The Charger backfired and bucked all the way home. Ran fine this morning.

[Triple Black 73]

Last night I drove from north Alabama to Atlanta, about 120 miles. The trip started out well enough. I did the normal stop for gas and a drink before hitting the road. The first sign of trouble was just after leaving town with a big backfire and partial cut out going up a big hill. Then lot more backfire. And bucking. Then whole lot of back fire and a lot more bucking. It was bad, real bad.

I almost called for a towed truck at 1:30 am just 30 miles from home, but I pushed on because I had good compression, plenty of oil pressure, and the water temp looked good. I manage to get home in the last 30 miles by driving it a bit, letting it cool, then driving it every 8 miles or so.

This morning? Well, I went out to cranked the 'ol girl up to move her into the garage and she was like "Rough night, eh? Everything fine now." Like nothing happen. WTH?

I noticed the following:

• The ignition coil was very hot
• Coil measured 1.9 ohms on primary side, 10.9 kilo ohms on secondary, which is within spec for this stock style replacement coil.
• Ran good at 55 mph / 1600-1800 rpm. Anything else was backfire city.
• It would run fine for a little bit, then started acting up, then would run ok again.
• Higher RPM made it run better when it acted up.
• I pull off when it got real bad.
• No engine noise beside the EFI injectors.
• Volts were 12.7 at idle, 13.2 when going down the round.

History:

• The ballast resistor went bad before upgrading the carb to EFI
• The car has progressively gotten worst over the last year or so

I'm thinking the coil has gone bad. I'm getting real tried of throwing money at this car. so do anybody have any second opinions? Or suggestions?

 

[6t4polara]

What do the plugs look like?

 

[dan juhasz]

my bet, bad ignition module, get a spare carry it with you and tools to swap it out on the road, you'll know lickity split, ps done buy a Chinese one , mancini racing has a decent replacement for 40 or 50 bucks

 

[mopar 3 B]

No test port for the EFI? So did you make it to Atlanta or turn around and go home?
Now for the serious stuff. If the coil was getting bad it will act up more on load or times when demand on it are greatest. This could also be a fuel related problem. Have you checked fuel pressure at the injectors? This would not explain the increased coil temperature. You say everything is fine now but is that sitting in your drive or going down the road. Assuming things are fine without trying to duplicate the problem could be a problem in itself.

 

[Triple Black 73]

What do the plugs look like?

The plugs have maybe 300 miles on them. The #8 plug had a small black mark on the insulator near the ground strap. All other looked normal. Compression was 165 in all the holes.

my bet, bad ignition module, get a spare carry it with you and tools to swap it out on the road, you'll know lickity split, ps done buy a Chinese one , mancini racing has a decent replacement for 40 or 50 bucks

I converted to EFI. The spark controller is a small device with four wires (power, ground, signal, coil trigger).

No test port for the EFI? So did you make it to Atlanta or turn around and go home?
Now for the serious stuff. If the coil was getting bad it will act up more on load or times when demand on it are greatest. This could also be a fuel related problem. Have you checked fuel pressure at the injectors? This would not explain the increased coil temperature. You say everything is fine now but is that sitting in your drive or going down the road. Assuming things are fine without trying to duplicate the problem could be a problem in itself.

Fuel pressure was the first thing I thought too. The ECU said the fuel pressure was a steady 59.5 pounds.

I'm suspecting the coil because it ran fine at 60 mph at 1800 mph with about 20 degrees of timing. I had to be real careful coming up to speed because it would act like it was ok, then fall on it face, fire, sputter, fire, backfire, fire, etc. It was having a hard time idling at the red light before my house. Then it was fine once I got up to speed and coasted. Touch the gas, and it would act up.

I removed the ballast coil because it was bad (35k ohms on one side 120k ohms on the other!) Then ran 12v directly to the coil. The spec said it would be ok. I think the coil was already damaged before the EFI upgrade.

Now one last thing to note. This was the first time I driven any distance with the lights on. The alternator is 22 years old, but puts out 13.6 volts at the stud. If course amps are what matters.

 

[mopar 3 B]

The plugs have maybe 300 miles on them. The #8 plug had a small black mark on the insulator near the ground strap. All other looked normal. Compression was 165 in all the holes.



I converted to EFI. The spark controller is a small device with four wires (power, ground, signal, coil trigger).



Fuel pressure was the first thing I thought too. The ECU said the fuel pressure was a steady 59.5 pounds.

I'm suspecting the coil because it ran fine at 60 mph at 1800 mph with about 20 degrees of timing. I had to be real careful coming up to speed because it would act like it was ok, then fall on it face, fire, sputter, fire, backfire, fire, etc. It was having a hard time idling at the red light before my house. Then it was fine once I got up to speed and coasted. Touch the gas, and it would act up.

I removed the ballast coil because it was bad (35k ohms on one side 120k ohms on the other!) Then ran 12v directly to the coil. The spec said it would be ok. I think the coil was already damaged before the EFI upgrade.

Now one last thing to note. This was the first time I driven any distance with the lights on. The alternator is 22 years old, but puts out 13.6 volts at the stud. If course amps are what matters.

Unfortunately no one but the car can tell you what is really required amp wise. It can be estimated but everything form all system will need to be included. I have seen stereo's draw more amps than headlights. Just an example.

 

[Dennis H]

EFI have a tablet?

 

[Triple Black 73]

The EFI does have a screen. That's how I was able to see the timing in realtime.

The issue was running the coil without a resistor. I bought a Accel 8140c which doesn't require one. Drove great.

Thanks everyone! EFI is awesome. Just upgrade your coil.