96 #5 Cyl Misfire problems

I just put new head gaskets in my 96 3.1L. When I started in back up after the rebuild, it started immediatly but after 5 - 10 minutes I got a SES light. I read the code and found it to be misfire on Cyl #5. I am going to try to switch #3 & #5 wires at the plugs and module to see if it is a bad wire. The plugs are platinum with 10K on them. Any other suggestions?

If you can feel a misfire and the plugs are on right, may have swapped a pushrod, different lengths as you know. Do a compression test on the cylinder, good luck here.

I am pretty certain the push rods are all correct. I punched holes in a cardboard box and put them in order as I took them out. I started the car tonight after pulling the #5 wire off and putting it back on. The engine sounded worse, sputtering and missing terribly. Again got the P0305 code for #5 cylinder. I tapped on the injector for #5 cylinder before stating it and again after starting. It sounded so bad I was afraid to leave it running. Asking for help!!

Did you swap the wires beween two cylinders like you said? Did the misfire move with the wire or stay on Cyl 5? If it moved, its a bad wire, if it didn't, it's either a bad plug or bad injector/injector harness on Cyl 5 (assuming compression is ok on Cyl 5). Also, did you have the heads checked for cracks and to make sure they weren't warped?

Did you swap the wires beween two cylinders like you said? Did the misfire move with the wire or stay on Cyl 5? If it moved, its a bad wire, if it didn't, it's either a bad plug or bad injector/injector harness on Cyl 5 (assuming compression is ok on Cyl 5). Also, did you have the heads checked for cracks and to make sure they weren't warped?


I have had this happen on one of my many Lumina's... Swap out the wires like you stated and see if it is still doing it. If it is misfiring, but now on a different cyl, than that is your problem. If it is misfiring on that same cyl, check the coil pack for that cyl. I've had a bad coil that would work fine for one cyl, and would misfire on the other!

common problem when putting intake back on the 3.1L is getting fuel injector wires pinched, OR one injector went bad during installation. yes, it could be a bad coil, but the odds are not common in this situation. call any garage that has done a dozen of the 3.1L intakes and they'll say the same. and comptech...watch the smartass remarks

and comptech...watch the smartass remarks

ooooooooooooooooooooook ;)

Well I found the problem!! I took the back valve pan cover off and found that one of the rocker arms on #5 cylinder wasn't tight. I used a cheap torque wrench and also forgot to give them an extra 30 degree turn per the spec. Got it back together and started it up ... ran as smooth and quiet as it ever has. Now I need to pull the front valve cover and retorque the front rockers. Thanks for all the suggestions and help.

Well I found the problem!! I took the back valve pan cover off and found that one of the rocker arms on #5 cylinder wasn't tight. I used a cheap torque wrench and also forgot to give them an extra 30 degree turn per the spec. Got it back together and started it up ... ran as smooth and quiet as it ever has. Now I need to pull the front valve cover and retorque the front rockers. Thanks for all the suggestions and help.

Glad to hear you got it fixed!

did you replace those torque-to-yield bolts? its recommended that they never be reused.

did you replace those torque-to-yield bolts? its recommended that they never be reused.

Yes, I put in new Felpro Head bolts. What is the torque supposed to be on the roller rockers?

oops, sorry,i dont know how that got in there twice. I looked it up, and there are two different types. roller rockers and conventional rocker arms. for roller rockers the torque spec is 124 inch pounds (about 10.4 foot pounds), and and additional 30 degrees. again torque-to-yield bolts, that should get replaced. hope this helps.

I finished up this morning with the front head> All the rockers are tight now and I refilled the coolant and started it up. Everythings sounds great. I ran the car through the neighborhood for about 1/2 hour and kept a close eye on the temp guage. It stayed below 1/2 way all but once when I pulled it back into the driveway. I opened up the two air bleeds on the engine and let out a little air. The temp came right down and the stabilized there for the next 20 minutes. I checked the coolant level after i pulled it back in the garage and it was right on the hot line of the overflow tank. After a couple hours I checked it again and it is right on the cold line of the overflow tank. Thanks for all the help from everyone.