so i have a 99 honda accord ex v6 at 160k miles on original tranny and lately i been noticing some problems. it might have been there earlier but i just actually noticed it a week ago. a few days after i changed my spark plugs, i have been hearing a consistent "puff.puff.puff" sound coming from my exhaust. i thought this was the cause of a "misfire" because my plugs weren't tight enough so i went back 2x and re-torqued all 6 to manufacturer specs or 13ft lbs(although i did this when i was changing them). However, this did not help in anyway. Moreover, sometimes when i start my car, it would start quicker than usual and RPM would drop below 750 to 500 on idle, and it felt like the car is going to stall. This usually happens after the 2-3 times i crank the engine (also another reason why i thought my car was misfiring). It started happening after i changed my rear spark plugs. On the hand, I recall 2 weeks ago my coolant reservoir had completely been emptied. Now i'm assuming my head gasket is blown and that the puff sound is from the engine burning the coolant and releasing it to the exhaust? i do see white smoke from time to time. this past week has been colder than usual so i thought white smoke would be normal but now that the weather is warmer, i still see white smoke coming out the exhaust. all in all, my question is why is the exhaust making puff sounds, why does the engine sometimes drops to 500rpm on idle, and is my car going to freaking die soon? sorry about grammar, etc. thanks.

I took of the spark plugs today (rear) and it had blackish/brown color on the rings(its new too!). The fronts were normal. After driving it to normal temperature, it would often restart like regular but sometimes the rpm drops to 500 and steadily make its way back to 750 if i leave it alone for 30-1min.

 

the white smoke not sure of, but the low idle probly is the plugs, mine would be sitting at a light , (warmed up ) and just drop off idle to like 500-750 rpm, I changed out the plug - make sure of gap and my issue went away.

 

If the 'smoke' you see from the exhaust is accompanied by a sweet odor, you're more than likely burning antifreeze. If, on the other hand there is no associated odor; it's more likely steam (water vapor) - a normal byproduct of combustion.
Is there a rythmic pulsing from the engine which corresponds to the huffing you're getting from the exhaust. This would be indicative of a dead (minimized) cylinder; either by and ignition deficiency or something as radical as a burned / or sticking exhaust valve(s).
Have you noticed any other issues?

P

 

hello thank you for responding. on the way to six flags today my car finally set off a CEL. i stopped by the nearest Autozone but just found out they did not pull codes anymore. they suggested i go to pepboys which i will do later today. when i was driving the car today, everything felt fine. it ran like usual. today was a good day because it did not have any problems starting up but the puff sound was still there. i tried to record a short clip of the puff, but its not long because i didn't want to melt my blackberry. i will tried to get a better one if needed. here is the link, its only the first 3 seconds of the video. http://www.youtube.com/watch?v=ui7rNC7XS4o

you can hear the puff sound in the background, that sound is consistent if i were to leave my vechile on idle. somehow i'm pretty sure it has something to do with the rear spark plugs. i only had difficulty with the rear right spark plug because it was a PITA to get out. felt like someone had stripped the thread and it did not want to come out. it made noises when i tired to remove it.

 

my cars do that when they idle.......i would not worry about it unless there is something else wrong like a loss of power, loss of coolant, lower fuel economy, or your plugs are getting fouled

 

See if you can find someone to pull that code for you. That will save a lot of speculation and help point the way.

P

 

hey guys thanks for all suggestions and advice. today i pulled the code off pepboys and it was shooting a P0420. He told me that it was the o2 sensor. is this a possible explanation for the sound at idle? i'm planning on replacing it real soon after i figure out which o2 sensor it is. what brand should i go with? bosch or NGK.

P0420 67 Catalyst System Efficiency Below Threshold

edited: after reading around its actually CATS not the o2 what the heck.

 

Boilerplate: Catalytic Converter Primer:

P0420
What can happen is that the ability of the Catalytic Converter to process the exhaust gasses and convert the harmful CO, HC and NoX to harmless CO2 and water may have diminished over time to a point where the capacity of the catalytic converter to do the conversions is less than 50% of its original capacity.

The Converter uses up a microscopic amount of the reactive metals in the chemical conversion of harmful exhaust emissions to harmless emissions each time the vehicle is used. Over time the amount of the material that causes the chemical conversion diminishes. Because of the federal emissions laws, when the on-board diagnostic system judges the capcity to be less than 50% of the original capacity then the failure code P0420 is set and the check engine light is turned on.

The car will not stop on you nor break down.
The check engine light simply means that the catalytic converter MAY have to be replaced to restore the car to compliance with emissions regulations.

There are two components which can set this code:
The Catalytic Converter or
The Secondary O2 Sensor (after the converter)(which monitors the Catalytic Converter)

Ironically, the cheaper of the two repairs is usually the one that fixes it; the O2 sensor. (way cheaper).

As to your secondary question, unfortunately NO.
The secondary O2 sensor only monitor's the cat's efficiency by the ECM comparing those readings from the Primary (before the converter) O2 sensor.
The primary O2 sensor has a direct influence on drivebility

P

 

At my shop we have a bluepoint tester, basically you use the tester in place of the radiator cap, with the engine running the tester has a fluid in it that will change color when it reacts with hydrocarbons. This tells you that they are leaking into the cooling system through the headgasket. I take it that it is not leaking anywhere else. If coolant is is the exhaust I'm pretty sure that can damage O2 sensors and catalytic converters. You might want to check the compression just to be safe.

P Adams is correct as always!
Replace the O2 sensor first! And keep an eye on that coolant!

 

hi, i been reading around different honda forums and found that many are using defouler as a way to tricking the system. i was thinking of install one of those then resetting the codes. do you think this might work? if it shoots again then i guess i will have to try a different route.

 

You're welcome to try (it is your car); but I never had any luck with it.
And I certainly don't advocate the use of them.
Let us know how it turns out

P

 

Update: as of 2000 miles with the defouler on, the check engine light has not come on yet. However, the rough idle problem is still there with a new leaking oil pan!!!!
"it idles a bit rough. it drops to about 500 rpm a couple of times, then kick up to the normal 900 rpm. once i start driving, it idles just fine (at stoplights, etc.). but if i shut it off after driving, then restart, it has the same rough idle."

some solutions after reading around: check for leaks, clean iacv, replace o2 sensor, replace cat