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mrma5b
03-24-2009, 12:03 AM
The vehicle in question is an 89 accord lx-i coupe with 5-speed. There's around 215,500 miles on it currently.

For the past week or 2, the engine seems to "stumble" after a cold start.

Normally, the engine will rev to 1800 RPM, and gradually lower the speed to 750 RPM once it has warmed up.

Now it will "stumble" around 1500 RPM, fluctuating within 50-100 RPM, with quite a bit of vibration. This only lasts for the first few minutes after the cold start. Once the engine has run for a few minutes, it manages to reach the usual 1800 RPM, and runs just fine.

Here's the story of what may have caused it. I was starting it up one morning, and i realize that my radio faceplate was locked in the glovebox. So i shut the engine back off so I can unlock the glovebox with the key. Just as I was shutting the car off, this other car came out of nowhere, speeding down the street.

Now, this caused me to flinch, and i managed to turn the key back to the "on" position just in time for the engine to start back up on its own. This is the exact moment when the "stumbling idle" first started.

I checked the ECU LED and there are no codes flashing. My only guess as to what is causing the problem is that the engine has become slightly flooded, but I don't know enough to be sure. I'm hoping you guys have other ideas as to what the problem may be.

MessyHonda
03-25-2009, 10:58 PM
yeah i would try to reset the computer...but it sounds like maybe its time to check your plugs and wires...also a buy seafoam and use it on your gas and brake booster

mrma5b
03-26-2009, 05:49 PM
The spark plugs and wires were replaced a few months ago, but i'll check them when I get the chance.

Forrest
05-07-2009, 11:18 PM
"it manages to reach the usual 1800 RPM, and runs just fine."
Did you mean 800 RPM? As in Idle? I had a wire break to one of the temp sensors mounted in the thermostat housing that caused a similar problem ... just a thought. But I see that this thread is old and you probably found the problem and just and just bailed out on the post.

AZmike
05-07-2009, 11:37 PM
"it manages to reach the usual 1800 RPM, and runs just fine."
Did you mean 800 RPM?

Cold idle is 1500-1800 rpm. Warm idle is around 750 rpm.

Forrest
05-08-2009, 12:01 AM
"also buy seafoam and use it on your gas and brake booster"

Sorry, new at this and don't know how to properly use the "quotes".
How do you use Seafoam on the break booster? Just replaced my master, bled them and all doesn't seem quite right. The little gasket at the base was thrashed and I just shined it on. Is that important? Guess I should probably have started a new thread for this.

mrma5b
05-16-2009, 04:47 PM
"it manages to reach the usual 1800 RPM, and runs just fine."
Did you mean 800 RPM? As in Idle? I had a wire break to one of the temp sensors mounted in the thermostat housing that caused a similar problem ... just a thought. But I see that this thread is old and you probably found the problem and just and just bailed out on the post.


I haven't found the problem exactly. The weather got warmer and the engine seems to cold start better now. It's probably that TW sensor acting up in freezing temperatures, but I don't have any error codes indicating the sensor has failed.

Once the engine does reach normal temps, the idle goes to around 750 rpm, but I can feel occasional misfires as it idles. Once the car is moving and in gear, I don't detect any misfires. My best guess for that problem is slightly dirty fuel injectors.

Warm starting is still somewhat of an issue, and always has since I got the car. Sometimes it will stall out if the engine was off for like 5 minutes and you try to start it again. Sometimes after starting warm, it will just idle roughly at like 300-400 rpm for a minute or 2. For this, it's probably a combination of the TW sensor and that main relay thingie, but I'm no expert.

Dr_Snooz
05-16-2009, 07:47 PM
it's probably a combination of the TW sensor and that main relay thingie, but I'm no expert.

Yep.

codyJDM
05-16-2009, 10:24 PM
Make sure your coolant is filled to the proper level and bled thoroughly. Air/bad coolant in your cooling system can cause you major headaches! Rough idle, bouncing idle, etc etc.

mrma5b
05-17-2009, 05:11 PM
Ok, so I tested the TW sensor using a multi-meter, and the sensor seems to be operational. I tested the resistance cold (weather is around 70 deg fahrenheit), and the meter read around 1.9 kOhms. I tested again after driving around and the temp gauge reached the middle of the normal zone, and the meter read about 0.4 kOhms. According to the chilton manual, these values are slightly higher than normal, but then again, I didn't do an exact measurement of temperatures. Should I replace the sensor anyways?


Make sure your coolant is filled to the proper level and bled thoroughly. Air/bad coolant in your cooling system can cause you major headaches! Rough idle, bouncing idle, etc etc.
The coolant level is correct, but I haven't done any flushing or bleeding of the cooling system. A new water pump was installed just before I bought the vehicle last July, so I don't know if the rest of the cooling system was serviced also. That'll be my next thing on my to-do list I suppose.