Slow acceleration and backfire - Pontiac G6 Forum
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post #1 of 34 (permalink) Old 07-27-2012, 10:20 AM Thread Starter
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Slow acceleration and backfire

07 3.5 LZ4 Over the past few months every once in a while when i accelerate from a stop it seems like my car seems like its not getting gas, unless I floor it then it kicks in. Yesterday was the worst its been. It did it a few times, and one of those times it let out a few backfires, or popping sound from engine.

Just recently claned throttle body and MAF. Almost feels like a timing problem. could it possibly be a coil pack going out? any thoughts are appreciated.

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post #2 of 34 (permalink) Old 07-27-2012, 11:02 AM
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This Is occurring without the a/c on correct?


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post #3 of 34 (permalink) Old 07-27-2012, 11:17 AM Thread Starter
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post #4 of 34 (permalink) Old 07-29-2012, 01:07 AM
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I don't think I've had backfire..yet. But acceleration lag yes. Once I've used the car throughout the day it goes away. Just has bad acceleration from a cold start. Is yours constantly laggy?


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post #5 of 34 (permalink) Old 07-29-2012, 02:13 PM
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It could be a coil pack, Causing a multi-cylinder misfire. Have you had it scanned for codes?
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post #6 of 34 (permalink) Old 07-30-2012, 08:38 AM Thread Starter
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Yeah I scanned it no codes.
....So friday evening I pulled the MAP sensor to see what it looks like, and the grommet looked a little worn so I fuguerd for 50 buck I'll change it and see what happens. Right off the bat I noticed it cleaned up my idle, and alot better throttle response. Plus I had a little over a quarter tank of gas and was driving on the streets and my MPG actually went up, Which never happens in that situation. I also used to notice that when my car shift gears and settles into the next gear it used to have a little shutter, but that gone now too. I dont know if this was the answer to this problem (only time will tell since it was intermitent) but it was definitly worth the 50 bucks to have my car running alot better.
Thanks for the replies, I should be able to tell in the next couple days if this solved my problem.

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post #7 of 34 (permalink) Old 07-30-2012, 11:45 AM
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Wow, good news! Hope that's the solution!
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post #8 of 34 (permalink) Old 07-30-2012, 03:07 PM
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07, G6, 3.5l, mileage unk
intermittent hesitation under load with occassional backfire
Steps taken: cleaned MAF sensor & TB, replaced MAP

Intermittents are such good fun!

A couple causes of intermittent backfire that often would not pop a code in the early stages of failure:

-a lean misfire due to intermittently low fuel pressure caused by a failing fuel pump (verify pressure with a pressure gauge taped to the windshield)
-intermittent problem somewhere in the secondary ignition circuit producing low voltage & poor or no spark (tough to find problem when it presents only briefly)

much less likely:
dead spot in the throttle position sensor response-normally would pop a code if the two TP sensors disagreed for more than 2 seconds


I don't have a lot of confidence that it was a bad MAP sensor but anything is possible. Eventually you are going to at least get some misfire codes which may help track it down. If you had access to a scan tool you could see if the misfire counts were adding up & on which cylinders.



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post #9 of 34 (permalink) Old 08-02-2012, 11:26 PM Thread Starter
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Thanks for the replies Im at 90000 miles. And it's not constant usually it's been doing it after I've been driving it for 30 mins.

She started acting up again, so I went home set up the dashhawk and went for a test drive. And wouldn't you know it. Multiple misfires in all cylinders.

Damn I hope it's not a fuel pump. ...Isn't it weird that. No CEL would come up, especially with that many misfires? Any chance that the coil packs going out, Or would It just be one cylinder going out and misfiring? I was also able to monitor the TPS and that didn't look like it was doing anything out of the ordinary. But I guess nexts step if monitoring fuel pressure. I'll have to hook up my gauge this weekend.

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post #10 of 34 (permalink) Old 08-03-2012, 01:03 AM
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I believe the V6 is setup with 3 coilpacks, Each handling two cylinders. Since you're getting misfires on all cylinders It makes me think it's the ignition control module which on older V6s is under the coilpacks, I don't think these newer cars have that, it's all in the PCM. I could be wrong.

How old are your plugs and wires? Maybe you have arching between wires causing misfires. Or maybe all the coilpacks are going, but that seems unlikely.
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post #11 of 34 (permalink) Old 08-03-2012, 07:42 AM Thread Starter
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wll after driving to work i noticed that the misfiring is happening when shifting gears, both upshift and down. And that the number 3 cyl is racking up the most misfires with #4 close behind. I guess its time to do some research.

oh did plugs and wires about two years and 40000 miles ago, and it looks like one coil pack for all cylinders

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post #12 of 34 (permalink) Old 08-03-2012, 11:02 AM
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Quote:
Originally Posted by waterfowler76 View Post
Isn't it weird that. No CEL would come up, especially with that many misfires?
Is the CEL on during the lamps test at key on? Maybe it's burned out.



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post #13 of 34 (permalink) Old 08-03-2012, 11:05 AM Thread Starter
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Yeah it comes on at start up.

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post #14 of 34 (permalink) Old 08-03-2012, 11:14 AM
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Quote:
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She started acting up again, so I went home set up the dashhawk and went for a test drive. And wouldn't you know it. Multiple misfires in all cylinders.
I'm not familiar with the dashhawk. Is that giving you codes? If so, which codes?



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post #15 of 34 (permalink) Old 08-03-2012, 11:25 AM
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Quote:
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wll after driving to work i noticed that the misfiring is happening when shifting gears, both upshift and down. And that the number 3 cyl is racking up the most misfires with #4 close behind.
3 & 4 are powered by different coils so that likely eliminates the coil pack as the culprit

The coil pack has 3 coils which serve 1&4, 2&5 & 3&6.

Is it just 3&4 that are misfiring?




Last edited by greenman; 08-03-2012 at 11:36 AM.
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