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2004 gmc envoy_slt
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6 Posts
Discussion Starter #1
I have a 2004 envoy with the 4.2 I replaced the plugs and coil packs 6 months ago and it has run perfect. I went to start it up las week and it ran like crap. I put my code reader on it and got codes for the cam position sensor and the vvt actuator solenoid. I replaced both. Now I onlt get the p0300 code and it runs horrible. Any ideas? Anyone? This has been a great vehicle and I can't afford to replace it.
 

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2003 gmc envoy_slt_xl
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66 Posts
My post is right below yours and these are the codes my headache started with. Good luck I'm still trying to figure it out although mine has been a little better running and haven't read the codes this week yet!
 

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2004 gmc envoy_slt
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6 Posts
Discussion Starter #3
sounds familiar.

Sounds like your issues are similar to mine, however mine is not drivable, A buddy told me valves, valve seals and possibly a head replacement. I will check back at the end of the day to see if we came across anything less intimidating.
 

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2003 gmc envoy_slt_xl
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Sounds like your issues are similar to mine, however mine is not drivable, A buddy told me valves, valve seals and possibly a head replacement. I will check back at the end of the day to see if we came across anything less intimidating.
Oh well this is getting old really really fast.
It runs and idles even better today BUT!!!!!! I was idling at a light for 2-3 minutes and it acts as though it going to stall. This is a first. Always something new!!!!
 

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2004 gmc envoy_sle_xl
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10 Posts
When you replaced the plugs and coil packs, did you also change the boots, as these usually go bad before the coil pack?
I suggest you use a scan tool, or an ODBII app such as Torque, to determine which cylinders are misfiring and try swapping coil packs between good and bad cylinders to see if the problem stays with the cylinder or follows the pack.
 

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2004 gmc envoy_slt
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6 Posts
Discussion Starter #7 (Edited)
I did replace the boots as well

My problem is getting narrowed down to a fuel issue, (I think.) I replace the fuel pressure regulator a few years ago o I had not even considered it, I just came back in from garage and the vac line off of the top of it has no change to engine while connected or disconnected. Anyone know if I am on the right track? I have been using a code scout from the beginning. I only get 2 codes now p0300 and p0300pd. I have yet to find out what the pd is.
 

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2004 chevy trailblazer_ls_ext
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6 Posts
I had exact same problem with my 2004 4.2L...rough idle no power. Changed plugs. And got the actuator and cam shaft sensor code.. checked the fuel pressure,replaced fuel filter... and it turned out to be the stupid O2 sensor! Swapped that out and it has been running good since August. Never did get a code for the sensor either. Pretty sure it was bank 1 sensor 1. First one on exhaust manifold. Can’t remember if I had to reset the ECM or not for it to relearn the adjustments though.(old age :)

God luck. I hope that works for you too!!!
 

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2004 gmc envoy_slt
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6 Posts
Discussion Starter #10
Update.

I ended up doing a compression test and there is 0 on number 5. I am going to pull the valve cover off and hope for the best. Good news is, compression is good on the rest.
 
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