Ignition coils keep burning out

[Ed Hall]

This is post is regarding my 1993 Allante with a 4.6 Northstar engine with 64k on the odometer.

My 2nd coil in less than 1000 miles took a dump this morning. The engine suddenly lost a lot of power and ran rough and it's symptoms were exactly the same as when the 1st coil went out so I knew instantly what was the problem. While the engine was still idling, I popped off one spark plug at a time and found the coil that was not producing spark on 2 of the cylinders.

Here is my question. Are my coils going due to:

1.) coincidence

2.) defective quality coils

3.) age or the coils

4.) something else causing the coils to burn out (MSD wires)

After my 1st coil went out, I installed a new coil but the engine continued to cough and buck at low rpms / high throttle positions. It also ran rough at idle. So I made a set of custom made MSD 8.5mm wires and that took care of the coughing and bucking but it did not take care of the rough idle. I also re gapped my A/C Delco plugs (from .065 to .045) and that made no difference. Anyways, the idle has gotten worse and it has degraded to the point that I just turn off the engine at stoplights. I also get no more than 10 mpg around town. Could my MSD wires be hastening the death of these coils?

Also, I have heard that these coils go out fairly frequently. Is there a better brand of coils out there? I'm not too impressed with AC Delco if I can only get 60k out of them. I replaced the 1st defective coil with an Autozone el cheapo coil. So far it seems to be fine. There are also other brands such as Accel and MSD. If the originals are at their end of lifespan, I might as well replace them all hopefully with something that'll last longer.

http://www.jegs.com/webapp/wcs/stores/serv...e%2Bmatchallany

[fivepointohman]

This is post is regarding my 1993 Allante with a 4.6 Northstar engine with 64k on the odometer.

My 2nd coil in less than 1000 miles took a dump this morning. The engine suddenly lost a lot of power and ran rough and it's symptoms were exactly the same as when the 1st coil went out so I knew instantly what was the problem. While the engine was still idling, I popped off one spark plug at a time and found the coil that was not producing spark on 2 of the cylinders.

Here is my question. Are my coils going due to:

1.) coincidence

2.) defective quality coils

3.) age or the coils

4.) something else causing the coils to burn out (MSD wires)

After my 1st coil went out, I installed a new coil but the engine continued to cough and buck at low rpms / high throttle positions. It also ran rough at idle. So I made a set of custom made MSD 8.5mm wires and that took care of the coughing and bucking but it did not take care of the rough idle. I also re gapped my A/C Delco plugs (from .065 to .045) and that made no difference. Anyways, the idle has gotten worse and it has degraded to the point that I just turn off the engine at stoplights. I also get no more than 10 mpg around town. Could my MSD wires be hastening the death of these coils?

Also, I have heard that these coils go out fairly frequently. Is there a better brand of coils out there? I'm not too impressed with AC Delco if I can only get 60k out of them. I replaced the 1st defective coil with an Autozone el cheapo coil. So far it seems to be fine. There are also other brands such as Accel and MSD. If the originals are at their end of lifespan, I might as well replace them all hopefully with something that'll last longer.

http://www.jegs.com/webapp/wcs/stores/serv...e%2Bmatchallany

Sounds too me like your having a grounding issue. I had a similar problem in my 88 Mustang GT. I would burn up Ignition modules within a day. The cause after many replacments was a bad engine ground. So the electronics were trying to ground themselves via the wiring harness rather than via the distributor shaft which was biuld to be the main ground for the Ignition module. So your coil may or may not be having the same issue. On the 4.6L i would check the ignition module ground itself to see if it is a good clean ground and By checking it I mean with a volt ohm meter. At the same time i could very well be a bad ignition module causing the coils to smoke up. Good luck!

[BodybyFisher]

This is interesting, Mike D has had a couple of coils go bad also. You might want to look at this thread. He still has a miss, and I wonder if he has another coil on the way out

http://caddyinfo.ipbhost.com/index.php?showtopic=17457

[Ed Hall]

I'm going to check and clean the grounds. I'm also going to check the resistance in the wires.

AC Delco coils are the most expensive and they don't stand behind them with a warranty like MSD. The warranty is nice especially if this car has a problem with eating them.

The other thing I could do is buy a the cheapest ones for $19.94 made by Standard Motors and carry 1 or 2 spares. Usually going with the cheapest is not the thing to do however.

[Ed Hall]

Update:

I replaced the Ignition Control Module and put in 4 replacement A/C Delco coils. The result was that it fixed all the driveability problems. When I was pulling out the old Ignition Control Module, I noticed that out of the 4 bolts that hold the ICM to the valve cover, 1 was missing. This would indicate that this has been worked on before.

The only thing I'm still griping about is the atrocious fuel economy. I reset the fuel economy meter while the car was warm and drove around town and only got 12 mpg driving conservatively. I notice that if I select instant fuel economy and release the accelerator while driving 45 mph, the instant fuel economy only goes to about 50 mpg. Should it be higher than this or is this consistent with others who have this Northstar engine?

[JimD]

Update:

I replaced the Ignition Control Module and put in 4 replacement A/C Delco coils. The result was that it fixed all the driveability problems. When I was pulling out the old Ignition Control Module, I noticed that out of the 4 bolts that hold the ICM to the valve cover, 1 was missing. This would indicate that this has been worked on before.

I have no clue how the ICM was intended to be connected to chassis ground on your year-model car. But it is at least possible that when you replaced your ICM and coils, what you really accomplished was cleaning up the threads on the bolts/connections that provided the chassis ground connection.

[JohnnyG]

The only thing I'm still griping about is the atrocious fuel economy. I reset the fuel economy meter while the car was warm and drove around town and only got 12 mpg driving conservatively. I notice that if I select instant fuel economy and release the accelerator while driving 45 mph, the instant fuel economy only goes to about 50 mpg. Should it be higher than this or is this consistent with others who have this Northstar engine?

You can't compare that to today's fuel economy at all, what year? 1993? A gallon of gas was what......$1.29? Nobody cared, particularly those that were buying a $60,000 car at the time!

The computer program might have changed, maybe today the "MAX" reading might be 70 mpg, but remember it's only a program. BS in = BS out. Also remember that this was not designed to be your everyday commuter car.....Class of the highest order as I recall, body handmade in Italy by Pinafarina. Probably shines it's brightest these days on the highway, and in parades!

BTW, 12 mpg is what my current Cadillac would likely average around town.

[KHE]

Update:

I replaced the Ignition Control Module and put in 4 replacement A/C Delco coils. The result was that it fixed all the driveability problems. When I was pulling out the old Ignition Control Module, I noticed that out of the 4 bolts that hold the ICM to the valve cover, 1 was missing. This would indicate that this has been worked on before.

The only thing I'm still griping about is the atrocious fuel economy. I reset the fuel economy meter while the car was warm and drove around town and only got 12 mpg driving conservatively. I notice that if I select instant fuel economy and release the accelerator while driving 45 mph, the instant fuel economy only goes to about 50 mpg. Should it be higher than this or is this consistent with others who have this Northstar engine?

Both of my Northstar cars display 70 MPG INSTANT when I am coasting to a stop. Could it be that your torque converter is not locking up? Resetting the average and driving in the city will result in a low average due to all the stop and starting. What does it do on the highway? Have you checked the fuel pressure regulator and the injectors to make sure they are not leaking?

[Ed Hall]

You can't compare that to today's fuel economy at all, what year? 1993? A gallon of gas was what......$1.29? Nobody cared, particularly those that were buying a $60,000 car at the time!

The computer program might have changed, maybe today the "MAX" reading might be 70 mpg, but remember it's only a program. BS in = BS out. Also remember that this was not designed to be your everyday commuter car.....Class of the highest order as I recall, body handmade in Italy by Pinafarina. Probably shines it's brightest these days on the highway, and in parades!

BTW, 12 mpg is what my current Cadillac would likely average around town.

This car has the same engine and programming as the same year 295 hp STS/Concourse so I would think it would be able to do as well as those cars. The way it is, I'm unable to attain the advertised fuel economy that this car is suppose to get. If I drive with the flow around town, my average would be more like 10 mpg but I can get 12 if I'm really easy on the throttle and do a lot of coasting before coming to a stop light.

[Ed Hall]

Both of my Northstar cars display 70 MPG INSTANT when I am coasting to a stop. Could it be that your torque converter is not locking up? Resetting the average and driving in the city will result in a low average due to all the stop and starting. What does it do on the highway? Have you checked the fuel pressure regulator and the injectors to make sure they are not leaking?

Thanks KHE,

This is the information I wanted to know. The only time I'm able to get 70 MPG instant is if I let off the throttle at speeds in excess of about 60 mph. If I let off the throttle at 40 mph, the instant MPG goes to only 35 mpg. This would lead me to believe that the engine is most likely running too rich while not under power or during high vacuum.

I get 20 mpg on the highway if I keep up with traffic, 65-70 mph. When I first got this car, I would get 27 mpg on the highway. I'm positively sure the torque converter is locking. I have not checked the pressure regulator or the injectors.

[Texas Jim]

Ed,

The only time mine displays 70 INSTANT, is when I am above 60/70 and let off on the gas. And even THEN, it may not do it INSTANTLY... it may take a couple of seconds.

With the AC compressor ON... it is not as quick to go to 70 INSTANT as it is with the AC compressor OFF and it won't HOLD IT at 70 INSTANT near as long (as you slow down) with the AC ON.

it will hold 70 INSTANT, down to about 55 mph or so... then change to somewhere around 50 INSTANT. As I slow down a little more, it goes to the 35/38 range.

[KHE]

Both of my Northstar cars display 70 MPG INSTANT when I am coasting to a stop. Could it be that your torque converter is not locking up? Resetting the average and driving in the city will result in a low average due to all the stop and starting. What does it do on the highway? Have you checked the fuel pressure regulator and the injectors to make sure they are not leaking?

Thanks KHE,

This is the information I wanted to know. The only time I'm able to get 70 MPG instant is if I let off the throttle at speeds in excess of about 60 mph. If I let off the throttle at 40 mph, the instant MPG goes to only 35 mpg. This would lead me to believe that the engine is most likely running too rich while not under power or during high vacuum.

I get 20 mpg on the highway if I keep up with traffic, 65-70 mph. When I first got this car, I would get 27 mpg on the highway. I'm positively sure the torque converter is locking. I have not checked the pressure regulator or the injectors.

I would think that if an injector was leaking or the FPR was bad, you would have other issues such as difficult hot starts and the fuel data computer would display proper readings but the car would be using more fuel.

I wonder if an oxygen sensor is getting lazy but won't set a trouble code - something has happened since you were able to get 27 MPG and now you're down to 20. Are any of the brakes dragging - particulary the rear parking brakes? Just some thoughts.

[BodybyFisher]

Both of my Northstar cars display 70 MPG INSTANT when I am coasting to a stop. Could it be that your torque converter is not locking up? Resetting the average and driving in the city will result in a low average due to all the stop and starting. What does it do on the highway? Have you checked the fuel pressure regulator and the injectors to make sure they are not leaking?

Thanks KHE,

This is the information I wanted to know. The only time I'm able to get 70 MPG instant is if I let off the throttle at speeds in excess of about 60 mph. If I let off the throttle at 40 mph, the instant MPG goes to only 35 mpg. This would lead me to believe that the engine is most likely running too rich while not under power or during high vacuum.

I get 20 mpg on the highway if I keep up with traffic, 65-70 mph. When I first got this car, I would get 27 mpg on the highway. I'm positively sure the torque converter is locking. I have not checked the pressure regulator or the injectors.

Hey Ed, if it works with OBD1 I can send you my Autotap engine analyzer you can watch O2 sensor activity real time on a laptop or computer that has a USB port. I have to see if it handles your car, its OBD1?, if it does I would be glad to send it to you. Let me check into this. Its possible that OBD1 does not report on O2 sensor performance if its lazy and Kevin might have hit the nail on the head. I will let you know what I find out about the Autotap. Let me know if you are OBD1

[Ed Hall]

Mike, thanks for offering to let me use your Autotap engine analyzer. My car is definitely OBD1. When I first got the car, it got better fuel economy but after several months of owning it, the fuel economy dropped and finally, the check engine light came on. I checked the code and it was associated to left & right bank imbalance. So I went into the onboard computer and monitored both 02 sensors and one sensor would just read 0 all the time. I installed a new A/C Delco 02 sensor and the onboard computer shows both 02 sensors functioning but fuel economy did not improve very much. Since I can monitor 02 sensor activity through the onboard computer, is there anything else that the Autotap engine analyzer can do that I can't already see on the onboard computer?