Frustrating month

[MotorMouth93]

Any idea why the VTEC flag is coming on when the engine clearly is not in VTEC?

If the ECU is throwing VTEC error codes I'd assume its related to that, perhaps the ECU is using VTEC fueling as a failsafe to protect against a lean condition in case somehow VTEC was stuck engaged? Next time I feel inclined to dig through assembly code I'll see if there's a code path for that related to VTEC errors.

If the VTEC flag is still set once the issue is resolved then we can try to figure out if something strange is going on.

 

[mskrotzki]

Well, I put my car back together and took it out for a run. The good news is there are no oil leaks around the pressure switch and spool valve. The not so good news is the car continues to bog down at 6944 RPM. I've uploaded a video of this morning's run on the Google Docs file here:

https://drive.google.com/drive/folders/1Q4Gp9o0bTzopCs24VK3hBu_S2OWP9luk?ths=true

where it is file: 2021-04-07 19-56-26.mkv

Tjhe colors on the dashboard match the colors on the monitor graph. You can see the two PE runs at about 8.5 seconds and again around 19 seconds, were the car seems like it is in a fuel cut-off situation.

When I disassembled the spool valve yesterday it did seem like the piston was stuck. I didn't realize the piston was under spring pressure stuck 1/4" above its body until I reassembled it after cleaning. That seemed like it might be a problem -- but it wasn't the problem.

I've double checked the bin file and VTEC is engaged at 6000 RPM (Hysterisis On at 5800 RPM).

Is there a way to determine if this is what the ECU is actually doing? There have been a flakey AFRs right around 5600 -5800 since I began this project. I guessed this might be due to the intake runners changing at ~5000 RPM. Perhaps there is more to it.

Anybody have any ideas?

 

[MotorMouth93]

Are you still getting the VTEC trouble codes? Fuel cut at 7k is completely normal if VTEC isn't engaging, it's the engine trying to protect itself from a potentially dangerous condition (or more likely a sensor or wiring issue).

 

[mskrotzki]

Are you still getting the VTEC trouble codes?

No. I haven' t had that issue in quite a while.

 

[Honcho]

Are you still getting the VTEC trouble codes? Fuel cut at 7k is completely normal if VTEC isn't engaging, it's the engine trying to protect itself from a potentially dangerous condition (or more likely a sensor or wiring issue).

I was thinking the same thing. If it is cutting fuel at 7,000, then the engine is not in VTEC and the ECU is running on Map 3. Aren't the criteria for the engine to switch over:

1. Throttle position
2. Load
3. RPM
4. Oil pressure

Also, from re-reading [MENTION=7151]mskrotzki[/MENTION] 's post, it seems quite unusual for both oil pressure switches to fail at the same time, as error codes 22 and 52 would indicate. I wonder if the engine isn't making enough oil pressure generally and the ECU won't switch over to protect the engine. It might be worth connecting an oil pressure gauge to the filter pedestal and testing from page 8-5. Also, I would do the VTEC oil pressure test sequence from pages 6-15 to 6-19. You'll need a M10 x 1.0 adapter for the VTEC oil pressure port and a 1/8-28 B.S.P. adapter for the oil pedestal. You should also use a tachometer- the dash gauge is unreliable for this purpose.

 

[mskrotzki]

Oy gevalt! I misintrepreted the trouble codes and thought 22/52 was the rear spool valve/oil pressure switch - not the front/rear pressure switch. The hurrider I go the behinder I get.

I'm going out right now to do the same thing to the front switch as I did to the rear. Saving grace is it should be MUCH easier than the rear. FWIW, it easier to get at the most rear bolt on the switch from under the car with the wheel removed, and it helps to remove the rear brace. The rear switch with the engine in the car is way more difficult that it would seam -- due to the tight quarters you need to jam your hands (and tools) into.

Stand by for further results

 

[mskrotzki]

Pulled off the front VTEC Switch and Valve and dissambled and cleaned. No different than the rear one. I just returned from a short pull on US 6 west (right into the setting sun) and there is no change. I was not able to watch the oil pressure gauge, but I doube if it was any different from yesterday -- were it stayed right at 6kg/cm[SUP]2[/SUP] . With a brand new engine I find it difficult to believe there is an oil pressure issue. Nothing in the charts is jumping out at me. I'll put the .xdl on the Google Docs page for anyone to look at.

I'll go through all the .xdf definitions to see if I can latch on to something. Until then, everyone stay healthy.

Mark

 

[mskrotzki]

If you want to look at the macro enabled excel sheet, download it and open in excel (doing whatever you have to do to open the macros). If you try to open it in google docs, it will open in google sheets, which can't do macros and therefore can't do the charts I have created.

 

[MotorMouth93]

If you want to share you bin file I can load it into my car and see if I have the same problem.

I don't think this will be solved in the tune, I think this is a hardware issue.

 

[mskrotzki]

I'll put the bin on the Google Docs page. If you run it and all is well, then it is clearly not the bin file. I've already put a known good bin ( one of Brian's that I ran for years -- and didn't very much like) and it make no difference. The more I can eliminate, the closer the solution will come.

Thanks

 

[Honcho]

What's weird is John's car goes reliably into VTEC on the same bin.

 

[MotorMouth93]

If you swapped back to a known working binary with the same problem then it sounds like it's not an issue with the tune then, and is an issue with the engine or wiring.

Have you disconnected the battery to reset the ECU memory? Just flashing a new tune can still leave old stuff in ECU RAM.

The factory oil pressure gauge is not reliable so doing as honcho suggested and hooking up an aftermarket oil pressure sensor is probably a good idea to rule out oil pressure problems.

 

[mskrotzki]

I talked with Paul Z this morning and he is looking for his oil pressure gauge. It is a good excuse for a pleasant drive down south. What we my find is a major concern -- but if it is low oil pressure, I'm sure SOS will stand by their work.

I haven't lobotomized my ECU, but will do so. Where do the CEL codes live? I get the same behavior from the car, but I haven't gotten a CEL in the last few runs. Are they in the inner working were we have no access?

 

[Honcho]

I talked with Paul Z this morning and he is looking for his oil pressure gauge. It is a good excuse for a pleasant drive down south. What we my find is a major concern -- but if it is low oil pressure, I'm sure SOS will stand by their work.

I haven't lobotomized my ECU, but will do so. Where do the CEL codes live? I get the same behavior from the car, but I haven't gotten a CEL in the last few runs. Are they in the inner working were we have no access?

My best guess is they messed up installing the head oil control orifices in the block. Either failed to replace the o-rings or the o-rings got pinched/cut when they pushed them in. The heads would still get oil, but at a lower pressure.

 

[mskrotzki]

I'll get an oilpressure reading as specified on page 6-18 of the manual before doing anything else. If Paul's best guess is right it is going to be a real PIA.

Would a skilled ear be able to determine low oil pressure/volume in the valve train during start-up or after? If it is too low I really don't want to drive very much. To my ear -- I determine nothing, but I'm only used to my car.

Anyone in Denver have an oil pressure test kit? They are not hugely expensive, but for a one time test I would just as soon not put out the cash (or have another thing cluttering up my home.)

Let me know

 

[Honcho]

I'll get an oilpressure reading as specified on page 6-18 of the manual before doing anything else. If Paul's best guess is right it is going to be a real PIA.

Would a skilled ear be able to determine low oil pressure/volume in the valve train during start-up or after? If it is too low I really don't want to drive very much. To my ear -- I determine nothing, but I'm only used to my car.

Anyone in Denver have an oil pressure test kit? They are not hugely expensive, but for a one time test I would just as soon not put out the cash (or have another thing cluttering up my home.)

Let me know

John pointed this out- the VTEC system is supplied with oil pressure from its own dedicated passages in the head (off of Main #4 ) that do not run through the oil control orifices. The VTEC pressure switches are there to confirm that the changeover has occurred. Basically, the solenoids are energized when on the low cam- this pushes the spool piston down and blocks engine oil pressure from reaching the VTEC pins inside the rockers. When the ECU sends the command to switch to VTEC, the solenoids shut off, which causes the piston to rise under spring pressure. This releases engine oil pressure to the rockers. The VTEC pressure switch looks for this change in oil pressure (~0 to 50+ psi) and confirms to the ECU that the changeover has occurred. If it doesn't see the pressure change, it will throw the 22/52 code.

In your engine, you have seen the 22/52 code, which is the ECU saying there was no oil pressure change after it commanded VTEC (also may explain why the VTEC flag is on in the log, but the engine is not in VTEC). So here's some of the potential causes:

• The solenoids are not working. Not likely, since if they were inactive, the spool valve would always be getting full engine oil pressure and the car would always be in VTEC. You would also get error code 21 and/or 51 and it would run terribly.
• There is a blockage in the oil passages that feed the rocker pins. This could explain why the ECU thinks the car is in VTEC but the engine is not. Oil is not getting to the pins in sufficient pressure to lock the rocker arms.
• There is not enough oil pressure generally at the heads to lock the rocker pins. This likely is due to a larger issue with the oiling system. Bad oil pump? Blockage in the mains?

That's why you/Paul Z should do both the VTEC oil pressure test and the general oil pressure test. The VTEC test will tell you if sufficient oil pressure is getting past the spool piston. If it checks out, then you know the issue is between the spool valves and the rockers. If it's a general oil pressure problem (e.g., there is enough oil pressure to fool the pressure switch at changeover, but not enough to lock the rocker arms), you'll have to look deeper.

 

[Honcho]

I helped Mark do the VTEC oil pressure test yesterday at my place. The first clue of a problem was that the test plug bolt was bone dry- meaning oil has never reached it since the engine was re-assembled. The engine failed the test- essentially no oil pressure with the solenoid plugged or unplugged. This means that the plunger assembly is closed and blocking the flow of oil to the rockers (and the inspection port). Considering Mark already removed and cleaned the plungers (we know they are not binding on anything), the only other thing we can think of is that the solenoids themselves are mechanically stuck open- preventing the plunger from moving up once VTEC is engaged. They use oil pressure to hold the plunger closed. I lent Mark my spool valves and he's going to swap them and see if the problem persists.
[MENTION=25737]Kaz-kzukNA1[/MENTION] any thoughts?

 

[mskrotzki]

I'm spending the morning pouring over the manual and web descriptions of VTEC and wiring. The spool valve/solenoids are such simple devices I'm finding it hard to believe that BOTH of them have somehow failed.

I'm trying to find the electrical circuit path from the two connectors on each mechanical device to their other ends, where ever they are, so I can test them for continuity. So far I've achieved no joy (but I've learned a hell of a lot I never knew (or cared about) before). Most interesting.

Another thing I've noticed is in all my data logging, I've never seen a load value over 82 psi. In the bin file I only see CTS and RPM criteria for switching to VTEC. Am I missing something?

I'd appreciate any thoughts or insights before I go out and change both controllers. It's pretty cool today and it's not an inviting job (and I don't think it is going to work.)

Thanks

 

[mskrotzki]

I think I see it on manual page 11-9:
Front spool solenoid valve goes to terminal F5 on the 8 pin connector on the ECU
Rear spool solenoid valve goes goes to F7 on ECU
Rear Oil Pressure Switch goes to F4
Front Oil Pressure Switch goes to F2

Perhaps later I can check it out on Paul's harness, which is sitting in a box in his garage before checking for continuity in my car. Expect a text Paul!

 

[MotorMouth93]

The load value as reported in the early XDFs is a unitless 0-100% value derived from the MAP sensor. You'll never see a full 100% as manifold pressure will always be slightly lower than atmospheric pressure due to the restriction of the intake system (air filter, throttle body, piping, etc.)

In my personal XDF files I've changed it over to an actual manifold pressure reading since that's a lot more meaningful but I don't think I've shared those files yet. If I ever make another release the load will read in PSI instead of percent.

The VTEC test plug is dry on my car too and I hit 8k/VTEC every time I drive it, I think there's an air bubble that gets trapped at the test point so you won't see much oil there.

 

[Honcho]

A really helpful description of the spool valve mechanism from Honda-Tech (from a D-series, but effectively the same system as the NSX):

Engine oil enters at A. A channel routes it to the solenoid at the top. When the solenoid is dormant, the oil reaches a dam and progresses no further. Oil is blocked by a plunger, called a "spool valve", from moving from A to B, and oil pressure has no affect on this valve as it can only apply force around the circumference. A spring at the bottom of the valve provides backpressure to the system and keeps the valve secure in its resting position. C and Z vent to the oil pan. Oil is allowed to vent from B to C through two small holes in the spool valve channel to purge any oil blow-by caused by a leaking plunger between A and B. B is the location of the vtec pressure switch, and vents back into the engine block to actuate the cam locking pins. In this configuration, B receives no oil pressure.

When the solenoid is energized by the ECU, oil pressure is applied to the top of the spool valve and causes it to lower, ventilating through a small restriction hole into C to maintain pressure on the spool valve. This opens the passage between A and B, allowing oil to reach the pressure switch and access the cam locking pins. At the same time, the spool valve closes on the purge holes in C, maintaining pressure in B. Z now serves as potential pressure relief, as pressure between A and B attempts to drive the spool valve down and escape through Z; this supplements the pressure provided by the solenoid and ensures the valve remains depressed while the system is energized. When the system is deactivated, there is insufficient backpressure to counter the force of the spring, and the valve returns to its original position, allowing B to purge.

**Note- this appears to contradict the language in the 1991 NSX service manual to the extent it states the ECU energizes the solenoid. On page 5-8, it states: The solenoid valve, in response to a signal from the PGM-FI ECU, closes the oil passage to the rocker arm at low speed. What is strange is that, if the service manual is right, then the default state of the engine is VTEC and it is only an electric signal from the ECU that keeps it on the low cam. Wouldn't you want the car to default to the low cam if there was a problem? I'm inclined to say this is an error and, when not in VTEC, there is no signal to the solenoid (defaults closed).

 

[MotorMouth93]

**Note- this appears to contradict the language in the 1991 NSX service manual to the extent it states the ECU energizes the solenoid. On page 5-8, it states: The solenoid valve, in response to a signal from the PGM-FI ECU, closes the oil passage to the rocker arm at low speed. What is strange is that, if the service manual is right, then the default state of the engine is VTEC and it is only an electric signal from the ECU that keeps it on the low cam. Wouldn't you want the car to default to the low cam if there was a problem? I'm inclined to say this is an error and, when not in VTEC, there is no signal to the solenoid (defaults closed).

The term "signal" here can refer to any sort of change in voltage on the VTEC control wires so the wording in the manual is valid. You could say the ECU signals the solenoid to turn on then signals it again to turn it off.

Looking at the ETM, the VTEC solenoids are grounded and then the ECU provides a positive voltage to activate them. So the ECU "signals" the VTEC solenoids to activate by supplying 12V to the control wires, then "signals" it again to disable VTEC by changing to 0V at the control wires.

The default state of the VTEC system is off, if it wasn't you'd be on the VTEC lobe just by unplugging the solenoids.