smcafee

It was the Engine Coolant Temperature (ECT) sensor. Failed at 303k.

If you experience any of these symptom, the ECT sensor is either fully or partially the cause:

1. Unexplained stalling and cutting-out when warm, but restarts Ok.
2. Rough running and low idle speed when cold.
3. Hard starting when cold. Will eventually start after multiple attempts, then run very rough while warming up, then runs Ok.
4. Temperature gauge is at maximum HOT all the time.
5. Power delivery seems a little off, not as sharp as you recall.
6. Feels sluggish, like a tune-up is needed, but you just recently had one.
7. Also you may notice that throttle tip-in is abrupt and it is difficult to get moving smoothly from a stop when warm.

I had (1) for the longest time, but purging air from the cooling system eliminated the stalling (I had recently replaced the radiator).
Then (2) slowly crept in, followed by (3) about 6 months later.
Last week (1) popped up again and I was getting more than a little concerned. Engine dying in moving traffic is ... problematic.
When (4) happened, I knew it was the sensor. Thirty dollars later and she is running like a top.
(5), (6), and (7) are more subtle indicators but nonetheless detectable to the discerning driver.

All the above symptoms resolved when the sensor was replaced.

When I changed the ECT, no coolant leaked out of the manifold when replacing on a cold engine. I think a 17mm combo wrench was all I needed. Easy-peasy.

I also changed both the ECTs on my 1990 Accord EX (1 for the ECU and 1 for the cooling fan control). It is running better than it has in years.

I am adding the ECT sensor to my 6-year/100k service as a routinely replaced item.

You should too.

Tosh

Thanks for the info!
Do you also recommend replacing the thermo switch on the TL?
I've added ignition coils to my preventive maint list.

smcafee

Emphatically yes. My experience is by 150k or these sensor begin to give erratic data. I also recall my 1988 Accord (bought new) had an ECT sensor go bad early in the warranty period as well.

frankjnjr

03 tls @ 227K, timing belt, water pump, plugs intake cleaning, iac valve adj. etc. @ 200K. recently, very very slight rough idle and lower than normal idle speed, only from dead cold start, (prominent when the ambient temp in under 35 deg. f). initially thought to be possible impending coil pack failure issue. bought two new coil packs and switched out all six coil packs with no correction to the problem. can you tell me, when you first noticed #2 "rough running and low idle speed when cold" exactly how rough was the idle, as in very obvious,or almost imperceptible. i am not experiencing any of the other 6 symptoms at present. this issue has not impacted performance or fuel economy and all spark plugs indicate uniform burn appearance. engine uses less than one pint of oil @ 5K service interval, some of which is attributable to a slight rear main seal leak. thank you for a most thorough and concise post.

smcafee

Hey, frankjnjr.

Thanks for the feedback. As an ex mechanic, I probably notice these things more than most people. For me there was definitely a noticeable and obvious change to the idle speed rpm and seat-of-the-pants smoothness. Idle speed was around 800-900 rather than the 1200-1300 I was used to for the first 30 seconds or so when cold. Engine roughness was experienced as minor vibrations through the steering wheel and seat as well as an audible rumble through the exhaust. The morning temps when I started the engine varied between 42 and 55 F.

Once the engine ran for 1-2 minutes (I drive off immediately after startup) it settled into a nominal 800 idle speed and smoothed noticeably. I've not check the plugs or coils and there were no codes thrown.

I just today purchased a 2003 TL-S with 177k to replace our 1990 Accord beater. Of course I will be replacing the ECT sensor.

frankjnjr

appreciate your observations. no codes triggered on my car as the slight miss-fire is so "subtle". NOTE: last December, (the car sat unused for 4 days), during a routine cold start, ambient 29 deg., i experienced a severe engine miss, rough idle ck eng light, warning triangle light etc. codes showed P1259 vtec syst. failure and P1399 random mis-fire. i reset the ecu and the car ran fine with no cel that day, but the problem occurred again the next day with only the P1259 code, and no accompanying mis-fire.. i diagnosed the issue as a failing vtec oil pressure sensor which i replaced and the problem appears to have been corrected. never experienced even a slight engine mis-fire at any time prior to this vtec incident. however, since the vtec problem, the subtle mis-fire during cold start is exactly as you describe " Engine roughness was experienced as minor vibrations through the steering wheel and seat as well as an audible rumble through the exhaust" has been present. i don't understand how or why the vtec problem could have triggered, and or been associated with the P1399 mis-fire issue, as it appears the vtec problem caused the mis-fire! i will order a new ETC sensor and see if it may be the problem. Thanks again for your very informative and thorough post.

smcafee

Hmmm... I'll have to look into VTEC issues and symptoms. So far so good with the ECT sensor replacement but I will order an Oil Pressure Sensor and replace it as a preventative measure.

Is this the switch you replaced? 17

37250-PR3-003 Switch Assembly, Valve Timing Oil Pressure
SWITCH ASSY., VALVE TIMING OILPRESSURE

frankjnjr

correct smcafee, #37250-PR3-003. it's odd though, in my area, we have 5 pick and pull yards and i make it a habit to look over all 2g models just to asses overall condition and note what has been replaced, ie.: transmission, suspension items, exhaust parts, alternator, starter, vtec oil pressure switch, egr valves, ign. coils etc. probably looked at over 100 cl and tl models since experiencing my failure and all vtec pressure switches look to be original, so i surmise that the vtec pressure switch is not a common failure. also of note, it is very very uncommon to see a 2g model with a replacement alternator. happy motoring and Keep the Shiny Side Up

smcafee

Yup, I've replaced Honda alternators, starters, and distributors at the 150k-200k interval regularly. Compared to the old days, this are long-lived components so I am not complaining. We have gotten used to cars lasting 200, 300, 400k+ miles with minimal maintenance whereas in the 70s and 80s a car was mostly used up by 100-150k.

I'm heading to the pick-a-part in Anaheim this weekend for a inside rear view mirror and dome light for the 2003 TL-S I just bought. I'll have a look at the sensors to see if they have been replaced as well.

frankjnjr

let me know if you have any problem locating the mirror. i have a nice one from an 03 S type onstar and navi equipped car you can have for $25 shipped. paid $15.78 at local pick and pull. it's uncommon for rear view mirrors here in the mid-atlantic area to suffer from the extreme heat issues affecting the mirrors in the southern and western areas of the country. p.s. if you happen to be going to the LKQ pick&pull in Bakersfield and would be willing to pull a fog light switch from a car they have there for me, i would trade you the mirror for the switch for whatever it costs me to ship the mirror.

frankjnjr

sorry, didn't realize Bakersfield was 3 hours away. lol

smcafee

If the 2003 in Anaheim still has the fog switch I'll pull it for you.

frankjnjr

the fogs i'm looking for are actually for a different car, which is a 1996 or 1997 Honda Accord, kind of a rare breed. sorry i didn't clarify that. if you do happen to stumble on a 96 or 97 so equipped, what i'm looking for is the entire fog set-up, minus the fog lamps themselves, which i already have. what i need are the front core support harness, the engine bay harnesses which contains the relays etc., and the "A" harness which is under the dash. certainly, i would compensate you for the time involved in such a removal. appreciate it. also, let me know if you could use the mirror( 2003 TL S type w/onstar and navi) i have. you can have it for $10.00 plus shipping which was my cost via LKQ pick your part. tx again

smcafee

Is your cc switch a combo With TSC?

PM me with your cell for a pic.

smcafee

That's a rare item. As a dealer installed option you don't see many of them even back in the day. Try ebay - 142277250061 or 332127675603.

smcafee

Sorry, the OnStar mirror is not plug-compatible with my non-OnStar mirror (afaik).