7.4L vortec running rough

Okay for starters, the motor ran fine had a slight miss in it pulled the codes one was O2 sensor and cam shaft poisitioning sensor. I ran seafoam through the PCV valve vaccum line to clean out the motor, once done I cranked it ran it blowing out all the garbage. It had a few really bad mis fires following. Not a huge deal, so I changed all the plugs found 8 fouled plugs.

Once the plugs were changed and the wires were changed I noticed a hole in EGR return. I have since ordered a new one however have not received to install. Nor have I fixed the cam shaft poisitioning sensor due to the fact that the right bank headers need to be removed to change it. (haven't had the time) once I changed the plugs and started the truck it ran really rough and became really hard to start... I went with a gapless iridium plug. It now has more than just a little miss, and it back fires very frequently.

My question is did the seafoam cause any of this? ( I don't believe it did) or is this just a cluster of the little things I previously mentioned?

I plan on changing the EGR return on Saturday and hooking up the right bank O2 sensor to hopefully help with the running issue, probably won't change the cam shaft positioning sensor until a week or two just to time on hand. Also once I installed the iridium plugs and ran it with the engine mis firing heavily I pulled A few of the new plugs to find they was carbon all over them. I plan on cleaning the new plugs up with some fuel and reinstalling them.

I know it's lengthy but any suggestions are welcome. Thank you

Header needs to be removed to do camshaft position sensor? You sure about that? It's inside the distributor, and usually doesn't go bad. What specific code #'s are you getting?

Plugs were fouled with what? Oil, fuel, ashy deposits...? Color and texture of what was fouling them?

Never been a big fan of putting any kind of cleaning agent into the engine then romping on it right away; if you dislodged any carbon chunks that's not what you want flying around in the combustion chamber while you're revving it. When I do these I use BG 44K which I have a lot more faith in than Seafoam (BG is shop-grade chemical products) and when I crank it up I let it just idle for a while, then go drive it gently a bit, THEN jump on it. My personal preference and for sure there's probably a lot of people that just romp on it with no issues, but I'm paranoid.

Richard

The new plugs were covered in a carbon like deposit (sooty if you will) from my digging around on the interwebs I found it to be on the right bank and the header appears to be blocking the 10mm bolt I need to remove it.

Like I said I haven't had much time to look at it thoroughly however I'm going to take a better look this weekend.

Thanks for the reply.

As for romping on it after the seafoam I let it idle out for a minute brought it to temp then eased into it with some higher revs later, it didn't smoke all that much and a friend told me it should have smoked more. It was my first time using a engine cleaning agent. I always used it for bad gas. Idk

X2 on camshaft sensor inside the distributor. I had to change mine a while back. It was an intermittent miss. They usually never go bad but when I put the tech 2 on it it was affecting the timing sporadically. I did it without removing the upper intake manifold but it was a royal p.I.t.a! The only way I use seafoam is in the gas tank if at all. The bg stuff works better and I have never had a sensor fail from using it but have with seafoam. You may have to clean plugs then run it and reclean them a few times. Good luck..

Yeah any distributor work on the Vortec 7.4, coil/module bracket removed, laying down on top of the intake...not fun. Watch out for that stud sticking up waiting to poke you in the ribs.

Richard

Oh hell yea! Forgot about that bastard stud! Never got my ribs but sure put an ass whipping on my elbow!

Didnt want to start a new thread, having the same issue. I bought my 98 3500 454 vortec dually ran fine, now running ruff and want to die when warmed up. Did throw some codes, said it was 02 sensors downstream . Replaced, still ran ruff not throwing codes. Just changed cap, wires, rotor, left the old plugs in, but looked like had already been changed. But are black from running rich. Can smell richness in exhaust. Could it be a cat? Goint to replace fuel filter today, and check fuel pressure. Any help much appriciated

Can't help much but I did have a cat totally plug up on my 2000, the honeycomb broke in half and wasn't flowing good so it melted down and plugged the outlet completely. I just cut them out and put in straight pipe since I am in michigan and don't have smog testing here.

Did it throw the 02 sensors off?

Yea, I changed two 02 sensors downstream, a temp sensor, cap , rotors , wires, fule filter, cleaned mass flow censor, put a fuel pressure gauge on, holding 55psi, once engine cuts of slowly bleeds down. Injectors might need to be cleaned or replaced?