04TLazine

I parked the car with no problems and came back to it the next day upon starting it the engine didn’t sound quite right, I began driving and it started shaking with an obvious misfire (RPMs were only ever at 850-3500 or 4000 for this 3-5 min drive) I turned around and parked it. After I used my cheap code reader (Innova 3030 f ) it came back with 13 trouble codes 12 of them were engine misfire codes listed twice cylinders 1-6 ( P0301 - P0306 ) and misfire in multiple or random cylinders ( P0300 ). The one code that was not a misfire code was P2647 VTEC Oil Pressure Switch Circuit High Voltage .

I removed the oil pedestal assembly and incorrectly tested the oil pressure switch and replaced it with a new one from Oreileys (import direct I believe) which included the sensor as well as the connector. I also replaced all of the gaskets on the oil pedestal assembly (Pressure switch o-ring, oil pedestal gasket, and VTEC solenoid seal).

After reinstalling the oil pedestal assembly I deleted the codes with the reader, started the car and had the exact same symptoms, rough running engine and bad sounds. I turned the car off, disconnected the battery and let it sit for 20-30 minutes after which I reconnected and turned the car on again. Still the same symptoms, I let the car run for long enough to get the Malfunction Indicator Light to come on. The misfire sounds from the engine changed slightly/slightly improved after 20-30 seconds but marginally.

I scanned again with my cheap code reader and this time had 11 codes 10 were misfire codes and the other was P2649 VTEC Solenoid Valve Circuit High Voltage . I pulled the Oil Pedestal again and removed the solenoid then tested the solenoid continuity read 14.5 ohms (FSM states 14-30 is a pass, I grounded on the metal case not the vehicle ground as in the manual). I couldn’t find a wiring diagram in the 2004 Factory Service Manual that showed what voltage the computer sends to the solenoid so I did what I saw shade tree mechanics on the internet doing (not a great plan I know but I was desperate) and powered the solenoid with 12v from my battery using a pair of jumper cables. Note: Before doing this I pressed the solenoid plunger with a pick to test for movement and it slightly moved (saw this suggested on a non TL specific post on a Honda forum. I put the Positive cable on the solenoid connector pin using a random electrical connector pin to extend the pin outside of the connector plastic and then placed the negative side on the metal case of the solenoid near where the bolts pass thru the case. The solenoid clicked and I saw movement from the plunger.

That is where I’m at. I will attach images of the FSM pages detailing the two VTEC related codes. My problem seems to differ from other forum posts on these codes in the way that my car is experiencing problems running at low RPMs while others with these codes experienced power cuts at RPMs above 3500 and 4000. The original VTEC Oil Pressure Switch has passed the continuity check detailed in step 8. I don’t understand why the MIL for the switch has gone away after replacing the part if it was okay and why there is now a MIL for the solenoid after it has passed its tests. In step 5 of the Switch troubleshooting the manual dictates if the Honda scan tool doesn’t find a fault with the switch then the solenoid is to be replaced… so after changing the pressure switch and that code going away doesn’t that indicate I should have in fact changed the solenoid when I was on step 5? But the trouble shooting of the solenoid only dictates changing it if it does not OHM out correctly?

04TLazine

For the first person who gives info that leads to a resolution of my problem I will buy a beer payable through venmo, cashapp, PayPal, or crypto. I mean I could send cash if you’re into supporting the US Postal Service.
posted in a separate section so mods can delete if not allowed.
Thanks!

Ron A

Good luck with solving your problem.

Valens

The tests aren't foolproof. Just today I replaced an actuator that tested okay according to the service manual (Toyota, not Acura but still). You're on the right track, I vote for changing the solenoid..

El_Cheapo

@04TLazine Some notes:

1. Always try to use OEM electrical components. Aftermarket is usually junk and could have you chasing your tail.
2. The FSM is written by engineers so their troubleshooting steps usually leads to resistance checks and updating ECM.
3. Honda misfire DTC strategy can be misleading. One true misfire can actually trip the ECM to throw misfire codes for other cylinders and P0300.
4. I am assuming you changed the oil and checked oil level.

All of the diagrams in my post are for the 04-05 TL

04TLazine

Thanks for the suggestion, I was hoping for this too.

I pulled a solenoid from the junk yard and tested the resistance of it, it passed. So I installed it and still had the same problem.

This time I had someone there next to the engine listening and they pointed out there is a mechanical noise going on like a banging (I thought it was the misfire) so I fear now it might be a problem with the valve train..

04TLazine

Thank you so much for posting these! I couldn’t find the electrical diagrams in my manual for the life of me.

Now I’m concerned it might not be an electrical problem, I’ve replaced the solenoid and sensor to no avail, and I had someone next to the engine when I tried it last and they told me the banging sound which I thought was the misfire actually sounds like a valve train issue.

I’ll be looking in the spark plug holes to see if there are any marks on the pistons or God forbid a valve and/or pulling the heads.

My TL had noisy valves which I didn’t pay any mind to until now when I started reading about valve adjustments.
The VTEC codes in my case accompany a misfire (and banging noise) from start/idle not just a limp mode so that’s different from the other threads I’ve seen on these codes which makes me more concerned it might be a mechanical problem.

I’m going over the diagrams you posted (thanks again) + looking up pages referenced on them in my hard copy (2004 edition) to try and see how the physical rocker arm could possibly trigger this code.

Would it help if I took a video of the noise?
At this stage if something catastrophic happened I’m not sure 10 more seconds of run time would make a difference.

El_Cheapo

@04TLazine

If the misfire happens at idle then it's easy to confirm the problem cylinder. Unplug the coil harness one at a time and notice if there's a change.

Just because you used new parts does not mean they're good. Did you use OEM or aftermarket?

Watch this video to see if you can use some of the testing methods for your case:

04TLazine

Thanks El Chepo for the suggestion to check misfire pathways. I found plug 5 (front bank middle cylinder) had blown out of the plug hole and was missing the prongs on the spark plug.

I have taken the front valve cover off and turned the engine over with no fuel or spark and did not hear the noise. But when I got the car back together the same knocking sound was there. Maybe someone can help identify what this noise is?

Calling a mechanic in the morning.

04TLazine

04TLazine

Hey guys, took her to the dealer. They heard the knock and suggested removing the oil pan to confirm the engine is dead. They quoted 600 for removing the oil pan to confirm there is a major problem with the engine and 5400 to replace the engine with an equivalent mileage engine. I don’t really see the merit in having them remove the oil pan for 600 dollars if there’s a 99% chance it will tell them what they already suspect the engine is dead.

So I suppose now I should start looking for an MDX engine and RL heads?

Thanks

csmeance

Use a boreoscope and check the #5 piston for damage. You can to a compression test too to be on the safe side. If the threads are gone, use a timesert or helicoil to get the threads back for the plug.

04TLazine

Thanks for the reply, I used a 10 dollar borescope off Amazon and didn’t see anything alarming. I didn’t bother giving it a compression test before sending it to the dealer because the banging sound was still present after I got it back together. Dealership thinks the engine is toast and wanted 600 to remove the oil pan to confirm.

04TLazine

I have replaced the engine in my acura and all problems have gone away.

I have now disassembled the original engine mentioned above, all of the rod bearings and crank rod journals are in perfect order, there was no metal in the pan. I’m completely stumped as to where this knocking noise could have been coming from.

There were a few very minor dents in the head and piston from the spark plug being eaten. The front cylinder bank, which was home to the cylinder that had a misfire and ate a spark plug, had more sidewall wear than the rear bank but it wasn’t super extreme.

Any idea where a knock on this engine comes from?

El_Cheapo

@04TLazine Were the threads on the Cylinder #5 good? I wonder if the knocking sound was caused by a loose spark plug in that cylinder. 🤔

Was the knocking sound caused by Cylinder #5?

04TLazine

Yes the knocking was caused by cylinder #5 front bank middle cylinder. I replaced the spark plugs and ran the engine and it still had a knocking. The threads appeared to be okay.
That’s a good thing to check tho.
i need to go back in my new engine and tighten the spark plugs down again. Seems cylinder 5 is the most common cylinder to loosen its spark plug. Also I noted cylinder wall wear as well as varnish on the valve train was much more present on the entire front bank than it was on the rear. The valve train varnish was true on at least 2-3 other j32s I’ve seen.

04TLazine

Upon reviewing photos I took of the troubled cylinder I noticed that the piston in cylinder 5 has a shiny mark on the lip of the valve relief cut that isn’t present on the 2 other cylinders in the bank. Here’s up close pictures

This is cylinder 5