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Discussion Starter #1
I've dealt with this surging idle ever since I did a head swap which leads me to believe that there is air in the coolant system. no codes at all Here is Everything that I've done:

1. I ran the car with the coolant cap off [jacked up the front end] and mashed the gas at about 2000 while the heat is on full blast. the fan kicked on and off. I did this several times and still idled up and down but I eventually got it to where it just idled at 1800 and stayed. no codes

2. bought a new IACV did the same thing; actually got worse. again I raised the car burped it for about 30 mins, no luck. I have since done this 3-4 times. no luck. no codes

3. I tried reset the ECU; pulled ECU fuse for 5 mins [sometimes longer because i;ve done this 10 times] then cranked the car up and didn't touch anything for 10-15 mins. still the same. no codes

4. I made a gasket and covered the IACV and the surging stopped, however the idle was very very low almost to the point of the car dying. no codes

5. reset everything, to normal. reset ecu cranked care and the idle stayed steady at 2000. after about ten mins i touched the gas and boom idle surge form 600-2000. no codes

6. reset ecu again; at this time the surge is constant. I pulled the map sensor- surging stopped but idle went to 2000. pulled the engine coolant temp sensor - nothing. pulled the IACV and the car idled from 900-1100 with less of a surge.

from reading and watching youtube videos this is seemingly an epidemic. and I read that the coolant temp sensor controls the fuel injectors by cutting the fuel with the idle gets too high, not sure about this but if the sensor is bad it could possibly throwing the computer off and the IACV is trying to make up for the inconsistency of temp.. thoughts on that one?

my next step is to take to the dealer and do a coolant flush and vacuum fill. hopefully this will rule out the air in the system .

Thoughts? advice?
 

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CRX ECODiesel Ram
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You listed a lot of things that you did but never said anything about following factory idle set procedures.
 

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easy fix, if nothing is bad.

pop out the idle set screw. if you pretend you are the intake tube, it is upper left of the throttle opening generally.

clean the screw. check that the o-ring is clean and free of damage. carefully popit off with a eyecare screwdriver or similar, or a pick.

a drop of fresh motor oil would not hurt to lube it up to reinstall the oring and the idle screw.

before re-install though, spray some brake cleaner or carb cleaner into that small hole on the throttle to clean the passage.


reinstall screw, bottom it out (no hulk tightening!). back it out 2 full turns.


fire up the car. let it completely warm up. that is, until the fans kick on in a REGULAR interval. this generally will take the fans kicking on 4-5 times before stuff levels off.

Once that is done, shut car off. pop the backup or ecu fuse out, it is a 7.5 amp or a 10amp generally. confirm it is the proper one by turning ignition on, and seeing if CEL appears. if it appears, you dont have power cut from ecu.


let fuse sit outside for 5-10 minutes, then pop back in, fire up engine, let it idle.

Let the fans get back to a regular interval, should only take a minute or two if its warm already.


either use a timing gun or a scanner (96+ chassis), watch rpms. use idle set screw to adjust to 700-800. I prefer 800 as its smoother for me, and since I have a stereo, this gets me a little more juice from alternator
 

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Discussion Starter #5
easy fix, if nothing is bad.

pop out the idle set screw. if you pretend you are the intake tube, it is upper left of the throttle opening generally.

clean the screw. check that the o-ring is clean and free of damage. carefully popit off with a eyecare screwdriver or similar, or a pick.

a drop of fresh motor oil would not hurt to lube it up to reinstall the oring and the idle screw.

before re-install though, spray some brake cleaner or carb cleaner into that small hole on the throttle to clean the passage.


reinstall screw, bottom it out (no hulk tightening!). back it out 2 full turns.


fire up the car. let it completely warm up. that is, until the fans kick on in a REGULAR interval. this generally will take the fans kicking on 4-5 times before stuff levels off.

Once that is done, shut car off. pop the backup or ecu fuse out, it is a 7.5 amp or a 10amp generally. confirm it is the proper one by turning ignition on, and seeing if CEL appears. if it appears, you dont have power cut from ecu.


let fuse sit outside for 5-10 minutes, then pop back in, fire up engine, let it idle.

Let the fans get back to a regular interval, should only take a minute or two if its warm already.


either use a timing gun or a scanner (96+ chassis), watch rpms. use idle set screw to adjust to 700-800. I prefer 800 as its smoother for me, and since I have a stereo, this gets me a little more juice from alternator
thank you for this I will try this today and keep you updated
 

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Mines a manual (z6) as well but it still has FICV. it for went it cold out, it raises idle until the car warms up.
 

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most obd1 hondas have a FITV or whatever its actual name is.

The IACV is the computer controlled valve. FITV is a "mechanical" idle helper.

No matter what, a IACV is equipped. Never 100% if a FITV is present, my 93 del sol did not have one, but that car had over 12 owners before I got it with jsut under 200k miles, so Mine may have been removed at some point if it was supposed to have one.
 

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CRX ECODiesel Ram
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I usually get a factory service manual out and follow the procedure as detailed in that. On my CRX (only one I know off the top of my head currently), you warm it up til the fans kick on, shut down, unplug IACV, then start it up and adjust idle screw to set idle at the indicated speed in the manual, this is often between 400 and 800 rpm on many engines.

I have found that surging idle is often from the idle being set wrong, especially when set way too high.
 

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Discussion Starter #12
I don't have a factory service manual.

Yesterday I did as mattliston said.

1. I pulled the Idle set screw out of the TB and sprayed carb cleaner in the hole, tightened the screw down completely (gently) and then backed out 2 complete turns.

2. crank the car up and let the fan kick on 5 times ( idle was steady at 2000) then shut down and pulled the ECU fuse for 10 mins.

2. afterwards, car began to run at 2000 Rpms and then a P0505 code and the idle began to fluctuate between 1500 -1900 rpms. cleared the code and idle maintained at 1900.

3. after complete warm up [ 4 fan cycles] the idle was still high so I closed the idle set screw completely and after about 10 seconds the idle went down to 800 rpms and stayed steady.

4. this morning the car cranked up and stayed at 1600 rpms until the car was completely warmed up and then stayed at 1200 rpms.

also this car has a cold air intake, I didn't think to mention it because it was on the car before the cylinder head was removed with zero issues. I have no codes after that P0505 code, it also had a P1298 code that went with it.

Should the screw be completely closed? and is there something else that could cause a high idle. I will check it again to see if it gets better, I'll try resetting the IAVC, but its not surging any more

Thoughts? thanks guys
 

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no, that idle screw should never be completely tight.

sounds like you have a vacuum leak. May have pinched the intake manifold gasket, an old line has a crack, or throttlebody is leaking a bit.

break out some brake cleaner or something equally as "burnable" and spray over the intake and watch where you spray if it revs up.

what rpms does it go to with the IACV unplugged? (do it as its running)
 

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Discussion Starter #14
The engine was completely warmed up, I discconected the IACV while it was running and the RPMs dropped to 600, i backed out the idle set screw one full turn to get the idle to stay at 900. then shut the car off, cleared the code (P1505) and cranked it back up and the idle was at 1600 and steady.

I also sprayed carb cleaner around the intake manifold and vacuum lines and there was no change in idle speed of the engine. only thing I noticed was the PCV valve line that goes directly into the manifold is pinched shut from the vacuum. could a plugged PCV or oil breather chamber box cause idle issues?
 

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with iacv unplugged, put idle around 500, maybe 600

no, a pinched lined wont cause a high idle.
 

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Discussion Starter #16
ok so I can drop it back down to 500-600 but the idle set screw will be completely closed. is there any way to adjust the IACV itself? what is that screw located on the solenoid?

high idle is always a vacuum leak right? the this is, there really isn't that many vaccum lines on this motor.
 

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do you have the cruise control nipple that is very close to the brake booster? back of plenum, near bottom. I had to plug mine when I did the Y8 manifold swap onto my Y7

if the idle screw is completely closed when setting idle, there is definitely a leak.

IACV is non-adjustable.
 

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2005 Legacy GT
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You mentioned you made a gasket ... for the TB?

Also you said you covered the IACV port and it almost died. IIRC it should die, that should be the only path for air to get in with the TB closed. Sounds like there's a leak somewhere to me. Sometimes the carb cleaner trick doesn't work and you have to get the engine smoked.
 

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Discussion Starter #19
yea, I just made something to block it off. update, pulled and plugged the air injection[4 holes on the upper intake] and the idle dropped a little bit and stayed constant at 0900 for the first day and the wasn't isn't as constant but does happen, just not as bad. I also popped a code misfire 1 and 3 cylinder. So I'm agreeing with AutoXCivic and believe there is a intake manifold leak or air in the coolant. I might try to put the car on a lift and spray up upper the bottom side of the air intake manifold
 

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CRX ECODiesel Ram
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I don't have a factory service manual.


Thoughts? thanks guys

You do have internet access I assume since you are on here. Not having a factory service manual just says I am lazy or I cannot use the Google.

Here, let me put this spoon in your mouth, the rest is up to you.
Civic - Downloads - Hondahookup.com


one more bit in the spoon, check 11-190 and 11-220
 
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