Yes, I did put Techron in fuel tank on last fill-up. Car seemed to perform little better after 1-2 days of driving but problem didn't go away. I will put once more as you advised.

 

We keep asking you to pressure test the radiator, but you haven't posted a test result. I think this is the next setp.

Also, remove the radiator cap when the engine is cold and let us know if you need to add coolant.

 

I didn't do pressure test myself but mechanic who did the work to replace water pump, hoses etc said he tested and there is no leak in cooling system anymore. He opened radiator cap to show me coolant level when I went to him 2 weeks after his work regd CEL coming back. I checked again today (2 weeks since I went to him) and coolant level is still full to top. I'll test myself also - auto parts shop is a bit further away so haven't gone yet.

 

He tested it so that's alright. If you check the level in the actual radiator every so often that's good. The pressure check is more for locating a leak vs. watching the level is the best way to know that it doesn't leak. Of course, if the antifreeze gets goopy or sludgy you'll see that too.

 

Hope you all are doing well. I had some more questions. Just to recap I had gotten new water pump/timing belt/balancer shaft belt etc, all the cooling system sensors, 3x transmission fluid change, new cap-rotor wire and spark plugs, distributor o-ring etc as well as brake disc/pad replacement in efforts to resolve P1486 engine code and the struggle to start when mildly warm yet CEL/P1486 kept coming back on 2-3 days, ~20 miles of an ECU reset and struggle to start was still happening occasionally - so I basically gave up - until I got CA registration renewal which asked for a smog check.

All this time what else was happening was that anytime I would drive on highway for 10-15+ miles when I'd stop I smelled what seemed like heated rubber from engine compartment. When I would open engine compartment though it did not seem like engine or radiator was overly hot. Coolant levels were as before. I thought smell may be because of all the new parts so did not pay too much attention. Anyways, reading advice on forums I got the ECU reset and drove around at different speeds for 30 miles in hopes to pass smog check. Luckily light did not come back on and car cleared smog check.

Interestingly though for some reason after this reset the CEL did not come back on for almost 4 weeks over which I drove 200+ miles. Since I was driving more the burning smell was coming more often. And one day as I had driven 35 miles at a stretch the temperature gauge fell down to below zero and after a while came back up and down again - it would never go beyond normal 45% level on the gauge range - only problem for me was it was falling below zero and I may be imagining but it seemed to me cooling fans were turning on/off as temperature gauge was moving.

This arbitrary movement of temperature gauge went on for 2 days of driving (80-90 miles one day, 25 miles next day). Burning smell however was not coming anymore. And then CEL/P1486 came back on the 3rd day and I have not seen temperature gauge arbitrarily after those two days (although I've drove over 15 miles on only one day since then).

I took the car to the mechanic who did the work and he checked out the cooling system and everything in cooling system seemed working fine. His explanation for gauge moving arbitrarily those 2 days was that the wiring or the ECU may be no longer good causing gauge to misreport or the gauge itself may not be working correctly anymore. As for burning smell he looked under the car and showed me small oil leak from transmission - he said that it is this transmission fluid that's burning which was causing the smell. My old mechanic had also told me about the leak in transmission 6-7 years ago - however it burning and causing the smell doesn't quite explain why I don't smell it anymore even though I can see the leak.

The couple days temperature gauge moving arbitrarily to low and burning smell no longer coming I thought something might have been burning all this time and now it has burnt out completely that's why I don't get the burning smell but temperature gauge is moving arbitrarily. But then it is no longer moving arbitrarily so I am not so sure. And visually looking at engine compartment nothing looks like has been overheating or burning. Even the times when I was getting burning smell the engine/radiator or any part I could see by opening the hood seemed like it had overheated or where smell was more prominent - so I suppose it is possible that transmission leak is what was burning and may be because weather has cooled down considerably it is not anymore - it's just weird.

There is probably not enough useful information in here but if anyone has any suggestions on what I can check or what I should watch out for please let me know. Thanks in advance!

 

Is the code still there. Seems like there are a couple issues going on but not being there would be hard to diagnose not seeing what has been done.

1. If you still have the code I would ask what brand thermostat was put in. Would change it to OE to see if it made a difference. OE only because not knowing. There are brands I use that are also good. If the change does not make a difference then I would have to think about the ECU

2. The temp fluctuation on the dash would be the temp sensor. If it was changed what brand was used. Going cheap on parts that your car depends on is not good.

3. The burn smell has to be coming from somewhere. Maybe there aiming on the engine that's just burning off. Short of driving the car around and parking it with it still on at operating temp to see where it's coming from is the only thing you can do. Maybe you'll get lucky.

 

I'll try to find out parts manufacturers of thermostat & temp sensor from the mechanic. Does the temp sensor have parallel wires running to ECU and the temp gauge on the dash or does it run to ECU first and then come to the gauge? ECU having some issue won't be surprise given Honda has TSB on the ECU for my model year and trim but I didn't expect one would wire the gauge via the ECU.

P1486 code is still there. It has been there for several years now. Diff mechanics have tried diff things in attempts to fix it - one guy replaced some gasket, another did thermostat & temp sensor replacement last yr, and then this guy replaced the sensors again (in addition to water pump radiator hoses etc). It always used to come back in couple days after ECU reset regardless of work performed so it not coming back for 4+ weeks and almost 300 miles was more of a surprise than it finally coming back on. All that said I am fairly sure none of these guys would have used OE sensors - I had said don't skimp on parts cost but I don't think they even consider OE part for these types of thing.

The burning smell hasn't come since those two days of temp gauge moving wildly even though I drove at 70+ mph for 55 mi within 2-hr window one of those days - I could drive around more to see if it will back on but it is no longer predictable like it was. What I was wondering was whether transmission oil burning on being blown by draft and getting to exhaust can even be a plausible explanation.

 

It's hard to say for sure, but it is possible the air under the car is blowing the mist toward the cat convertor. I only say that, as the head pipe runs right under the oil pan (about 8 or so inches left).

 

As far as oil leakage blowing towards the exhaust, that makes some sense because the O2 sensor actually measures the oxygen DIFFERENCE inside vs. outside the exhaust. Smoke or oily stuff blowing onto the outside of the sensor will throw off the measurement.

About the temperature sensors, for 1998-1999 there's a separate temperature sender for the dashboard gauge. It's got only 1 wire, and it's in the cylinder head next to the 2-wire temperature sensor for the PCM. For model years 2000+, there's only the 2-wire sensor for the PCM, and the PCM in turn drives the dashboard gauge.

All years of 6th-gen (1998-2002) have a radiator fan switch in the thermostat housing.

 

Thanks a lot Jim & Bob. It all makes little more sense now.

May be I messed some wiring back in Oct 2014 as I was installing antenna bypass FM modulator (iSimple IS31 Antenna Bypass FM Modulator at Amazon). I'm not 100% sure how much after CEL came on but it definitely has been on at least since early 2015 - iirc I did not disconnect battery before I started installing the modulator. I remember seeing a spark close to wires near the small digital clock above ac controls - light to digital clock went out after that, my wife says many of the lights behind the cabin climate control buttons also went out at the same - eventually most of those cabin climate control lights came back when I jumped some pins on climate control board to fix the problem on a/c button not working following instructions from one of the forum threads. Light to digital clock remains out as does the light behind vent open/close button. May be wiring to temp gauge got frayed also.

Anyways, I was thinking I won't get transmission leak fixed (I see only 3-4 drops show up on the garage floor in last 1 week) but I guess I'll let the mechanic take a look - he was saying it'll be depending on where leak is it'll cost either ~$400 or ~$1500 and that he can tell which of the two it might be once he puts car up.