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There is a big rubber seal that goes on top of the filter that seals it to the box cover. Sorry about the valve adjustment post, I should have read more closely.
Four cylinder engines are rough by their nature. That's why they use balance shafts on modern four cylinder engines of around 2 litres and larger. Our 3rd gen engines have no balance shafts. Also Honda thought it was a good idea to place the rear motor mount on the same subframe as the steering rack. DUH
 

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Discussion Starter #62
Dano, you are correct. My first post on the valve adjustments had wrong units; you might've read that one. The post after that corrects it.

If anybody has went to aftermarket intake and has one of those "big rubber seals" just collecting dust, please let me know.

Yes, I noticed our engines didn't have balance shafts, oh well.

Would IACV only resolve the "more-common" fluctuating idle?, where you have sinusoidal highs and lows? I'm 95% sure I have my vacuum lines correct.
 

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A fluctuating or hunting idle would indicate a LEAN idle mixture. Try screwing IN the idle mixture screw. Remember that once you open the throttle even just a bit, the idle mixture is no longer in play. I can make my lawn mower have that fluctuating idle. If your Prelude is a five speed a rough idle is of not much importance. If it's an automatic (like mine) it can drive you crazy at stoplights. Over the years I have learned to apply the brake with my left foot while feathering the gas pedal with my right. The light turns green, let off the brake and away you go. Hahaha
 

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Discussion Starter #65
So i buttoned the splash guard and wheels and hood back on and thought, "hell with it, let's just take it for a spin." Once warmed up, the engine runs smoothly (thank goodness.) It's been a long while driving an older Prelude.

Here are some more observations...

When I cold start it, it sputters at around 500-600rpm, it just won't go to 1500RPM cold idle speed, and I can't figure out why. So I will just give it some gas and and hover it at that 1500 for about 30seconds or so, and then let off the gas so the engine idles a bit more smoothly.

I have cleaned the ground strap by the thermostat, the ground strap on the valve cover, the ground strap on the intake manifold, cleaned the fast idle valve and tightened it down, and checked (again) the screen on the IACV opening.

I have checked the spark plugs, they are white, meaning car's running lean. But I have no problems running higher RPMS, the fuel delivery seems fine to me.

I have stared at the vacuum diagram under the hood a few times and my hoses are marked with "dots" to the corresponding outlets on the throttle body by the previous owner.

No CELs; the CEL only comes up if I decide to pull off the IACV (for curiosity reasons). The disconnected IACV will make the engine want to die. MAP sensor? O2 sensor destroyed by too much water (steam from previous blown head gasket)?

At this point I've thrown in the towel and will take it to a mechanic tomorrow, I sincerely hope it won't be a huge diagnosis. But here's a picture; once the idle is fixed I will put new tires and an exhaust on. It sounds ricey with the rusting muffler.

27547
 

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Just for haha's...what kind of plugs and wires do you have installed? And when were they installed? The fitv is what should be kicking your cold start idle up. The good news is it doesn't sound like you had the issue I had with the idle which was intake gaskets (high idle. Surging idle when warmed up). I had an iacv that seemed to be working perfectly fine but I changed it just to see in my 90 white lude before I sold it and the low idle problem I had at cold start went away. I guess sometimes the iacv can be faulty and not throw a code. Finding one is another problem on its own. Though I do have one installed on my parts car at the moment which ran fine when I parked it last summer.
 

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Discussion Starter #68 (Edited)
Plugs are NGKs that have....15 miles. Wires have about 10k miles, and were installed by the previous owner about a year ago.

I have been reading that the FIV shouldn't be tightened down all the way. Tightening it down all the way removes your high idle, as this link explains a bit of it:

Honda Tech Link 1

Notice that in this link, and towards the end, the poster mentions not screwing the threaded wax piece all the way down, as his idle was fine at this "level." The second-to-last picture shows the wax partially blocking the air passage.

Honda Tech Link 2

This poster also mentions that when he screws the FIV all the way, he can't blow any air in, and that when it's loosened it bit will air pass through.

My FIV is on tight. Will check tomorrow.
 

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Discussion Starter #69
....and loosen it I did. I took it back about 2.5 turns intiially. Tightened it up, started car and voila, the engine went up to about 1200RPM. I opened the cover again and loosened the wax just a bit more, and closed it up. The outside temps didn't drop too low last night, so it never hit 1500RPM. Turning on the headlights dropped my warm idle down, so I adjusted the idle control screw a little bit.

I will have to start the car a few more times in the cold to get more confidence, but this is very promising. I understand a lot of people have mentioned tightening down the wax until it bottoms out, but I don't exactly follow that thought process if "tight" prevents any car from going through.
Inputs / insights helpful here.
 

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Discussion Starter #70
I did another startup this afternoon, and it fires up at 1000 and climbs up to 1500 cold idle. My idle is that the valve is slightly dirty, I guess i could clean that up a bit more. Timing is 15degrees, and warm idle is 730ish, so I will up that number a bit more.

I did a 20mile drive; the exhaust drones, the shocks are blown, and the dry-rotted tires are on borrowed time. However, it accelerates linearly, no funny smells / sounds, A/C works, and idles fine. The mechanic who checked the timing for me said he hasn't seen one of these cars in ages.

I bought a Bosal OE replacement exhaust / muffler, and after installing that and the tires, it'll be time for some suspension work.
 

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Discussion Starter #73
Car starts right up, but does not have that "zing" right to cold idle 1500RPM, so I will take apart the FITV this weekend and clean it better. Hopefully that'll ameliorate it.

The old muffler just rices, I feel like I'm back in the 90s in my high school parking lot. I better PB blast the nuts / bolts in preparation. Will also be looking for some exhaust tips.

Azenis will be mounted on tomorrow, gonna be so meaty. The old Michelins are dry-rotted hard.

I had strongly considered buying KSport / Megan / D2 coilovers, but just didn't feel get a warm fuzzy from the mixed reviews. I ultimately bought some H&R Sport Springs and KYB Excel-G / Sachs OE shocks. I have driven with Eibach Pro Kit matched with KYB Excel-G OE shocks in the past, and they provided OE+ stiffness and about 1.5" drop. The H&R Sport Springs and the KYB / Sachs should be the same, with about 1.7" drop. It's crazy that all these companies have abandoned Prelude aftermarket support.
 

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I am running Eibach Pro + KYB Excel with poly bushing on lower and upper control arms. They are really good and, stiffness is way more than OE, and i am happy with it so far. Same as you I considered getting either Ksport or BC, but decided against it due to cost prohibited. May be one day I have good funding, I will get those coilovers.
 

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Discussion Starter #75
Unfortunately the vendor selling the springs informed me their inventory was not accurate, and therefore the springs were not in stock. Therefore I'll need to see who else might still have these laying around.
 

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Discussion Starter #76
Shocks are in, but any decent lowering spring setup has been long discontinued. Talk about abandonment. Spacemaster, do you have a picture of what your car looks like with your current suspension setup?

Tires are mounted, but the clearance between brake calipe to inner barrel of the wheel is just too small, and the wheel weights were grinding against the caliper itself. Fortunately the caliper is stronger than the wheel weights themselves. I'll have to ask the mechanic to see if he can clock the tire to reduce the number of weights.
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Next was to replace that old exhaust. Universal muffler, missing rubber hanger, welded-on tip, rusting probably from all the water that was coming from the failing head gasket.
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I bought a Bosal OE replacement unit. The welds aren't that great, but the dimensions are correct and it was a straightforward bolt-on affair.
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Installed and ready to go. I haven't had a chance to start it up, but I hope I can hear the actual engine now. Maybe free up another horsepower or two. I also bought some OEM muffler tips, that should make things look a lot better.
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The fast idle valve has also been given a thorough cleaning. I'll see if I am willing to take the FITV housing off (and deal with dripping coolant all over) and clean that as well. After that I hope it'll quickly go to high idle upon cold startup.
 
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