My idle surges from 1k to 2k as soon as my car warms a bit. This only happens in park or neutral. I'v have checked all the vacuum connection and they all look ok. Is there any way to do an overall vacuum check on all the connections? What is the origin of the vacuum, can I put a vacuum tester there and test both ways? If there was a vacuum leak, wouldn't it also affect the engine while in gear?
I have two 1990 accords One is a 5 spd and the other is and automatic. Can I swap the EAVC valves and fast idle valves. The service manual shows O-rings instead of gaskets, so I would think I could swap them without replacing the O-rings. Thanks JIm

 

The origin of vacuum is: the engine running! As the engine sucks air to breath it creates vacuum (hence when you have a turbo that compresses air and makes BOOST you have then overcome VACUUM). Anyway with that said:

Triple check your vacuum connections (INCLUDING cruise control), this is 99.99% a vacuum leak when this happens.

With the car at normal operating temp, please disconnect the EACV and note what RPM it idled next time the car is surging... it should be around 550-650RPM. If it stops then I reccomend setting the base timing back to spec if its off (its in your helms manual, but if you dont have one let me know and I'll post the proceedure), reset base idle back to spec if the idle ISNT @ 550-650 with the EACV disconnected. Let me add that all of your idle checks should be performed with NO LOAD.. what I mean by that is the radio, lights, AC, and wheels centered so no power steering draw is happening.

After you've done all that reconnect the EACV and let the car idle (without touching the gas) for 5-10mins to re-learn its long-term fuel adjustments and see if it starts hunting idle again. If it starts hunting idle again you can check the FIV without removing it, just remove the top cover and stick your finger on the thing in the middle. If the car stops hunting idle in THAT case replace FIV.

i hope I was clear enough ... this is how i always trouble shoot Honda idle problems no matter what the car, but I just woke up so i might not be talking in english


[Modified by GimpyAccord, 11:54 AM 3/1/2003]

 

Thanks for the reply
Is the vacuum origin the thottle body. If I pull each hose of the throttle body and plug it would that be a good test? I have a vacuum pump and guage. Should I be able to hold vacuum on each hose going into the throttle body.
I dont have a timing light so I could not tell how the timing is. Do you really think this could be a timing problem. The engine runs great when I am driving, just idles too high.

I pulled the cruise control hose off and the rpms went up few hundred rpms still surging, put it back and it fell back to the 1200 to 2000 surging. I took the wires of the EACV and the surging stopped, the rpms were at 1200 but the engine was not running smooth. I adjusted the idle screw all the way in (clockwise) the lowest rpms I could get was 1100. I plugged the wire back in and waited 10 mins but it still ran at 1200, no surging but ran rough. I pulled out the reset fuse waited ten seconds put it back and restarted the car. It still surged .
When the engine was cold I had opened the FIV and the plunger was down and open. I put my finger over the opening and could feel the vacuum. After the engine warmed the plunger was up and I could not feel any vacuum. Pushing it down would open it and up the rpms. Does this sound like the EACV? Can I swap the one from the 5 spd to the automatic.

 

Theres vaccum all over the intake manifold on the 4th gens.. the drivers side for cruise/fuel pressure regulator.. the back for the vacuum boost on the brakes ... etc etc ... under the hood is a vacuum diagram.

The pump wont do you anything because uh.. hooking a vacuum pump to a port thats PULLING vacuum = does nothing. The pump you'd use if you wanted to test EGR, booster etc. The guage you could use to see what Hg the cars pulling... but you will definatly need a manual to do that because thats just way too much for me to type. Have you also checked the EGR/control box hoses?

Yes, you can swap EACV's but the fact that you were still sitting at 1100-1200 with the EACV unplugged means a vacuum leak MOST likely.

I also forgot to tell you to check the PCV valve, if that things stuck it will cause your engine to idle higher. another thing you should check is on the drivers side of the intake is a lil gizmo, thats the Idle Air Boost, if that somehow got stuck open (which actually happend to my 1991 LX) it would allow a lot of air in.. effectivly creating a vacuum leak. When mine went bad i just removed it and blocked it off.

I think your FIV & EACV are good, the ECU and EACV are doing their job, it detects a really high idle and then cuts duty cycle on the EACV in an attempt to get the runaway idle back in check.

And yes, if your timing somehow got way advanced it could very easily make your idle above 1000rpm.

So:

1. Check vacuum again and again.. use your ears to listen it out a bit if you have to.
2. Check EGR hoses
3. check idle air booster
4. Check timing ... borrow a light if you have to. (might as well cover all the basics)
5. If all else fails, swap EACV's but I doubt that'll do anything. Every EACV I've seen go bad threw a CEL.

It still very well be the FIV, last time mine went bad it passed all the tests I gave it... but in desperation I replaced it and my idle went normal.


[Modified by GimpyAccord, 2:53 PM 3/1/2003]

 

Ok Gimpy

So I checked every connection on the vacuum diagram on the hood of the car. I lifted each line off the throttle body and checked out towards the air boost valve,cruise control,engine mount solenoid,fuel pressure regulator,control box,intake control solenoid,purge control diaphragm, and erg valve. they all held vacuum.
I m not getting any ECU codes. but the service manuel says to check the EGR
Valve the car must be a normal operating temperatue. with the engine at idle apply 8" of vacuum to the EGR valve. the engine should stall and hold the vacuum. Well my car holds the vacuum but does not stall. it runs rough and the surging stops. Is there any other way to test the EGR valve. Can it be taken apart and cleaned? Thanks Jim

 

Not really big guy. I do have a spare EGR, but its for 5th gens.. so that doesnt help ya much. Odd that the EGR isnt throwing a code, the ECU monitors the amount of lift the EGR is applying at all times, but strange things can happen.


[Modified by GimpyAccord, 11:12 PM 3/1/2003]

 

my pops has a 90 accord auto, and it had the same problem, lemme describe his prob, his car's idle would surge when its warming up i.e morning b4 work...i fixed the problem by swapping a what cha ma call it? ...uhh..nutz..i forgot whats it called, but i'll describe it to u, its a mechanical sensor in front of the firewall. it has kinda of a bronze top w/ 2 philips screw on it, two outlets are on the bottom where coolant flows through, if u unscrew the top there will be something like a ball which u can press down and u'll hear air be sukked in. thats what the problem was w/ pop's car, dont start the engine, take that mechanical sensor out, clean it out, cuz pop's sensor had coolant buildup clogging the sensor. thats it, that might be the solution..good luck

 

Thats called the FIV.

 

copied crown royal from a post on hs

im going to be your saving grace on this subject, listen to how i explaine this and your problem will be solved... on your intake manifold you have part on there that has a lid on it thats held with two phillip screws, if your in front of your car look where your pcv valve is then its on your right of that. it has two rubber hoses connected to the bottom of it, do you see it haha, now that piece when your cars on has air going through there, when your cars cold unlosen the screws and open the lid up inside it will be a piece that almost resembles a small thermostat, surrounded by a yellow housing. there are two flat head like inserts in that yellow housing now start your car and when it starts idling funny turn the yellow housing using a flat head clock wise, that will bring your rpms down and the erratic idle to a stop. when you find the sweet spot close the lid back up and fine tune your adjustment by adjusting the idle screw thats right behind your bracket for your vacumm lines on the back of your intake manifold, what that does is increase or decrease the amount of air your intake sucks in.. just play around with those two pieces until your satisfied with how your car idles/runs you might have to adjust it again the next day or so until you get it to where its supposed to be. mine used to do it bad. until i fixed it now it doesnt do it at all, i also fixed my boys 4th gen as well.. do that before you even think about buying a throttle position sensor because the dealers want like 450 for it... sorry for being so long....hope it works out for ya..

 

You can't even buy a TPS if you wanted to, honda sells them all as one with the TB. You can, however, slot the screws on them with a dremel and adjust the TPS to get it back to .50V (assuming thats your problem). If the TPS is reading much above .50V the ECU is out of idle mode so to speak....

Unless I'm reading this wrong: Thats the first I've EVER heard of anyone adjusting an FIV and I have one here from a 5th gen and its unadjustable. ...........

 

Well I have not been able to get a timing light yet but I did swap out the EACV, FIV and Air Boost Valve from my other 1990. Still surging. The EGR is good. It holds vacuum and the voltage varies from 1.3 volts to 4.3 volts when I increase the vacuum. The Throttle Sensor varies from .49 to 4.58volts. The map sensor varies from 2.8 to .875 volts. So that looks ok.
Now I noticed that the surging starts about two minutes after the car is started if I step hard on the gas. If I dont step on the gas it takes longer.
I took the plastic tube that runs from the air filter off the Throttle body. There are two air holes inside the body. the lower one which goes to the EAVC was sucking in air like the EACV was wide open. The other hole I guess is from the idle adjusting screw. I have the screw all the way in so there was no vacuum there.
When I cover the lower hole to the EACV with a piece of duct tape the surging stopped and the RPMS dropped to about 1K.( Now I am reading the tach from the dash board and I assume that it is correct.) When I put the car in gear the rpms dropped to about 800.
When I disconnect the connector on the EACV the vacuum also stops from the lower hole in the throttle body. Now with the adjusting screw closed and the EACV closed I would think the car would stall. Could I have a leak in the intake manifold? What device would be holding the EACV open. Anyone have any ideas. thanks jim