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Want to diagnose coil packs without damaging engine

Tiny
COOLOLDS85
  • MEMBER
  • 1989 BUICK REGAL
  • 2.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 55,900 MILES
I want to diagnose the coil packs on my V6 Chevrolet engine (car listed above) when the engine is running when checking for a good known coil firing. Cannot check them without removing the coolant recovery tank and dog bone motor mounts. Would this hurt the engine by doing so? I do not want to make the engine overheat etc. Just want to make sure each coil has a good consistency.
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Sunday, April 15th, 2018 AT 7:24 PM

7 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,003 POSTS
Is the engine running okay, if yes and it is not misfiring you are in good shape. Those coils either work or not, I have never seen any that fall in between. What normally fails is the ignition module under them. Then you get random firing or none and because they feed two cylinders as a waste spark system you will know if one fails as you will lose two cylinders. The wires can fail as well but those are easy to change, just be careful to route them properly.
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Tuesday, April 17th, 2018 AT 8:27 PM
Tiny
COOLOLDS85
  • MEMBER
  • 173 POSTS
Engine was rough at idle then it got worse when accelerating and engine was shaking and stumbling. I than let it sit and drove it again a couple days after and was driving fine. I already replaced plugs and wires. I just wanted to inspect if each coil was firing all together. I wanted to pull each plug and see if the coils were firing properly. That is why I asked the question. On the 3300 they are easier to get to without removing coolant recovery and motor mounts.
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Wednesday, April 18th, 2018 AT 1:03 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,003 POSTS
Not likely to be the coils. Those coils fire both towers at the same time. Easy way to test them is to just put a spark tester onto one tower of each coil and see what the spark looks like. Your problem sounds more like low fuel flow causing a lean mix. As the rpm's goes up so does the need for more fuel, low pressure or volume, like a blocked filter or bad pressure regulator.
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Wednesday, April 18th, 2018 AT 1:45 AM
Tiny
COOLOLDS85
  • MEMBER
  • 173 POSTS
Do you know know the fuel pressure specs for checking the pressure regulator and pump? I did research and it said idle is 40 to 47 with KOEO and 30 to to 44 at at idle.
What specs would I have to look for when tapping the throttle and decelerating?
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Wednesday, April 18th, 2018 AT 3:44 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,003 POSTS
Those look like good numbers. Basically you want the higher side for a good pump. Then if you apply vacuum to the regulator it should drop 3 to10 psi.
As the vacuum drops as the throttle opens you want the pressure to rise and the opposite when you do a decel test. It will not hurt to verify you have good vacuum at idle as well. 18-22 inches would be good.
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Thursday, April 19th, 2018 AT 2:22 AM
Tiny
COOLOLDS85
  • MEMBER
  • 173 POSTS
I was thinking about buying this to check the coil packs. Would this work? Steve you said use spark test to check each tower on each coil at a time for spark.
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Sunday, April 22nd, 2018 AT 3:13 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,003 POSTS
That will work. I use one similar to it all the time just to verify if there is spark while I turn turn the key.
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Sunday, April 22nd, 2018 AT 5:52 PM

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