Random multiple miss fire P0300

Tiny
MIKEDEROUIN88
  • MEMBER
  • 2006 CHEVROLET EQUINOX
  • 3.4L
  • V6
  • FWD
  • AUTOMATIC
  • 166,000 MILES
My customer had a valve drop on his 2006 Equinox. He asked me to replace his motor with a used one from a reliable used motor and transmission dealer.

After installing the used motor there is a P0300 trouble code. I double checked all my work. I replaced the spark plugs with new AC Delco Iridium OE plugs. The coil pack and plug wires are off of the original motor which had no problems prior.

Can you please give me the cylinder identification and possibly give me a few pointers on where to look next.
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Monday, November 25th, 2013 AT 9:44 PM

11 Replies

Tiny
HMAC300
  • EXPERT
Misfires are extremely hard to diagnose. If you have a pro style scanner look at your reading and see if anything is out of whack. Also check for vacuum leaks, hoses off etc.
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Tuesday, November 26th, 2013 AT 6:17 AM
Tiny
MIKEDEROUIN88
  • MEMBER
I am a ASE certified and have a fairly good scanner. Im just wondering if there may be a common problem with this model vehicle. Since it is a used motor its hard to find a starting point. I was leaning towards a fuel injection problem but I have not checked for vaccume leaks so I will start there. That's very helpfu. Thanks for the pointer and if theres any way you can get me the cylinder identification so I can double check my wires that would be great. I assumed it was just standard General Motors. With 2 4 6 on the front and 1 3 5 on the back.
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Tuesday, November 26th, 2013 AT 9:49 AM
Tiny
HMAC300
  • EXPERT
I dont' think you get a misfire code with cwires crossed but hell you never know. Here ya go
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Tuesday, November 26th, 2013 AT 9:53 AM
Tiny
HMAC300
  • EXPERT
Another pic with firing order
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Tuesday, November 26th, 2013 AT 9:54 AM
Tiny
MIKEDEROUIN88
  • MEMBER
I have seen a P0300 caused by crossed wires but only if its 2 or more cylinders and the was they make cars now I doubt it would even start if that was the case. But I have been fooled before. This motor is such a simple designe there's not a lot to it and being that its a used motor that we know nothing about I want to be extra sure everything was installed perfect before I start pointing fingers at the used motor. This is exactly why I try to avoid installing used parts. But with todays economy you have to take whatever work you can get. I am going to put the smoke machine on it tomorrow and check for vaccume leakes. I will let you know.
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Tuesday, November 26th, 2013 AT 5:12 PM
Tiny
HMAC300
  • EXPERT
If you have mode 6 on your machine run that and it might single it out prior to doing smoke test.
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Wednesday, November 27th, 2013 AT 6:14 AM
Tiny
REDNECK306
  • MEMBER
  • 2005 CHEVROLET EQUINOX
  • 3.4L
  • V6
  • AWD
  • AUTOMATIC
  • 103,000 MILES
Okay this is a good one. I just bought this 2005 equinox and the person had the wrong plugs in it, auto lite platinum so I bought ac delco plugs and new wires to change them. I broke the plug for cylinder #2 and we could not get it out so we pulled the head, and a 1700lbs torque snap on impact gun could not pull out the broken plug (with an easy out). We drilled the plug out and re tapped the hole for a healicoil (or how ever it is spelled). Then we put everything back together and new head bolts and gaskets, the works not cutting corners on anything. And cylinder #2 has only 30lbs of compression and is misfires on an idle but runs perfect once you start to drive it. The check engine light would flash for a bit then stay solid then flash again. After about 60 miles of driving continuously the light when out and would only come on flashing for about 2 secs every 10 miles or so. I am so F'ing aggravated and confused. Any help would be greatly appreciated! When I say "we" I mean me, my step dad who owns the garage and a friend with 20 years experience working on cars. I really do not want to pull that head again.
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Thursday, February 21st, 2019 AT 4:54 PM (Merged)
Tiny
JOHNNYT73
  • MEMBER
Did you do a wet test on the cylinder to check for bad rings?
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Thursday, February 21st, 2019 AT 4:54 PM (Merged)
Tiny
CADIEMAN
  • MEMBER
U should have the head checked by a head shop.U have a crack or bad valve on #2 cyl. And need another head or repair that one if poss.
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Thursday, February 21st, 2019 AT 4:54 PM (Merged)
Tiny
REDNECK306
  • MEMBER
I did not do a wet test, what is a wet test? And I did not have the head checked because the vehicle ran fine before we tore it out and all the valves looked fine. I ordered a new head but I really hope I do not have to use it.
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Thursday, February 21st, 2019 AT 4:54 PM (Merged)
Tiny
CADIEMAN
  • MEMBER
Wet test is when u squirt oil in the cyl. To ck. The rings.U don't need a new one u need a one from the head shop rebuilt. Take the valve cover off and ck. The rocker arms on #2 cyl.
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Thursday, February 21st, 2019 AT 4:54 PM (Merged)

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