This is the Acell performance ignition coil http://www.autozone.com/R,APP1198510/vehicleId,2142402/initialAction,partProductDetail/store,505/partType,01566/shopping/partProductDetail.htm If yours looks like this, it could create enough voltage to punch through standard spark plug wires.
If the spark plug threads were coated with dielectric grease, THAT could cause enough resistance to cause the spark to take an easier part to ground (through the covering to the engine block). To check, take a resistance reading from the disconnected end of the spark plug wire at the ignition coil, through the spark plug wire, through the spark plug to the engine block (the “ground”, or “neutral”). A resistance higher than specs would be too much.
I have to respectfully, but strongly disagree with some of what is being related here about the coil ground. That includes the part about conventional coils being grounded through their case into the mounting bracket. Not true.
Wiring diagrams do not show this, the cases are painted (which they would not be if this were true), and one can remove a conventional coil from it’s bracket, insulate it with a towel, and the engine will run fine. Done this many times.
Some conventional coil cases are even plastic.
Conventional coils have 3 terminals: power in, power out (to contact points or a module; a ground of sorts), and the secondary winding center-tap which grounds through the plugs.
There’s a few other theories on what could cause this problem but these are my last words on the subject and I’ll just bow out.
I really want to thank you all, especially ok4450, cougar, and hellokit.
With all of your information, I’ve gained a pretty good understanding of the subject. After screwing around in my garage for quite a while with an ohm meter and a spark plug gapper, I’ve given up. I’m running short on time (if I had a spare car at the moment, I would love to keep this around to solve the problem myrself), so I submitted to the recommendation of taking it to a Ford dealer (I know!). They spent a while with it today, but told me they they “need more time to diangose” the problem.
I will let you guys know what they find as soon as I find out.
What kind of spark plug wires did you use? What brand? You should be using only an OEM type spark plug wire, other types, even high performance types may not work well with your coil and can cause problems.
Have you tried watching for sparks with the engine running in the dark to verify that the arcing is from the wires to the block? Did you clean out the interior of the distributor cap. Sometimes minute particles of metal blow off the terminals and stick to the inside surface of the distributor cap and then will arc to ground on the inside of the distributor cap.
Sometimes a coil will develop a crack in the case and arc between the terminals.
The stock spark plug wires that came on the car were Motorcraft wires, wich is the OEM brand. Resistance measurements showed them to be in good condition.
Regardless, I REPLACED those with NGK spark plug wires - known to be the best for this engine in this car and other cars with the same engine.
The first mechanic had to see for himself, so they tried yet another set of spark plugs, but I am unaware of the brand.
The arcing was seen between the wires near the plugs to the block. It can also be heard, but there is nothing to say its not going on inside the distributor (sort of my own theory).
The distrubotor cap was removed, brushed off, and inspected.
Interestingly, I have a new cap and rotor in the car… I just really don’t have the time nor the inclination to go outside right now and replace it in 25 degree weather right now.
I’ll keep you all updated!
Automotive coils are typically autotransformers and therefore ground their secondaries through the same connection that grounds the primary.
Use a voltmeter and check that there is continuity between the intake manifold, the cylinder heads, the engine block, the car body, and the battery negative. For some reason (rubber gaskets?), there may be high electrical resistance between the metal parts.
As everyone has been telling you, the spark can’t get through the spark plugs to common ground. You could provide positive grounds by attaching wires to connect the bodies of those parts, to each other, which I named.
That dielectric grease used on the spark plug boots is an electrical insulator. An excessive amount may have been used. Wipe it out of the spark plug terminal (use a cotton swab, etc.) and off the spark plugs metal part.
When dielectric grease is used on the spark plugs boots, it is used sparingly. It is used to help the boot to slide on, and off, the spark plug. If the dielectric grease comes between the top of the spark plug, and the metal clip inside the spark plug wire, it could block the spark.
In response to OK4450’s comment about the correction of the way coil works, I do agree with you and thank you for the correction on that. My comments were not accurate and I got off on one of my tangents again. The heads have to be bonded well to the battery ground for the spark to go through the plugs.
Brian,
Your welcome for the help. I would have the shop put some good bonding leads from the heads to a known good ground. I think that will clear your trouble. Again though, there may be damaged parts that need to be replaced due to the acring that went through them.
Dielectric grease is used to insulate the cable from ground. The grease is put into the plug socket to fill any miniscule gaps between the rubber boot and the body of the spark plug. Any un-filled void would result in the eventual leak of spark plug voltage by way of an arc to either the head or the external part of the plug’s body.
Furthermore, unless the plug wire’s metal clip is so loose that it makes no contact with the spark plug the grease will have no effect on that contact. Provided the clip grips the tip of the plug firmly as it should, there will be an electrical connection regardless of how much grease is used.
Finally, the fact that the grease also makes it easier to slide the boot on and off is a side benefit, it is not the primary intent.
I hope the OP does not put much faith in the info provided on the link. There are several errors in the text and the coil schematic diagram is seriously flawed and misleading.
You are right, JayWB, that if there is metal to metal (or, conductor to conductor) contact, the dielectric grease won’t prevent current (and voltage) from passing from one to the other.
What I was thinking of is, if there isn’t physical contact between the spark plug metal cap and the metal clip in the spark plug wire, and that metal clip to the central spark plug wire conductor, the dielectric grease could prevent, even, arcing from the spark plug wire to the metal cap of the spark plug. Then, the path of least electrical resistance may be through the spark plug wire covering to ground on the engine.
The coil is an autotransformer so it doesn’t have a secondary “ground” so to speak. The case does not have to be grounded for it to work. The fact the wires arc to the head means that the block is appropriately “grounded”. It’s just that the energy sees the wire insulation as the path of least resistance as compared to the spark plug gap.
Once the wire insulation is punctured by an arc, that wire is essentially shot. As long as the puncture sits close enough to the engine block, it will be the preferential path. Electrical tape is not an effective insulator for high voltage. I would lose all faith in any mechanic that thought that might work. Just compare the tape thickness to the silicone insulation on the wire and you’ll see it is clearly insufficient. So just be careful you’re not chasing your tail. For example, arcing occurs so I change the wires. The fault still exists so the new wire insulation is compromised. Now I change the plugs (the actual problem) but since the wires are already damaged, I don’t see any improvement. Just an example to highlight the death spiral scenario.
OK4450 gave you excellent suggestions on probable causes. Start with the simple stuff and go from there.
Let me give you all an update, and maybe you guys can comment on the situation.
I went to the dealer. They slipped on a distributor that they know works, but the problem did not change. They determined that the ignition timing was off. They adjusted the timing, wrote up a significant labor charge, and gave me a call. It solved the problem, as far as they were concerned.
Nobody would give me a legitimate reason for why the timing was off. The technician who worked on the car said “it was probably because of the way the previous mechanic put your original distributor on”. Well, that makes no sense. The car ran perfectly for about a year, then the timing somehow got changed to cause my misfire.
It is clear to me that the screwed up timing is a SYMPTOM of another problem that was ignored by the dealer.
So… I got the car back today and drove it on my normal routes. After about 20 miles, there was a misfire. This time was different though, as the check engine light was triggered.
Obviously I am going back to the dealer, but on my commute home I stopped by an auto parts store to read the code to satisfy my own curiosity. The code is for a “Camshaft Position Sensor Malfunction”.
My questions are, is the CPS on this car part of the ditributor? Is my distributor what is causing the timing to be thrown off?
What can I expect from the dealer in this situation? I paid $460 for diagnosis and the ignition timing adjustment. That’s riduculous, but if it fixes the problem, I can live with it. Unfortunately, it clearly hasn’t fixed the problem. The missing is coming back gradually, just as it did when this problem first showed itself 2 weeks ago. Advice on how to deal with this situation with the dealer would be greatly appreciated.
I will most likely be able to drop it back off at the dealer tomorrow.
Ooh this is not good news. What would make the ignition timing jump would be if the timing belt jumped a tooth. Maybe you should get your cam timing checked.
I have no idea what steps were used as diagnosis but 460 bucks is too high IMHO. I also have no idea what the flat rate book there gives for checking and adjusting the ignition timing but one could figure .5 an hour and that’s being very generous.
The part about them changing the distributor out points to some guesswork and a customer should not be charged for something like this, if they did indeed charge you for a dist. swap and see what happens kind of thing.
How was this timing business explained if they pulled your distributor out? Something is missing on this part of it. How did they determine you had a timing problem if they had already yanked your dist. in the name of checking things?
I’ll throw out a few things here. One is that your car uses the infamous TFI-IV ignition module. This module has a couple of terminals that go to the engine computer. One is called the SPOUT and the other is the PIP. When setting the ignition timing this SPOUT connector MUST be disconnected or the timing will be severely retarded.
Just wondering if by some chance there could be a problem with the SPOUT circuit and it could be randomly losing the signal to the ECM?
Did the new distributor come with a new ignition module? It’s the little gray module on the side of the dist. These modules were trouble prone at times and since they provide the SPOUT signal and influence the dwell on the coil maybe that could be the problem. These modules were prone to heat failure and problems can be erratic in nature.
However, a code should be set if there was a problem in these areas and I still don’t see the timing being off being the cause of arcs from the plug wires.
Still wondering if there could be a coil problem or possibly an ignition module glitch which could be causing the coil to break down too early.
The cam sensor is not part of the distributor and this part may be hard to find if needed.
Just some random musings anyway while pondering this some more.
This is the Web page from Auto Zone about testing the camshaft position sensor (cps), which is inside the distributor: http://www.autozone.com/az/cds/en_us/0900823d/80/14/47/c1/0900823d801447c1/repairInfoPages.htm The last sentence says that the distributor has to be changed to change the cps inside. The engine computer trouble code identifies the cps circuit. This doesn’t necessarily mean the cps, itself; but, signal to, or from, it. Thus, the need for testing.
The signal from the cps may be ok. The fault may be in the circuit, or component, which receives the signal from the cps.
Is the question of the spark jumping from the wire to the engine block solved by (intermittently) mistimed spark? Good question.
No engine has 100% spark success. The emission standard allows up to 2% misfire before the engine computer is required to set a trouble code. These normal mis-fires don’t punch through the spark plug wires.
Look for an independent shop which WILL perform the needed diagnosis.
Hopefully the CPS error code is due to just a bad connection to it.
From your last comments Brian I see no referal to checking the grounding between the heads and the negative side of the battery to clear the arcing problem. As a test, you may want to try just running a jumper wire between these points to see if that will clear up the arcing.
The CURRENT diagnoses from the dealer is the VRIS (Variable Resonance Induction System) Solenoid. There are two, the bad one is the one that needs to operate at lower RPM (has to stay open until 4200 RPM or something like that). I’m sure you all know a lot more about this system than I do. This just happens to be another extremely common problem on these cars, which I’ve often read about on the Probe boards.
The new part will go in Wednesday. I’ll keep you all updated.
I am not familiar with the ignition system and hopefully they are on the right track but, I have some doubts. Did their solution take care of the trouble?
Simply put, the VRIS (Variable Resonance Induction System) is a tuned intake air induction which has solenoids to divert intake air one way, or the other, through the intake ducts during a certain rpm band, and through another duct during another rpm band. This is to increase intake air efficiency and engine performance. It works when it works, which is most of the time.
If the VRIS solenoids don’t control the ducts diversions properly, lean misfires can result.