I've done some searching here and tried several things I've found but still have a hunting/surging issue on my 95 so I"m looking for things I've missed or overlooked.

The car is a 95 Civic 1.6 SOHC V-Tech engine with an automatic transmission, it is all stock. It was running fine when I went to work and when I started it after work the idle was very low around 300 RPMs and it was surging/hunting around 1200 rpms. Check engine light was on with a Code 14 set. It runs fine except for the surging and the check engine light.

Attempted resolution steps:
Removed and cleaned the IACV, the valved ohm'd out at the right value, no change - Replaced with a cleaned one from the junkyard, idle came up to about 500, still low but was still hunting/surging around 1200 and check engine light was still on. Reset computer Check engine came back on immediately.

Removed and cleaned the FITV, FITV was pretty clean to begine with, no change. Reset computer Check engine came back on immediately.

Checked for vacuum leaks, none found.

Replaced throttle body with cleaned one from junkyard this included TPS, MAS, & FITV, no change. Reset computer Check engine came back on immediately.

Sprayed Carb cleaner down the intake at idle and high idle, no change.

Dug around back and replaced the PCV valve, it was pretty cruddy but still rattled, no change.

I'm out of ideas here, I think it's possible but unlikely that I got the exact same bad parts from the junk yard. Does anyone have any ideas of what I may have overlooked or what I need to focus on?

 

Remove the air intake system when the warmed up engine has the high hunting idle. Use your finger to cover the hole inside the TB running to either the IACV or FITV. Does covering one of these holes drop the idle speed and prevent the surging?

 

Thanks Ron, you've helped me before. It's late here so I'll check it tomorrow and post what I find.

 

Ok, so I found 2 ports, one about the 7 o'clock position which I presume to be the FITV and one at the 10 o'clock position which I presume to be the IACV. Both had suction but the IACV had more at all times which is what I would have expected given it's function. I covered both ports one at a time and opened the throttle and the hunt was there at 1200 -1500 RPM's. I cracked the throttle plate and covered both ports and the hunt was still there. Does this eliminate the 2 idle valves as a cause of the issue? If that is true than what can set a code 14 that doesn't involve the IACV?

 

You have an intake air or vacuum leak.

 

There is a small crack in the hose from the air filter but that is before the throttle plate so should not be an issue. I sprayed around the intake manifold but detected no leak, i.e. engine RPM's did not change. I could go over it again with propane and see if that gives a different result. When I slowly cover the intake plenum the engine dies quickly so the leak, if exists, would be pretty small I would think. It sounds like the focus is still on the air coming into the engine and/or looking for a vacuum leak.

 

Post a picture of the cracked hose.

An intake leak can also come from the TB gasket.

 

Have you checked the tps? I know you changed it but did you test it?

How about the gasket on the iacv, they get brittle with age.

The fitv, when warm should let very little air through, almost none. It's the lower hole. From what i understand you can thread the wax plunger down tight and stop some leaking air if not all.

Just because you replaced with junk yard parts doesn't mean they are better than what you had

Also did you properly set the idle after changing the tb?

With engine warm and iacv UN plugged set idle to 550 rpm then plug in iacv and reset ecu

 

Posting a pic is a challange I haven't set up an outside pic account yet and if I remember correctly, I can't post a pic directly.

The crack is about an inch long at the throttle body under the clamp at the seam in the hose. The car hunts the same with the hose on or off so I don't think that is the issue, if anything it will let a little dirt in past the filter. Actually, I may have cracked it when I removed it to change the throttle plate. The throttle plate gasket is new as I bought a new one to prevent any sealing issues. I'll try the propane after work tomorrow.

 

If you reply under advanced mode you can click "manage attachments"and upload directly to ht

 

You can post pictures.

1) Click Edit Post>Go Advanced

2) Click picture icon

3) Drag picture into "upload images" window>click insert

4) Click save changes

 

Nice, these boards have gotten much more user friendly than what I'm used to. See attached pic.

 

Yeah, that's the breather hose. It isn't causing the high idle, but replace it so that no debris is drawn into the engine.

 

Yep, this weekend taking a trip to the junkyard for that and parts for my 87 CRX. In the meantime I'll focus on using propane to check closely for vacuum leaks. Any other suggestions on something that can be sprayed to identify vacuum leaks?

 

Vacuum leaks
All vacuum hoses attach to the IM, so you can disconnect one at a time and then block the IM nipple to see whether the surging stops.

Intake air leak
You can also replace the IM and TB gaskets and torque the nuts and bolts to spec. Also inspect the IACV and FITV gaskets, as mentioned.

 

So I pulled every vacuum hose to the IM and plugged it with no change. I did think it was interesting that when I pulled the booster or the PCV hose which momentarily introduced a lot of air, the engine started hunting at idle, normally it will hunt in the 1200-1500 RPM range. I ran propane all over the gasket areas and found no rise in idle speed. I'm at a loss here, it seem like an air issue but I have no idea where it could be coming from.

 

Did you also inspect the IACV and FITV gaskets/seals? If so, redo the tests blocking the IACV and FITV holes in the TB. If neither has an effect on the idle speed, then replace the TB and IM gaskets. Torque the nuts and bolts to spec with a torque wrench.

 

So you are not hunting at idle, only at a certain rpm (slightly raised to the 1500 range by the sounds).

Have you cleaned the map sensor with electrical cleaner (isopropyl alcohol based)?

You've pretty much rules out the FITV and the IACV and sounds like you've pretty well covered the vacuum leak angle.

To me that only leaves the MAP as on of the sensors that has an impact on the engine based on air flow.

 

Or tps. I mentioned checking it with a meter. I forget the exact wire color but it's the middle wire.

.45v closed 4.5 v wot. Make sure the throttle cable does not have too much tension on it or too little as it will skew those readings

 

So it took me awhile but I finally got around to doing some tests on the car this weekend. Replaced both FITV and IACV O-rings with no change in symptoms, I also tightened the FITV all the way down. I set the idle per recommendations but after reconnecting the IACV it was idling over 1000 RPM so I had to back it off a little. Started doing some other tests:

MAP - Reference volts = 5V, Signal voltage - 0 in hg = 2.97, 10 in hg = 1.93, everythign in the correct range according to my book.

TPS - Reference volts = 5.05V, Signal voltage - throttle closed = .5V, WOT = 4.36, a little low on the WOT but I don't expect to ever get there.

Going out on wild goose chase since I don't have any of the symptoms, I checked the timing belt, I change it about 5 years ago and it was still pliable and soft, no issues there.

I will change the TB gasket this weekend but I really don't think that is the issue.

Do these things have an EGR system, I don't see anything familiar like that? The Accords will give similar symptoms when the EGR ports get plugged.

I haven't checked fuel pressure yet which also may be a long shot but it could be an issue, I had to make an adapter for testing it this last weekend and haven't had time to get back to it.

I'm still at a loss as to what is going on.

 

When checking the tps make sure it flows from .45 to 4.5 smoothly and does not lower or raise when it is not supposed to.

I have a feeling that at slight throttle it's reading lower than normal telling the ecu it's idling making it hunt for idle with the plate slightly open. Just make sure I have checked the full range

 

Post a video of these problems.