D16HighMileage

iTrader: (1)

This is what I have and used for the RPM test. It refreshes ever second for the live RPM data

muellersfan

I have an Actron too. Works great, but I think the other scanners you and D16HIGH have are equally fine for adjusting idle speeds. Just never use the cluster tach for this purpose because it lacks accuracy at idle speeds.

D16HighMileage

iTrader: (1)

MY RESULTS :
Engine at operating temp (fan came on twice)
Timing checked
Disconnect IACV- RPM at 817-844
Idle screw all the way in
Reconnect IACV- RPM at 875-888 BUT.......
It did EVENTUALLY settle to 715-756. Still not the normal 670 BUT the manual does state it can be +/- 50rpm

This idle is all over the place. It surged today on ride home. It surged briefly while performing this test (surged maybe 5 times then settled with IACV connected)
During this test it even went up to 1,100 rpm for a bit and there was NO LOAD on the engine, as if the fan came on but it didn't. Then it settled. It's fussy.

I believe the tailpipe could be emitting excessive smoke sometimes ( not all the time). I can't tell the color but it seems to have an odor other than exhaust. I'm no expert here though.

VERDICT?

Is it possible I have a valve or valve not seating fully, or even one or more sticking? This could explain the smoke, correct? And possible poor gas mileage? Slight sluggishness? I feel it's lacking power and it doesn't accelerate perfectly smooth through the rev range.

muellersfan

The ignition timing cannot be set correctly unless the engine idles perfectly (670 rpm) and vice versa. It's a Catch 22.

You should be able to drop the idle speed to 450 rpm or below with the IACV unplugged, especially with the idle adjust screw fully tightened. This indicates a problem.

Possibility #1: Maybe the O-ring of the idle adjust screw is leaking.Possibility #2: There is a small but significant intake air leak (TB or IM gasket) or a vacuum leak (any hose attached to IM, such the hose for CC, PCV, FPR, brake booster, or EVAP).
Possibility #3: The throttle cable adjustment is too tight, thereby preventing throttle plate from fully closing.
Possibility #4: Someone increased the idle speed by turning the throttle stop screw (see diagram). This too would prevent throttle plate from fully closing.

D16HighMileage

iTrader: (1)

Before I perform these tests, it's worth noting :

The idle adjuster screw DOES NOT have the plastic/rubber cover on it. It's missing.
I'm confident there's no vacuum leak as I've smoke tested it AND used carb cleaner to spray around the engine bay. No changes in engine rpm during the carb cleaner test.
The throttle body gasket is brand new.

I don't think the throttle cable is too tight. It rests fully on the set screw (no clearance). I don't think it's the throttle set screw either, as I've observed the butterfly valve (with TB removed) and there's no visible light passing through. This would indicate it's closing fully. I'll check these again regardless, and perform this test tonight and report back.

I must ask again. : could it be the valvetrain? Clearances to great or too small? I'll be checking valve lash soon.


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California98Civ

I would wait with valve lash until after I knew the condition of the head gasket better. Your borderline out of spec low compression test results suggest that either the head gasket or the valves are leaking. If the head gasket is healthy then it's the valves. But either way you'll be pulling the head to fix the valves or the head gasket. In doing that you'll be setting valve lash again. Checking the valve lash now might confirm whether it's out of spec or not but it won't definitively answer why your compression is low and why your idle is high. If the valve lash has been set with too smalle a gap, then I suppose it's possible that the valve stems have been bent because they've been banging into the pistons.

muellersfan

^Inconsistent with the surging idle.

A small air leak might be missed by these tests.

A small air leak in the IM gasket is another possibility. In addition, the TB and IM nuts and bolts must be torqued to spec to prevent air leaks.

There should as much as 1/2" of deflection in the cable.






The throttle stop screw should never be adjusted. It would likely be impossible to know if a previous owner adjusted it. If it has been adjusted, it would be very difficult or impossible to bring it back to the factory adjustment, and the easiest fix to replace the TB.



.

muellersfan

Are we looking at the same numbers?

D16HighMileage

iTrader: (1)

D16HighMileage

iTrader: (1)

I'll be checking the TB nuts and bolts to make sure they're torqued to spec. What's the spec exactly? It may be in my Haynes manual.
I'll also be checking the throttle cable for proper deflection tonight.
Lastly, next week, I'll be checking valve lash. I have a sneaking suspicion the issue may lie in the valvetrain. Why? Well considering the poor gas mileage and fumes emitting from exhaust and all these idle issues, it's quite possible, right?
I'm at about 1/8 a tank and I've driven about 270 miles. What's the miles per tank on these? I was thinking it'd be much more than this. This is why I think it may be running rich.

Muellersfan, if I come to the very last test, and everything checks out, and it's determined that a new TB is recommended (due to not knowing if the idle set screw was messed with by previous owner. It's possible considering these idle issues were present before I bought it), I'd have to buy a brand new Genuine Honda one right? Do they even still make them?

TomCat39

As seen in the Factory service manual, 135 PSI is minimum "GOOD" specification on a brand new motor. What this means is a brand new engine of this model that has 135 PSI is considered perfectly fine and will not be touched by Honda. The engine in question has 200,000 miles on it and STILL has compression numbers that are within range of a brand new engine. A touch lower, but it's also not a new engine.....

I have to reiterate muellersfan, are we looking at the same numbers?

California98Civ

We're interpreting the same numbers differently. Mullersfan appears to be quoting the 1996-2000, which does not offer a nominal number on page 3-2. But page 3-2 of the 1996-1998 edition lists 184 as nominal, meaning the stated, expected, or ideal number between maximum and minimum. So I am looking at 135 psi as borderline low and worth examining. I am aware it does not resolve the surging idle, but the OP is also observing low power and a fast idle. Right or wrong, I think there seems to be a compound of problems. My 1998 D16y7 tested at 165-170 psi at 240,000 miles (before replacing leaking head gasket).

muellersfan

135 PSI is minimum pressure for a NEW ENGINE. OP's engine has >200K miles. I would not call this borderline for a 200K mile engine especially when you consider that all cylinders have nearly identical compression. The compression numbers with versus without oil further indicate that the piston rings are like new.

The OP compares his Civic's power to a 150 hp engine. There's no comparison. And a high idle has NOTHING to do with cylinder compression.

muellersfan

Not sure what point you're making. In this thread, I have interpreted the OP's compression numbers as perfectly fine for 200K mile engine. Do you have a different opinion?

muellersfan

If you feel that your gas mileage is poor, then please calculate the actual gas mileage (miles/gallon) for three tanks of gas. Also note that your gas mileage will not be optimal until you resolve the idle issue.

D16HighMileage

iTrader: (1)

Let me start by thaking you personally muellersfan. Your guidance throughout this nightmare has been more than anyone has ever given me in anything. There have been a few other members (you know who you are *wink*), but muellersfan has and continues to offer the support that this community thrives off of.

So......
Throttle cable has plenty of deflection. Actually, it's slightly outside of spec, (a little "loose") but not by much. So, we can rule this out.

​​​​​​Also..... THIS MAY BE IMPORTANT

​I noticed a hissing coming from the engine bay. Now, I'm not sure if this hissing is normal or not, because both a smoke test and carb cleaner test didn't show any vacuum leaks. This hissing is coming from the 2 hoses that meet at this junction. When I pinch either hose, the engine chokes and almost stalls and the hissing stops. Is this a normal vacuum sound? What is this junction (circled)? Is this the FUEL INJECTION AIR CONTROL VALVE? One hose comes from the intake tube and the other goes to the top/back of the valve cover. Apologies, I probably sound like a noob here. I just don't know what this junction is and what purpose it serves. Some kind of vacuum check valve?

TomCat39

Not at all, OP and others were thinking the compression is low and a problem even after you made your point. I was repeating what you indicated as it seemed it was either missed or ignored. Also It was on different pages so I put it all together in one spot to make the same point I believe you were making. Motor is healthy compression wise for a 200,000 plus mile engine.

I will say I now understand California98civ's perspective due to the latest clarification however I personally think it's a non issue as well as a side track from the issue at hand, a high and erratic idle.

muellersfan

You, sir, are overly kind. It's been a joy trying to help you.

Very odd.

Only the D16Y8 engine from the 99-00 Civic EX has the FIA system. It appears that somebody installed the thermostat housing and FIA system from the 99-00 Civic EX in your Civic but used it as the breather hose for the PCV system.

This is bad because it means that intake air can only purge the crankcase of poisonous blowby gases when the engine is cold. Your engine oil likely looks and smells toxic on oil changes.

In addition, air from the PCV system factors into the intake air that determines the engine idle speed. Have you inspected the PCV valve attached to the breather box on the rear of the engine and its hose that runs to the IM?

Please post many more pics of your engine bay. You may have purchased Frankenstein's monster.

D16HighMileage

iTrader: (1)

Muellersfan, could you clarify this? My engine IS the D16y8 as you mentioned: "Only the D16y8 engine from the 99-00 Civic EX has the FIA system." This is my Civic, a 99 EX with the D16y8 engine.
The area in question looks stock to me. The hose clamps, the hoses themselves,even the rusting on the clamps is consistent with the rest of the car.
I'll post some engine bay photos in my next post as well. I sure as heck hope I didn't purchase Frankensteins Monster!
By the way, I have not checked the PCV but will be attempting to do so on Tuesday. It's hard to reach location is what has stopped me from doing so thus far.
Lastly, what is that diagram suggesting where it says "gently pinch here"? What does that test diagnose?

Alao: Should mine have an EGR valve? Maybe these passages are clogged?

ONE THING IS CERTAIN : I have (I believe it's white) smoke exiting the tailpipe constantly. I can be driving 45mph and I can look out the back glass and see the smoke. It looks more like exhaust fumes.
ALSO WORTH NOTING: it's winter here in NH and seeing some fumes is obviously normal. I'd need to be driving it in the summer month to accurate observe these fumes. But it definitely seems EXCESSIVE for sure.

muellersfan

Haha...that's what happens when I rely solely on memory. I thought you had a 98 Civic EX. Can you post more pictures of the FIA hose routing. Hose should run to a nipple on the IM not the valve cover.

Only if it was a 98 Civic EX.

It's a bitch to get out. When I had a 00 Civic EX, I would lie on my back under the car with front end on jacks and reach my hand upward past the oil filter to pull the valve out of the breather box.

If you pinch the PCV hose with engine idling, you should hear the PCV valve click, indicating it's working.

Only the 96-00 Civic HX has an EGR system.

As you say, determine whether smoke persists on a warm day and is accompanied by a slightly sweet odor.

D16HighMileage

iTrader: (1)

No worries at all. Before I verify the hose routing, I'm almost certain it does indeed route to the intake manifold. It only looked like the back of the valve cover.

I'LL POST PICTURES THIS AFTERNOON.

Imagine if it's this damn PVC valve causing all these issues. Is that even possible?

Woryh noting : I'm at 300 miles traveled and my gas gauge is nearly on the red line. Isn't it common for a failing or failed PVC to contribute to idle issues and poor fuel economy?

muellersfan

You should definitely ensure that the PCV system is working properly. However, let's first return to the hissing noise from the FIA valve.

The FIA is designed to increase the idle speed when the engine is cold by bypassing air from the air intake system directly to the IM. To do this, the FIA valve is open when the engine is cold and is closed when the engine is hot.

Was the engine fully warmed up when you heard the hissing noise from the FIA valve? If so, your intuition may be correct that the noise was potentially relevant to the idle issue.

Method to calculate gas mileage:

Fill tank with gas.

Zero tripmeter.

Drive car until gas tank is low.

Refill gas tank, and note gallons dispensed.

Gas mileage = miles on tripmeter/gallons dispensed

Repeat 3 times

Report numbers

D16HighMileage

iTrader: (1)

Engine WAS fully warmed up when I heard the "hissing" noise.
ALSO : When I pinched the hose off the PCV valve, I DID NOT hear a clicking sound. This could indicate a failed PCV, correct? I ordered one through Advance Auto (not a Honda part of course, but it should suffice, right?) and I'll have it Tuesday. I'll have it installed either Tuesday or Wednesday.
REGARDING THE FIA VALVE : This is something you can order through Honda, correct? If we determine it's worth addressing however.

LASTLY : A few engine bay pics. Muellersfan, you scared me for a minute into thinking I had bought "Frankensteins Monster". These should confirm it is indeed a 99 D16y8

muellersfan

Over here in Houston, I'm pretty excited for you because your keen ears may have finally identified the cause for the idle problem, assuming that the hissing noise represents the FIA valve not closing fully and improperly feeding air to the IM of the warmed up engine.

Do you have a clamp that can be used to tightly pinch the FIA hose so that it is unable to feed air to the IM?

If so, hook up your scanner to monitor engine rpm and determine whether clamping the hose (1) causes the idle speed to drop substantially when the engine is fully warmed up and (2) eliminates the hissing noise.

muellersfan

You can often fix a non-functioning PCV valve by cleaning it with carburetor or brake cleaner.

It's important to point out that a clogged PCV valve would reduce the idle speed not increase it. Nonetheless, it's important to have a functioning PCV valve so that your engine oil is kept as clean as possible between oil changes and we can breath clean air.

Sorry, I took you at your word when you said the FIA hose was attached to the valve cover.