Hi again,

Okay over the past few days I have got my prelude running and drives well, but ran into a few problems which still needs to be fixed, hopefully i can do myself and not have to take it to a mechanic. Problems listed below;

* Check Engine Light is always on when car is running.
* Idle seems to go up and down between 700rpm - 1,200rpm in park and neutral only
* Idle is fine when in drive or reverse

When i took it for a good test drive last night, i noticed the lights on dashboard and headlights etc started to dim as if battery was going flat..the speedo started going nuts and same with the rpm just went to 0 and started going up and down. and then the power in the throttle started to drop, and then a light started flashing S4 on the dashboard, then i turned off the engine and i couldnt start it again.

Had to get a jump start from a passerby, and got it started again but power and lights were dimming again, made it home and changed the batteries over to a freshly charged battery, went for another drive and the S4 light was gone and car was driving normal. (except for the CEL was still on, and idle was still surging between 700rpm - 1200rpm.)

A mate told me i have to go to a honda mechanic to have them check the computer chip to see whats wrong. Is there any remedy i can do myself, anyone had this problem before and know how to fix it???

Any help would be great,

Thanks,

Ren

 

IACV is sticking - search the forum for Idle problems. There is one called something like "End of all Idle Questions." It is very thorough.

 

Yeah I'm pretty sure I came across a thread on here about fixing idle problems..but what the hell does IACV mean? And what exactly is it?

Cheers,
ren

 

IACV - Intake air control valve. It is on the front of the intake, just behind the injectors. It is held onto the manifold with three bolts and looks kind of round, like a cylinder.

The computer sends a very quickly pulsed signal (PWM = pulsed wave modulation) and inside, there is an electromagnetic valve. The pulses cause the valve to "chatter". The more pulse, the more air it lets through and the idle speed increases.

If you take this off, there are several screens or filters and passage ways that can be cleaned. If the valve is sticking, it will cause the idle speed to hunt.

But...

700-1200 RPM is a sure sign of a problem with the COLD AIR VALVE. This is on the bottom passenger side of the intake throttle plate, right where the plastic intake tube from the air filter attaches to the manifold. This guy does much the same thing as the IACV, except in a different way. Inside is a "plug" made of temperature sensitive wax. When the engine is cold, air passes around the plug and lets more air into the engine..... thus, increasing the idle speed. When the engine starts to warm, hot water is circulated around the valve with some 3/8 inch or so hot water lines. Wax expands and idle speed drops.

When the engine temperature sensor indicates that the engine is warm enough, the computer will start using the IACV to control the idle speed more closely.

Problem: Again, remove the CAV and check screens and passage ways. There is a screw that holds the wax plug in place - 90% of the time, idle problems are because either this is loose or the IACV is sticking.

Put it all back together and set the idle speed. Do a search for idle set procedure. The key is that you adjust the idle speed with a bleed air screw (top of intake, above the CAV) and NOT with the throttle cable. There should be a tiny bit of slack on the throttle cable or the computer will not know to control the idle speed. The throttle position sensor (TPS) MUST register fully closed for the IACV to start working.

Sorry for being wordy, hope this helps a bit. FYI: you can also search on the internet for a copy of the shop manual. There is a nice one out there for 92-96 (4th Gen). Even if you have a different model, this manual will be better than nothing and much of the wiring and procedures are very similar across a large variety of Honda engines and cars.

 

i would start by pulling the cel to see what it is, and go from there.

but yeah i agree, prob either IACV or FITV.

might be having alternator probs as well...

 

hey man, your alternator, or ground contacts are bad..., start your car up, then pull the battery cable off..., if it dies, bad alternator, if not, check all ground connections...

one coming from valve cover, one behind the intake manifold, one at distributor, of course the one at the battery location... these are important..

once the battery thing is delt with, shut car off, pull battery cable for 30 sec to reset computer..., start car.., I'm sure you will get a cel..., once car is running for a few minutes, shut it off..., don't pull battery cable, grab a paper clip or some jumper, and find the yellow rubber plug in the upper left hand corner of the engine compartment..., jumper that little two wire plug with whatever works, then go and turn your key to the on position.., two clicks I think.., your cel will come on for a couple seconds, then it will go off.., then it starts flashing codes..., I'm sure you know the details of how to read the codes.., 3 short is three.., 3 long is 30.., there might be multiple codes..., once the codes are delt with, finding the root of the problem is quick... you might already know all this stuff, so no disrespect intended from my school book procedure...lol and don't forget to pull the jumper, and either pull battery cable again, or pull the radio fuse under the hood for 30 seconds..

and the other problem could be the iacv..., but from my 3g prelude experience, I would say the fast idle valve..., and sounds like your idle screw is damn near all the way out.. you don't even need the fast idle valve.., the iacv can compensate when warming up your car.. when I had my b20a, I unhooked water lines, and put a piece of cardboard to block it off..., and I sure as hell don't have it hooked up on my H22

the reason for your engine surge, (in my opinion) is the idle is too high, and the computer uses the iacv to reduce the amount of intake.., (which causes the rpm to go low..., then rpm's shoot up because the screw is still turned too high...., too high for the iacv to compensate..., thus hi low revs