2003 3.5 6 speed car. 191k, just replaced all spark plugs, replaced rear coil packs with new units, new rear valve cover and valve cover gasket, replaced the ignition condenser thingy, replaced front valve cover gasket. The issue is at idle I get a random misfire CEL but it will turn on and off randomly. I have sprayed brake cleaner all around the intake to make sure there were no intake leaks and none were found. What I find odd is, it seems like when I disconnect the front coil packs individually it makes almost no difference in how it idles, good or bad. Im at my wits end with this car but when it runs, it runs amazing.

 

Aftermarket coil packs? They don't work.

Go get some junkyard ones or stick in the old ones if you didn't have an issue.

 

There problem was there before the tune up but didnt seem to be as bad before the tune up. Would a idle relearn possibly fix this?

 

What problem do you mean exactly? Please be very specific.

 

could also have a stretched timing chain or low compression in a cylinder

 

likely going to be your coil packs like other guy said. Also you didn't say whether you got aftermarket or not? Did you gap the plugs?

 

Random misfire cel was the issue before and after the tune up. It would come and go randomly. Coil packs were new aftermarket units, plugs were gapped to .044. I have also done the coolant bypass on it as well. It will, at times, die if I am rolling up to a stop sign and throw it in neutral.

 

Boy, maf sure is a mighty suspect on a lot of recent threads.

 

Hitachi or OEM. Other aftermarket coil packs are a piece of crap

 

Two things I would check. First check your throttle body for excessive oil/grime at the throttle plate. If it is, clean it up...the engine will starve for air when going from driving to throwing it in idle. Second is to check the PCV hose coming from the back of the valve cover into to the back of the intake. If the hose is deformed, cracked or soft it will cause the engine to run like crap and throw CEL.

 

You should go hunting for bad coil pack only when it idles badly: when disconnected the faulty pack won't make it worse while any good one will. The problem with them is they often come back alive and become indistinguishable from the rest.