Got the hot starting problem solved with repairing the main relay..so got that out of the way, now it was back to the idle..

Car bounces idle when hot after driving.

We unplugged the IACV and there was no change at all, then we checked continuity on the plugs and one of them had continuity to ground when it shouldn't and one showed battery voltage when it should have none. If that makes sense...

Anyone have ideas where to look next?

 

i disconnected and plugged my pcv and my bouncing idle went away.

 

So you just unplug it and leave it?

 

initially i did it to test it, and since my car is beyond emissions testing i ended up plugging the ports on the manifold and then putting an expanding plug in the hole in the block and removing the black box. I left the hose on the top of the valve cover hanging loose as well.

 

Ok so you completely too the IACV off and plugged the ports on the intake manifold? Which black box are you talking about?

The hose on the valve cover is hanging loose already, when I bought the car it was like that.

 

Well I unplugged the IACV when it was hot and bouncing, that cured it...

Then I plugged it back up and then blocked the port on the intake for the IACV and that also cured it...

So bad IACV?

 

Now I have another symptom..

When it is bouncing idle, if i'm drawing enough current from accessories like the fan or headlights...the bounce will go away. Ideas?

 

FITV: https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/how-fix-your-idleing-woes-fitv-iacv-2153910/

 

I don't have a FITV...this is a dual point engine

 

I want talking about the iacv. I said PCV. I would start by making sure the base idle is set correctly per the service manual, if it its not correct the iacv will bee operating when it shouldn't and cause weird idle issues.
In my car i cleaned iacv, made sure timing was close and then set property base idle of 420 plus our minus 50 rpm, and then ended up ditching the pcv valve and that was when things cleared up. My car was i had a bad connection to the black box on the block.



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My "PCV" is just a hose coming off the valve cover not hooked up to anything. If I plug that hose up, there is no change..

 

Did you remove the IACV and clean it thoroughly?

 

Cleaned it earlier this year, will clean it again tomorrow and see if that does anything along with other things..

 

that is part of the PCV....

actually the PCV system includes the hose going from the manifold to the valve to the black breather box on the back of the block AND the valve cover vent tube going to the intake tube.



what is your base idle set at?

 

So by following Haynes manual, it tested with 12v showing on the plug probed on both terminals which in Haynes says "if voltage is showing, the ECU might be faulty." Then says to take it to a certified Honda dealer or repair shop.

Also, anyone know the proper impedance spec on ground that goes to the ECU from the IACV?

Mine was showing 36 ohms

 

look for 8-15 ohms between the two terminals of the eacv.

measure voltage between the wires on the plug with the ignition ON.
if you get battery voltage disconnect the a connector on the euc, measure between the two terminals on the plug again. if you have batery voltage then you have a short, if not then new ecu.

measure voltage between the wires on the plug with the ignition ON.
if you get NO battery voltage check voltage between the black/yellow wire and body ground. if you have NO voltage you have a short on the black/yellow wire, if you do have voltage then check voltage between a11 and a2, if no voltage then repair the short on the blu/yellow wire to the eacv, if you DO ge battery voltage then jumper a2 to a11 and you should hear the eacv click, if no click replace the eacv.

there is no other spec listed in the service manual.

 

What motor are you running? I was going to suggest that it might be the throttle position sensor. When I would take my car out of gear it would surge to high Rpms 4-6,000 but when in gear it would run at the right rpm. Also the dizzy was going out once upon 2 times and it would cause the tach to not respond at all then start when it would warm up or hit the right bump. But my surge was the TPS. And I had to order it twice cause the 1st replacement was jankie. 2nd went on and fixed the crazy surge.

 

Bouncing idle is the problem I have had in all my Honda's at one time or another. I drive my cars a lot and put tons of miles on them. That being said, I have had some experience with bouncing idle.

Bouncing idle can be caused by several factors that by themselves will not cause a problem. But put them together, as they seem to do when the engine gets older, and you have bouncing idle.

I have found that a dirty PCV system, the EACV system and the intake system seem to have caused my bouncing idle problems.

I solved my problem on all my Hondas by first putting in a new PCV valve and cleaning the passage ways. On a 90's era Honda, the EGR passage ways are prone to getting clogged up with carbon deposits that make passing any air quality testing impossible. I cleaned mine up by removing the intake manifold, drilling holes in the manifold to access the EGR passage ways and then cleaning out the passage ways.

I was amazed at how clogged up the passage ways were with carbon and all kinds of crud. I drilled the passage ways open and then I cleaned out the junk with acetone and carb cleaner. I then tapped the holes and installed allen head screws into the manifold with plenty of sealer to prevent leakage. I now can open up those passage ways without having to take the manifold off and hit them with SeaFoam every 80 to 100K miles.

On the newer 4 cylinder Honda's, they have a plate on the intake manifold that can be removed for easier cleaning of the passageways.

I also replaced the EGR valve and cleaned the EACV. I also replaced the O2 sensor and adjusted the idle speed and did a complete tune up with new plugs, cap and rotor. Idle speed is important and the Honda engines are picky.

Those things together have solved my bouncing idle problems. I've had that problem on all my Honda's and I finally figured out what to do about it by trial and error.

I now can pass E-Check with no problem and my bouncing idle is a thing of the past. Hope this helps.

 

that is great egr information for F series, H series, and the crx HF and civic VX engines...but will not help a dual point d15...