Idle issue in 95 Civic

[JZiggy]

Hey guys, I posted this over on a Honda board but BITOGers are famously good troubleshooters, so I thought I'd try here too:

My D15B7 (95 Civic LX) is stock and had been running well up to this point. Idle was rock solid for the 2 years I've had it but recently began to randomly go low at stop lights. I cleaned the IACV (or EACV as per FSM) and the FITV with the help of the FAQ and they both got new o-rings.

Today the idle got rough; you can feel the engine shaking at a stop light. When I push the brake pedal, the idle drops further. Turning on the blower fan drops it even more. Pulling into my driveway I stopped, mashed the brake, and it stalled. It has NEVER stalled out on me before. I'd appreciate any pointers as I start the troubleshooting game.

Investigating further it almost sounds and feels like one cylinder isn't firing, or at least not consistently. If I pull plug wire #1 while idling, it dies. If I pull #2, idle drops or sometimes doesn't seem the change. Wires 3 and 4 seem to just drop the idle.

Here are a few of the obvious things:
- Engine seems to run well once it's out of idle mode
- No obvious or audible vacuum leaks, but I'm not sure the best way to check
- Spark plugs are new NGKs and in good shape
- Wires and new NGK
- Cap, rotor are pretty new
- Timing is right at 16*
- Fuel injectors all read 12.5 Ohms
- Recent coolant exchange, bled like usual (but could be worth checking again)
- Valves adjusted maybe 10-15k ago
- Does not overheat
- Disconnected the battery for a while with no change

Thanks for the input.

 

[Quest]

for distributor-type Honda engines, I always make sure that the cap and rotor are factory OE units and not some aftermarket garbage.

(* I had issues with non-OE in the past, almost to the point of being 100% failure*)

Then proceed to checking for vacuum leaks. I typically use a spray can of ether (known as spray starter for cold climates carb'ed engines) to check/look for vacuum leaks.

Once you managed to identify that no vacuum leaks of any kind (including the intake manifold mating surfaces, etc.)

then it's quite likely that your IAC valve is gunked up. While cleaning it properly may help to restore the functionality somewhat, if this symptom returns shortly afterwards, you know that you may need to get a brand new IAC valve replacement.

Q.

 

[Mr Nice]

Vacuum leak around the manifold ?

 

[Slacker]

I would run a compression test.

 

[Tegger]

Originally Posted By: JZiggy
Investigating further it almost sounds and feels like one cylinder isn't firing, or at least not consistently. If I pull plug wire #1 while idling, it dies. If I pull #2, idle drops or sometimes doesn't seem the change. Wires 3 and 4 seem to just drop the idle.

When the idle is low and rough, do you observe an EVEN roughness, with a definite rhythm to the roughness? or is it an UNEVEN roughness, with no discernible pattern?

 

[JZiggy]

Definintely an even roughness, like 1 cylinder not firing.

Good thought on the compression test. The engine has ~240k, uses a little oil, and has cold piston slap. Runs good, decent power, and gets 38mpg so it's not doing too bad

If I can't get anywhere with the "easy stuff" I will definitely consider pulling the intake off and resealing everything.

 

[OB4x4]

My money would be the dist. cap. Small nearly imperceptible flaws can have an incredible effect on a cap. Had one on a d16a1 motor that had no visible flaws, but was found to be causing a misfire. Almost drove me to insanity.

 

[mechanicx]

From what you've said it sounds like your #2 cylinder is dead or misfiring. Check to see if #2 cyl is getting good spark and check plug conidtion, maybe check compression. You said injector resistance was ok but #2 injector could be restricted or other inoperative.

 

[yonyon]

From what you've posted so far I'm inclined to think this still more of an idle control problem than an ignition, fuel, or engine problem. You might have one cylinder that's stronger than the others and another that's weaker, but the ECU should still have some control over the idle speed and not die out from pressing the brake. Does it seem to idle faster when warmed up than when it's stone cold or the other way around?

You say you've cleaned the IAC. Have you also cleaned the IAC screen and the throttle body? A clogged IAC screen or a throttle body that's full of schmutz can cause this problem.

Did you clean the IAC off the car using solvent in a spray can? Allowing solvent to sit inside an IAC for more than a few seconds can kill it. Cleaning can't fix a dead one.

 

[Tegger]

Originally Posted By: JZiggy
Definintely an even roughness, like 1 cylinder not firing.

Good thought on the compression test.

Check the valve adjustment. If you find one with NO clearance on the #1 cylinder, then you've got a burned valve.

If the valves all have all least SOME clearance, then have a compression test done.

 

[Chris142]

Pinch off the vacuum hose that goes to the brake booster

 

[LeakySeals]

Been there on different makes, maybe some will apply. Most recently the DBW TB Camry in my sig. Was driving me crazy. Yeah, I4's are not very well balanced, will shake over any little thing. But this was excessive. Once warmed up the idle would get stuck too low when the fans or AC came on. Especially at a light with foot on the brake. Lousy shaky low idle. was a vacuum leak coming from a resonator on the air intake box. I had overlooked that for 4 years. Did not know that clamped on, thought the airbox was basically 1 piece. It was allowing air to get behind the MAF throwing things off, especially the vvt-i

If cleaning the TB/IAC/EGR/MAP/MAF doesn't work..

vacuum leak
- Intake manifold gasket
- injector o-rings
- Air Box. Take intake all apart, put it all back together again all the way to the filter seal
- PCV hose
- brake booster hose

Combustion chamber and fuel system deposits.
- Burn oil?
- Valves don't seat right built up with deposits
- misfires from dirty plugs
- bad fuel injector spray pattern
- clogged fuel distribution/pressure

Others
- Oil too thick. Oil consumption?
- Valve clearance. Exhaust valves too tight.

Where to start? Cheapest to most expensive. 3 bottles of fuel system cleaner with PEA additive in 3 consecutive 1/2 tanks of fuel. cleaning the TB/IAC/EGR/MAP/MAF. Take airbox apart, put back together again. PCV and brake booster replacement hoses. Then proceed to gaskets intake and injector o-rings. Then ultimately to valve clearances or compression tests.

 

[yonyon]

Originally Posted By: Chris142
Pinch off the vacuum hose that goes to the brake booster


I read this and immediately felt an urge to start name-calling. That line of thought has me thinking it might be worthwhile to make sure you don't have a stuck open EGR valve. It's not something that happens much on Hondas, but it can happen to anything with an EGR and would tend cause a low, rough idle and is easy enough to check.

 

[Tegger]

Originally Posted By: yonyon
I read this and immediately felt an urge to start name-calling. That line of thought has me thinking it might be worthwhile to make sure you don't have a stuck open EGR valve. It's not something that happens much on Hondas, but it can happen to anything with an EGR and would tend cause a low, rough idle and is easy enough to check.

OP reports an even rhythm to the idle. This rules out the EGR, IACV, MAF, MAP, SOP, NFG, DDT, CIA, FBI, KGB, and any other acronym you care to name.

OP's problem is almost certainly a burned valve or bad rings. Unless it's simply a bad plug or plug wire, which is unlikely, but I didn't think of that until now.

 

[LeakySeals]

Another cheap try is a new TPS. The symptom for that is usually a fluctuating idle, but who knows.

 

[JZiggy]

Well fortunately this model doesn't have an EGR.

Cold idle works fine. When it's cranked up, it goes immediately to 1500-2000 rpm, and settles to 1300. Then it slowly makes its way down to normal idle speed (750).

Drove to work this morning, runs normally and smoothly with plenty of "power" (maybe 80rwhp?). Cold idle is a bit rough but not worrisome. Hot idle will feel perfectly fine, then slowly drop down too low and chug, then pull back up. Not threatening to stall this time.

As far as cleaning the IACV, I went through these exact steps:

http://honda-tech.com/showthread.php?t=1575913

Replaced the screen and o-ring pictures, flushed out the unit with brake cleaner. I also pulled off the plate with the coolant pipes to change its o-ring.

Right now I'm thinking about:

- Double-check that coolant system is totally burped
- Set idle speed as per FSM (need an external tach)
- Check valve clearances
- Replace Bosch cap/rotor with OEM
- Compression check

 

[mechtech2]

You have a dead cylinder.
Go investigate why.

 

[ThirdeYe]

I have the same issue with my Integra. Mine actually stalls on me, though. Usually after first starting the car and putting it in reverse. I was told by the Acura dealer that it's because my IACVs are bad. One is leaking, and one is not operating properly. I didn't even know they had more than one IACV... I also have a hunch it could be my valves being out of spec as well, contributing to the issue. Mine usually only does it when the engine or ambient temp is warm.

 

[harry j]

Clogged injector?

 

[JZiggy]

Yeah I need to investigate the dead cylinder, but it's definitely not dead in non-idle conditions. Runs fine and smooth.

Also considering getting the injectors cleaned and balanced, along with replacing all gaskets and O-rings in the intake.