Coil Problem

[Locobob]

So my car was running a little rough and progressively got worse so I did some testing. Initially I thought it was a fuel issue but after checking a few things I decided to ohm the plug wires through the coil packs. All were in the 15K range except the 8,5 coil which was OL. Pulled the plenum and here is the 8,5 coil. Lots of corrosion on the #5 tower, not sure what would cause this, all the other towers were nice and clean. All the plug wires ohm'd out good.


http://i418.photobucket.com/albums/pp270/locobob68/ZR-1/IMG_3795.jpg (http://s418.photobucket.com/user/locobob68/media/ZR-1/IMG_3795.jpg.html)

[Paul Workman]

So my car was running a little rough and progressively got worse so I did some testing. Initially I thought it was a fuel issue but after checking a few things I decided to ohm the plug wires through the coil packs. All were in the 15K range except the 8,5 coil which was OL. Pulled the plenum and here is the 8,5 coil. Lots of corrosion on the #5 tower, not sure what would cause this, all the other towers were nice and clean. All the plug wires ohm'd out good.


http://i418.photobucket.com/albums/pp270/locobob68/ZR-1/IMG_3795.jpg (http://s418.photobucket.com/user/locobob68/media/ZR-1/IMG_3795.jpg.html)

Corrosion = mouse or meeses (if you prefer!);)

[Young1]

That mouse is not prostate challenged to pee up the insulator boot! I shall give him due credit.


Sent from my iPhone using ZR-1 Net Registry (https://siteowners.tapatalk.com/byo/displayAndDownloadByoApp?rid=90383)

[XfireZ51]

Bob,

How does the #5 plug look? The question in my mind is whether the corrosion caused the misfire or is there a misfire in #5 resulting in the corrosion?

[Locobob]

Bob,

How does the #5 plug look? The question in my mind is whether the corrosion caused the misfire or is there a misfire in #5 resulting in the corrosion?

The plugs all looked good

[XfireZ51]

So 5 was firing as good as the others then?

[Locobob]

So 5 was firing as good as the others then?

I doubt it considering I had an OL OHM reading from the #5 wire to the #8 wire. But I didn't see anything too awful at the plugs, they were all intact and had proper gaps.

[Locobob]

Ugh, and now I'm having more annoying issues. The throttle appears to be hanging up sometimes. Won't rev down on coast down occasionally and sometimes the idle is a little high, both cured by a blip of the throttle. I pulled the airhorn and checked the throttle blades, cleaned up the IAC and reset the TPS to .54 (it was slightly low at .52). Don't see any issues when manually manipulating the throttle, it appears to snap shut just fine every time. Hmmmm

[Locobob]

Well the problem is back, apparently the coil was not the root cause of the problem as wires 5 and 8 through the coil are once again OHMing at OL

[Locobob]

The #5 spark plug looks a little cleaner than the others. It tested good on the multimeter, no sign of ground leaks and the center electrode was within the same OHM spec as the others.

[XfireZ51]

Ugh, and now I'm having more annoying issues. The throttle appears to be hanging up sometimes. Won't rev down on coast down occasionally and sometimes the idle is a little high, both cured by a blip of the throttle. I pulled the airhorn and checked the throttle blades, cleaned up the IAC and reset the TPS to .54 (it was slightly low at .52). Don't see any issues when manually manipulating the throttle, it appears to snap shut just fine every time. Hmmmm

Bob,

Did you disassemble the throttle blades?

[Locobob]

No I did not disassemble the throttle body or remove it from the plenum. That issue seems to be better so I'm focusing on the original problem of the ignition system. Looks like I'll have to pull the plenum again. Need to take another look at the plug wire on number 5, it ohm'd okay on its own but I didn't completely remove and inspect it, perhaps it rubbed on something and is grounding? Also going to check the wires between the coils and the DIS module.

[LGAFF]

Any chance something is arcing off the starter, thinking of the fuse problem I keep having on the 91 build

[Locobob]

Fuses look good, no codes set.

[Locobob]

I also checked the primary side of the 8-5 coil I removed and it OHM'd within spec so it appears the coil is not the root problem.

[Locobob]

I just talked to MSD's tech support and they are favoring a problem with plug wire #5, specifically a bad connection where the wire snaps on the coil tower causing arcing and corroding the tower. The wires are Magnacore and probably 10-12 years old. Looking at the ignition schematic from the DIS each coil has its own hot wire and two coils share a ground. This would seem to limit the possibility of a problem with the DIS module, phew, I hope.

[XfireZ51]

If you haven't already, how about just starting the motor and then twisting the #5 plug wire to see if u can induce a miss. Obviously protect yourself from any
shock.
Also wait till it's dark out and then start the motor. See if any arcing is visible either under the plenum or from wires.

[Locobob]

If you haven't already, how about just starting the motor and then twisting the #5 plug wire to see if u can induce a miss. Obviously protect yourself from any
shock.
Also wait till it's dark out and then start the motor. See if any arcing is visible either under the plenum or from wires.

Yeah I think I'll try killing the lights and looking for an arc. I've heard it's a bad idea to pull plug wires on a running engine though.

[XfireZ51]

Yeah I think I'll try killing the lights and looking for an arc. I've heard it's a bad idea to pull plug wires on a running engine though.

Not suggesting u pull the plug wire, but try twisting it and see if it affects anything.

[GOLDCYLON]

I just talked to MSD's tech support and they are favoring a problem with plug wire #5, specifically a bad connection where the wire snaps on the coil tower causing arcing and corroding the tower. The wires are Magnacore and probably 10-12 years old. Looking at the ignition schematic from the DIS each coil has its own hot wire and two coils share a ground. This would seem to limit the possibility of a problem with the DIS module, phew, I hope.

Swap the coils around and see if the problem persists. to rule out bad coil / Wire

[Pete]

Swap the coils around and see if the problem persists. to rule out bad coil / Wire

Ditto.
Also back in the hey day they had a problem with the lower spades on the coils being too loose.

Pete

[Locobob]

Ditto.
Also back in the hey day they had a problem with the lower spades on the coils being too loose.

Pete

I've already replaced all the coils and the problem came back so pretty sure its not a coil at this point. I did notice when I plugged the coils onto the spades they really didn't seem to have much resistance, they just dropped on kinda dropped on and felt loose. What have people done to get a better connection from the coils to the coil spades?

[Locobob]

Ditto.
Also back in the hey day they had a problem with the lower spades on the coils being too loose.

Pete

What symptoms were people seeing with this problem? Failure of the coil to fire at full strength or just not at all?

[Pete]

What symptoms were people seeing with this problem? Failure of the coil to fire at full strength or just not at all?

It was like they had a miss.
Like a bad coil.
See if u can stick something small and sharp like a dental tool to tighten up the spade in the coil.

Pete

[Locobob]

You know now that I think about it I seem to recall someone adding material to the coil spades for a tighter fit.... does that sound familiar?

[XfireZ51]

You know now that I think about it I seem to recall someone adding material to the coil spades for a tighter fit.... does that sound familiar?

You would think however that would affect the coil itself. Here we have an issue w one of the towers.

[Locobob]

You would think however that would affect the coil itself. Here we have an issue w one of the towers.

Yes I would think that would be true, and it may be that I am dealing with more than one issue here and am getting too focused on the one coil tower.

[Locobob]

So I decided to do some testing on the fuel side:

Doing the FSM chart A7 fuel pressure test with FP2 removed resulted in 45psi - about 4psi below the minimum okay range for the test.

I also used the fuel pump test circuit with a multimeter, I saw just over 4 amps draw on each pump and about 8.5 amps with both pumps running.

Activating each pump through the fuel pump test circuit and checking fuel pressure I got the following:

FP1 fuse removed resulted in 51psi

FP2 fuse removed resulted in 42psi

Shouldn't both pumps be the same PSI when activated individually through the fuel pump test circuit?

[GOLDCYLON]

It was like they had a miss.
Like a bad coil.
See if u can stick something small and sharp like a dental tool to tighten up the spade in the coil.

Pete

Unless the DIS is failing. But I haven't seen that happen yet

[Locobob]

Just did some more testing:
MAP checked out okay
Fuel pressure at idle is 42psi
Right Block Learn at 128
Left Block Learn at 144 - indicating fuel is being added

[mike100]

You might have to get fancy and scope out the injector current with a current probe and an oscilloscope to see if any of your injectors might not be working right...even if they are new and you have a pintle sticking. Outside of replacing them all, this is a good way to check them.

like this, except you are not looking for shorted injectors per se... all C4's are the same- put a wire into the fuse panel. https://www.youtube.com/watch?v=RkKfoA7LSR8


I'm assuming you are not on the original multecs...

[BlackZR1]

So I decided to do some testing on the fuel side:

Doing the FSM chart A7 fuel pressure test with FP2 removed resulted in 45psi - about 4psi below the minimum okay range for the test.

I also used the fuel pump test circuit with a multimeter, I saw just over 4 amps draw on each pump and about 8.5 amps with both pumps running.

Activating each pump through the fuel pump test circuit and checking fuel pressure I got the following:

FP1 fuse removed resulted in 51psi

FP2 fuse removed resulted in 42psi

Shouldn't both pumps be the same PSI when activated individually through the fuel pump test circuit?

Yes, I got the same on both. Here are my numbers:

[Locobob]

Yes, I got the same on both. Here are my numbers:

Thanks for the info, that is what I suspected, looks like one of my pumps is a little weak.

[Locobob]

You might have to get fancy and scope out the injector current with a current probe and an oscilloscope to see if any of your injectors might not be working right...even if they are new and you have a pintle sticking. Outside of replacing them all, this is a good way to check them.

like this, except you are not looking for shorted injectors per se... all C4's are the same- put a wire into the fuse panel. https://www.youtube.com/watch?v=RkKfoA7LSR8


I'm assuming you are not on the original multecs...

I'm running RC's, interesting testing set-up.

[Locobob]

So my worst drivability issues have gone away. I'm starting to think those were related to water. I went on an extended road trip a couple of weeks ago where the car was parked outside and it rained non-stop the whole time. I noticed quite a bit of water standing in the fuel filler area, and looking at it yesterday I noticed that I have a pretty good tear in my filler neck boot. Perhaps some water found it's way into the gas tank and it's mostly cleared out now? I checked the filler boot drain and it seems functional but somehow a lot of water was sitting in there. And with the torn boot and the filler neck gasket may not be all that great I could see where water may have leaked into the top of the gas tank. Think I'll just replace the fuel pumps for good measure and install a new filler gasket and boot in the process.
My new plug wires arrived so I'll probably be back under the plenum today to see if I can't get cyl #5 fixed up solidly this time.

[Locobob]

So new plugs and wires are on and #5 should be firing solidly again. The wire on #5 was super loose at the coil, I think the wire terminal itself was actually broken as squeezing it with pliers had little effect. Block learn on the left side is still high indicating fuel being added so apparently the ignition problem is not the cause of that issue. I seem to recall that the left side rail is more susceptible to issues when fuel pressure is low so we'll see what happens when I get the new pumps and filter installed.