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2008 Pontiac G8 v6
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Discussion Starter #1
hello all, This is my 1st post but I am desperate to find out what is wrong with my G8. The original problem was that when I am driving down the road minding my own business going about 65 all of a sudden my car will jump or surge. I don't really know how to explain it. I had taken it to my mechanic because check engine lights were on and they said it was probably the timing chain because it was throwing out the P0008 code. I had the timing chain replaced this week and the AC compressor which has nothing to do with the problem I'm having I'm just telling you what all I had done. I also had two oxygen sensors and I am going to have the purge valve replaced as well. Anyways I picked up my car day before yesterday AND IT drove great the 1st day, the 2nd day I was driving along and all of a sudden it jumps it is so out of the blue it startles me. She has 154,000 Miles on Her and she purrs like a kitten and has always drove really well and quiet even when they thought she was having the timing chain issue she still made hardly any noise when she was idling. I have never spent money on her besides lower control arms 2 years ago. I pd almost 4,000 the past month and I can't afford to just guess on what's going on. Any help would be greatly appreciated.

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Is the check engine light currently illuminated? Contrary to popular belief, P0008 does not necessarily equate to timing chain failure. Considering the car was behaving erratically is indicative of some type of failure, however, General Motors updated the parameters/programming to allow a greater tolerance for timing chain stretch. Did they replace all of the timing chains? Guides? Tensioners? Etc.? Why were the oxygen sensors replaced? Why is the purge valve being replaced? $4,000 later and you're still having a variety of issues so where any of the issues resolved, exacerbated, or created after the repair work?
 
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The electronic throttles are known to go bad on these too, sometimes without much warning.
 

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Are you sure it’s not the tranny?
 

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Does your mechanic have a GM Tech2 scanner, one thing I harp about on this site is generic scanners not being able to diagnose problems like a Tech 2. In some cases owners like yourself pour parts and money needlessly into cars based on an improper diagnosis.
 

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2009 G8 GT
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The Throttle Position Sensor in the V6 tends to go as well, easy enough to change yourself and they are about $20.
 

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2008 Pontiac G8 v6
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Discussion Starter #7
Is the check engine light currently illuminated? Contrary to popular belief, P0008 does not necessarily equate to timing chain failure. Considering the car was behaving erratically is indicative of some type of failure, however, General Motors updated the parameters/programming to allow a greater tolerance for timing chain stretch. Did they replace all of the timing chains? Guides? Tensioners? Etc.? Why were the oxygen sensors replaced? Why is the purge valve being replaced? $4,000 later and you're still having a variety of issues so where any of the issues resolved, exacerbated, or created after the repair work?
Thank you for responding.
All of the CEL are off now and it didn't display one after the surge.
They replaced absolutely everything that has to do with the timing chain.
I had an oxygen sensor error on diagnostics
I think my purge valve needs replaced because when I get gas it acts like it's out of gas when I try to start it
 

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2008 Pontiac G8 v6
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Discussion Starter #10
Does your mechanic have a GM Tech2 scanner, one thing I harp about on this site is generic scanners not being able to diagnose problems like a Tech 2. In some cases owners like yourself pour parts and money needlessly into cars based on an improper diagnosis.
Oh God I hope that's not the case and I don't know what they have but I'll find out Tues when I take my car back in
 

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Suggest taking the car back to the mechanic, let them troubleshoot/diagnose it further and post their suggestions on the thread. Are you the original owner of the vehicle? Generally and loosely speaking, a transmission problem "should" produce some sort of diagnostic code, however not all scanners can detect/read them. By the way, the V6 has three timing chains.
 

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2009 G8 GT
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Don't dismiss the Throttle Position Sensor, the contact points inside tend to wear out.
20200803_104723.jpg
 

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20200803_105245.jpg
Not sure if that's what the issue is with yours, but in changing it in my son's V6 was a huge improvement in throttle smoothness and response.
 

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I agree with replacing the TPS and checking all of the wiring and grounds associated with it.
 

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Should of put his complaints down.
1. Feels like I kneed to put more "pedal" to it than before.
2. Jerky acceleration at low throttle input and when I have the cruise on going down the highway.
He also has had the timing chains done on his.
 

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Discussion Starter #16
Suggest taking the car back to the mechanic, let them troubleshoot/diagnose it further and post their suggestions on the thread. Are you the original owner of the vehicle? Generally and loosely speaking, a transmission problem "should" produce some sort of diagnostic code, however not all scanners can detect/read them. By the way, the V6 has three timing chains.
I am the 2nd owner but I've had it for 10 years. I'm taking it back tomorrow morning. On top of the receipts I also had a cam/crank sensor and an oxygen sensor. I also found out the hard way about a mechanic in pryor Oklahoma who goes by G8 Nation that he's a thief and a liar. He is the one who put my new struts on and didn't even tighten the washers and I took him the struts and strut mounts, lower control arm and an oxygen sensor. It started making a noise so I took it to my own mechanic and it was the washers bouncing around. Also, I do not believe he replaced my new one on or why would it throw the exact same diagnostic code?
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Discussion Starter #18
I literally have no issues with accelerating or hard shifting. It doesn't even do it every day. It just did it the other day while it was set on 65 cruise control on a straight away and jerked, jumped or surged. I really wish I could explain it. Ugh
 

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Looking at that receipt reminds me of why I started working on vehicles in the first place. Female relatives used to go to various automotive establishments and the amount of money they were paying for minor repairs was astronomical and downright ridiculous. Awhile ago, the timing chains were replaced under the power-train warranty and the vast majority of the parts listed on your invoice were not replaced. They literally only changed the timing chains along with a few other minor tidbits. $600 for a timing chain set is laughable especially coming from Auto Zone (comments withheld). Get in the zone. Auto Zone. At this point, it's probably best I comment no further on this thread and hopefully others will be able to steer you in the right direction. Read this "article" at your leisure, General Motors P0008 on-board diagnostic code.
 

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2009 G8 GT
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In the fuse panel, on drivers side left foot, look for fuse F9, pull it and check it, BCM fuse. In under hood fuse panel look for F1, F9 and F28, pull and inspect, and switch R2 with R5, these are all communication fuses an relays, after 11 years their contact points may not be as good as they used to be and not talking to itself as quickly, it's free and easy to do.
 
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