sgull

I've got a surging idle problem with my 92 Accord, where the idle will rev up and back down rythmically as though a ghost is pressing down in letting up over and over again when the transmission is in either park or neutral. It happens only after the car has been driven around a while and the coolant has had a good chance to heat up to regular operating temperature. Doesn't happen when the car is cold. Happens a few times (the up and down rhythmic surging) when the car is warm after a short drive, but then quits on its own. But after a good long drive, it does not quit on its own. As I mentioned it happens only when the shift selector is in either park or neutral; as soon as I put in into gear it will stop.

Researching online about the problem it's apparent/obvious this is a common issue for this car that countless people have had to deal with, and the remedy for which seemingly varies, as do the specific symptoms. Some seem to have the problem all the time, some when the engine is cold. Mine happens to be as described above, when the engine is warm, and it seems the warmer it is the worse it is.

I understand the importance of trying to make sure that any and all air is bled out of the cooling system because air pockets can cause erratic idle. I'm fairly certain I've bled all air out, but not absolutely positive. The way I did it was to open the 12 mm bleed valve on the engine block and fill coolant into the radiator until a steady stream of coolant is emitted from that valve and then shutting it.

Another thing I've done was to thread the inside plastic thing all the way down inside the FITV (fast idle thermo valve) because some have said this can remedy the problem. It didn't so I even installed a brand new FITV in case the old one was shot. That didnt help either. I've taken off the IACV and sprayed it out and cleaned it good with carb cleaner but that didnt help.

Among other threads/discussions online I've read through about this issue, is the following one:
https://honda-tech.com/forums/showth...1979500&page=2

Within that thread is (quoted below) one method described to bleed the air from the coolant. I'd appreciate some feedback from others as to the correctness of the method described. Before moving too far into other possible sources of my surging idle issue, I'd at least like to be sure I've got the system bled properly to rule out an air pocket causing the dang problem.

"To bleed the coolant, first, make sure the car is cold, completely.
Take the radiator cap off, if you can fill it any, fill it almost completely to the brim.
Try squeezing the radiator hoses and moving them a bit without making all the coolant gush out of the open radiator, to try and work any air bubbles out, remember air will be at the highest point in the hose, so work it away from there. After that is done, top it off again, cap the radiator.
Start the car, and use a 12mm socket to open the bleeder nipple on the thermostat housing, it is located on the left side of the valve cover towards the back of the block. You may want to put a towel or rag there to catch the coolant as it sprays out.
Leave it open until the car is good and hot, and then wait for there to be a completely constant spray of coolant, that means all the air has worked its way out for now.
Let the car cool completely, when it is completely (I mean completely) cool again open the radiator back up, you will need to top off the coolant.
Done. Check it again a few hours after your next drive."

Thanks for any comments/advice.

TexasCheddar

I'm a newb mechanic. I really don't know much about these cars. HOWEVER I had the same problem. and I fixed it.

My vehicle is a 1994 Honda Civic EX AT coupe

I should state that my condition may be SLIGHTLY different. I had the same surges that you're talking about. The RPM's would spontaneously go up and down up and down, however it only happened when the car was actually moving. For instace if I went up to say 30 mph and let off the gas, the RPMs would bob up and down up and down. If I put it in park it didn't do it... it was a while ago so I'm not 1000% sure that it didn't do it in neutral but I think it only did it in drive.

First I tried all that you did.
1. Replaced Fuel Filter
2. Changed Spark Plugs
3. Cleaned Idle Air Control
4. Bleed out coolant bubbles
5. Fuel Additives

Solution:
My Vehicle Speed Sensor had gone out. I know that sounds completely unrelated but apparently the computer needed the speed to accurately calculate the RPMs. Go figure.

I bought a Vehicle Speed Sensor on ebay for like $8 and suddenly the bobbing was gone.

Note however that it was OBVIOUS that the speed sensor was bad as my speedometer had stopped working. In addition, the car threw a check engine light, and when I looked it up, I found VSS as the culprit.

Maybe this didn't help you any, but i thought I'd give my $.02

sgull

TexasCheddar,
Thanks for the description your symptoms and how you were able to fix it but I really think the fault/fix for mine would not be anything to do with the VSS. Mine symptoms are as I described, the idle surge never happens when the car is in moving gear.

I'm noticing now the surging in park and neutral does not happen all the time, but most of the time after the car has been driven a while. Never happens when the car is cold. I can drive is a while, then put it in park, and then get the surging. The surging might happen several times and then quit on its own, or might just continue. I can shut the car off a while, come back after its cooled some, start up and the problem is gone.

sgull

I came across this old thread in a different forum where the owner of a 4th gen Prelude was having what sounds like the same symptoms as mine. http://www.preludepower.com/forums/s...d.php?t=353126
So I'm leaning toward the answer being for me to either try to do what I can to bleed out any possible air in the air in the cooling system (whatever the apparent big mysterious trick to that is) or maybe replacing the dang IACV valve. I thought I'd already bled any air in the cooling system out, but maybe I haven't, I don't know how the heck you're supposed to be sure. And, as I mentioned, I have "cleaned" the IACV valve by spraying carb cleaner in it and all that, but who knows whether it really got clean enough or whether it's either shot or malfunctioning for some other reason.

holmesnmanny

Since you replaced the FITV which normally causes that problem I would guess that the iacv is now bad. Did this occur after you cleaned out the iacv...a lot of times you can damage an old iacv by spraying carb cleaner into an otherwise fully functional iacv. I only use water to spray inside it. Carb cleaner can have an adverse affect on the inner seals ESPECIALLY if you spray it with the carb cleaner when the iacv is piping hot.

At any rate, unplug the iacv and start the car. It should idle at 500-600 rpms(keep in mind that the very first white line after 0 rpms is 500 not 200). If not, then I would think the iacv is bad. Even if it idles at that range it could still be bad. Next, test the iacv by unplugging the connector and giving the iacv 9v and ground. It should click. Then measure for ohms across the pins it should be 8-15 ohms, normally it'll be 12 for a perfect iacv.

sgull

I'd like to try that. I have a multimeter with which I could check ohms across the pins, but am uncertain about how to hook up to see if it will click. Just run a lead from one of the IACV terminals to a 9v battery and run another lead from the other IACV terminal to a ground? If it clicks should it be obviously perceptible to someone with normal hearing in a quiet environment? Also, I suppose to perform this test the IACV needs to be unbolted/removed from the intake/throttle body first?

Thanks

Lost Again

Just me....but I bleed the coolant differently and it has always worked for me.

Set the heat to max - this opens the heater control valve, some of the newer accords you need to turn the key to on as a motor "drives" the valve.....not the case in your 92 but wanted others to know.

Open the bleeder....heck pull it all the way out and be sure the small hole at the bottom is not clogged, a wire bread tie is a good cleaning tool if it is. SLOWLY add coolant until a steady stream comes out of the bleeder. Make sure there is at least a little coolant in the overflow res.

Close the bleeder. Put the rad cap on to THE FIRST CLICK ONLY - WARNING, this is important. Turn the blower motor off. Start the car (blower off, ac off and heat still set to max).

Let the car idle until the cooling fans cycle - this could take ~20 min and depends on outside temps. Of course keep an eye on the temp gauge and shut off the car if it overheats. I personally let the fans cycle at least twice....but that is me.

Once the fans have run. Shut the car off. Remove the rad cap - WARNING, the reason for the ONE CLICK on the cap is that pressure will not build in the system.....hot coolant will burn you.

Top the rad and the overflow and call it a day.

sgull

Thanks Lost Again. But a few questions about the procedure as you described:
1. Do I have the car running or turned off before starting? I'm assuming off.
2. The step of turning the blower off -- sure I can do that but I'm curious why to turn it off.
3. Car shouldn't overheat with radiator cap not on tight? Seems like if I was to run it 20 minutes or long enough for the fan to cycle at least twice that it might want to overheat with the cooling system not sealed. Apparently not though, eh?

Mishako129

Silly rabbits, its a vacuum leak, I can almost guarantee it. Look where the intake manifold bolts on to the cylinder head, and where the plenum bolts on to the runners. Also check your hoses, they very well may be cracked.

To check the intake gasket, spray some brake cleaner where it mates up to the head with the engine idling. To check the hoses, physically inspect them. If you are a beginner and do no know what vacuum hoses are, the vacuum hoses are rubber and ALL of them attach to the intake manifold. They may be cracked or one may be disconnected.

Is your engine the F22A6? Just check the vacuum hoses and the intake manifold gaskets... All of them even the throttle body gaskets. Also clean your throttle body.


I've had this rythmical idle issue more than a few times and every time it was a vacuum leak. Nothing to do with the coolant, IACV or FTIV's. What's happening is the engine is trying to create vacuum for idle but it won't hold vacuum because of the leak. Basically its like having a hole in your intake manifold.

holmesnmanny

I meant to use a 9v battery and pick up a set of test leads. Connect one lead to one side of the battery and to one side of the iacv and connect the other lead to the other side of the iacv and the 9v battery.

Just do the ohms test first. If it fails then you don't even have to bother doing the 9v test.

sgull

In response to your asking, no my engine is not the F22A6 but happens to be the F22A1. Thanks for the advice to check for vacuum leaks and I'll definitely go ahead and check that out as you described. I recently did a head gasket replacement on this vehicle and did not notice any cracked vacuum lines and was careful afterwards to reconnect any that I disconnected during disassembly. Although of course it's possible I missed something so is certainly a good idea to double check, so will do. Also, I did clean the throttle body while I had it removed. I replaced intake manifold plenum gasket(s) and throttle body gasket all in the course of the head gasket job also, and followed torque specs doing so, so those such bolts shouldn't be loose but still I'll do the spray as suggested and see if I can detect a leak. Also, one thing I wonder about in regard to the possibility of a vacuum leak causing my issue: do my specific symptoms of the surging as I described seem to definitely indicate a vacuum leak, even though the surging does not occur when the engine/coolant is not warmed up but only after a significant amount of driving around and also only when the car is in park and neutral? Would not a vacuum leak cause idle problems all the time, or not necessarily? thanks

Mishako129

You said "when i put it into gear it will stop". This is exactly how a vacuum leak will act. The extra load on the engine causes it to go away, my car did the same thing which is why I used to put it in drive to idle it (with the E-brake on lol). That's how I remember it.

sgull

How about the way mine acts, which is it happens only after the engine car has been significantly warmed up and driven around a while. Seems after a good long time driving around it'll happen. Then after it sits and cools off and I start the car again the problem doesn't happen. If I drive around just some, a little while, then it'll surge maybe a few times but then the surging stops. Almost seems like the more the car is driven, the warmer the coolant is I guess, the more I'll have the continuing surging when put into park or neutral.

sgull

Also, just to throw this out there too, isn't it the case that a malfunctioning IACV can somehow mimic an apparent vacuum leak?

Mishako129

Still sounds like a vacuum leak. The iacv may be part of what's causing it you did clean it, right?

If you replaced the FTIV then the only explanation is a vacuum leak.. Did you clean your throttle body also?. I would not put it off anymore, just look for the leak. And I would either try and take it back (the FTIV that didn't fix your problem) or re sell your old one. They can go for 20-25 $ on ebay. Throwing parts at your car is a very good way to throw money away, I learned this first hand.


I just can't think of anything else that has to do with the heat of the car other than the FTIV, did you buy a used one or a new one? Perhaps it is not adjusted correctly. Take off the top of the housing and you will see a threaded wax thingy, use a flat bladed screwdriver and tighten it up, not all the way tight, leave a half of a turn.

sgull

Yes I did clean the IACV. It was suggested that because I used some carb cleaner to clean it that perhaps I damaged it. If that is the case (that it's damaged) does that in itself cause a vacuum leak?

Not possible (or very likely) that there remains an air pocket in the cooling system causing the problem? Narrowed down to vacuum leak for sure because I've replaced the FITV already? If IACV is bad that causes a vacuum leak?

Yes, as I did mention in my one of my previous posts this thread.

Should I look for the leak (by spraying break cleaner around as suggested) only when the surging is happening?

I did try before replacing the FITV screwing the threaded thingy inside the housing down (on the old one) as you describe. Did not resolve the problem. Got a brand spankin' new FITV valve and put it on because I read somewhere if screwing down the thingy inside on the old one doesn't help that I'd probably need a new one. I don't like the idea of throwing parts at the car either and only did so after trying to research what do to and thinking this might resolve the issue but no. On the new one I have not screwed the thing down inside, figuring maybe thats not necessary on a new one.

I won't be able to check thoroughly for a possible vacuum leak until after a few days from now because I'm out of town, but when I get a chance I will, and will post back. thanks again

Lost Again

1. Yes, start with the engine off.

2. Turning the blower motor off helps in letting it warm up a bit faster......the heater core acts like a min rad and fan. Might cut the warm up to cooling fan cycle time by a few minutes.

3. Again....one click of the cap. The suggetion to keep an eye on the temp gauge is just a general rule

of1accord

Was this resolved?? Mine's doing it now...

sgull

No I still haven't resolved my issue. Does the surging stop when you put the car into gear? Mine does. I've decided it's probably a vacuum leak (per Mishako129 posts here, threads #9, #12, and #15) but I still haven't taken the time/effort to find/fix the leak.
Otherwise the other suggestions posted are worth investigating too. Good luck.