Changed spark plugs, and all heck breaks loose.

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Dtfanning

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My 1999 Ram 1500, with 5.9L and 51k miles was running just fine. It bought a new air filter for it, and while I was at the parts store, I thought I may as well get some spark plugs for it, seeing as the original spark plugs were still installed. Get home, pop in the air filter, and change the old spark plugs with a new copper core plug. Crank it up, truck will barely idle, and is knocking horribly. I shut it off immediately. Pull out the plugs, double check the gap, all was well. Put the old plugs back in, crank the truck, but the same issue. Truck was running fine on the old plugs before I pulled them, but now it will barely idle with them as well....same symptoms as the new plugs. What the heck am I missing.....any ideas on what could have happened? Only thing I did was air filter and plugs. Im stumped.
 

crazy_luck

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First thing that comes to mind, you did one plug at a time and left the others alone (plug and plug wire)? I've seen people pull all plug wires at one time and manage to mix them up when putting everything back together, which will screw up the timing, causing it to not idle with a bad knock.
 

Micchi

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Sounds like what happened to me when I mixed up my wires. Maybe double check that they're correct?

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dodge dude94

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Verify your wires are fuctioning correctly.
Sounds as if when you messed with it you broke one or more wires inside and it's causing the truck to misfire badly.
 

SYKRAMMAN

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Check your firering order against cap/rotor, 1-8-4-3-6-5-7-2, the cylinder numbers are stamped on the heads for reference.
 

Yeret

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+1 for checking your firing order. Trust me, it's a lot easier to screw up than you might think.

I had a 4-cylinder Honda Prelude a few years back and I decided to change the plugs and wires. Like a noob, I pulled all the wires off at once because I was "certain" where cylinder 1 was on the dizzy. So, finished the job and lo and behold, the engine wouldn't start. First thing I thought was "firing order" but of course, being stubborn and insistent that I didn't screw it up, I started screwing with a bunch of other stuff that of course did nothing.

Finally, I conceded and pulled up a diagram. Turns out my firing order was correct, however the wires were all advanced 90 degrees on the cap! :idiot: Needless to say, replaced the wires to where they were supposed to be and engine fired right up.
 

Yeret

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^ Certainly something to consider. You know how back in elementary school, they teach you to always pull out a cord by it's connector and never by the cord itself? Spark plug wires are no different. Always grab ahold of the boot and pull them out that way.

So, did you pull the wires out by the plug boot or by the wire itself?
 
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Dtfanning

Dtfanning

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Yes, I pulled all wires one at a time, and I pulled them by the boot. Regardless, I just finished replacing the plug wires with new ones. Problem is probably 50% better, but definitely not back to normal. Im stumped I guess I'll take it to the shop.
 
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Dtfanning

Dtfanning

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Well, after replacing plugs, and wires and still having the issue, turns out the back side of distributor cap was cracked. Obviously, wasn't easy to see, but felt it when I rubbed the back side of the cap. Replaced it, and all is well. What a crazy couple of days. Geez. Its like Dodge said, "Hey, just for laughs, lets cram the distributor as far back into the firewall as possible."

Thanks for all the feedback. I appreciate it. While I had the air filter housing off, I snapped a few pics down into the throttle body. Also took a pic of the plugs. All plugs looked identical, so just posted the one plug pic. Are you able to tell much about the condition of the plenum via these pics? Back in 2002, the dealership has a record of "Plenum repair", but they dont have notes as to what was actually done....was it repaired or death flashed...they dont know. Do these pics look like bad news? Mainly the plenum pics. These plugs are the original ones from 1999.
 

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Casper

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Well, after replacing plugs, and wires and still having the issue, turns out the back side of distributor cap was cracked. Obviously, wasn't easy to see, but felt it when I rubbed the back side of the cap. Replaced it, and all is well. What a crazy couple of days. Geez. Its like Dodge said, "Hey, just for laughs, lets cram the distributor as far back into the firewall as possible."

Thanks for all the feedback. I appreciate it. While I had the air filter housing off, I snapped a few pics down into the throttle body. Also took a pic of the plugs. All plugs looked identical, so just posted the one plug pic. Are you able to tell much about the condition of the plenum via these pics? Back in 2002, the dealership has a record of "Plenum repair", but they dont have notes as to what was actually done....was it repaired or death flashed...they dont know. Do these pics look like bad news? Mainly the plenum pics. These plugs are the original ones from 1999.

Don't beat yourself up for missing that, its not like you're driving an old chubby after all.
Cracked distributor caps happen to them all the time as the engine mounts begin to show play from rubber deterioration. The distributor starts slamming into the fire wall on hard acceleration--holds together while driving, but falls apart when engine is stopped stranding the vehicle.
 

07MegaCabRam

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Glad you figured it out. I was going to get there and say replace the cap etc -

Everything looks good. Plugs look like the burned well.
 

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