Testing Coil packs; 1999 S70

MikesS70 · Post by **MikesS70** » 07 May 2009, 19:19

I have a non-turbo '99 S70, 2.4L I5 with a suspect coil pack.

Are there any testing procedures ...such as using a VOM and measuring resistances, continuity, etc. ...to trouble shoot these packs?

Thanks,

Mike

Post by **JDS60R** » 07 May 2009, 19:38

I did not find the specs on VADIS.
Usually you swap to a know good cylinder and see if the problem follows the coil or stays with the original cylinder.

This would prove or rule out the coil.

MikesS70 · Post by **MikesS70** » 08 May 2009, 04:23

JDS60R wrote:I did not find the specs on VADIS.
Usually you swap to a know good cylinder and see if the problem follows the coil or stays with the original cylinder.

This would prove or rule out the coil.

Thanks for the reply ....I guess the engine would shake a little differently by switching the suspected coil pack? If the pack is bad and the engine already runs rough then swapping it to another cylinder will do what? I'm willing to try it ...see what happens...

Post by **vegasjetskier** » 08 May 2009, 09:14

MikesS70 wrote:
JDS60R wrote:I did not find the specs on VADIS.
Usually you swap to a know good cylinder and see if the problem follows the coil or stays with the original cylinder.

This would prove or rule out the coil.

Thanks for the reply ....I guess the engine would shake a little differently by switching the suspected coil pack? If the pack is bad and the engine already runs rough then swapping it to another cylinder will do what? I'm willing to try it ...see what happens...

The spark plug for the bad cylinder should show more black carbonaceous material on it or possibly a film of unburned fuel. Compare 1 and 2 in this PDF: http://www.boschautoparts.com/NR/rdonly ... gFaces.pdf

Post by **Brucebo** » 08 May 2009, 11:08

JDS60R wrote:I did not find the specs on VADIS.
Usually you swap to a know good cylinder and see if the problem follows the coil or stays with the original cylinder.

This would prove or rule out the coil.

I had a coil pack die on my '99 S70. The engine started to misfire suddenly. Holding a Fluke non-contact voltage light over the coil packs will show if they are sparking (http://us.fluke.com/usen/products/Fluke ... itedStates). Trouble was the bad coil pack was also sparking, 'cept not thru the spark plug. So that didn't work too well in my case. The next thing I did was unplug the low voltage connector to each coil pack in turn while the engine was running to see which one it was (I didn't have an OBD-II scanner then). I can't in good faith recommend this procedure 'cause you're unplugging a live connection and I'm not sure the connections are designed to be "hot swappable", but it didn't seem to cause any damage in my case. Once I found the suspected coil pack I swapped it with another cylinder and verified that it moved with the coil. It did. I then installed a new one and everything was then good.

By the way I wouldn't suggest driving too far on a misfiring cylinder. The unburned fuel is being dumped into your cat turning it into something similar to those Coleman catalytic propane heaters (http://www.coleman.com/coleman/colemanc ... 000&brand=)

-Bruce

MikesS70 · Post by **MikesS70** » 11 May 2009, 05:28

Thanks guys for all the input. I've been out of town over the weekend so I haven't been able to fiddle with the car.

After reading the responses so far, an idea came to me ...rather than swapping or trying to sense voltage/current, I will simply unplug each coil pack, one at a time, and when nothing changes in how the engine idles then I've found the bogus pack. I'll start with the suspected pack and see what happens.

The spark plugs are all new so none of them will show much in the way of deposits ...but I will check them also.

Will let you know what I find ....

Mike

MikesS70 · Post by **MikesS70** » 11 May 2009, 09:48

Just an update on my progress so far. The car is a '99 non-turbo S70 with the I-5 2.4L motor and auto tranny ...96K on it. Here's my initial post for some background ...it's a bit long ...

https://www.matthewsvolvosite.com/forums ... =1&t=20425

I started the engine this morning and it runs as it has previously ...sounding/acting like it's running on 4 vs 5 cylinders. I removed the wire lead from #5 coil pack and restarted the engine ...same symptoms. I then removed the wiring from #2 coil pack and the engine got significantly rougher. Based on this I am pronouncing #5 coil pack inop.

When removing the new plugs to do the compression check I did note the #5 plug to show less deposits than the other four.

I also posted a request regarding any special procedures for doing a compression check.

https://www.matthewsvolvosite.com/forums ... =1&t=20457

Okay ...things are looking up. The engine tested quite well for a car with 96K on it. My readings, the average of three test rounds, are:

1-203
2-207
3-203
4-209
5-203

The truely correct way to run a comp chk is for the engine to be hot, the battery checked fully charged and the throttle plate fully open. In this case the motor was cold and the battery was in good condition (not checked fully charged) ...it seemed to spin the motor the same for each test. The throttle was propped open with a piece of rubber hose.

I'm greatly relieved that #5 showed good compression as I was worried about the four missing grounding prongs from the Bosch Platinum 4 plug (see original post) becoming stuck under a valve and preventing it from closing.

So it seems the loose #5 plug caused a lot of hot combustion gases to blow up into the plug cavity "cooking" the coil pack. It also seems the four platinum plug ground prongs have exited the motor through the exhaust.

I have a set of Champion RC9YC's that I'm using. None of the local chain parts stores carry these Champions nor the OEM Bosch's. I got the RC's at Summit Racing of all places.

I'll be placing an order with FCP Groton for an OEM coil pack.

Will post the results when I get the coil installed.

Thanks for all the help and if any of my "logic" seems "fuzzy" ...by all means help me adjust the focus....

Mike

Post by **vegasjetskier** » 11 May 2009, 10:01

MikesS70 wrote: I started the engine this morning and it runs as it has previously ...sounding/acting like it's running on 4 vs 5 cylinders. I removed the wire lead from #5 coil pack and restarted the engine ...same symptoms. I then removed the wiring from #2 coil pack and the engine got significantly rougher.

I'd go ahead and do the the same thing with cylinders 1, 3, and 4 just to confirm.

Also, I'd swap coil pack #5 to a different cylinder and retest to confirm. Cylinder #5 should light up OK.

MikesS70 · Post by **MikesS70** » 11 May 2009, 10:08

vegasjetskier wrote:
MikesS70 wrote: I started the engine this morning and it runs as it has previously ...sounding/acting like it's running on 4 vs 5 cylinders. I removed the wire lead from #5 coil pack and restarted the engine ...same symptoms. I then removed the wiring from #2 coil pack and the engine got significantly rougher.
I'd go ahead and do the the same thing with cylinders 1, 3, and 4 just to confirm.

Also, I'd swap coil pack #5 to a different cylinder and retest to confirm. Cylinder #5 should light up OK.

Thanks ....yeah, I thought about doing what you mentioned ...at least the part about swapping #5 into another position. I'll have some lunch and go back down to the garage and finish up with your suggestions.....let you know what I find.

Mike

Post by **Brucebo** » 11 May 2009, 11:00

MikesS70 wrote:
vegasjetskier wrote:
MikesS70 wrote: I started the engine this morning and it runs as it has previously ...sounding/acting like it's running on 4 vs 5 cylinders. I removed the wire lead from #5 coil pack and restarted the engine ...same symptoms. I then removed the wiring from #2 coil pack and the engine got significantly rougher.
I'd go ahead and do the the same thing with cylinders 1, 3, and 4 just to confirm.

Also, I'd swap coil pack #5 to a different cylinder and retest to confirm. Cylinder #5 should light up OK.
Thanks ....yeah, I thought about doing what you mentioned ...at least the part about swapping #5 into another position. I'll have some lunch and go back down to the garage and finish up with your suggestions.....let you know what I find.

Mike

I second the swap suggestion. These coilpacks aren't too cheap. A dead fuel injector would cause the same symptoms. Swapping the coilpacks lets you verify it is really the cause, and it is farely easy to do.

-Bruce