I have a 97' Ram 5.2L....CEL P0300 P0305 P0308 (random and cyl. 5 and 8 misfire codes) I have dumped loads into trying to get this problem resolved. Recent related repairs include, plugs, plug wires (rerouted per TSB), distributor cap, rotor, new cat, air filter, replaced intake plenum pan gasket. The only thing left I can think of would be injectors or fuel related problem, but I can't keep spending without knowing I am correcting the problem. Its frustrating because My cat was bad the intake plenum pan gasket was blown...I thought for sure I had the problem pin-pointed, but CEL is throwing the same codes as before. At low RPM I can here what sounds like intake back-fire upon excelleration.

I hope I have explained this to make sense and someone can help me. Thanks in advance.

 

Have you RESET the computer after doing all these things? Unhook the battery and turn the key to "run" for a few minutes. Rehook it up - do a couple of wide open throttle runs in the first 40 miles to "relearn" the computer. Are you positive the plug wires are routed right and in the correct firing order? Any chance you might have cracked a plug insulator when you installed them? Unscrew the underhood bulb and check for sparks (arcing) around the wires after dark with engine idling. Take the throttle body off and clean it and the attached sensors. These suggestions are all free and worth a try........

 

thanks for your reply...I reset the computer and cleared all codes (after every new part) and it pulls the same codes within 10 minutes of driving the truck. I also looked for arcing at night and could see nothing. I cleaned the throttle body etc when I did the intake plenum pan gasket...nothing seemed to help. Is there any (easy) way to check that the injectors are funtioning properly? I can't seem to find a port on the injector rail to check the fuel pressure.

the only cylinders showing misfire are 5 and 8...

thanks again

 

easiest way to check the injectors I think would be to take out injectors 5 and 8 along with two others and switch them around. If the misfire follows the injectors then you know that was the problem if not then it is something else.

 

also it could be the heads are cracked... hope not but it is a source of miss-fires that cant be fixed... the heads will crack between the valves causing this exact problem.

what kind of shape is the cat in? take a look at the FAQ at the top and do the test on the cat to see if it's plugged. excessive heat will cause problems with the heads. aka cracking.

 

I just had te cat replaced last week and the "honey combs" inside were broken lose, but still flowing. I just left a mechanic shop and the guy is telling me it could be the coil or cam sensor located under the distributor cap....anyone heard of either of the two causing this problem or do you think he was feeding me to get $$??

The odd thing is that the truck seems to run perfect after I clear the codes for about 30 miles or so, then I can feel it stumbling or hesitating at low throttle which is followed by my CEL coming back on...Thanks for the input guys. Anyhing else you think might be the cause feel free to post and I'll go from there.

 

i like the injector swap... wont take long and you can find out if wiring and or injectors are messed up... if the heads are cracked.. R/T R/T R/T R/T R/T R/T R/T!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!

 

After you unplugged the battery, you said it took ten minutes for the CE light to come on. Can you fell the misfire? Was one of the problems actually the plenum? Because if the plenum was one of the problems, then with all the oil getting through, it could have burnt the valves in those 2 cylinders, especially 8 (back right). This will usually cause it to vibrate when idling then smooth out once the rpms rise.

 

My 97 did the same thing but only when it was cold.It kicked up #1and8 multiple missfires,never did figure it out,traded it in.

 

a coil would cause misfires on various cylinders, not the same ones over and over. the cam sensor is probably the same way.

take the earlier suggestion of swapping the injectors and see if the missfire follows.

the next step would be to do a leakdown test... put the piston @ TDC and fill it full of air and see if it bleeds down thru the intake or exhaust, or (gulp) crank case... the bottom ends are pretty tough. i'll bet your problem is in the heads.

I take it that you've swapped the plugs, cap rotor and wires already, one other thing you could try before diving into the motor is to swap the #8 & 7 wires (because they are close in length, swap them on the cap too) and see if you get a miss-fire on #7. you can also do this with the other cylinder that is missfiring. worth a try and doesnt cost you anything.


r/t heads are the way to go for sure...!