SO 2003 CRV, FWD, hot humid climate, previous owners idiots liek the rest of them here, they all insist on removing their thermostats to make their lives simpler.
So the only time i see my heat needle anywhere near the middle range is when driving over the hills where there are some steeep steep roads.
In the past, we had an issue where it felt underpowered, so I had a simple oil change at honda, everything was fixed. First time in my life (and all my ****box cars) that an oil change has fixed a driveability issue.
So i worked out that this was due to the VTEC being so pedantic that it needed fresh thick oil.
Its happening again.
Now i suspect that ive worked out more of the problem.
I checked the oil and i was upset to see the oil level above the second dot. Honda did the oil change and im certain they put the right amount in about 6 months ago. so i recon i have an oil diluton problem, caused by any of or all of the following:
1. The lack of a thermostat, leading to cold engine, useing more fuel, and also more fuel clinging (condensating) to the cooler cylinder walls and getting rammed through the piston rings during compresion getting stuffed straight into the sump. OBD2 sais coolant temp was about 65 degrees while idling in carpark. driving over the hills ive never checked it but the guage does get to half way.
2. Air intake temp sensor. i was parked the other day, started the engine and plugged OBD2 in for a quick check and it seems to be impossibly high in my opinion, the OBD2 sais the IAT was at 50 degrees celcius. This is in the philippines, hot and humid, but that seems high to me. The weather man tells me its 32 degrees outside, and the internet tells me these things usualy raed give or take 10 degrees celcius aroudn the current ambient temperature. I do remember I had some kind of temperatture related check engine light DTC in the beggining, ignored it coz it seeme unimportant at the time, but havent seen it in a while, and i have a slight memory that it was related to the air intake when i google it, so i have ordered a new IAT and ill see how that goes. I beleive that a high temp reading should actually cause the opposite of too much fuel, but also i know that engine fuel management is a complicated beast. I would love it if someone could just confidently definitively tell me that im barking up the wrong tree here.
3. i had a leaking oring in teh VTEC solenoid at that time, i replaced the oring with a non genuine, random oring form an oring kit which looked like it would fit, and it did, and it stopped the leak completely. I cannot see it being related to this because all that Oring did was hold oil inside the connection between the VTEC solenoid valveand solenoid body. if it was that, id have an oil leak. but maybe, just maybe theres something im not aware of, and this dodgy hack fix is a probelm maybe.

Im having a local jungle mechanic swap the oil out later today for some 5W40 fully synthetic (the only oil i can find in the nearby town), and i am confidetn that after that, it will all go back to normal.

WHen i googel forums and other ppl askign this question, everyone is saying is its impossible for thinned out oil to cause the VTEC to stop wokring.
I want to put that all to bed. If it thins out like mine, from diluition, the VTEC starts playing up.

 

Aaaaaaaand changed the oil to a toyota 5W-40 (all that is available here) and it idled incredibly quiet and felt good, I was happy until i got out to the main road and realised it was still stumbling.
Drove all the way back over the hills and its definitely using less fuel, and it has improved the situation, but its still hesitating, and im almost certain its the VTEC.
I reaad that VTEC is onyl supposed to kick in at a minimum of 2500 RPM, according to the wikipedia article on i-VTEC.. is this true? thats about where im getting the stumble. It feels very underpowered until VTEC is fully kicked in, just totally gutless.
Fuel consumption definitely improved, I cant give u an exact figure, but my rough calculation for before the oil change would have been somewhere close to 20L per 100km., thats 11.7 MPG for you in the US. Vomit much??
After the oil change, no idea, but the needle didnt realy move, compared to the previous tripbefore oil change starting at the exact same position on the gauge droped about half a tank.

The trip back over the hills is a substantially differeng gradient profile to that on the way., a more cradual climb followed by an extreme engine braking downhill section for 6km, so this may be a factor. See the elevation profile:



Can anyone provide any insight into issues with VTEC and what RPM they occur?

 

The CRV uses 5w-20. Thicker oil will not make it run better.
You should have clean the VTEC screens
This requires taking off the solenoid off the back side near the firewall.
Here is video that shows where it lives. You just need to clean the screen.

 

yep couldnt get my hands on anything 5W-20 unfortunately.
Do you think that being to viscous might actually continue to cause problems with vtec? I guess if being to thin mucks with it, being to thick possibly could too, on top of all the other clearance related flow issues in the rest of the engine. I nderstand abtou 50% of how this VTEC thing works, i know that there are 3 places that oil "pressure" is required in VTEC and things fail if it isnt high enough.
1. the sensor in teh solenoid body which tells the system there is adequate presure
2. the actual actuators in the rocker arm rails
3. also the VTC system for varying the advance and retard ofthe exhaust camshaft. (EDOIT: no wait its the intake. wikipedia sais its the exhaust)
Thats a lot of opportuinities for oil related problems to mess with it

I have had the solenoid off in the past when it had this issuelast time, and couldnt find any evidence of sludge and the screen was perfectly clean, and after cleaning it stil had the problem, it wasnt till i took it to honda and asked for a simple oil change that it magicaly fixed itself. Perhaps it was the genuine Honda 5W 20. maybe i really do have to take it back to them and fork out the cash
But, duly noted, ill take it off again and check this time! and also the VTC thing in the side too, the long one with all the screens. Ill be damned if im removing the power steering pump to get to that crazy located VTC strainer at the front of the engine !!! hah. Stupid stupid design that. I simply cant do it. im too unfit and cant handlte the thought of somethign going wrong wiht the power steering. I jsut lost all my moneyu to the hospital so cant afford the risk of anythign going wrong.

I was out in the middle of the province when i did the oil change, not much available out there, and was desperate to not drive home in such a terrible stumbling state so i just had to do it.

 

nup, all filters sparkling clean, and the inside of the vtec solenoid looks fine and the ohms across the solenoid check out to the honda manual.
I really hate removing these things, theyre in such a difficult spot.
i accept that oil shouldnt affect it, but it seems to be.
Theres no sludge in the top end, its all clean.
Maybe the wiring is just all mesed up and resistive. heaps of electrical problems and the flex conduit around the wires in question is all brittle and torn, I previously taped them up and attached it all in such a way that it wont short to the body or engine. Possibly just all the copper inside is all broken down from age perhaps.

 

i cant find anything wrong, its just ****. incredibly frustrated.

 

I know the feeling.

 

so i drove back over the hills again, after an insane amount of work removing the old empty thermostat housing which had a bolt that couldnt be removed because the brass sleeve it threads into in the other plastic housing was just spining around due to poor design, i had to cut out the bolt from the plastic and melt in a nut with a soldering iron. that has actaully worked, and i drove over the hills and to my amazement, it drove cooler ( on the OBD computers coolant temp figures) with a thermostat than it ever did without one.! constant 83, wheras previously, it was always shooing up to 95 on the way over the hills. that prooves that theory that the water pump needs some back pressure to work effectively, probably cavitaton related.
Ayway the stumbling is still there, and now theres a new symptom, maybe a new issue..
Wen i first got it back togetherm, it was hunting like a vcauum leak, and gave a CEL for the ide air control. so i wobbled the wires a bit and it actually fixed it, CEL woudlnt come back and the hunting stopped.BUt driving through the city, through terribel traffic after botu 30 minutes, i realised there was this horrible sound form the engine, a litle bit like detonation, but each ping lasting longer than detonaton. I know my engine sounds, but i dont know this one. It sounded liek an incomplete combustion related issue, in that the sound was similar to detonation, and the engine was totaly lacking of power, and it only happened from idle up to 2200 (ish) rpm, ( the magic VTEC engagement region) and it would resolve itself at that point like turning off a switch. IT litteraly was liek ON and OFF. no gradual change, it was an immediate cange from terribel , to everythigns fine.
So when the VTEC engages, it masks the issue. sticking valve? the one that isnt controlled by the VTEC arm??
Its just that it seems like every single cylinder is experiencing it, it seems to be a smooth rattle and not such a jolty problem, i feel that if it was only one cylinder, it would be more jolty.
I wonder now if its the VTC system. apparently, symptoms of a bad VVT solenoid include:

• Rough Engine Idle.
• Check Engine Light.
• Misfiring engine under loads

These tthings work by pulsing open and closed incredibly fast, maybe it cant move fast enough.

hmmm

ANyone had one of these go bad wiht simialr symptoms? Long shot, but i have to ask.