Multiple missfiring

[1998Ramtuff]

I am almost sure that several threads have been posted on this site concerning this issue but I had a difficult time searching this site to find exactly what I am experiencing. I own a 1999 Ram 1500 2wd, 81,000 miles on odo. About a month ago I got the check engine light with a ruff idle and a hard to start. I got a autozone reading of P0300, multiple missfire. I changed the cap and rotor, wires and plugs. light went out though not right away, then came back on again, still with ruff idling and hard to start symptoms. I then changed the #3 and #8 cylinder fuel injectors because the autozone gentleman told me it was multiple missfires on #3 and #8 cylinders but I'm not sure he knew how to read it. I think the code means 8 cylinders missfiring. I dunno. After replacing the injectors, it is still missfiring, still hard to start and the check engine light keeps going on and off over time(Not flashing). I have since run BG44K fuel injector cleaner through the system twice, no help. I am taking it to the shop Monday but I thought to post this first to possibly avoiding a huge bill. Help! Thanks.

[Austin8214]

Are you sure that was the only code they got at Autozone? Sounds like you may also have an 02 sensor going bad. Also the scanner will tell what cyl are miss fireing. So i am sure they atleast got that part right.

[Kevcules]

I know someone with an Intrepid with the same issue you have "multiple misfires". The dealership diagnosed it, but coudn't seem to fix the problem. He said it would start some days and others not, he soon got rid of it. I'm wondering if this is a "dodge" problem.

[f250e350]

check your ignition coil with an ohmmeter,,,, primary should be 0.95-1.20 ohms
secondary= 11,300-13,300 ohms

to test....remove coil....
primary= insert the 1 of the probes of the ohmmeter on positive terminal and the other on the negitive terminal....
secondary= put probe on one of the terminals at bottom and the other at the large center terminal

[1999RamTuff]

Originally Posted by f250e350

check your ignition coil with an ohmmeter,,,, primary should be 0.95-1.20 ohms
secondary= 11,300-13,300 ohms

to test....remove coil....
primary= insert the 1 of the probes of the ohmmeter on positive terminal and the other on the negitive terminal....
secondary= put probe on one of the terminals at bottom and the other at the large center terminal

OK, I checked the coil and got the following results:

primary = 1.2 ohms

secondary = 14.64 kohms

Chiltons manual says secondary should be between 12 and 15 kohms. You said 11300 - 13300. Do I have a problem? This would be to easy.

[TurboSW]

It's most likely your Cat. I had the same problem.

[f250e350]

Originally Posted by 1999RamTuff

OK, I checked the coil and got the following results:

primary = 1.2 ohms

secondary = 14.64 kohms

Chiltons manual says secondary should be between 12 and 15 kohms. You said 11300 - 13300. Do I have a problem? This would be to easy.

depending on your coil type
the specs i gave you are for the toyodenso coil
the specs for diamond coil is
primary= 0.97-1.18
secondary= 11,300-15,300

i am not sure how you can tell which one you have....i checked the diamonds ignition coil website and it didnt have the coil i had in my truck so i assumed it was a toyodenso

[f250e350]

Originally Posted by f250e350

depending on your coil type
the specs i gave you are for the toyodenso coil
the specs for diamond coil is
primary= 0.97-1.18
secondary= 11,300-15,300

i am not sure how you can tell which one you have....i checked the diamonds ignition coil website and it didnt have the coil i had in my truck so i assumed it was a toyodenso

oh yeah....by the way....it dosent matter which ignition coil u have... you said the primary was 1.20 ....a diamond coil's primary is 1.18 but the secondary on a toyodenso is 13,300....so it seems that your readings are a little to high....i think you should replace it it is like $29

[1999RamTuff]

Well, I took the truck to the shop, so I'm waiting to hear about the damage. I told the techs everything I have done up to this point. Could a fuel filter cause this problem? I haven't changed that yet. Turbosw, you say that your catalytic caused the same P0300 fault code and hard to start problem? How did you find out your cat was the problem?

[A97]

If your wires aren`t routed correctly you`ll get a missfire through magnetic induction. These missfire problems with the dodge are all over this forum

[f250e350]

Originally Posted by 1999RamTuff

Well, I took the truck to the shop, so I'm waiting to hear about the damage. I told the techs everything I have done up to this point. Could a fuel filter cause this problem? I haven't changed that yet. Turbosw, you say that your catalytic caused the same P0300 fault code and hard to start problem? How did you find out your cat was the problem?

let us know when you find out!!!

[TurboSW]

Originally Posted by 1999RamTuff

Well, I took the truck to the shop, so I'm waiting to hear about the damage. I told the techs everything I have done up to this point. Could a fuel filter cause this problem? I haven't changed that yet. Turbosw, you say that your catalytic caused the same P0300 fault code and hard to start problem? How did you find out your cat was the problem?

The fuel filter is in the fuel tank and is connected to the fuel pump. I highly doubt it is the problem. I have removed the pump a few times and unless you poured sand inside your tank the filter should stay clean for ever. My cat started to rattle, which means it started to break up, causing too much back pressure, leading 6 and 8 to misfire.

[1999RamTuff]

Originally Posted by A97

If your wires aren`t routed correctly you`ll get a missfire through magnetic induction. These missfire problems with the dodge are all over this forum

Well, I pickup the truck yesterday from the shop. They couldn't find anything wrong with it. They checked my fuel pressure and said it was good. They also said that the fuel pressure held after the truck was shut down. They did change the negative lead to the battery due to high corrosion and being loose. I thought they found the problem but after driving it yeterday evening I started to feel hesitation, missing a little at idle and it took a long crank to get it started again. Back to square one. I am getting new 10mm wires tomorrow, so I will replace the 8mm new wires. I will be sure to keep them seperated to eliminate the possibility of croosfire. We'll see what that does. Frustrating.

[1999RamTuff]

Another thing I noticed is it seemed to start missing after it was hot for a while. I wonder did yours start to missfire after it heated up? Could it be the cat heating up and breaking down? I dunno.

[f250e350]

didnt you say you did test your ignition coil?? did you also say the readings on the coil were to high??....hmmm...well....it is only a $29 piece....well....???