rickshadey

I have a 94 Honda Civic, manual transmission. Basic model that doesn't have a tachometer. I am not a mechanic and have no fancy computer or specialty tools.

Car starts fine. RPM sounds a little high on warmup, but I'm not sure. No Tachometer in the car. After warmup, I get a large repetitious idle seek. Lets call it Vrrrrrum, Vrrrrrm, Vrrrrrm for now.

I removed IACV and cleaned out. Wasn't really dirty.
I also had good continuity between the leads and 11 Ohms resistance. I applied a 12 volt power source and I heard the click.
Re-installed IACV.

Same symptoms.

I then removed FITV. The plunger wasn't snug so I had hope. Took it apart and cleaned it. Wasn't all that dirty though. Reassembled and snugged up the plunger.

Same symptoms.

I start the engine again and after warm up, remove the power to IACV. It now drops to a low slightly fluctuating idle. Vrrm, Vrrm, Vrrm. Sounds better but still not steady. Check engine light comes on. I plug IACV back in and nothing changes. I turn off the car and restart. Check engine light is off and car goes back original symptoms.

I've now removed air intake off throttle body. Intake manifold is closed, no obstructions.
I cover the bottom hole (inside intake) with my finger (It is sucking serious air). The engine goes to smooth idle. Possibly a little high to my untrained ear.
If I cover both holes, the engine still runs smooth and drops to what I consider a perfect idle.

Having read A LOT of other posts, I'm now leaning towards a vaccum leak because (from what I've read) the bottom hole isn't supposed to suck much air and covering both holes is supposed to stall the car. No?

I'm closing in on this thing...

Update...

SO I 'bled" my coolant. Started engine with radiator cap off and let run for a few minutes. Placed the cap back on. I still have the air intake disconnected so the intake is exposed. I then put my finger on the bottom hole and NOW I'm getting a solid idle with no fluctuations.
Before I go disassembling the throttle body and cleaning, I'm leaning to a bad IACV again. Grrrr....

Final Update!!! I found it!
The intake gasket is blown. PhilStubbs' quick reply's is what led me to find it!

Lizardslap

take your throttle body off and clean it real good and passages and buy a new gasket there like 1.20$

and if you end up at advanced discount the gasket is under fuel injection not gaskets section

PhilStubbs

On a stock car I have only seen 2 things cause a fluctuating idle in over 10 years of repair and performance work. Intake leak(I put that first cause its the most likely) and coolant lines removed from the fast idle valve. Nothing wrong with removing them, but either the whole thing needs to be removed and a plate in its place or pull it, make a gasket with only bolt holes in it and put it back on.

Edit: just want to add. The IACV works like a fuel injector. It opens 100%, then closes 100%. Incoming airflow is adjusted by how long the valve is open each time it opens. It can't sorta work and it doesn't partially open when it's working properly. If idle fluctuates that means its working and trying to compensate for something else. Cleaning them is a waste. It either works or it doesn't.

rickshadey

I really want it to be that but have no idea how to go about it. I'll read up in the forms now, but since you just responded, I'll ask you.
Know of a thread that shows how?

PhilStubbs

I usually just spray flammable brake cleaner or carb cleaner on the intake while its idling. The idle will stabilize when it sucks the brake cleaner in the leak. Just pinpoint your spray so you know what you are hitting that makes the difference.

rickshadey

Thats the black cover sitting right over my pistons right?
On the back right corner. Sprayed there and heard it. The idle goes down for a second.
Am I looking at a huge job or is this easy fix?
Researching now.
Thanks for your quick response.
Update:
Is my nomenclature correct? Is it the head gasket? Not deep down in the engine. Just the cover on top?

PhilStubbs

Spray it on the intake manifold. The silverish aluminum part that attaches to the cylinder head and has the black intake tube. I don't mean this in a negative way, but I wasn't expecting to "dumb" it down that much.

Try each fuel injector specifically and right where the intake manifold bolts to the head. Next try vac hoses and then the throttle body.

rickshadey

I use Vrrrrrm and Vrrm to describe my problems man!
What your doing is great. It's not the head gasket.
Its the valve cover! Back right hand side. When I spray around it I hear the engine drop and hear suction coming from there.
Probably it right? I've never heard mention of the valve gasket as a possible source for a vacuum leak though.

PhilStubbs

No, it can't be the problem. Sounds like either the intake gasket or lower injector seals.

And yea, I should have caught the vrrrm. Lol

rickshadey

OK Phil,
I looked online for where the intake gasket and lower injection seals were.
Upon further inspection and more accurate spraying of carb cleaner I can actually see that the intake gasket is shot!
Thanks for all the help!
Now to learn how to replace...
Any suggestions before I start?

PhilStubbs

It's simple. Remove the bracket under the intake attaching the intake to the block. Then remove the 7 nuts holding the intake to the head, push it back, clean up the 2 gasket surfaces and install the new one

rickshadey

All joking aside, found this helpful video from "eric the car guy" that shows how its done:

http://blip.tv/ericthecarguy/p0301-1...carguy-6431360

Its a 98 civic, so it may be slightly different. After watching it I wouldn't say simple...
But yeah Phil, I think I can handle that.

Side-note:
I joined this forum 2 days ago. After committing to doing the research, a guy (me) with almost ZERO car mechanical knowledge found and hopefully will fix his car problems thanks to this forum (with Phil)!
I'll update after Thanksgiving if all works out for me!

By the way, any mechanics know how much would this cost me to diagnose and repair at a shop?

aaronhume

according to automd.com where you can enter your car and select a service to be done, they will calculate shop hours and take in shop prices by zip code.

an intake manifold gasket replacement on a 95 civic is listed at 2.7 hours = $240-$270
not counting your diagnostic which you said you were quoted at $150 in your other thread

Parts: $10-20 (gaskets, coolant)
labor: $150+$250
subtotal: $420
WA sales tax (9.5%): $40 (not sure where you live)

Net Shop cost: $460

My cost to do it myself: $10-20 plus time to research if needed and downtime on the car
It pays to be able to fix your own car, unless you are made of money and actually lose money for downtime