Hello Everyone, Im new the Prelude Scene But not the Automotive Repair Scene.
I Just Bought a 94 Vtec Prelude (139k) for 4k. Thing Runs Great, has alot of power.
BUT heres the problem:

First: There are NO engine Codes Thrown, So im lost

Some Times The Idle Will Drop Down From about 800, to about 550 or so and when this happens the Car Will Lug and shake a little(this is at idle). So i will give it a little gas To raise it back up and the car will hesitate kinda bog down then catch up and rev up. Even when the idle is at Normal(8-900) the car will bog if you give it a little rev, It Never acts up at high speeds or High RPM Mostly Right at idle to off-idle. It wont Do this when Cold only after Warmed up, I also Noticed if i turn on the blower/Power windows it will lug it down also, and if it already is lugging it will lug alittle more, But Never Stalls!!

The Car Idle's Smooth as Silk most of the time @ 800 or so, So I know the Engine has to be in good shape Plus it Runs So Strong(like when its cold) so it has to be a sensor or Something..

I have Changed the following parts So Far:

Plugs
Wires
Dizzy Cap/Rotor
Fuel Filter
Air Filter
PVC
Battery

I Need To Figure This Out Cause It is Very Annoying, Please Anyone that Can Give and Advise or Point Me in the Right Direction Because, I Next things i was thinking Would be 2 Try The Following:

o2 Sensor
Knock Sensor(so expenisve)
Coil
EGR Test?

Please Help, Im a N00b at this need your guys help!

Thanks, Brett

 

Sliver Lude Thanks 4 reply , i Will Check The IAC Next, cant it just be cleaned? or should i just Replace It? i will let you know what i find...

I Have Heard Of People Doing a Mod Where They remove the IAC Valve Internals or something, i want to keep it CARB friendly cause they really crack down on us here in California

Please any other Suggestions would be greatly Appreciated
Thanks Guys

 

Clean the IAC with brake cleaner or choke cleaner. The IAC valve will hunt if the idle screw has been backed out too far. Unplug the IAC, set the idle to between 500 and 600 RPM, plug it back in and clear your code. Idle should return to 750 and stabalize. The FITV can also cause this problem. It has a donut with a thimble in the middle that controls air bleed. Sometimes the dunut gets loose and can be screwed back down so that it seats properly. Brake parts cleaner will work as long as it is methylene chloride based like Gumout. Choke cleaner is methylene chloride based.

 

Thanks For the Reply Amckee, i Want to Check The IAC but My Chilton Manual Say Nothing of a IAC, it talks of a EACV (eletric air control valve) But no IAC.
Is that the same thing?

Also It Says Nothing of the FITV system Ethier so im tick'd off at this piece of crap chilton guide

Please if anyone can tell me Where my IAC and FITV Locations are

Cause Chiltons just not cuting it!! thanks guys

 

EACV might incorporate the IAC and FITV together in those models. They did so in the Accord starting in 96. Clean the EACV then. If tis is not the problem, you need to check for vacuum leaks preferably with a guage/pump.

 

Heres something Weird,

The Chiltons never Says/Describes the IAC , but after Searching through the Emissions Schematics Diagram, i have found it does show one but it's location is not specified, and shows it separate from the TB(like a hose in/hose out along with wire connections) So i Have to Have a IAC, but still lost on its location

I have looked around the compartment and Found The Coolant Temp/Intake air Temp and few other sensor locations But not the IAC or FITV...

Also i noticed it can be alittle rough on the START (as in turning the the engine on)
But Will Then Idle up to 1400 for a sec then idle down to about 800, and idle smooth and Normal, so maybe that can help out

What Does The FITV abbrev stand for?

Thanks 4 taking the time to help guys

 

EACV or IAC will be attached to the Throttle body or on the throttle body side of the plenum. It will have wires running to a small electric motor and will have small coolant lines attached. FITV is the fast idle valve. It raises idle when the engine is cold. I beleive they are combined on your car.

 

they are not combined, the fitv is on the bottom of the tb

Fast Idle Thermal Valve

the IACV is on the front of the intake manifold..

clean the IACV with brake clean and make sure there are no vacuum leaks

 

Okay guys im going to try to locate and clean the iac Next and also check 4 leaks, i will Keep you guys posted

P.S. im goin to have to get it smoged here very soon what would you guys suggest to ensure a good test(pass) i live in CALIFORNIA so its crunch time...(all Calif residents can Understand my pain, that im sure)




Modified by VoLCoM26 at 3:00 PM 10/24/2005

 

Okay Guys Check This Out,

I Pulled The IAC and it was dirty the screen was nasty gummed all that crap out.

Next Pulled the EGR, It Was alot of carbon Built up, So i clean alot of that crap off, it seemed to hold vacuum.

Next Pulled the Coil and tested it(compared to new one had same spec's (ohms))

So these things didnt look like they had ever been cleaned which makes me wonder if Are other things like this that need attention,....


So i took her for a spin, and she Ran alot smoother and the Idle seems to be Nice and Constant and no more low shake...

BUT<U></U>

Now i Seem TO Have a Miss Between 1500 and 3500 that depends on How Hard a give it gas, it will spit and sputter for a sec then catch-up and take off

My Tach has started acting up alittle to!! It will read 2000 higher than my rpms really are
And then Bounce Back to Normal, it only does this sometimes.

Does this mean My Ingiter is going south?
Or Should i Go Knock sensor/02/Intake temp sensor?

I have checked all connectors to distributor and they are good...

Im Getting lost on what else to do Please advise Guys i Need You!!!
Thanks