[hr]a little bit of back story. in my friends(same as mine but a 5.2 with 260k) truck we have had a random misfire code for about 4 months so we put in new plugs, wires, coil and rotor. and we still have this problem. you can feel it in the idle. so we go home for spring break and take it to a shop, they do a little test on it and thery say we think its your wires. apparantly it was taking some around 60000 volts or something to get the cylinder to fire. i think it was number 8 i cant recall. although the wires were only about 3 weeks old we go and get new ones and this time pay special attention to how we route them, and we buy alot better wires than the cheapest autozone had(hey we are pooor college kids) so we get some good wires, and we are like cool maybe it was bad wires, then it starts to happen, so we take it back to the shop and they say well it could be bad compression or injectors. hmm well damn. so we cant afford them to do that so when i get back i did a compression test and all of em had good compression up around 130psi in each cylinder. so that was good. today i decide to pull the injectors and look at them and clean em up using the sonic cleaner with mineral spirits. well as i was taking them off and looking at em some of them were pretty good. and a few were bad, but number 8 was completely clogged, so i was tihnking alright i think we found our problem so, i cleaned em and washed em, and cleaned out the fuel rail, and everything else. got new orings, put it all back together, and fire it up and its not any better. im waiting to see if the code comes back, im sure it will. at idle it is stumbling all over the place you can ehard and feel it, and it even moves the tach needle.

i just dont know what else to do. maybe new injectors? maybe new engine? haha i have no idea on where to start looking. anyhelp would be much appreciated.

 

Plugged cat maybe??????????

 

a plugged cat will cause a misfire on the back cylinders. take the truck to a muffler shop and have it pressure tested. if not that, then pull the heads and make sure there isnt a crack on em or a blown head gasket.

 

the cat was just replcaed barely a year ago. but i guess things happen. ill check it out.

i dont guess you could be able to hear it? i know sometimes you can, but not always?

i know it was replaced because the old cat was clogged, like bogged the whole motor down and silent exhaust (its usually pretty loud) but it still sounds good.

 

What year truck is it? I had a problem with pinging in my 2001, and it only had 30,000 miles on it at the time. I changed the cap, rotor, plugs, and wires, but nothing worked. It turned out there was a technical service bulletin (TSB) for 2001 Rams that fixed the spark knock issue:

TSB 18-006-01

 

its a 97 5.2. there isnt any pinging or anything like that. not that i can hear. also ive notcied on the pcm its gotta sticker saying it was reflshed. im thinking its probably the "death flash"

its just a rough idle, and a random misfire CEL code.

 

Check Cat first. Rough Idle can be caused by lots of things. bad IAC, really loose timing chain (which could also cause random misfire), wires, cap, rotor, etc. Also, you mentioned that the misfire was random (or was it definitely #8)??? I bad coil can cause a ramdom misfire.

This would be worst case, but you might have a cracked cylinder head. If the cylinder head has cracked, you can have a misfire on one or both cylinders.

 

it was throwin two codes, one was a random misfire, and one was like cyl. 7 or 8 i cant remember. im gonna see if i cant get the exhaust pressure checked at work. we havent tried the coil, i dunno why the shop wouldnt have told us to do that. i have no idea if the timing chain has ever been changed or anything. my friend got it about 15k miles ago for 1000$ bucks. couldnt get a better deal! haha

im thinking its just old and the usual stuff is all ready to be updated and its just slacking at once. thanks for the replies! other suggestion/ input still welcome!

 

cat could be pluged. I your having a missfire as a regular accurence your sending all that unburnt gas right into the cat. Rough idle and misfire sounds like it could be a timing chain.

 

youll be suprised what the shop wont tell you. i took mine in a while ago to have them check my cap and rotor. they said it looked fine and it wasnt causing a misfire. i pulled it off, rotor was burnt and the cap was corroded and shot.

i get that alot with my truck. its almost like they wont touch it cause its too mean lookin or somethin [8D]

you should hear what these shops say when i ask for a u joint swapped out... only place that will touch it is 4 wheel parts.