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Old 05-24-2010, 01:01 AM   #1 (permalink)
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Date registered: May 2010
Vehicle: 1995 C280 143K mi
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Engine misfiring? Does a popping sound mean misfire?

The popping sound in question occurs almost instantly as I press my gas pedal to accelerate.

Scenario: This popping sound occurs when I have suddenly accelerated from a stop or especially after braking to slow down and depressing my gas pedal to accelerate back up. A few milliseconds after pressing my gas pedal, I hear a popping sound closer to the center firewall of the engine. I seem to feel the pop on my pedal as well, like something came loose!

Sometimes the car hesitates for half a second and then picks up and goes as nothing happened. Other times it hesitates further and I have to let the pedal completely off and then gently accelerate and the car recovers and goes as nothing happened.

This doesn't happen often time and is very hard to duplicate. But does happen. I have never had a check engine light come after the event. My gas pedal linkage is fine and there are no binds anywhere.

Is this a misfire? If this is a misfire shouldn't the car continue hesitating or misfiring more often?

I changed my spark plugs with Bosch F8DC4 plugs 25K miles ago.

Your analysis is appreciated.
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Old 05-24-2010, 07:45 PM   #2 (permalink)
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I would check your coils for cracks and the plugs from what you said. Your year may be subject to wiring harness issues as well. A cleaning of the throttle body may help.
The EGR tube is suspect to carbon build-up that may contribute to what issues your having too. B
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Old 05-24-2010, 08:34 PM   #3 (permalink)
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Thank you. My model year is subject to wiring harness failures. Strangely enough part of my wiring harness seems like it was replaced and there are parts of it fraying. I'll check the ones close to the coils and plugs.

Btw, is it possible the previous owner replaced only parts of the wiring harness??

How far in do I clean the throttle body? I can easily clean the end tip of it with WD40.

The EGR usually don't go bad but your point on carbon buildup is something I didn't think of. How far do you clean? The little tube that runs to the vacuum lines?

Thanks


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Originally Posted by bmeister View Post
I would check your coils for cracks and the plugs from what you said. Your year may be subject to wiring harness issues as well. A cleaning of the throttle body may help.
The EGR tube is suspect to carbon build-up that may contribute to what issues your having too. B
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Old 05-24-2010, 11:28 PM   #4 (permalink)
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Yea. its possible the previous owner did some repairs (damage control) to specific parts of the wiring they found to be crackly crunchy, if it was the rest probably is/was not far behind. If I am not mistaken doin12volt can repair the harness for you if need be. Also the connector to the throttle body can get the same way, uhgg! Usually for a proper throttle body cleaning it should come off so you can do a decent job, there are several write ups on that.
The EGR tube can be wire wipped (wire attached to end of drill) with a drill but again the best solution is to remove so you can operate on the tube easier. B
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Old 05-28-2010, 10:39 AM   #5 (permalink)
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My car was doing that until I took it in.
I ended up needing new spark plugs, and I had an oil leak. My engine was misfiring because of all of this.

Maybe you have a a bad spark plug?
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Old 05-28-2010, 02:09 PM   #6 (permalink)
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Barbie, you most likely are right. I changed my plugs 2 years ago. Maybe it is time again.

Did your popping issue completely go away after the spark plug change?



Quote:
Originally Posted by MorbidBarbie View Post
My car was doing that until I took it in.
I ended up needing new spark plugs, and I had an oil leak. My engine was misfiring because of all of this.

Maybe you have a a bad spark plug?
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Old 05-28-2010, 02:24 PM   #7 (permalink)
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misfire

Quote:
Originally Posted by MB-W202 View Post
The popping sound in question occurs almost instantly as I press my gas pedal to accelerate.

Scenario: This popping sound occurs when I have suddenly accelerated from a stop or especially after braking to slow down and depressing my gas pedal to accelerate back up. A few milliseconds after pressing my gas pedal, I hear a popping sound closer to the center firewall of the engine. I seem to feel the pop on my pedal as well, like something came loose!

Sometimes the car hesitates for half a second and then picks up and goes as nothing happened. Other times it hesitates further and I have to let the pedal completely off and then gently accelerate and the car recovers and goes as nothing happened.

This doesn't happen often time and is very hard to duplicate. But does happen. I have never had a check engine light come after the event. My gas pedal linkage is fine and there are no binds anywhere.

Is this a misfire? If this is a misfire shouldn't the car continue hesitating or misfiring more often?

I changed my spark plugs with Bosch F8DC4 plugs 25K miles ago.

Your analysis is appreciated.
I would change your air mass meter or also known as m.a.f sensor. when these go wrong you can get lack of power, bad throttle response and a feeling of a misfire.They dont always throw a fault code up either as it always gives out a voltage but the wrong one! This would be the first thing i would change from experience. Just make sure it is a genuine part & not aftermarket as these tend not to work.
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Old 05-28-2010, 02:57 PM   #8 (permalink)
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the repair adds up. i can do most of these myself so it will only be parts. the coils, plugs, maf and ultimately the damn harness. maybe it is time to sell the car! naaa i love the car.
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Old 05-28-2010, 02:57 PM   #9 (permalink)
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It's been fixed for about 3 weeks now, and no more sounds.

One particular occasion, I was turning sharply around a corner and then slammed on the gas. I heard the noise... once I was on the freeway it ran fine, and no noises. It was just during times of rapid acceleration.
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Old 05-28-2010, 03:20 PM   #10 (permalink)
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Spirited driving Barbie... So it is you who was blasting past me the other day.
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