1988 Honda Accord the old car is going bat-nuts

1988 HONDA ACCORD
200,000 MILES • 4 CYL • FWD • MANUAL
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TMONROE
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Original problem: engine overheating. Replaced head gasket, water pump and belt, water pipe and all the small water hoses, radiator, cleaned out all the passages in the head and intake manifold, radiator cap, flushed heater coil (was fairly clean), thermostat, temperature gauge send unit, and TW sensor aka coolant temperature sensor. New problems:
1) temperature gauge pegs on HOT when simply turning the key on, about 6 sec.
2) cooling fans will not come on
3) after about 5 minutes “engine light” comes on
4) diagnostic indicator under drivers seat flashes every two seconds continuously; no pattern.
However, the engine is not running hot as long as I jump the fans and keep them running. I haven’t tried it without the fans running. I have checked it with a laser heat sensor on all areas such as thermostat housing, upper/lower radiator hoses, engine block, exhaust manifold, various small water hoses and it is well within specifications. One other item; there is another sensor next to the TW sensor which does not show in the shop manual, Chilton’s, or Haynes. It has a larger base nut than the TW sensor, it takes 22mm. No, haven't changed the thermosensor on the radiator, and it is running smoother than it ever has; go figure.
Any ideas?
Apr 5, 2010 at 10:17 PM
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KHLOW2008
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Hi tmonroe,

Thank you for the donation.

1. Temp gauge pegged at HOt during intial ignition on could be due to a poor ground circuit. Did this occur immediately after the repairs?

2. Bridge the thermosensor terminals and turn ignition switch to RUN. Does the cooling fans turn ON? If yes, then the thermo sensor could be faulty.

3. + 4. The CEL turning on indicates an eror has been detected and you mentioned a flash every 2 seconds. That is the trouble code, a Code 1, meaning the O2 sensor or its circuit is at fault.

If no trouble codes are present, turning on the ignition switch would cause the LED to flash once and turn OFF. It would remain off till a problem is detected.

The temperature gauge sending unit is a 1 wire small 12 mm hex unit under the distributor. The one next to it with a 2 wire sensor is the Engine Coolant Temperature sensor.
Apr 6, 2010 at 2:40 PM
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TMONROE
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thanks for the response, well one at a time,
1) temp gauge: I suspected ground also and metered from back of gauge to contact on sender. Also ran a jumper. Everything seemed fine. I replaced the guage sender sensor anyway; nothing new. I will move on for right now.
2) Thermo jump does make fans go on. This car has two thermoswitches which affect the fans, one in lower radiator and one next to the TW sensor (engine coolant temp for fuel purposes) in thermostat housing. That one looked trashed, had to order and can pick it up in the morning. It has a 22mm mounting nut. Talked with Darrell Waltrip Honda about it, they say some had it and it works with the one in the lower radiator. Hopefully that will do the trick on fans when its replaced.
3) Error code: yes, you are correct, I read the manual wrong, appears to be O2 sensor related. Thanks for the tip. When I put the exhaust manifold, etc. back on I noticed two differently colored connectors for the two O2 sensors ends, does it make any difference which sensor goes to which connector? upper connector is clear, lower connector is green. Since I found no identifying marks, I figured it didn't matter. What say you?
The fan and O2 sensor events should not be that hard to fix. Once they are correct I will go back to the temp gauge issure.
Thanks again for your help, can I get back with you to follow up?
Apr 6, 2010 at 5:51 PM
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KHLOW2008
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Some models do have 2 fan switches. Radiator fan switch is for operations when the coolant temperature activates it.

The other one if is located on upper radiator hose outlet of cylinder head would operate when the temperature is rather hot after the engine is turned off.

The O2 sensor do not matter if the wires are crossed connected as they both do the same work.

Any reply that you make to this post would keep me notified so I can follow up on that.
Apr 7, 2010 at 10:01 AM
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