Coil packs, firing order

[Sky King]

I had rescently done a tune up on my wifes 95 SL-2 which included wires and coil packs. She reported a MAJOR improvement in the running of the car. Because I had not ever changed the wires on my 99 SC-2, I decided to change the wires just as a precaution. After changing the wires, and the wires ONLY I had a real performance problem. The car stumbled on acceleration. It also had real drop outs or misses. I DID NOT think I had mis wired. To get a bit ahead, I subsequently found that I had crossed two wires.

As a result of this I have a question for members of this board who are knowlegable of how this system works like Wolfman, Saturntech or Razorbak. With two coil packs, one that fires cyls 1 and 4 and the other that fires 2 and 3, why does it matter if 1 and 4 are not correct? I did rewire my 95 to allow a better routing of the wires and it did not make a differance. But on later models I have been told that even though 1 and 4 are paired, and will fire on the power AND the exhaust stroke, why does it make a differance?

Like I said, I did find that I had reversed 1 and 4 and the car ran like crap. BUT when I hooked up my Snap-On Mt-2500 scan tool, it showed NO mis fires for any cyls and NO fault codes.

Because I had no idea what the problem was, and I knew that the coil packs can sometimes be a problem, I purchased two new coil packs and changed them on the road only to have this NOT fix the problem. I should have listened to my own little voice in my head and looked at the plug wires and check to see if I had possibly crossed a couple. Which I did. After fixing the mis wiring, the car ran great. I now have two new coil packs that I don't need but will keep them for the future.

So again the question is still this, if 1 and 4 are up together, and 2 and 3 are together and the iginition system fires on power and exhaust, why did the car run like crap? I should not have mattered if 1 and 4 were reversed.

ps
because I have been out of town for the last 3 days and the weather here right now is GREAT, I am going to jump on the Harley, enjoy some riding in this great weather and get somthing to eat and I will be back later. You guys are great and I really enjoy all the input, I always learn somthing.

[wolfman]

Coil packs are firing 1 cylinder STRONGLY on the COMPRESSION stroke, it's "paired" cylinder WEAKLY (waste spark) on the EXHAUST stroke. Reverse them and you will get a WEAK and slightly off time spark on the COMPRESSION stroke and a STRONG spark on the paired cylinder's EXHAUST stroke. While this might not always set a misfire SES light, under less than ideal conditions (acceleration, cold operation etc..) it WILL or at least will result in a car that runs less than wonderfully.

[the_new_raceman]

plug wires---1234
coils---4123

[Sky King]

Originally Posted by wolfman

Coil packs are firing 1 cylinder STRONGLY on the COMPRESSION stroke, it's "paired" cylinder WEAKLY (waste spark) on the EXHAUST stroke. Reverse them and you will get a WEAK and slightly off time spark on the COMPRESSION stroke and a STRONG spark on the paired cylinder's EXHAUST stroke. While this might not always set a misfire SES light, under less than ideal conditions (acceleration, cold operation etc..) it WILL or at least will result in a car that runs less than wonderfully.

First let me say thanks for the reply. And while I have to accept the expaination I still have some question. If there is a "strong" and "weak" spark, why does it result in a VERY erratic "mis fire"? I can certainly understand your explaination but it would seem that it should result in a regular mis fire or hesitation but it did not. it was VERY erratic. On the highway, it seemed to run fine at cruise. The hesitation only occyurred when you tried to accelerate and then only when the acceleration was FIRST initiated. The miss seemed most erratic at below 3K rpm while cruising in 5th gear at speeds below 60 MPH.

As I have said in the past, the proof is in the pudding, and having fixed the wiring, Wolfmans explaination HAS to be right especially in light of the fact that the car ran like a champ after I corrected the wiring order. I would only ask again why if the wires were in the wrong order, the miss or hesitation was not regular?

I am not trying to be argumenative here, just wanting to understand what is happening here. Wolfman you are obviously right because the car is now running like a new one. Like I said, looks like I have a spare set of coils in that you can not reutrn electrical parts once installed. Oh well, chalk it up to experience.

[Razorbak]

Originally Posted by Sky King

looks like I have a spare set of coils in that you can not reutrn electrical parts once installed. Oh well, chalk it up to experience.

Can't add anything to wolfman's explanation, but I can suggest a way to get at least some of your money back on the coil packs. Sell them on this forum or on eBay.

[wolfman]

Cruising mixtures are stoic (ideal) and relatively easy to ignite even with weak spark, cold start and/or acceleration mixtures are not, and harder to ignite, especially with weak or off time spark.

[ssicarman]

Let me add to Wolfmans explainations.

The 99 is OBD 2, the 95 OBD 1. The OBD 2 cars will be more sensitive to mixed up wires at the coils and the newer the car even the more sensitive. The PCM controls the ignition and fuel injection that much more tightly for emmisions.

[Sky King]

For Razorbak, I could probably sell them but since I have two DOHC cars and mine has about 115K miles on it and I really have no plans to get rid of it, I will most likely need them some time down the road anyway so I guess I'll just hang on to them for now.

To Wolfman, thanks for the explanation. I can say this, when it did cut out, it would really jerk the car hard. I really didn't think I had reversed the 1 and 4 wires when I replaced the wires.

To ssicarman, I know my wifes 95 is OBD 1 and my 99 is OBD 2. Like I mentioned in the first post, I had moved a couple of the wires on her 95. When a tech at the dealer saw that, he told me that it would not make a difference on that car but on the newer ones it would but he did not explain why as you and Wolfman did. He only indicated that it was an issue of the ignition system being more thoroughly monitored and not a strong vs residual spark issue. Because of that, I really didn't think it would effect the operation as drastically as it did. Thanks to all.