Multiple missfiring

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.

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.

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.

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

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.

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

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

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

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?

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 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!!!

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.

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.

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.

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....???

Someone I know with a similar problem had a bad camshaft position sensor, so that's worth a check.

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....???

They were on the high side but within tolerance. I'll change it and see what happens.

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....???

OK, I changed the ignition coil and sparkplug wires. The wires are the second set. These are 8.5mm. Made sure of the seperation when I installed them. Still, no help. I am beginning to wonder if the catalytic is causing my problem.

OK, I changed the ignition coil and sparkplug wires. The wires are the second set. These are 8.5mm. Made sure of the seperation when I installed them. Still, no help. I am beginning to wonder if the catalytic is causing my problem.You should go to a shop and ask them to remove it and then let you drive it around for a second to see if it is. Don't just have them replace it.

You should go to a shop and ask them to remove it and then let you drive it around for a second to see if it is. Don't just have them replace it.

I have it scheduled at the dealership for tomorrow. AAARRrrggghhhhh!

Let us know.....

sounds like a pain to find out what the problem is....only on a dodge!!!

I have it scheduled at the dealership for tomorrow. AAARRrrggghhhhh!Why would you take it to a dealer?

had the same problem on my 02 just curious - what kind of plugs are you using. mine runs terrible with anything but champions. dealership has had a lot of problems with other brands causing misfires. bosch platinums made mine misfire terrible

had the same problem on my 02 just curious - what kind of plugs are you using. mine runs terrible with anything but champions. dealership has had a lot of problems with other brands causing misfires. bosch platinums made mine misfire terrible

I use the OEM champion plugs. I have changed the camshaft sensor and the #8 cylinder sparkplug again just for the heck of it. I did drive it up to Dallas from Houston and I never got the check engine light. It ran pretty good actually. I will wait to see how it does up there. I did talk with a mechanic at the dealer and he said it may be a blown head gasket. Haven't checked that yet. I will have to perform a cylinder compression check to see.

I use the OEM champion plugs. I have changed the camshaft sensor and the #8 cylinder sparkplug again just for the heck of it. I did drive it up to Dallas from Houston and I never got the check engine light. It ran pretty good actually. I will wait to see how it does up there. I did talk with a mechanic at the dealer and he said it may be a blown head gasket. Haven't checked that yet. I will have to perform a cylinder compression check to see.


good way to tell if its a blown head gasket is to check the oil....check for engine coolant in the oil and check the level of the oil IE: oil level above the mark you might have a blown head gasket

good way to tell if its a blown head gasket is to check the oil....check for engine coolant in the oil and check the level of the oil IE: oil level above the mark you might have a blown head gasket
This is not always the case. The gasket blowing does not always let water into the oil.

OK, I started to get a flashing check engine light, so I took it to the dealer on Friday. They said I had missfire codes on 7 out of 8 cylinders. I went back to OEM mopar parts on the distributer cap, wires and rotor. I drove from Houston to Dallas this weekend and it is still hard to start and is running rough on the lower rpms. I'm gonna check for a blown intake manifold gasket tomorrow. I want to get a compression check on the cylinders to see where I'm at with that.

My move to Dallas was a success. My truck is back at the dealer. I explained everything that has been done. The dealer in Houston told me the anylizer came up with multiple missfires on 7 out of 8 cylinders. I have replaced everything I did previously with OEM Mopar components. Still nothing. The mech thought possible headgasket blown 2 ea. or blown intake manifold gasket. I checked the intake when I got up here and saw no oil in the plenum. I am keeping my fingers crossed and my pocket book handy.

I have a long shot...you said it runs rough at low rpm, and hard starting. On the older Mopar motors, the timing chain would stretch enough to cause the problems you're having. It's worth a check to open the timing chain cover and see if there's slack in the chain.

I have a long shot...you said it runs rough at low rpm, and hard starting. On the older Mopar motors, the timing chain would stretch enough to cause the problems you're having. It's worth a check to open the timing chain cover and see if there's slack in the chain.


I thought exactly the same thing. I do have an annoying wine that at first I thought was comming from the tranny, but I believe it may be from the tensionometer stressing to keep the timing chain tight. I will call the dealer first thing Monday to have them check that. I would do it my self but I now live in an apartment complex so I don't have anywhere to work on it temporarly.

Thanks for the input. I will keep you all updated.

I talked with the technician at the dealership this morning. He told me that I was down 2 quarts of oil(with no oil leaks) and found 2 oil fouled plugs. The intake manifold gasket has been leaking on the lower end causing oil to get into the combustion chambers. I looked into the manifold last week, but I didn't see anything(untrained eye). I will update you guys after I get the truck back to let you know the conclusion to this nightmare.

you will not see oil down there unless the gasket is leaking near the throttle body, if its not near it, the oil will be sucked through the engine before it reaches sight from the TB opening.

you will not see oil down there unless the gasket is leaking near the throttle body, if its not near it, the oil will be sucked through the engine before it reaches sight from the TB opening.

Update - I got the truck back from the dealer $1066.00 OUCH!!!! They changed out the intake manifold gasket, thermostat due to leaky gasket. I also had them perform the fuel injection flush and the tranny flush. The truck is now running great and have been driving it for 3 days now and no "Check Engine" light, however, it is still hard to start. It takes some cranking to get it running. The dealer did mention that he heard a growling from the exhaust which he believes is coming from the catylitic converter. Could this be my problem for the hard starts? Thoughts?

Update - I got the truck back from the dealer $1066.00 OUCH!!!! They changed out the intake manifold gasket, thermostat due to leaky gasket. I also had them perform the fuel injection flush and the tranny flush. The truck is now running great and have been driving it for 3 days now and no "Check Engine" light, however, it is still hard to start. It takes some cranking to get it running. The dealer did mention that he heard a growling from the exhaust which he believes is coming from the catylitic converter. Could this be my problem for the hard starts? Thoughts?

It's back!!!!! I have recently had the catylitic Converter R&R'd and still no help. The truck is still hard to start at times (Long crank required)but not always. I am about ready to trade this darn thing in and get one of them employee discounted chevy silverado 4x4s!

It's back!!!!! I have recently had the catylitic Converter R&R'd and still no help. The truck is still hard to start at times (Long crank required)but not always. I am about ready to trade this darn thing in and get one of them employee discounted chevy silverado 4x4s!
Why not buy a new Ram? Everyone and their grandma's have crap ass Chevy's.

Question for you. Why would you take your truck to a dealer? They are the worst. I have heard horror storys about the dealer mechanics. My Ex's bother was a dealer mechanic and he used to sabotage customers engines just to create work when it was slow.

Did you have a diagnostics test done?

Why not buy a new Ram? Everyone and their grandma's have crap ass Chevy's.

Question for you. Why would you take your truck to a dealer? They are the worst. I have heard horror storys about the dealer mechanics. My Ex's bother was a dealer mechanic and he used to sabotage customers engines just to create work when it was slow.

Did you have a diagnostics test done?

Yes, I did. Multiple missfire code is all it's giving me. Breakdown showed missfires on all but 1 cylinder #4. I'll consider anew dodge when I hear that Dodge has totally revamped their tranny. This dealer was pretty good. I have no coplaints about how I was treated. I'm sure their are some out there that pull that kind of stuff but I think unethical people travel in all walks of life.

I just ghad the same thing with no code thrown on a 2000 eam 5.2. The dealer had a hard time finding the problem and guessed tht possibly the o2 sensor could be sticking. there were multiple missfires. They tried an o2 sensor and it did the job. the truck runs fine now.

I just ghad the same thing with no code thrown on a 2000 eam 5.2. The dealer had a hard time finding the problem and guessed tht possibly the o2 sensor could be sticking. there were multiple missfires. They tried an o2 sensor and it did the job. the truck runs fine now.

I took your advice and replaced both O2 sensors. No help, still intermittently runs ruff at lower rpms with a check engine light soon to follow. It is killing me in gas too.

everybody is missing the obvious.... fuel! the first thing I would do is obtain a fuel pressure tester. fuel pressure should climb to spec.s within 2 seconds or so as yo turn key on (pump will run for 2 sec.s when key is turned to "run" position) and it should hold pressure for a while (@ least 5 min.)
if it doesn't reach spec.s AND HOLD (usually 30 - 40 psi), possible problems:
1. bad pump
2. bad/leaking fp regulator
3. restricted/plugged "filter"
All these components are in the fuel tank.... but your fuel test port is on the fuel rail.... I would definitely confirm/rule out these items!:wink:

actually, you're missing the obvious.

and that is that this thread has been dead since '05.

well done, give yourself a pat on the back for reviving an old thread.

Well, why not close it Chris? You're a moderator remember.

it may be a dead topic, or the R1500 may have been sitting in a BARN since '05.

as you were....


and yes, I assumed that it was still an open ended thread, as most top notch forums close or lock threads after a certain length of inactivity.

the rule here is that if a thread hasn't been posted in for 3 months, it's dead. and we don't bring back old threads.

i can't close this because i'm a regional and not assigned to this section.

Closed. Hopefully he got it fixed.