I changed the plugs about 5 weeks ago and every since then the engine is running rough. After 3 sets of different plugs (the last set being AC Delco Iridiums) and two different wire sets the engine still mises at idle and runs rough all the way through the rpm range. The engine seems to have a stumble at idle and gets worse as you rev the engine. The gear shift, the steering wheel, and the seat all vibrate while the car sits in the driveway or going down the road. The clutch can be in or out, it does not matter. It’s worse under load going down the road. The vibration seem to be tied to the engine running rough as you can hear popping through the exhaust the whole time you’re driving. During a hard acceleration it is really bad almost to the point that it makes the car uncomfortable to drive. At cruise speed the engine runs rough and my gas mileage is affected.

I tried a timing light on the driver's side bank and it's firing just fine on all four cylinders (1-3-5-7). On the passenger side there is a slight pause in the timing light strobe on all four cylinders (2-4-6-8). This seems to be tied into the engine stumbling at idle. I checked the connection for that bank at the top of the engine and the connection is good. I've not gotten an SES light throughout this whole ordeal. Do you think that this could be an oxygen sensor (before the cat) that is on the verge of going out or is it something else? Any ideas as to why all four on that side would be misfiring?

Thanks

 

check your o2 sensor on that bank, we see that same problem in the gen3 trucks all the time

 

Was it OK before the first plug/wire swap?

 

Yes, Everything was running fine before the plug change. I can’t remember which side of the manifold the O2 sensor is on. I may have damaged the wire or the connection when I had to reach up to change the number eight plug from the bottom. I wont have a chance to look at it until this afternoon. It is also possible that it’s just a coincidence that I’m having trouble after the plug change.
Thanks for your help

 

Check that all your injector plugs are on tight, maybe you accidently loosened one of the connectors while changing your spark plugs.

 

Usually if the wiring is damaged to an O2 sensor it will turn on the SES. Maybe you broke a plug while installing them or a plug wire isn't on all the way.

 

OOPS the title is wrong. It should be the passenger side coil bank. Well I removed the O2 sensor last night and it looks fine on the outside. I’m going to replace both O2’s as someone suggested as I have 82000 miles on the car and who knows it may fix the problem. When I had the bosh plugs in I thought I may have broken one and replaced them all with Autolites. The engine still ran rough and I replaced them with the AC Delco’s. When the engine still ran rough I replaced the plug wires. Went back and triple checked all of my connections and made sure all the plug wires snapped in. All four cylinders on the passenger side are missing. The driver’s side is fine it’s just the passenger side giving me the problem. The timing light will blink fine for a few seconds and skip for a split second. This is on all four cylinders on the passenger side. The driver side is a continuous blink. How does the O2 sensor tie into the spark of the plugs? I always thought that the O2 sensor controlled the air fuel ratio. The crank sensor was the one that I thought always controlled the spark but I could be wrong. Could someone please explain this to me? If it was the crank trigger it would be all eight plugs misfiring right or not running at all? Just thinking out load. I just don’t know its very puzzling wish I had a SES light to go on.

 

Swap the coil packs from side to side. If the miss follows, replace the suspect coils. If the miss stays on the passenger side, post up...

 

Id say it might be your plug wires.. Are you using stock? I know with the full metal jacket it might be hard to pull them off the plugs and cause a small crack in the wire or worse. Ive broken the stock wires a couple of times and I went ahead with the stronger MSD 8.5's. Good example of cracking is to take a pulg wire and play with it to see if theirs small cracks in the wire, visually like dry skin. My old truck had an engine swap and the wires off the newer engine were badly cracked and the same problem u had was happening to me. I replaced all the wires and its runs perfect.