Coil pack?

R

ricp

New Member
Messages
27
Had a good run yesterday to the BIAMC day at Bristol but developed a slight low rpm mis-fire on the way back. Clears at higher revs and seems to be worse if the car is heat soaked in traffic or parked up and then re-started. The previous owner had done very few miles as it appeared to be part of a collection. Carrs at Exeter picked up a dirty plug on no. 2, which once cleaned, solved the problem when I had it serviced.
Would the consensus be a failing coil breaking down due to heat under the bonnet and a good place to start as they are a relatively easy swap? And I can also check the plug again if necessary. If so, where is the best place to pick one up from?
Are coils a fairly consumable item with a finite lifespan, or should they last forever thus I need to look further for the cause?
Thanks in advance.
 
CatmanV2

CatmanV2

Member
Messages
48,891
Dead easy to swap, and definitely prone to failure due to the conditions under bonnet.

If you have a code reader, you may be able to check that the misfire is indeed on that cylinder. Then you could move the pack to another cylinder and check that the mistfire moves as a concrete diagnosis. I did exactly this.

NB if you order a new pack, make sure you get the right one

C
 
G

gerlad

Junior Member
Messages
37
Have had exactly the same today. Car just started running really rough at idle but cleared completely when revs picked up. No warning light lit up and stayed on but engine management light flickered then disappeared when revs picked up. Are these coil packs expensive or fairly reasonable as I have no experience of them. Many thanks on advance.
 
CraigWaterman11

CraigWaterman11

Sponsor
Messages
762
I think Chris did a great job on explaining how to diagnose this issue. You don't want to throw money at this situation. I would suggest just a generic code reader to see if you can pick up which cylinder is doing this. Also I think the first gentleman stated he cleaned the plug and the issue went away briefly. I've really had no permanent success in just cleaning a plug I've always had to go back and replace them. It is a great temporary fix to show you what the issue is sometimes.

After you hone in on what cylinder you're looking at (from the code present), if you want to be sure in your diagnosis. You can first swap the plug with the cylinder next to it. Next, if that's not the issue swap the coil pack. As Chris stated above you're looking for the code to move to the next cylinder. If none of that works lastly try switching the fuel injector. Be-careful with the O-rings on the injector. You will find it's normally one of those issues. Highly unlikely it's a burnt valve or any of that.

Personally, I would recommend just for giggles and grins, to look closely at the color of the plug to make sure it's not oil/coolant fouled. If that checks out change all of the plugs. If you only change one, and the one you changed is normal, it won't be long before you're in there changing another, and then another. My suggestion is just change them all out at once.
 
G

gerlad

Junior Member
Messages
37
Thanks all that's put my mind at rest! I didn't think it was too serious as no warning light flashed up and all the gauges were rock solid. Many thanks once again.

Kindest regards

Gerlad
 
voicey

voicey

Member
Messages
660
Worn spark plugs are the biggest killer of coil packs. If the plug was dodgy in the past then it is likely it has damaged the coil.
 
CatmanV2

CatmanV2

Member
Messages
48,891
Contigo said:
Usually resistance from bad spark plugs causes the coil packs to degrade.
Click to expand...

Interesting! I'd rather assumed that the resistance of the plug was just about infinite, given it's an air gap, right up until the moment the PD across the terminals reaches the point at which the spark can fly.

I have no idea what happens to the PD ramp when a spark is harder to generate.

Cherers

C
 
Wack61

Wack61

Member
Messages
8,809
My 4200 ticks over at exactly 1000rpm , the tick over isn't exactly lumpy but not as smooth as other V8s I've owned , jags and Audis , is it normal for the odd stutter, no lights on ever, not even flickers
 
CatmanV2

CatmanV2

Member
Messages
48,891
Wack61 said:
My 4200 ticks over at exactly 1000rpm , the tick over isn't exactly lumpy but not as smooth as other V8s I've owned , jags and Audis , is it normal for the odd stutter, no lights on ever, not even flickers
Click to expand...

Me again :) Always been like that. New plugs or not. No codes were being shown or pending after the coil pack change. If you want to throw money at it a new set of packs all round might even things out (but I doubt) Plugs should be good for 20k+ more.

C
 
Wack61

Wack61

Member
Messages
8,809
CatmanV2 said:
Me again :) Always been like that. New plugs or not. No codes were being shown or pending after the coil pack change. If you want to throw money at it a new set of packs all round might even things out (but I doubt) Plugs should be good for 20k+ more.

C
Click to expand...


It's like having free 24/7 support :D

I'm very much in the if it ain't broke don't fix it camp so unless it gets a lot worse it'll be fine

I keep going outside to look at it , went to a boot sale yesterday and bought one of those autoglym kits you get with new cars for £7 so when it stops raining I'll be out with the Polish
 
CatmanV2

CatmanV2

Member
Messages
48,891
Wack61 said:
It's like having free 24/7 support :D

I'm very much in the if it ain't broke don't fix it camp so unless it gets a lot worse it'll be fine

I keep going outside to look at it , went to a boot sale yesterday and bought one of those autoglym kits you get with new cars for £7 so when it stops raining I'll be out with the Polish
Click to expand...

Free? What makes you think it's free? ;)

C
 
jluis

jluis

Member
Messages
1,703
voicey said:
As plugs wear the gap gets bigger and a higher voltage needs to be generated to overcome the resistance of the air gap.
Click to expand...

I agree with you but I have a slightly different theory.
In our coilpacks the triggering electronics are built into the coil itself (which is why it has 3 pins instead of 2 like in the old coils)

When a spark plug misfires, the stored energy in the coil has to go somewhere and a part of it ones back to the electronic circuit that controls the discharge causing it to fail over time.
 
davy83

davy83

Member
Messages
2,827
coil packs degrade for a number of reasons, it is true that the gap getting bigger in plugs will require more voltage and if the coil pack is on the way out it can make it worse. Plugs usually fail with HV tracking and general contamination of the insulators causing current leakage across the face of the plug insulator which gets worse until it wont spark. The 3200 uses very high grade plugs which are rated for 30,000 miles of running, so erosion of the contacts is not common. I think the coil packs suffer because of heat, which eventually starts to cause insulation breakdown inside. the long tube connecting the coil pack to the plug also has spring contacts in it and these can suffer from corrosion causing heat and sparking in the rubber tube area, which also will degrade with time to a failure point. bottom line is they wont last forever!
 
R

ricp

New Member
Messages
27
New front coil pack ordered and inbound from Italy as none available in UK or Northern Europe having stock checked with Carrs and Meridian. It mis-fire is on no. 2 cylinder. Does anyone have the numbering or a service manual to show the cylinder numbering. Thanks.
 
CatmanV2

CatmanV2

Member
Messages
48,891
The leads are numbered. You can go back to my misfire thread, but I *think* it's second from the front, LHS as you're looking at the nose of the car.

<Edit> Just checked my thread, and I'm >99.99% sure I'm right. I had the same one go

C
 
You must log in or register to reply here.