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Username Post: Coil Pack Replacement on 3.1l        (Topic#358432)
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
10-13-19 02:43 PM - Post#2777806    

I'm trying to replace the coil packs on my 1990 Chevy Celebrity Eurosport Wagon with the 3.1L V6. The bottom bolts on each coil pack come out fairly easy but the top bolts all seem like a different size or all rusted out. The 5.5mm socket slips on one of them and the other two it won't grab onto at all. I have tried metric and SAE from a little bigger to a lot smaller and nothing will grip onto these. I have also tried female torx and still no luck. On one I finally got sick of it and ground the head of the bolt off so that I could get the coil pack out of the way and have room to get the bolt out. The joke is on me, now the bolt is frozen in place and even vice grips won't break it lose. I have had it soaking in penetrating fluid for days but it won't free up. To make things worse the coil packs are mounted on the front of the engine so I am working blind and there is almost no room to get anything in the small space where the bolt head is. Any ideas?



 




junkman104 
Frequent Contributor
Posts: 1479
junkman104
Age: 60
Loc: Murphy N.C.
Reg: 01-25-14
10-14-19 03:15 AM - Post#2777839    
    In response to Turbo2

I would replace the entire coil packs and module with a used unit.



 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
10-16-19 01:08 PM - Post#2778045    
    In response to junkman104

It looks like the same bolts that hold the coil packs in place also hold the module in place.



 
paulo57509 
Senior Member
Posts: 415

Loc: Tracy, CA
Reg: 07-18-00
10-20-19 12:34 AM - Post#2778283    
    In response to Turbo2

  • Turbo2 Said:
I'm trying to replace the coil packs on my 1990 Chevy Celebrity Eurosport Wagon with the 3.1L V6. The bottom bolts on each coil pack come out fairly easy but the top bolts all seem like a different size or all rusted out. The 5.5mm socket slips on one of them and the other two it won't grab onto at all. I have tried metric and SAE from a little bigger to a lot smaller and nothing will grip onto these. I have also tried female torx and still no luck. On one I finally got sick of it and ground the head of the bolt off so that I could get the coil pack out of the way and have room to get the bolt out. The joke is on me, now the bolt is frozen in place and even vice grips won't break it lose. I have had it soaking in penetrating fluid for days but it won't free up. To make things worse the coil packs are mounted on the front of the engine so I am working blind and there is almost no room to get anything in the small space where the bolt head is. Any ideas?



Doing a coil or module R&R on a 3.1 is a pain even when everything goes smoothly. I remove the entire coil/ignition module/bracket assembly from the engine block.

It'll be easier for you to remove that buggered up coil mounting screw if you do this too.

The only issue is the bracket mounting bolt shown below.



For some reason (IIRC, the starter is kind of in the way), it's difficult to next to impossible to see it and get a socket on it properly. I have resorted to removing just the coil that's directly under it in order to get to that bolt.

Before I bolt the assembly back onto the engine block, I make that hole a slot and partially install that bolt into the block allowing me to slide the bracket into place.

And yes, please consider replacing the module while it's on the bench.


1987 IROC-Z 5.0L
1992 Lumina Euro 3.1L
2003 GMC Safari


Edited by paulo57509 on 10-20-19 12:40 AM. Reason for edit: No reason given.

 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
10-29-19 12:55 PM - Post#2779063    
    In response to paulo57509

Do you know off hand what size the bolts are that hold the module on?



 
paulo57509 
Senior Member
Posts: 415

Loc: Tracy, CA
Reg: 07-18-00
11-01-19 10:48 PM - Post#2779342    
    In response to Turbo2

  • Turbo2 Said:
Do you know off hand what size the bolts are that hold the module on?



I'm sorry, I do not.


1987 IROC-Z 5.0L
1992 Lumina Euro 3.1L
2003 GMC Safari


 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
12-01-19 08:24 AM - Post#2781329    
    In response to paulo57509

Well I finally got the coil packs replaced and now have a different problem. If I start the car from cold it runs great and even after it's all full temp it still is running well. If I shut it off and go in a store, when I come back out and start it up it runs like it is running on 4 cylinders. It misses and bucks down the road making the car shake and when I park it, it smells very hot (coolant temp is normal). If I wait till the next day it starts up like a champ and will run great again until I shut it off.



 
paulo57509 
Senior Member
Posts: 415

Loc: Tracy, CA
Reg: 07-18-00
12-07-19 04:57 PM - Post#2781681    
    In response to Turbo2

I don't have a good answer for you but a few questions.

Other than the three coil packs, what else was replaced?

Was the battery ever disconnected?

The engine runs fine when started from dead cold. When the engine gets up to temp, does the idle surge and does the engine act like it wants to die?

1987 IROC-Z 5.0L
1992 Lumina Euro 3.1L
2003 GMC Safari


Edited by paulo57509 on 12-07-19 04:57 PM. Reason for edit: No reason given.

 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
12-08-19 11:42 AM - Post#2781712    
    In response to paulo57509


  • paulo57509 Said:
I don't have a good answer for you but a few questions.

Other than the three coil packs, what else was replaced?

Was the battery ever disconnected?

The engine runs fine when started from dead cold. When the engine gets up to temp, does the idle surge and does the engine act like it wants to die?



Spark plugs were also replaced.
Battery was not disconnected.
Starting from cold it runs great and continues to run great even at full temp as long as I keep driving and don't shut it off. The problem only seems to happen after it's up to full temp and then shut off.




 
paulo57509 
Senior Member
Posts: 415

Loc: Tracy, CA
Reg: 07-18-00
12-08-19 01:35 PM - Post#2781718    
    In response to Turbo2

  • Turbo2 Said:

  • paulo57509 Said:
I don't have a good answer for you but a few questions.

Other than the three coil packs, what else was replaced?

Was the battery ever disconnected?

The engine runs fine when started from dead cold. When the engine gets up to temp, does the idle surge and does the engine act like it wants to die?



Spark plugs were also replaced.
Battery was not disconnected.
Starting from cold it runs great and continues to run great even at full temp as long as I keep driving and don't shut it off. The problem only seems to happen after it's up to full temp and then shut off.




I forgot to ask, why did you replace the coil packs in the first place?

For the "new" issue, I'd confirm that all the plugs are firing when it's acting up. I think they still make those pen-like testers that you touch to the plug wires. If the plug is firing, the pen lights up. I've done this same test with an inductive timing light.

If all the plugs are firing, you can look elsewhere for the problem.

Link

1987 IROC-Z 5.0L
1992 Lumina Euro 3.1L
2003 GMC Safari


Edited by paulo57509 on 12-08-19 01:39 PM. Reason for edit: No reason given.

 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
12-09-19 09:58 AM - Post#2781783    
    In response to paulo57509

  • paulo57509 Said:
  • Turbo2 Said:

  • paulo57509 Said:
I don't have a good answer for you but a few questions.

Other than the three coil packs, what else was replaced?

Was the battery ever disconnected?

The engine runs fine when started from dead cold. When the engine gets up to temp, does the idle surge and does the engine act like it wants to die?



Spark plugs were also replaced.
Battery was not disconnected.
Starting from cold it runs great and continues to run great even at full temp as long as I keep driving and don't shut it off. The problem only seems to happen after it's up to full temp and then shut off.




I forgot to ask, why did you replace the coil packs in the first place?

For the "new" issue, I'd confirm that all the plugs are firing when it's acting up. I think they still make those pen-like testers that you touch to the plug wires. If the plug is firing, the pen lights up. I've done this same test with an inductive timing light.

If all the plugs are firing, you can look elsewhere for the problem.

Link



I originally replaced the coil packs for misfiring and rough idle. 2 of the 3 coil packs were out of spec.
I'll have to look into getting a spark tester.



 
Texasray 
"4th Year" Gold Supporting Member
Posts: 103
Texasray
Loc: Texas
Reg: 11-01-16
12-16-19 09:11 AM - Post#2782243    
    In response to Turbo2

Not usually on this forum since I have a 1966, but I saw your title and had a shiver... lots of memories.
Just a thought about your latest question, be very careful in checking spark on this system. It was called a "waste spark" design because it fires both plugs on that coil each time. If you reduce the needed voltage on one of the cylinders then the other cylinder will look like it is firing just fine, but not the case.
Example: say the coil will only put out 40K, when it needs to put out 60K plus. Then the cylinder that is firing takes 35K because of the need to overcome the compression trying to squish the spark out. Now the "waste" cylinder needs 5K to 7K to overcome the spark plug gap and the plug wire resistance. You now can't supply the needed voltage to cylinder on compression stroke.
So you install a spark checker in the "waste" plug wire and the dead cylinder starts working. It can be very challenging to properly diagnosis this system without a tech 1 and some experience. You could use a meter like a Fluke with true RMS and mapping but you have to check it at the output of the pickup which is can be very difficult. I was "bit" many times back in the day.
Check all your plug wire resistances when it's acting up (hot) and if you have a scanner of any type check that you have a steady pick up (rpm) signal so you know it's not the pick up. My experience (as I remember it) is I replaced about as many pick ups as modules for these type of complaints. The problem is that it's not all the time. But I think from your description of the symptoms one of those will be your culprit.
The pick up is a extra bit of fun to get out if it's been in there for years! No Fun!!!

Sorry for the long post. Good luck.

Sam



 
Turbo2 
Newbie
Posts: 21

Reg: 07-26-16
12-17-19 06:50 AM - Post#2782323    
    In response to Texasray

  • Texasray Said:
Not usually on this forum since I have a 1966, but I saw your title and had a shiver... lots of memories.
Just a thought about your latest question, be very careful in checking spark on this system. It was called a "waste spark" design because it fires both plugs on that coil each time. If you reduce the needed voltage on one of the cylinders then the other cylinder will look like it is firing just fine, but not the case.
Example: say the coil will only put out 40K, when it needs to put out 60K plus. Then the cylinder that is firing takes 35K because of the need to overcome the compression trying to squish the spark out. Now the "waste" cylinder needs 5K to 7K to overcome the spark plug gap and the plug wire resistance. You now can't supply the needed voltage to cylinder on compression stroke.
So you install a spark checker in the "waste" plug wire and the dead cylinder starts working. It can be very challenging to properly diagnosis this system without a tech 1 and some experience. You could use a meter like a Fluke with true RMS and mapping but you have to check it at the output of the pickup which is can be very difficult. I was "bit" many times back in the day.
Check all your plug wire resistances when it's acting up (hot) and if you have a scanner of any type check that you have a steady pick up (rpm) signal so you know it's not the pick up. My experience (as I remember it) is I replaced about as many pick ups as modules for these type of complaints. The problem is that it's not all the time. But I think from your description of the symptoms one of those will be your culprit.
The pick up is a extra bit of fun to get out if it's been in there for years! No Fun!!!

Sorry for the long post. Good luck.

Sam



That does not sound like fun seen as it is still the original part. Thanks for the information.




 




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