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Discussion Starter · #1 ·
Recently, I've come to notice that something weird has been going on with the idle on my 2000 Lude (15,000K miles).

I've noticed that after the car is warmed up, the idle has a tendency to dip down into the 500s before settling at its normal 750.

I'll be driving up to a stop (a light or sign or corner or whatever) with the engine under load, obviously, and, as is my driving style, I disengage the clutch and coast to the stop for like the last 20 feet or so, usually disengaging the clucth around 2,500 RPMs.

Normally, the revs roll off in a two-stage process, usually making a first stop around 1,000 RPMs, then settling down to 750 RPMs. However, lately the revs will roll down to 1,000 RPMs, but then roll all the way down to like 500 RPMs, causing a rough feeling idle, before going back up to 750, where the idle can still be slightly harsher, but very, very slightly. Once back at 750 RPMs, it stays there fine.

I've also noticed that the car only does this during the first 15-20 minutes of warming up.

So I went about checking some stuff last night. I checked and cleaned the Iceman's K&N filter in the front fender, and while it did have a couple of leaves stuck to it, nothing was that bad. Then I checked the idle air control vavle and, per the Helms manual, verified that it is indeed working right.

My next step is going to be to change out the plugs. I'm probably going to check the fast idle control and see what happens. Does anyone else have any suggestions? It's really starting to bug me.

Also, I haven't checked the Helms yet, but I assume there's a way to bleed air from the engine coolant system without changing the fluid correct? I was thinking that maybe the coolant lines have some air bubbles in them, which could cause an erratic idle, but I would think it'd be a constant problem if this were the case. I think the thermostat housing has a screw that allows bleeding, but I'm not sure.

Any suggestions would be greatly appreciated.

BTW I haven't thrown any codes or anything either. Also I noticed the car developed a rougher idle in the start of the winter when it started getting really cold (don't know if this matters, but I figured I'd mention it.)

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2000 5-speed Prelude
Nighthawk Black Pearl
Momo Alumsport shift knob
Iceman Competition Intake
Mugen cat-back exhaust
Mugen headers
AEM underdrive pulleys
 

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I had the same problem with my 99 starting at about 30000 miles. The check engine light eventually came on too. The dealer replaced the plugs, distrbuter, distributer cap and rotor. It was fine for about 1000 miles then the light came on again and the rough idle came back. I took it in and they had it for a few days and finally tracked the problem down to a defective coil. It's been about 5000 miles since the new coil and the car runs perfectly.
 

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Discussion Starter · #3 ·
I assume you're referring to a new ignition coil, right?

I'll check the coil out and see what happens. I sure hope that's the case, cuz it would take forever for me to go through the air intake and throttle body system, then the coolant, then the fuel, the the ignition and so on.

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2000 5-speed Prelude
Nighthawk Black Pearl
Momo Alumsport shift knob
Iceman Competition Intake
Mugen cat-back exhaust
Mugen headers
AEM underdrive pulleys
 

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I had some weird idleing, too, but my 'Lude only has 15000 miles. And my problem wasn't an erratic idle, just a slow, rough one.

There was a really bad vibration if the system was loaded (a/c fan, radio, headlights, radiator fan all on) and the idle appeared to be below 550, which the Helm's manual says is the baseline.

So I kicked it up a notch, adjusting the idle screw on top of the TB. I turned it counter-clockwise about 1/2 a turn. Everything's been smooth since.

(This was all before I got my AEM pulleys, and I'm due to clean my air filter, so I may be able to lower it a little after that.)
 

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<font face="Verdana, Arial" size="2">Originally posted by Pete:
I had some weird idleing, too, but my 'Lude only has 15000 miles. And my problem wasn't an erratic idle, just a slow, rough one.

There was a really bad vibration if the system was loaded (a/c fan, radio, headlights, radiator fan all on) and the idle appeared to be below 550, which the Helm's manual says is the baseline.

So I kicked it up a notch, adjusting the idle screw on top of the TB. I turned it counter-clockwise about 1/2 a turn. Everything's been smooth since.

(This was all before I got my AEM pulleys, and I'm due to clean my air filter, so I may be able to lower it a little after that.)

</font>
You guys realize that idle isn't supposed to be adjusted on our engines? I've seen a few people post that they've done this... I'd suspect something else is "wrong" and that this is just covering up the symptom, not fixing the problem. Just MHO.
 

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Discussion Starter · #6 ·
<font face="Verdana, Arial" size="2">Originally posted by marcucci:
You guys realize that idle isn't supposed to be adjusted on our engines? I've seen a few people post that they've done this... I'd suspect something else is "wrong" and that this is just covering up the symptom, not fixing the problem. Just MHO.</font>
I agree with you completely Marcucci. That's why for the last two days I've been going through the painstaking process by elimination method to narrow down the issue to some concrete areas.

Like I said, I've ruled out air cleaner and throttle body issues, with the exception of the fast idle control (I think that's what it's called), which I don't think is the problem. So I'm gonna check out the plugs and see what's up with their condition But hopefully Jallen1217's right. The ignition coil could definitely be a problem.

Any suggestions?



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2000 5-speed Prelude
Nighthawk Black Pearl
Momo Alumsport shift knob
Iceman Competition Intake
Mugen cat-back exhaust
Mugen headers
AEM underdrive pulleys
 

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<font face="Verdana, Arial" size="2">Originally posted by marcucci:
You guys realize that idle isn't supposed to be adjusted on our engines? I've seen a few people post that they've done this... I'd suspect something else is "wrong" and that this is just covering up the symptom, not fixing the problem. Just MHO.</font>
I agree that adjusting the idle could just be covering up the problem. But why isn't the idle supposed to be adjusted on our engines?



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1999 Prelude SH

http://www.hondaprelude.com/setups/setupsdsply.asp?id=3136
 
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