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Discussion Starter · #1 ·
This is bizarre. So had the not too uncommon rodent chew through the yummy soy based wire cover of the knock sensor wire. Was lazy, knowing it wasn't a critical component so got around to having it replaced a couple months later. Vehicle drove as normal. A week before taking it in, when I was parked on a steep hill (sideways) I got a low oil warning. I do my oil myself. While at the shop (reputable Japanese independent) they mentioned they saw one other code besides the knock sensor, something about an actuator sticking on cylinder 0 or something. They said typically that was for low oil. I told them I had just ordered oil on Amazon so I could do the job myself and had them hold off on the oil change.

So they cleared all the stuff and said they "ran the computer through diagnostics" and he mentioned the "rough idle" was due to the low oil and I should put some in. I thought, hmm, hadn't ever noticed a significant rough idle? So when driving home, when coming to a stop the car was really idling rough periodically to the point the engine died twice in my driveway. WTF!? Nothing like this ever happened before taking the car in! So whatever they did, something during the process screwed it up. Could reseting everything in the computer cause it or could they have screwed something up on the knock sensor replacement? It's just basically an R&R of the intake manifold and they replaced all the gaskets.

I'm quite embarrassed to say I was 1.5 quarts low (that's what it took for the dipstick to register the oil -- was thinking back to my lecturing of girlfriends in the past about not checking their oil once in a while - duh.) But again, everything was running just fine up to the visit to the shop. In the past I've been an oil fanatic like a lot of people using Mobile 1 (5W-20) and replacing every 5,000 miles. After reading lots of info in the years past I went to 10K miles recently and stupid me didn't dawn on me I never had to check oil previously because I was replacing the oil twice as often and so more of a chance of burning more oil when replacing it much less often (and it was Castrol Full Synth, not their Extended I don't think.) The idle issue diminished 75% after putting oil in but I've only driven it 5 miles since adding the oil. This is a 2010 with only 67K miles! I guess it's pretty normal to burn 1.5 quarts in about 8000 miles on a full synth but not extended life oil.

The shop definitely did something to exacerbate the problem, which pretty much didn't exist before.

Hoping I'm not going to need a valve job or something and it just needs some more time for the oil to get the actuator fully lubed/ungunked or whatever. Will be doing a full oil change in a couple days. Mobile 1 Extended Life. I'm not using anything else anymore.
 

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I would get the codes read first, Do you have a TECH? Engine Codes are Registered in Messages > Diagnostic Info that would give us a good start to help you out, If you don´t have a TECH then go to an Autozone to get the codes read. The Idle in these cars are 100% electronically controlled via the Electronic Throttle Body so there is no way to Mechanically Adjust the Idle.

If engine oil was that low, for how long do you think the engine was ran with that low oil?
"something about an actuator sticking on cylinder 0 or something" Perhaps they were talking about the VTEC rocker getting stuck on that specific cylinder..

What I would personally do:
1.- Remove each spark plug, Check for oil contamination (To discard damage done to the rings)
2.- Top off the oil and clear the codes (FIRST and more Important; Write down any existing codes in the car) you clear the codes by disconnecting the battery for 10 seconds, This will also help reset the idle relearn procedure.
3.- Run the car in the highway cycling through all the gears at max RPM (Don´t do this if you notice oil in the spark plugs), Idle will relearn itself after a couple of miles.
 

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Discussion Starter · #3 ·
Well looks like they didn't clear the codes after all as the P0325 for the Knock Sensor is still in the history with a date from 3 months ago and the oil level warning from a week ago. The third code is the one they are mentioning, P2646. It has a date from 3 days ago but as I said no difference in driving since then up to the point I picked it up from the shop. Sounds like it's going through the idle reset process. I drove 3 miles from the shop to get oil and it was semi-rush hour so didn't get above 50MPH with no high RPM. Then probably 2 miles from the parts store after adding oil. I've probably got some pretty dirty/used oil mixed in with the 1.75 quarts I added. When I just went to get the codes it idled fine for a couple minutes before I shut it off.

How do you clear the codes? I do have an ODBC reader somewhere around or can you do it from the TECH in-dash system?

I bet the plugs are original as I bought the car used at 35K and haven't changed them so probably would be prudent to change them anyway now that I'm at 67K?

Not sure how long it's been low on oil as I'm sure the amount that is burnt isn't linear and is an upward curve over time. All I know is it took 1.75 quarts to get it to the middle of the dip stick, been about 8K miles since putting Castrol Full Synth in. I drive like a Grandpa trying to eek out every last MPG. No significant change in average mileage.
 

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You can clear the codes and reset the ECU by disconnecting the battery for more than 10 seconds (NAV and Stereo will require codes after that).

I did my plugs at around 73K and they were the OEM Densos (Most likely the original factory ones) and they were noticeably corroded, I would not go further than 75K on the stock plugs, I changed my plugs for NGK Laser Iridiums instead of the Densos.

P2646 is in most cases an issue with the VTEC Solenoid, Probably clogged?
 
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