Im new, hope this post is in the right place...I have a 1998 Dodge Ram 1500, 5.2, 4 X 2, automatic, no modifications at all.. Today. I replaced the Cap, Roater, wires and plugs due to the engine running a little rough and the check engine light would flash. She has 146K on her and its time for maintenance..Well all were replaced and she purred for about three miles and then I heard that back fire popping noise in the breather..It stopped and she was running strong..Drove about 25 miles and the Check Engine light came on, back fires ( Muffled Popping) and she really started to shake, vibrate??whats that about. its not the tires...When the engine down shifts it has power not all of it but its okay. THe check engine light is back on and its flashing..It will flash then just stay on, flash and stay on its all very random..I have been around a lot of cars in my day, but Im no pro. how ever I have never seen one act like this..That vibration is very odd. as if the engine is missing so bad its shaking things up? The Diagnostic machine did say the Computer is telling the tranny to down sift at odd times..Other than that it was clean..What gives here? ALL WIRES, PLUGS, CAP AND ROATER WERE REPLACED TODAY..LAST CAP had a worn spot in it, and I think it was arching there..Now??? I got no clue uless something got bent there..I know I have to re trace my steps, but I am pretty dang sure its right..If its not some error I made? what on earth could it be? ThanksRonnie

 

Here's a few thoughts for you. Did you for sure get the rotor seated all the way down before you put the cap on? Are the new wires routed exactly as the factory ones were? (these trucks have misfire problems if the wire routing isn't exactly right) Did you get the wires in the correct firing order? Is the dist cap seated correctly? Did you knock any vacuum lines loose?

 

All that stuff is correct. I am having it double checked today at the shop...I hooked it up again to the puter and it says #8 is missing and it sounds like it..The distributor is running between 4-6 and should be at 0 gonna adjust that and see if that fixes it. Then if that doesnt work, retrace all work from yesterday..If that doesnt work..Crank Sensor????? That shaking makes me think sensor, only because my sensor messed up on my 95 dodge and did the same thing...Fingers are crossed. C.C. converter needs replacing as well, its rattling around..Thanks for your input..

Ronnie

 

ouch, #8, sounds bad... I can't remember if someone else on the board had a problem with 7 and 8 misfiring, but I read somewhere that they had it, and it was lead back to cracked heads... =/ Hope its just the crank sensor.

 

Yank the front o2 sensor out and then drive it again if it runs ahellof alot better than you just found your problem a bad cat. The symptoms sound exactly like mine. To much backpressure from a clogged cat can cause cylinders 7 and 8 to misfire like a sob. That is where I would put my money.

 

Replacing the Crank sensor now.....The O2 is my next bet, going to get the CAT fixed next..It is making some noise and gas mileage went to crap..With mileage that bad I should be pulling down atleast 600hp, but not today>>>LOL LOL
Letting engine cool off so I can get to the sensor and yank it, then CAT is coming off...Thanks for the help guys...The truck has been a super truck over the years. This month was Major maintenance month. Front, Rear, Tranny, Oil Pan, all seals replaced, plugs, wires, battery, ac service all that stuff. I think the crank sensor is making more sense right now due to when dropping the transmission I think it got hit...So, far I dont like being a mechanic.....Damn fat fingers of mine.If I ever open a shop Im going to hire a 80lb Asian to work under the hoods .I cant reach crap, too tall, too big..
Thanks for all the help

Ronnie I will post what was found and if it helps, Maybe it will help someone else one day

RB

 

I would bet that either the #8 wire isn't seated all the way on the cap, and is arcing and not making a good connection 100% of the time, or the cat is clogged. If the cat is clogged replace it ASAP, or further more expensive repairs will be in order.

 

It seems to be the computer or a wire going to the computer...I checked the CAT. today and it is new, I forgot about it and to be sure I had it tested. I took my puter off my truck and put it on my other one and same thing.EXACT same thing...I now have to find out why that puter is sending those signals and not letting the injector fire..I was supicious of a cam lobe, but dont think that is it. When I replaced all seals I may have a pinched wire in the bell housing area, just a hunch..Any more ideas are good,

Ronnie

 

On the 96-up dodges, when there is an on-going mis-fire condition, the cel light will flash until the mis-fire stops. When scanning the computer, look at the misfire counter. That will tell which cylinder is having problems, indicated by a high number of misfires on a cylinder...

 

I think ive covered everything.CAT, Cap, wires, button, plugs, crank sensor, the works, Even checked all rockers, valves, compression test all were great, at idle and at Normal and higher RPMs while testing compression. Did a injector test all were great.Whats left? CPU?
I think, hope its the CPU causing this problem..I am at my witts end on what else it could be. I am relieved my compression is so high, motor, tranny all are strong. No after market anything to mess up the CPU. and when that CPU was placed on another ram it got the same conditions..I hope thats the last thing to be replaced. if its not that...........Adios RAM hello new RAM..