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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > Air Induction

Air Induction Performance Air Intake/Air Induction Modifications

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  #11  
Old 06-09-2009, 12:35 AM
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CoyoteFireGuy CoyoteFireGuy is offline
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In my experience, usually if it is a faulty coil, it will indicate on which cylinder the coil is on. With it throwing a general misfire code, I'm not quite sure how to narrow which one it is. Is it actually missfiring horribly or is it only doing it randomly? Have you reset it since you cleaned the plugs? Where the plugs gapped to .042?
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  #12  
Old 06-09-2009, 01:26 AM
andresmontalvom andresmontalvom is offline
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Quote:
Originally Posted by CoyoteFireGuy View Post
In my experience, usually if it is a faulty coil, it will indicate on which cylinder the coil is on. With it throwing a general misfire code, I'm not quite sure how to narrow which one it is. Is it actually missfiring horribly or is it only doing it randomly? Have you reset it since you cleaned the plugs? Where the plugs gapped to .042?
It just happen when idle, on a red light or a stop sign (with A/C on it get more often) and you can feel it inside the truck, then the Check Engine light comes on. After some days, the Check Engine Light comes off and everything is smooth and nice again.
I reseated it after changed the plugs and they were gapped to 0.043.
I was thinking that may be it could be a vacuum leak, then I sprayed carburetor cleaner all around the hoses close to the throttle body and nothing happened. May be I have more than one bad coil... Don't you think?
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  #13  
Old 06-09-2009, 01:34 AM
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Could be or could be you have just over greased them and they now need to be replaced. How many miles on your truck? From what your describing, it almost sounds like a vacuum leak. With the hood up do you hear any suction noise? If it is a vacuum leak, I am stumped at how that is causing a missfire.

EDIT: also with it being random like you are describing, I am back to thinking it is a coil/grease issue, I would get 6 new coils, pull all the plugs clean them of all the grease and put the new coils in. You only need about a pea sized amount of grease for the coils.
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  #14  
Old 06-09-2009, 11:22 AM
andresmontalvom andresmontalvom is offline
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Quote:
Originally Posted by CoyoteFireGuy View Post
Could be or could be you have just over greased them and they now need to be replaced. How many miles on your truck? From what your describing, it almost sounds like a vacuum leak. With the hood up do you hear any suction noise? If it is a vacuum leak, I am stumped at how that is causing a missfire.

EDIT: also with it being random like you are describing, I am back to thinking it is a coil/grease issue, I would get 6 new coils, pull all the plugs clean them of all the grease and put the new coils in. You only need about a pea sized amount of grease for the coils.
My truck is almost 85K. I think that it is not a vacumm leak because of the random as you said. I cleaned preety well all the grease from the coils, springs and sparks, may be that's the actual problem. Before I buy ($$) new coils, I will try to regrease correctly the coils, but before I have two questions for you:
1. You said that I have to replace the coils because the over grease, Do you think I damage them because of that? (I just overgrease the spring that conect the coil with the spark and the sparks).
2. Can you tell me the correct procedure to grease the coils? Do I have to grease just the conecctions coil-spring-spark, all of them about a pea sized amount?

I really appreciate your help. Thank you very much.
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  #15  
Old 06-09-2009, 11:39 AM
FlyingTiger FlyingTiger is offline
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P0300 Code and Random Misfires

If your CHECK ENGINE light is on and you have found a P0300 diagnostic trouble code (DTC) by plugging a scan tool or code reader into your vehicles diagnostic connector, your engine has a "random misfire" problem.

A random misfire code can be set on newer vehicles with OBD II onboard diagnostics when multiple misfires occur randomly in multiple cylinders. The cause is typically a vacuum leak in the intake manifold, throttle body or vacuum plumbing, a defective Exhaust Gas Recirculation (EGR) valve that is leaking exhaust into the intake manifold, or even bad gasoline. Less common causes include bad spark plug wires, worn or fouled spark plugs, a weak ignition coil, dirty fuel injectors, low fuel pressure, or weak valve springs. If a misfire is occurring in only one or two cylinders, you will usually find a misfire code for that specific cylinder rather than a random misfire code.

Here is the link to how to diagnos the problem:

http://www.random-misfire.com/
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  #16  
Old 06-09-2009, 11:52 AM
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^^^^Sounds good, give it a try too.^^^^^

Quote:
Originally Posted by andresmontalvom View Post
My truck is almost 85K. I think that it is not a vacumm leak because of the random as you said. I cleaned preety well all the grease from the coils, springs and sparks, may be that's the actual problem. Before I buy ($$) new coils, I will try to regrease correctly the coils, but before I have two questions for you:
1. You said that I have to replace the coils because the over grease, Do you think I damage them because of that? (I just overgrease the spring that conect the coil with the spark and the sparks).
2. Can you tell me the correct procedure to grease the coils? Do I have to grease just the conecctions coil-spring-spark, all of them about a pea sized amount?

I really appreciate your help. Thank you very much.
1.Yes you can try cleaning them, but once you pull one, you will see that this may be either very difficult or not work.

2.When you buy the new coils, they should come with little packages of a whitish grease. Open the package along the 2 sided perforated section. It should look like the icing pack from a Toasters Strudel. Apply a drop about the size of a pea at the opening of the bottom of the coil pack where it meets the spark plug. When you seat the coil on the spark plug, try not to twist it to much.
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  #17  
Old 06-09-2009, 11:55 AM
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Quote:
Originally Posted by FlyingTiger View Post
If your CHECK ENGINE light is on and you have found a P0300 diagnostic trouble code (DTC) by plugging a scan tool or code reader into your vehicles diagnostic connector, your engine has a "random misfire" problem.

A random misfire code can be set on newer vehicles with OBD II onboard diagnostics when multiple misfires occur randomly in multiple cylinders. The cause is typically a vacuum leak in the intake manifold, throttle body or vacuum plumbing, a defective Exhaust Gas Recirculation (EGR) valve that is leaking exhaust into the intake manifold, or even bad gasoline. Less common causes include bad spark plug wires, worn or fouled spark plugs, a weak ignition coil, dirty fuel injectors, low fuel pressure, or weak valve springs. If a misfire is occurring in only one or two cylinders, you will usually find a misfire code for that specific cylinder rather than a random misfire code.

Here is the link to how to diagnos the problem:

http://www.random-misfire.com/
That is a very good possibility, did you make sure you have all the hoses back correctly and in the right order from when you cleaned the throttle body? Especially the EVAP line. It is the little line that connects to the big black box over the engine before the Throttle Body.
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  #18  
Old 06-09-2009, 12:06 PM
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There is also a vacuum port on the intake near the rad. It has a rubber plug that tends to crack. You might want to look at it as well.
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  #19  
Old 06-09-2009, 04:37 PM
andresmontalvom andresmontalvom is offline
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I'm pretty sure all the hoses are in good shape and connected, but I'll double check them again, may be I can find something wrong. But I'm not sure is a vacuum leak can produce a random problem. Remember that half of the time, the TB works pretty nice at idle; all the time shows great performance and power at speed and acceleration, and just misfires at idle 50% of the time.
I forgot to mention, I made a small test removing the resonator box and cover with my hand the throttle body air intake, wondering that may be if there is a vacuum leak, the air to keep the motor running will be going throw it the leak, but nothing; the suction at the air intake was so strong and the motor shuted off very quick.
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  #20  
Old 10-05-2013, 12:14 AM
debbieauman debbieauman is offline
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cam pos sensor

2004 gmc envoy. I have 4 codes that went off.
p0106 map sensor
p0301 cylinder 1 misfire
p0128 coolant temp. sensor
p0014 cam pos sensor.
So far changed out spark plugs and map sensor.
I do not know where to locate the cam pos sensor. Can anyone tell me where it is, or give me a site to look at. Car is running rough.
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