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Discussion Starter · #1 ·
I'm currently having issues with a rough start of my 2006 Accord I4. The driving of the car is fine. The idling of the car is typically fine, having occasional sputtering immediately after the rough start. The rough start seems to be unaffected by the climate. I'm in SoCal and its been ~70 degrees in the day, and ~55 degrees at night. If I start the car within 5 minutes of turning it off, there will be NO rough start. But if it's about 10 minutes since the last start, then it will have a rough start.
Also, I'm facing periodic overheating. My first encounter was on Saturday (Nov 18). I pulled the car over, let it sit and filled the radiator with coolant and let it bleed. I drove the car that night and Sunday day. Come Sunday night, after doing nothing at home for 3 hours (hence the car sitting for 3 hours), I drove to an event about 26 miles away from home. Driving around of surface streets looking for parking, the thermometer started raising so I pulled over. I seen the coolant reservoir having more coolant than before. I let the car cool down and sit. Unfortunately, the car wouldn't start now. It would crank, and occasionally start to turn, but to no avail. Battery was good as I checked it with a multimeter. I waited another 10 minutes, and tried to start the car. I kept pumping the gas pedal while turning the car and eventually the car started. That was the first time I had to pump the gas to start the car. So now this is bugging me. To end the story, I found parking, went to the event (5 hours), then drove home with no issues (besides the same sluggish start, without pumping of gas).

I would like for a walkthrough of things for me to check to resolve the issue of the sluggish start, and the occasional overheating.

Thanks.
 

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When you are moving, does the engine overheat?

When it overheated? Were you very slow traffic and did the cooling fans turn on?
 

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Discussion Starter · #3 ·
When you are moving, does the engine overheat?

When it overheated? Were you very slow traffic and did the cooling fans turn on?
The first time I noticed the engine overheating, I was stopped in the drive-thru of a fast food restaurant. The second time (last night) I was slowly driving the streets (no traffic) looking for parking.
I can also add for today, I seen the thermometer sort of shoot up while braking for a stop light. Then it quickly went back down. I was able to finish driving to work (5 minutes from that point) and clock in.
 

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Check thermostat first.

After that, check to make sure there are no mixing of fluids.

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Back to the basics, are both cooling fans running when the AC compressor turns on? Are both cooling fans coming on when the car is sitting idling (once the Engine heats up). If the fans are good then you may have a bad thermostat and or air bubble in the cooling system. Or possibly a bad radiator cap and maybe a blown head gasket.

I would also pull the spark plugs and take a look at them as well as do a quick compression test. If the plugs look worn you should replace them.

I suspect that you might have a bad coolant temperature sensor and you should verify that the coolant temperature sensor for the gauge and the one for the ECU are registering correctly.


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His startup symptom sounds like a bad ECT sensor, but if the car is overheating, that should be resolved first. I'm guessing the fans just aren't coming on with bad motors. If the thermostat is bad and stuck shut, it would be overheating any time even when moving. If the thermostat fails open, then it would cool only when moving, but cooling capacity diminishes once stopped, causing the temp to rise again.
 

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Discussion Starter · #7 ·
Check thermostat first.

After that, check to make sure there are no mixing of fluids.

Sent from my SAMSUNG-SM-J320AZ using Tapatalk
Is there a simple way to test the thermostat? Also where should I check for mixture? In engine and radiator reservoir?

Back to the basics, are both cooling fans running when the AC compressor turns on? Are both cooling fans coming on when the car is sitting idling (once the Engine heats up). If the fans are good then you may have a bad thermostat and or air bubble in the cooling system. Or possibly a bad radiator cap and maybe a blown head gasket.

I would also pull the spark plugs and take a look at them as well as do a quick compression test. If the plugs look worn you should replace them.

I suspect that you might have a bad coolant temperature sensor and you should verify that the coolant temperature sensor for the gauge and the one for the ECT sensors are registering correctly.


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Both fans work fine. They turned on with the AC on, and they also came on when the engine warmed up. I don't see any bubbles coming from the cooling system. How do I test the ECUs?

His startup symptom sounds like a bad ECT sensor, but if the car is overheating, that should be resolved first. I'm guessing the fans just aren't coming on with bad motors. If the thermostat is bad and stuck shut, it would be overheating any time even when moving. If the thermostat fails open, then it would cool only when moving, but cooling capacity diminishes once stopped, causing the temp to rise again.
You're leaning towards the thermostat being fine?
 

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There is no way to tell unless you test the thermostat. The only way to test a thermostat is to get it out and throw it very hot water over 190 degree F and see if it opens up. Then you watch it close as temp drops below 190 degree. So the logical thing to do, if you are going that far to drain the coolant and dig out the thermostat is simply to replace it. It costs just $25. But before you do that, you need to turn on the A/C and make sure you see both fans spinning. If you see one fan not spinning and when you push it with a rod and it starts spinning, or it simply still doesn't spin, then the fan motor is or the relay that triggers it on is bad. A bad relay on this car is not likely. You can test fan motor by taking the fan blade off, then supplying the electrical plug with a 12v source of power, such as a spare battery with 2 wires.

I suggest you start with turning on the A/C to see if both fans are spinning.
 

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@t-rd and I are thinking along the same lines, first thing to do is fix the cooling issues. In general the issue with a bad thermostat is a stuck closed condition. That would mean the engine would overheat quickly. However, it could not be opening enough restricting the flow of coolant. When you are moving slowly or just idling and the car overheats it is generally a problem with airflow across the radiator, because while your moving air is forced through the radiator. While you are moving slowly and stopped the fans move air across the radiator.

I assume you have a 50/50 mixture of antifreeze and water in the cooling system and you have changed the coolant on a regular basis. You need to make sure the system has no air bubbles, the way you do that is to wait until the car is cold. Then open the radiator cap and make sure the radiator is full, if it is not fill it up to the top. Then start the Engine, turn the heat on in the car to full hot low Dan speed and let it idle and add coolant to keep it full, you are waiting untill the fans come on 3 times. Each time the fans come on the level in the radiator will drop, add coolant then. It will overflow while the fans are not running. After the third time of the fans coming on fill the radiator to the top and turn the engine off and fill the overflow tank to the full line and let the car cool overnight. Check the overflow bottle in the morning and it should be at the low level line. Add more coolant to the full line. That should get rid of any air in the system.

The ECT is the Engine coolant Temperature sensor and if it is not reading the correct temperature the mixture to start the car will be incorrect.

Sent from my Nexus 5X using Tapatalk
 

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Discussion Starter · #10 ·
There is no way to tell unless you test the thermostat. The only way to test a thermostat is to get it out and throw it very hot water over 190 degree F and see if it opens up. Then you watch it close as temp drops below 190 degree. So the logical thing to do, if you are going that far to drain the coolant and dig out the thermostat is simply to replace it. It costs just $25. But before you do that, you need to turn on the A/C and make sure you see both fans spinning. If you see one fan not spinning and when you push it with a rod and it starts spinning, or it simply still doesn't spin, then the fan motor is or the relay that triggers it on is bad. A bad relay on this car is not likely. You can test fan motor by taking the fan blade off, then supplying the electrical plug with a 12v source of power, such as a spare battery with 2 wires.

I suggest you start with turning on the A/C to see if both fans are spinning.
It was mentioned earlier that the fans are working properly.

@t-rd and I are thinking along the same lines, first thing to do is fix the cooling issues. In general the issue with a bad thermostat is a stuck closed condition. That would mean the engine would overheat quickly. However, it could not be opening enough restricting the flow of coolant. When you are moving slowly or just idling and the car overheats it is generally a problem with airflow across the radiator, because while your moving air is forced through the radiator. While you are moving slowly and stopped the fans move air across the radiator.

I assume you have a 50/50 mixture of antifreeze and water in the cooling system and you have changed the coolant on a regular basis. You need to make sure the system has no air bubbles, the way you do that is to wait until the car is cold. Then open the radiator cap and make sure the radiator is full, if it is not fill it up to the top. Then start the Engine, turn the heat on in the car to full hot low Dan speed and let it idle and add coolant to keep it full, you are waiting untill the fans come on 3 times. Each time the fans come on the level in the radiator will drop, add coolant then. It will overflow while the fans are not running. After the third time of the fans coming on fill the radiator to the top and turn the engine off and fill the overflow tank to the full line and let the car cool overnight. Check the overflow bottle in the morning and it should be at the low level line. Add more coolant to the full line. That should get rid of any air in the system.

The ECT is the Engine coolant Temperature sensor and if it is not reading the correct temperature the mixture to start the car will be incorrect.

Sent from my Nexus 5X using Tapatalk
Should I do the bleeding first and drive the next day or test/replace the thermostat first followed by bleeding?
 

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With the radiator cap off, turn the temp dial to hottest and fan to high inside the cabin, turn on the engine and let the engine warm up. To speed up this process, you can hold the engine rpm higher between 1500 and 2000rpm, until you hear the fans kick on. Put a towel around the neck of the radiator as overflow might happen. If you have a OBDII reader, you'll see that the fans come on between 190 to 195F. You'll see some bubbles, this bleeds the air out. And you should be getting constant heat inside the cabin. If you get heat sometimes, then it turns cold, you still have air in the system. Air in the cooling is very easy to bleed out unlike bleeding brakes.

I suggest you buy a thermostat with gasket plus 2 gallons of Honda OEM blue coolant before you attempt to start the job. You'll have to remove the intake manifold for an I4 engine to get to the thermostat housing underneath. The thermostat should be replaced every 100k miles in my opinion, for a peace of mind. Or you get a thermostat that fails open, such as the one made by Motorad.

I also suggest you getting a relatively cheap bluetooth OBDII reader (~$20) so you know the engine temp during the test, this also identifies possible problem with the ECT sensor near the thermostat housing, which might just be the cause of your engine stumbling when starting. One question though, does the engine start normally when stone cold? Or does it stumble when it's warm?
 

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Discussion Starter · #12 ·
With the radiator cap off, turn the temp dial to hottest and fan to high inside the cabin, turn on the engine and let the engine warm up. To speed up this process, you can hold the engine rpm higher between 1500 and 2000rpm, until you hear the fans kick on. Put a towel around the neck of the radiator as overflow might happen. If you have a OBDII reader, you'll see that the fans come on between 190 to 195F. You'll see some bubbles, this bleeds the air out. And you should be getting constant heat inside the cabin. If you get heat sometimes, then it turns cold, you still have air in the system. Air in the cooling is very easy to bleed out unlike bleeding brakes.

I suggest you buy a thermostat with gasket plus 2 gallons of Honda OEM blue coolant before you attempt to start the job. You'll have to remove the intake manifold for an I4 engine to get to the thermostat housing underneath. The thermostat should be replaced every 100k miles in my opinion, for a peace of mind. Or you get a thermostat that fails open, such as the one made by Motorad.

I also suggest you getting a relatively cheap bluetooth OBDII reader (~$20) so you know the engine temp during the test, this also identifies possible problem with the ECT sensor near the thermostat housing, which might just be the cause of your engine stumbling when starting. One question though, does the engine start normally when stone cold? Or does it stumble when it's warm?
I have a OBD II reader for my laptop, so I'll be able to get that data.
The engine stumbles for both cold and warm. For example, when I first start the car in morning (cold) and when I start the car 15 seconds after turning it off (warm). More occasionally now, I have to pump the gas to start the car. So it does seem like the ECT sensor. Should I replace both? Are they both the same part number?

An update on the overheating:
I was doing some testing a few minutes ago. I found out that if I constantly drive at a slow speed (tested at 20mph), the temperature gauge increases and basically starts to overheat. When I speed off, the temperature gauge drops back to normal. Also, while idling, after about 2-3 minutes, the temperature gauge goes very slightly over the half marking. About 5 seconds later, the radiator fan kicks in. It will stay at this marking for about 3 cycles of the fan, then drop below the half marking (normal range I believe). It will basically cycle like this while idling.
From this information, it gives more belief to be a bad thermostat?
 

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Discussion Starter · #14 ·
^ sounds like fan issue. stat is working cuz when you drive it and push cool air through rad, its circulating coolant through block and driving down temps.
The fan works while idling, so that's strange to me.
Is there a part I need to replace?
 

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@RickBlaine and I love 20 questions, so lets begin...

How EXACTLY are you determining your car is "overheating"? Is coolant spewing out of the rad cap and/or overflow tank? Do you get a warning light on the cluster? Are you seeing the dummy gauge temp needle in the cluster move in one or other direction?
 

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Discussion Starter · #18 ·
@RickBlaine and I love 20 questions, so lets begin...

How EXACTLY are you determining your car is "overheating"? Is coolant spewing out of the rad cap and/or overflow tank? Do you get a warning light on the cluster? Are you seeing the dummy gauge temp needle in the cluster move in one or other direction?
Going based off the temp gauge. And one time, I seen it push coolant to the reservoir.
 

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^ your temp gauge is a dummy gauge. you've owned this car for about a month now, so perhaps you are paranoid? what did you find out about your cylinder #1 misfiring issue? my edumahcated (like that one @qman?) guess is your car is not overheating and you should move back to your starting issue. what say you, @t-rd?
 

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Discussion Starter · #20 ·
^ your temp gauge is a dummy gauge. you've owned this car for about a month now, so perhaps you are paranoid? what did you find out about your cylinder #1 misfiring issue? my edumahcated (like that one @qman?) guess is your car is not overheating and you should move back to your starting issue. what say you, @t-rd?
I supposed I had the improper spark plugs and that they weren't tighten. All I did is get Iridium plugs and tighten to spec. No more misfire.
 
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