My bouncing idle condition remains. Actually, it has gotten worse.

My original post is here: https://honda-tech.com/zerothread?id=410522

Now the idle bounces all the time, even when it's warmed up. The ONLY time it doesn't do it is when it's been parked overnight in the freezing cold. Then it'll do a normal fast idle for a few minutes before the bounciness sets in. When it's fully warmed up, it'll bounce between 1 and 2K RPM. It will also exhibit this condition when cruising. (Both with cruise control on or with a steady foot on flat road.)

In addition, it's running hella rich. This is evidenced by the blackness covering my spark plugs, the loss of about 7-10 MPG on my fuel economy, the strong smell around the car that resembles an old Zippo lighter, and the faint redness of the catalytic converter (Only visible at night. It's not clogged, as I can feel strong exhaust coming out the tailpipe.) It has also flodded once, requiring me to remove the plugs and crank as gas spews up out the plug holes, forming a nice flammable cloud.

I've checked for vacuum leaks using a can of carb cleaner. No dice... I cleaned the throttle plate with the rest of it.

On the rear of the intake manifold, close to the passenger side (LHD Model) there is a motor of some kind. I assume it's the cold Idle motor... It it bolted flatly to the intake and has a hose going to it and a 2 pin connector. The hose, I found out was a coolant line. It goes to something mounted directly below the throttle body. Unplugging the connector makes the idle stable, but very rough. It also throws a code. Unbolting it from the Intake manifold, there were two holes in it, mating with two holes in the manifold. One had a LOT of carbon crud in it. I cleaned it with carb cleaner.

On the bottom of the MAP sensor there is a T... It is upside down. The hose from the Intake manifold goes into the left side. The middle has a short length of hose that goes into the bottom of the MAP sensor. The right side has a short length of hose that is plugged.

Unplugging the electrical connector from the MAP sensor causes the engine to not run at all. (Haynes manual says that the ECU should fallback to a default fuel map in the event of a MAP sensor failure. I've driven this car without a MAP sensor before.) Unplugging the plugged hose end makes a stable, although rough idle. Unplugging teh hose from the intake manifold causes mixed results. Once it made the engine idle stable, but rough, the others, it caused the engine to not run.

Unplugging the O2 Sensor causes the idle to get lower and rougher, but it still bounces. Unplugging the TPS has similar, but more severe effects as the O2 sensor.

I know unplugging sensors isn't the best way to do diagnostics, but I don't have any of the cool tools that the shop I used to wrk at had, like the Snap-On power graphing meter (For testing sensors. Has a database of the pinouts of connectors and nominal readings.) or the Scan tool (Extracts codes from the computer and tells you what to check using the power graphing meter.) So, the best thing I can do is unplug **** and see how it changes the problem. Although I can probably dig up an osciliscope and digital multimeter, I won't know what to do wiht the readings, as I don't know the nominal readings.

Any help would be greatly appreciated. Thanks.


[Modified by Pele, 10:25 AM 2/24/2003]

 

IACV.....block it off with a piece of aluminum between it and the intake manifold......Yes, that irritating decieve on the back left of the intake manifold.

But, that may or may not fix your fluctuating idle.

I have a 2000 RPM idle with that thing un blocked.....blocked I run at 750 rpm. But, my idle still fluctuates a little without the IACV. *Shrug* It takes a little getting used to but, you don't need the IACV. (except for smog)

N-E-Way, you can take that sucker off and clean it with Carb Cleaner...hopefully yours is not past repair yet.

 

The fast idle valve, on the bottom of the throttle body, the one with the coolant line in it may be the cause of the problem. If you take that off (3 - 8mm bolts) you will see this plug type thing inside. There is a hole in the top of the valve that goes to the throttle body, there should be a cap turned on its side on a spring. That sometimes can get stuck to one side of the valve with the spring being more compressed than it should be. Try wedging the spring loose and back to full extension (with the cap in the middle) with a flat head screw driver.

 

I took the throttle body off the intake manifold and then took that fast idle valve off the throttle body. (3 x 10mm Bolts BTW... Not raggin, just letting you know for future reference.)

The way I'm lookin at it, it's got three holes, Left to right, there's a tall oval, a tear drop, and a circle. The coolant hose is aimed diagonally, up and right.

The Tall oval has a white thing in it. The tear drop is a coolant passage to the throttle body. And in the circle, I see a spring.

I think there's something VERY wrong with this, as all the parts inside are shaking around.

Is it normal, or should I get a new one, or should I take it apart further.

On the right side with the coolant hose, it's got two normal phillips head screws. On the left side is a flat plate. It's got two 8mm bolts that will also take a phillips head to remove.

 

um....without the IAC your car wont hold an idle when it's cold. Trust me on this. You'll have to sit there and give the car some throttle until it's warm enough.

 

Yeah.. what he said.. And I have to pass smog in this state.

I'm used to driving carbed ****. The 85 Wagon has a carb with electric choke, and my RX-7 has a 4 barrel down draft carb with a manual choke. (Sounds nice when you take off the air cleaner and floor it. If you tweak the mix just wrong enough, it'll spit fire out the intake. Really shitty when you set your air filter on fire and shoot it's ashes out the exhaust.)

When the chokes aren't closed for fast idle, they don't like the cold too well... Plus they lean out.

Although I do like the lack of vacuum lines in this new fangled fuel injection.


[Modified by Pele, 5:47 PM 3/2/2003]

 

for some rerason my fluctuatng idle has something to do with my radiator fluid level, you should look into that

 

Radiator is full, although it's a nasty shade of green. This summer, I'm probably gonna replace the radiator and thermostat.

The fast idle is controlled by the coolant temp. If it's cold, it revs up to warm up faster. If the coolant level drops, you can't read the temp and it won't kick into cold/fast idle.

 

I *JUST* had the SAME problem! It turned out to be my fast idle valve. Same thing happened to mine, I shook it and stuff inside was rattling around. I swapped it out with a used one, no problems. Adjusted the idle again, and she's solid at 750-800 rpms.

When I had bouncy idle, it would go from 1000rpms to 2000rpms and then drop back down again to 1000rpms so on, and so forth. I think when it his 2000rpms, the ECU senses a problem and shuts down the injectors until the rpms drop again, that's why you get that bounciness.

Toss out the fast idle valve and put in a new one, you should be fine!

Fixed mine yesterday...


[Modified by Westsideboy, 11:01 PM 3/2/2003]

 

cool, this post might have fixed my problem as well

 

just had the same prob last week, i ll bet the check engine light isnt on either, it is the fast idle valve, careful it could be putting coolant into your intake which will cause a hell of a smell

 

That could be the nasty smell.. Although it smells a whole lot different than a blown head gasket that also dumps coolant into the cylinders...

Anywhozer.. what's a fast idle valve go for? I dismantled it and played with the spring... No dice. Does it come with the necessary three O-rings?

Thank y'all very much for your help.

 

i remember my friends civic w/SiR2 swap. he had type r intake manifold and throttle body. his idle bounced, i remember hearing that it was because the engine was getting so much air. idk though

 

Fast idle valve brand new from Honda goes for about $65

 

They quoted me 80 bucks on fast idle valve and 157 on the IACV... I promptly jumped up on the parts counter adn took a large dump.

 

don't buy the iacv that thing rarely breaks....and for 165, it sucks to buy and not be able to return....find out exactly whats wrong before you buy parts