Symptoms of a sticky I(E)ACV?

[ltslimjim]

As many folks are aware, these Honda's can have tempermental idle issues at times, and in my case with an older 1992 Civic it's no exception.

Lately, I've had some issues during stop 'n go driving and idling. I know the common 'raise/fall' of the idle RPM being caused by a sticking or failed IACV(usually the former). This happened yesterday while out for some late fast food. My question is what other symptoms would a sticking idle valve cause??

The car felt 'choked' or 'robbed of power' during takeoff and also choked while coming to a stop/slowing from highway speeds. I know I have a rear brake job due, got the 'pulse' while braking going on now, so unless a brake is grabbing I don't know what else would be affecting this air starvation feel it had yesterday.

Of course, I learned to drive this car with a worn out clutch and I'm now getting to used to a shorter disengagement, it seems the car can more easily make torque/lurch forward than before, but last night was annoying for me. Tonight it drove just fine, strange...

FWIW, this car has the D15Z1 engine(lean burn) and it could be a 'stuck in lean' mode while accelerating from takeoff I suppose. It is a more finicky model Civic.

 

[tomcat27]

a sticky IAC usually will have an inconsistant idle and perhaps stall. It should not alter the air/fuel mixture to the point that the car lacks power. you can normally clean iac's - remove carbon the the valvle portion by using q-tips, rags soaked with carb cleaner.

 

[Lead Shoes]

Inconsistent idle, jumping idle and low or high idle are signs of a dirty IACV, stalling out at a stop light is another one, but is mainly from too low of an idle.

I notice a butt dyno power loss when winter blend gas comes out with my Honda, and mpg loss, which is probably causing you the same feeling.

Any engine codes? I don't see why it would feel sluggish one day and not the next. How up to date are you with routine maintinance like air and fuel filters, plugs/wires, cap/rotor, ect? (I assume pretty up to date if you care enough about your car to join a oil site to learn about every aspect of getting the most out of your car).

If I had 5 dollars for every time I had to fix a temperamental issue with my Honda, I would have enough for another car.

 

[chrome]

A friend's Prelude had similar symptoms, bogging down occasionally when taking off to a point it was getting dangerous.

A new set of plugs and wires solved the problem. When was the last time it was done on your Civic?

 

[ltslimjim]

Did plugs just this past summer after new one's looked funny/strange, IMO it was from a fuel system cleaner overdose(put entire bottle of Red Line SI-1 to the 10 gallon tank)...

link the thread:

http://bobistheoilguy.com/forums/ubbthre...316#Post2366316

Cap/rotor was replaced 2 years ago, new plug wires as well. Most everything is done maintenance wise. A mechanic did this for me, a shop I no longer use for a few reason. Had a set of CVs this shop installed have the outer CV joint boots both fail/started making noise only 1 year in...this shop claimed to only use OE parts so I suppose they may have used cheapo cap/rotor? It gets an occasional 'hiccup' at idle (not a backfire mind you), almost like a 'skip' in firing?

The plug wires are OE Sumitomo so no worries there...

It does have the following symptom:

At times, lately(before and even since the clutch job), I've noticed a 'metalic' or 'ceramic' like sound 'only' when the throttle is applied, loudest at WOT while cruising in any gear(easiest to hear with lower engine RPM, generally from 1,500-2,500 RPM range)...

It almost sides like a bearing or brake dragging, but only happening with the throttle applied? That has been throwing me off lately too.

I'll just order myself a can of Amsoil's Power Foam and go to town on the intake...or maybe simply use some TB cleaner like Valvoline(unless an uber product I dont know about is available)?

IACV was cleaned about 2 years ago now, same with EGR ports/valve.

When the clutch was replaced, the mainshaft had no play, and the transmission was deemed in great shape by the latest shop based on what they could tell otherwise without a tear down.

I suspect; if not brake drag(it needs a rear drum brake servicing), camshaft or distributor shaft, the noise sounds top-end, what else would be under more stress on the top-end while using the throttle, to make some sort of higher pitched grind-like sound???

 

[Vikas]

Nothing is simpler than checking for dragging brakes. After you have driven the car, just find the single hot wheel. Don't burn your fingers!

 

[ltslimjim]

^Will the front brakes feel hotter because they are disc? They usually do when I check them, that is to say the rear wheels with the drums always feel 'cooler' than the fronts. The fronts don't ever feel scalding or super hot, but have felt 'cozy warm' before.

 

[ltslimjim]

So, I found out the idle issue is probably the IACV indeed:

http://ecomodder.com/forum/showthread.php/honda-iacv-explained-967.html

The sound while driving is another issue.

PS: and no CEL by the way. I replaced the 02 sensor, it was the stock one at 230,000...so who knows how long it had been running in open loop. The car can't use lean burn with CEL light on, the code was for the 02/LAF sensor anyway... FWIW I used a Standard Motor Products part, other Civic VX users to use this one haven't had any issues to my knowledge.

I suppose another possibility is the alternator might be going or charging longer after these cold starts in the winter???

 

[vaboom123]

Older Honda models have what's called a Fast Idle Thermo Valve located under the throttle body. It controls the idle of the car. They gunk up over time and cause the idle to be goofy. They just require normal cleaning.

 

[ltslimjim]

Originally Posted By: vaboom123
Older Honda models have what's called a Fast Idle Thermo Valve located under the throttle body. It controls the idle of the car. They gunk up over time and cause the idle to be goofy. They just require normal cleaning.


I believe the VX does not have the Fast Idle valve, but mine does have the IACV.

I though the Fast idle is for cold starts only anyway?

 

[vaboom123]

I also believe that the FITV only controls the cold idle. Wasn't sure if you were having cold idle issues also. Just wanted to put that out there. I'd also put my money on the IACV.

 

[ltslimjim]

Originally Posted By: vaboom123
I also believe that the FITV only controls the cold idle. Wasn't sure if you were having cold idle issues also. Just wanted to put that out there. I'd also put my money on the IACV.


Oh, I see. Right on. I also suspect it as well, especially since it's given the definite 'raise/fall' symptom recently anyway. going to clean it removed from the Intake Manifold this week since I have some off time.

Any other advice on the 'wheel test' for brake drag? Are the front wheels(disc) supposed to be warmer than the rear brake?

 

[mechtech2]

A faulty valve would not affect the acceleration of the car.

Idle variations can indeed be the valve, but you also HAVE to have a clean throttle body bore and plate to work with.

You have multiple problems.

 

[vaboom123]

The front brakes do most of the work and would run hotter. I'd invest in a cheap temp gun. They sure do come in handy. I'd also double check for vac leaks with the idle issue just to be safe.

 

[ltslimjim]

Alright, I think the idle can be explained, then. Will check for brake drag.

I found out it's normal for this car to weep a small amount of coolant at the weep hole, in relation to another thread I have that I don't want to bring up.

 

[ltslimjim]

I just remembered something.

It has not stalled on me, but the shop that replaced the clutch said it stalled on them twice and was hard to restart once. I've never had this happen while I drove the car. While the shop had the car it was pretty low on fuel, if that relates in any way. This could have been a sign of the IACV sticking bad as well.