the RPM at 2k/3k or any RPM the RPM would go up and down. I know this does this if the IAC/FITV is bad at idle but while the RPM is up and trying to hold it steady? t

The fluctuation is around 500rpm for it goes up and down pretty steady and you can feel it slightly when driving in gear.

Thinks checked/tested:
Injector seals, checked and changed
Intake manifold for cracks - crack free(mani is new)
Changed Manifold gasket twice
EACV/IAC/FITV - checked, swap for testing and same
ESS - plug was changed (old one was corroded but sensor is good)
compression is 185-190psi on all 4

nothing is registering on the S300 for there are no errors what so ever

The TPS and MAP are 2 items that I had not tried but before I continue to troubleshoot in the wrong direction it is best to ask for help.

[big mac]

I don't think the map sensor would cause it to fluctuate. When I had the problem I got a new iacv and adjusted the fast idle valve on throttle body and cleaned the throttle body and was good to go

[wwli]

Just to clarify, before you changed your IACV you had the same issue where the RPM would just fluctuate if you try to hold the RPM steady?

I actually yanked the TB out and cleaned that baby like it was infected but this is worth taking a 2nd look.

Then again it could be another bad IACV of cause but anything is possible.

anyone else?

[EmminoDaGreat]

Check coolant level?

[wwli]

Coolant level is good for I bleed the coolant after doing a coolant flush but since I just changed the Rad, I will re-bleed but coolant is not the problem.

[gsrteg]

Just to clarify, before you changed your IACV you had the same issue where the RPM would just fluctuate if you try to hold the RPM steady?

I actually yanked the TB out and cleaned that baby like it was infected but this is worth taking a 2nd look.

Then again it could be another bad IACV of cause but anything is possible.

anyone else?

Any check engine light codes? You say you running an S300 chip, but I'm not sure how that affects the stock data. But from your symptoms it sounds like a bad Intake Air Control Valve (IACV). My accord was idling rough and fluctuating awhile back. I cleaned the throttle body and the IACV with some throttle body cleaner and a toothbrush, wire brush & q-tip. Afterwards, I installed a new OEM Honda throttle body gasket, and torqued everything back in. I reset the ECU, and made sure the coolant was bled properly. I cycled the engine to run for a few minutes, and test ran it. The car drove fine ever since. Try tapping on your IACV if anything.

Let us know if you get it fixed! Lets get if resolved.