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Chevy misfire...need help

Pinosan

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One mechanic did move the coil and it was still missing on #7. They wanted to take that piston to a machine shop. It was going to be $1300.

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I did change the wires but not the coils
His full of it, Once you open the crankcase, you have to rebuild the engine, can't change the rings in only one piston. Yes it would be above 1500 but you need to make sure that is the problem.
leak down test.
monitor the fuel rail and ignition system
as well as the pump operation

I hope this works out.


whats you code or codes??
 

Qwikdry

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*running

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check your upstream 02 sensors. the sensors closest to the exhaust manifold as it comes out the engine. those are very important and they do go bad. running rough all the time is a good indicator that an 02 sensor is bad or sluggish (responds slowly) basically your van is computer run. the air to fuel ratio is controlled by those two upstream 02 sensors. they get feedback of fuel to 0xygen and tell the computer to make corrections for air to fuel ratio.. spray more or less fuel from the fuel injectors. all computer controlled on newer vehicles like your 2008. their is one upstream 02 sensor for bank 1 (half your cylinders) and bank 2. (the other half of your engine's cylinders) good luck. does it only have 1 engine code. the misfire on cylinder #7? or multiple cylinder misfire code as well?
 

Tony from Chicago

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I had the exact same problem this summer with my GMC 2500 after a lot of searching I found the problem was a gummed up exhaust valve on cylinder 6
The code was misfire cylinder 6 . Look on YouTube for dollar bill trick. If the dollar sucks into the exhaust you found the problem. My mechanic suggested either a valve job which is way too expensive for the year of the van or sea foam he crap out of it - which I did...... successfully. Other than that . A head gasket leak is a possibility also. Sea foam worked great , it just took a lot of applications in the intake as well as the gas tank.


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Tony from Chicago

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If your only code is misfire cylinder 7 - it is unlikely it's anything else than a valve or head gasket leak - anything else would trigger lean codes or show up with another code - do a compression test on 7 also . If your mechanic didn't do that already find a new one


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Sep 4, 2010
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check your upstream 02 sensors. the sensors closest to the exhaust manifold as it comes out the engine. those are very important and they do go bad. running rough all the time is a good indicator that an 02 sensor is bad or sluggish (responds slowly) basically your van is computer run. the air to fuel ratio is controlled by those two upstream 02 sensors. they get feedback of fuel to 0xygen and tell the computer to make corrections for air to fuel ratio.. spray more or less fuel from the fuel injectors. all computer controlled on newer vehicles like your 2008. their is one upstream 02 sensor for bank 1 (half your cylinders) and bank 2. (the other half of your engine's cylinders) good luck. does it only have 1 engine code. the misfire on cylinder #7? or multiple cylinder misfire code as well?
We replaced both o2 sensors before we did the tune up. Same kind of deal...replaced the sensors it worked for a day or two and then went rough again.

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Sep 4, 2010
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Yes it's doing that. Thank you for the help. I'm going to give that a shot with the sea foam. How much do you think I'll need?

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Qwikdry

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We replaced both o2 sensors before we did the tune up. Same kind of deal...replaced the sensors it worked for a day or two and then went rough again.

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does your van leak or drip any fluids? check the connections on the 02 sensors. i replaced one on my astro van. ran good, then few days later rough again. i found that their was an oil leak that dripped on my connector and fried my 02 sensor i had just replaced. i put di electric grease on it before pushing the connectors together to keep oil out of it better. no more problems, and i also fixed the oil leak.
 

Tony from Chicago

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You will need to spray it directly into the intake- do not spray the MAF sensor! It took about 4 cans over 4 weeks plus sea foam liquid in the tank for the check engine light to stay off permanently- it will go off and on after the first treatment but my truck is a 2000 so it may take less for you . As long as the cylinder hasn't bent the valve you should be good . Check out YouTube for how to- lots of info


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Sep 4, 2010
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You will need to spray it directly into the intake- do not spray the MAF sensor! It took about 4 cans over 4 weeks plus sea foam liquid in the tank for the check engine light to stay off permanently- it will go off and on after the first treatment but my truck is a 2000 so it may take less for you . As long as the cylinder hasn't bent the valve you should be good . Check out YouTube for how to- lots of info


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Thank you!!

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Ken Raddon

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just one thought and it's going to sound rude but here it is anyway...

Start your own thread if you want more answers.
 
Sep 4, 2010
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So quick update...I have put 6 cans of sea foam in the air intake as well as 2 in the gas tank. Sometimes it runs smooth and I don't feel any misfire. It will run like that for a 30-45 mins and then the misfire comes back and it runs really rough.

If anyone has any suggestions I am open. Otherwise I am going to sell it since I already purchased a new van and system 3 months ago. (I don't need this one). I'm not real mechanically inclined so I'm sure if one of you guys got your hands on it you could make it work. I just don't like this side of the business much. :) Thanks again!!
 

Qwikdry

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So quick update...I have put 6 cans of sea foam in the air intake as well as 2 in the gas tank. Sometimes it runs smooth and I don't feel any misfire. It will run like that for a 30-45 mins and then the misfire comes back and it runs really rough.

If anyone has any suggestions I am open. Otherwise I am going to sell it since I already purchased a new van and system 3 months ago. (I don't need this one). I'm not real mechanically inclined so I'm sure if one of you guys got your hands on it you could make it work. I just don't like this side of the business much. :) Thanks again!!
how much for it? i am in northern Utah bordering Idaho.
 

Ara Klujian

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If you are putting e85 ethanol fuel in your tank that could be the problem. If memory serves me correctly GM/Chevy used the CSFI (central sequential fuel injection) in the upper intake manifold. What happens is the e85 destroys those older fuel injectors and GM/Chevy does not cover any recalls for it. What they did was switch the fuel injection system to CSMPI (central sequential MULTI-Port injectors). The kicker here is you need to buy all 8 CSMPI's. Try running fuel that is not e85 or better yet has no ethanol.
 

Ara Klujian

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And if your wondering why only 1 cylinder is effected... It's just a matter of time before they all start going bad. Those older fuel injectors where never designed for todays fuel.