SureTrack Users General Discussion

[Witsend]

So you have an old engine, 300,000 miles. It's running rich, both by the tail pipe smell and the 02 and fuel trims. You pull the PCV out and feel all the blow by. Just to prove it you do a compression test, it's at the lower limit. The valve adjustment is ok as is the timing. So maybe it's incomplete combustion that's causing the rich smell. But what about the 02s and the fuel trims. The PCM sees the 02 and MAP (speed density system) for trims, the 02 sees a lack of oxygen as rich correct ? How does incomplete combustion contribute to a lack of oxygen in the exhaust? The fuel trims indicate the PCM is leaning the fuel as much as it can

First thing I would rule out an over fueling condition caused by a leaking fuel pressure regulator, causing flooding and washing down the cylinders walls effecting ring sealing and further diluting worn out crankcase oil and sooting up the spark plugs.

[dodge90]

Well, Maven, Thats quite the interesting way of explaing it. Never heard it that way. Makes sence. All I go by is low voltage,Less fuel, Lean, High voltage, more fuel, Rich.
On the low compression issue, unless the compression is that low and my personal psi is 100, depending on the other readings that is,might conclude that it,s not completly burning the fuel thus more co and nox over powering the oxygen. with 300,000 miles on eng. I would think more of dirty injectors not spraying right causing the unburnt fuel. just my 2 cents
Another good point Witsend.
Good question BOB

[greasybob]

A real car, 97 Accord 2.2. I'll post a screen shot and/or scanner movie later.

[Crossland Auto]

V.W. From hell!!!

The final resolve (though it is still in theory until the Granddaughter tells the truth).
Out of desperation, with the head on the bench, I decided to install the cams (with no followers installed), found the Exhaust cam was easy to turn by hand, the Intake was damned near rock solid. I had to install the old phaser and bolt, and use a ratchet to turn it.
(This head does not use Cam caps, just one big guide plate with 29 bolts. The guide plate covers the entire surface of the head, the cover bolts to it.
The plate is machined to the head with guide pins installed in the head).
I can only guess that someone had been here before, cracked the guide plate, found a used one.
After 2 days of using "Dykem" bluing, I was able to SLOWLY file the openings for the guide pins, and free up the Intake cam.

[Crossland Auto]

My only guess is that the engine was jumping time when being shut off.

My theory is that it was being shut down, loosing oil pressure on the upper tensioner, 1 of the 5 pistons was stopping on a compression stroke. The crank would reverse direction for a few degrees. That would run the lower chain and intermediate cog backwards. That would suck in the tensioner in on the upper chain, feed the slack to the Intake Phaser, (since the cam was tight) the chain would jump a tooth at a time.

RESULT: Intake cam would end up off time in an advanced state.

Could also explain the initial reason of why it 1st came in. Intake cam tight, the direction of the chain drive may have backed off the bolt since the phaser is press fit.

Still just a theory, but gone 3 days now.

X

[Witsend]

I bet that engine needs to be stone cold, have the followers removed, and then be gradually de-torqued in a specific sequence. Damn cams look composite , like lobes pressed in to tube sections that are also pressed into each other. Wonder if the valve crashing caused pressed intake cam sections to get slightly twisted out of alignment with cam saddle bore. Scary , hope it never comes back

[Crusty]

X-land
Everyone knows that crankshaft journals in a block need to be line bored.

SAME THING for overhead camshafts that sit in a flexible piece of metal (aluminium cylinder heads).

Ran into that argument with an engine rebuild company back in 1994-!! Funny thing was, the very next month there was an article regarding that very issue in a local trade magazine. The camshaft journals in the cylinder head need to be line bored as well.

The previous issue I had was at a dealership I worked at back in 1985-!! The service manager and the warranty company sent a block out for piston resizing but they refused to line bore the mains. The crank wouldn't spin even before anything else was assembled....no timing chain, no pistons & connecting rods.

Witsend brings up a good point that isn't common knowledge on today's engines. Even the clamping bolts need to be removed IN SEQUENCE when disassembling an engine on some designs.

Learned my machine work back in the 1970's and the more things change, the more they stay the same.

Your theory regarding the binding sounds plausible. Very sorry to hear it happened to you on this convoluted engine design-!!

The grand daughter may not know or may not even remember a simple overheat event in the past.

The devil is in the details.

[greasybob]

Here is a of screen shots from the accord. I see a problem with the down stream 02. Maybe it's having more effect than I thought. The second screen seems a bit better, but never goes to closed loop but I'm suspecting that that PID is wrong as it will show closed when the throttle is snapped.. Also long term never changes ? Should add that compression is at 125 psi, timing is correct as is valve lash and no injector or fuel pressure regulator leak down. Also no evap leaks. 125 psi is at that bottom end of the specs.

[maven]

Greasy, is 8.5"hg a common idling vacuum on one of those? seems insufficient to me. Low vacuum = high load to the ECM. Fueling for high load and finding that causes a rich condition and therefore start pulling fuel.

[maven]

Well, Maven, Thats quite the interesting way of explaing it. Never heard it that way. Makes sence. All I go by is low voltage,Less fuel, Lean, High voltage, more fuel, Rich.
On the low compression issue, unless the compression is that low and my personal psi is 100, depending on the other readings that is,might conclude that it,s not completly burning the fuel thus more co and nox over powering the oxygen. with 300,000 miles on eng. I would think more of dirty injectors not spraying right causing the unburnt fuel. just my 2 cents
Another good point Witsend.
Good question BOB

Yeah thats just a way I like to use to explain how typical zirconia type O2 sensors work. Seems to help some guys wrap their head around what the sensor is actually doing. Didnt know if this was a real car or a mental exercise so was kind of thinking via type so people could follow my lean incomplete combustion proposition, Haha.

Youre right though Low Voltage=Lean, Lean=Lotsa oxygen is all you really need to remember 99% of the time, that and that this is just what the sensor is telling the ECM, its not necessarily what is going on in the exhaust stream.

[Witsend]

Here is a of screen shots from the accord. I see a problem with the down stream 02. Maybe it's having more effect than I thought. The second screen seems a bit better, but never goes to closed loop but I'm suspecting that that PID is wrong as it will show closed when the throttle is snapped.. Also long term never changes ? Should add that compression is at 125 psi, timing is correct as is valve lash and no injector or fuel pressure regulator leak down. Also no evap leaks. 125 psi is at that bottom end of the specs.

Late valve timing will cause lower compression readings and low engine vacuum. I wonder why the baro reading isn't like 14.7hg?. Engine temp is kind of at the point I would like to see a radiator fan kick on. I would zip off the 3 or 4 valve cover bolts , take the upper timing cover off and check the T-belt, and take a peak at a cam journal cap to make sure the head's not junk from overheating. Try unplugging the downstream O2 sensor, High volts could be the heater circuit starting to short to the sensor side that you really shouldn't see much more than 1 volt

[Robin]

Baro is reading 28.6, map is reading 8.5
Doesn't this mean the engine vacuum is 20.1?
If so, that seems about right.
Or am I way off base?

[maven]

Baro is reading 28.6, map is reading 8.5
Doesn't this mean the engine vacuum is 20.1?
If so, that seems about right.
Or am I way off base?

I didnt even notice the BARO reading honestly. If the MAP sensor is reading 8.5"hg absolute then yes youre correct, its 20.1" vacuum. Stupid Hondas, haha.


That O2 sensor at 3.5+ volts is definitely a problem. If its anything like certain GM ECM's it will perform a rationality test on the system to determine if the rear sensor is still there. It does this really similarly to the way it performs P0420 checks, but on a more aggressive scale. GM cars with missing,disabled or otherwise dead rear O2 sensors that use this strategy suffer from drivability issues when this test is going on. Its strange that the ECM hasnt set a P0138 yet, but stranger stuff has happened. Id disconnect the rear O2 and short the signal circuit to the ground circuit, verify that HO2S-2 voltage goes low. If it does youve got a bad HO2S-2, if it doesnt youve got a wiring issue or an ECM failure.

28.6"hg seems low for atmospheric. You have a nasty low pressure system where youre at Greasy? you well over 1000ft above sea level?

[Witsend]

Baro is reading 28.6, map is reading 8.5
Doesn't this mean the engine vacuum is 20.1?
If so, that seems about right.
Or am I way off base?

I doub't if the engine vacuum gets that high if compression is only at 125psi (warm). I would use a vacuum guage and see what it says. My guess is the cam is retarded a tooth and I would look at the distributor to see if it appears reclocked to achieve proper ignition timing (If that year even uses a distributor)

[greasybob]

Timing is dead on, but I'll check to see if vacuum is what the scanner says, thanks.