Idle Problem - Here's a Challenge

[DBMaster]

I have had this weird idle problem for about four years. It has been looked at by my favorite independent Honda mechanic as well as the local dealer (who actualy charged me nothing because they could not find anything wrong).

When the weather is hot and the engine is good and warmed up the idle witll fluctuate (surge) as you are coasting to a stop light or down a highway exit ramp. It only does this during the summer and it doesn't really cause any major problems like stalling, but it is annoying.

I have done quite a bit of self diagnosis during which I replaced the EACV and fast idle valve. I have cleaned the throttle body, the distributor cap and rotor are new, plugs and wires are new. There are no vacuum leaks and the PCV valve was changed (I overpaid for a genuine Honda part due to a recommendation.) The engine has 196,000 miles on it.

It was suggested to me that it was wear on the distributor shaft bushing. If that's it I am going to put up with it because a rebuilt distributor ain't cheap.

I have learned about fixes on this board that no one else knew about so let's see if anyone else has dealt with this one.

Thanks!

[tyne89]

do you have an auto or 5spd.?

[DBMaster]

Auto. I think I also may have read somewhere that this could be related to the transmission. It works fine otherwise and I have changed the fluid regularly for the car's entire life.

[Jareds 89 LX-i]

If it's not a huge flucuation, then maybe a spring broke or something on the centrifugal weights in the distributor, causing it to advance and retard. You could get a used distributor from the wreckers and see if that fixes it.

[rocky2]

It's most likely some type of pollution control devise. Like a deceleration valve or maybe diveter valve if Honda even has one.As your engine is let up from working hard there s mucho vacum.

[ACCORD EX]

what about air filter ?

MIKE

[DBMaster]

Air filter was recently replaced, but then it has been doing this for several years and I have been through several air filters.

[cruznz]

hi, what about Map and cyl/tdc sensors?

they can cause an erratic idle prob.....just a thought.:bandit:

[DBMaster]

Cruznz,

Those seem like valid suggestions, especially the tdc sensor, but how do I tell if it's bad if I do not have a diagnosis code? According to the manual either one of those things going bad should turn on the check engine light and flash a code on the ECU.

That would be so nice and simple, wouldn't it?

[ACCORD EX]

main realy ???

MIKE

[rocky2]

Look at pleum or intake anywhere wheres theres vacum plus wires for a part. EGR?

[monsonhonda]

this happened to me, its really simple, there is a switch in your transmission that tells it what gear it is in, this is most likely damaged. my car would always fluctuate like yours did until i replaced the switch. just go to a junk yard and pick one up.

peace

fussell

[carotman]

What happens when you unplug the EACV ?

Does the idle drops and the engine dies? Does the problem go away?

[DBMaster]

Main relay was just replaced (starting problems). I also replaced the EACV trying to diagnose something else, but there was actually nothing wrong with my original.

I am thinking it is probably a transmission issue (either going in and out of gear, or up and down shifting) as it only does this coasting.

Monson, where is the switch you are referring to? I do not see it shown in the automatic tranny section of the shop manual. Considering that it was doing this both before and after replacement of the EACV, fast idel valve, and main relay I am inclined to think it is not one of those items.

I really got you guys thinking, though!

Thanks!

[cruznz]

yeah,it would be nice if it was that easy,.....i've come across situations where check lite doesn't come on,but there have been trouble codes come up on ECU

Tdc sensor was last to check,(apart from ecu), in troubleshooter manual,and if resistances are in spec ....well....was a long shot...:eek: lol.....looks as tho monson maybe on to it tho.....

[DBMaster]

I haven't checked the TDC sensor yet so I have not ruled that out.

I guess this is going to come down to just how annoyed I get with this minor issue. I could drive myself crazy over this while everything seems to be in perfect order otherwise.

[Mike Murrell]

To be perfectly honest, I'm not strong with Honda FI systems.

Is your EACV Honda's version of a HOT IDLE COMPENSATOR VALVE? If so, forget it. If not - something to consider.

Another remote possibility is the coolant temp. sensor.

My 2 cents.

[DanG86LX]

Searching the web for some of my problems, I found this:
http://www.smpcorp.com/download/view/TT2Q98.PDF
Look at page 3, "HONDA-1985 TO 1996 WITH PORT FUEL INJECTION-SURGING IDLE"

DanG

[DanG86LX]

... or this "HONDA VEHICLES-ENGINE SURGE AT STEADY SPEEDS" here:
http://www.smpcorp.com/download/view/tt1q00.pdf

[DBMaster]

Dan G,

This looks pretty promising. With all the vacuum hoses on this car it may be hard to find a leak if there is one. I had some cold idle surging problems in the past so I replaced the fast idle valve even though my old one appeared to be working correctly. Coolant level looks good so it looks like it might be necessary to try the TPS idea and/or start hunting for leaks.

Oh, joy!

Thanks!

[DBMaster]

The only thing I don't get is why my idle does this only when the ambient temperature gets above 85 or so (summer only). Knowing that the problem is related to heat I wonder which cause is most likely. Hopefully, it is not the TPS as the only way to get one is to get a whole new throttle body. Honda's TPS is riveted into the TB and is not sold separately.

TPS's are not very expensive. I actually had one go bad on a Ford Escort we used to have and it only cost me about 40 bucks to replace it. The problem with that car was that the idle would go off the scale after coasting down from the highway. I had to take it in to the local Ford dealer to get the problem diagnosed.

It almost looks like if you could buy an aftermarket TPS you could drill out the rivets on the factory unit and attach a new one with self tapping screws. Is such a thing available?

Thanks!

[88turboaccord]

I had that problem where the idle stayed up, I ended up replacing the throttle body. It turned out to be the butterfly was not sealing properly.. The TPS was fine.. To get your TPS off, you put a groove into it so a standard screwdriver can fit in it, and it screws right off... Voooolllaaaaaaaaaa..

[DBMaster]

Ah, but can you buy a replacement TPS once you get the original off? I cleaned the throttle body about six months ago (it was not terribly dirty) for the first time ever. The butterfly LOOKED good, but the kind of leak you are talking about probably would not be visible.

I am going to do a little searching for a used one, maybe even take a little trip out to a couple of import salvage yards. I just need to find one with lower mileage. I have 196K miles now, but the problem started back when the car had about 150K or so. It may be hard to find one with lower mileage than that as old as these cars are now.

I am gonna fix this if it kills me!

Thanks!

[Sean]

to answer a simple question. checked yr throttle valve cable lately. if its over adjusted the trnamision will not downshift properly causing alot of the problems yr talking about. ive had this problem before and a simple cable adjustment solved the problem. usually the torque converter was disnegageing to late. or it could just be that yr notice the tranny downshifting.

[LX-biker]

Hi, i had same year ago-was ignition coil.
When hot-intermidient shortcuts inside.