miss after tune-up

[Gunboat]

ok,I have a 92' lumina z34 3.4l.My problem is this,first I re-gapped the plugs,at 45,(had a slight miss,so thought that this might help) they had them gapped between 50 and 60,got that problem fixed,After doing this I replaced the plug wires and..replaced two plugs in the rear middle and drivers side,were and they still are missing,swapped the injectors out and it still misses on the same two 2 back plugs (middle and drivers side,new plugs in those 2 cylinders.new wires.new ecm.what could possibly be the problem?any help here would be greatly appreciated.thanks in advance.

stumped! I also checked the timing belt,looks pretty new,so I know it hasn't jumped time...I also had to replace a coil pack,it is just those two plugs (middle and driver side rear).I also did a ohm check on all injectors,all are real close to each other so it doesn't seem to be the injectors.possibly the plug and wires going to the injectors?need some help..please....oh by the way it ran pretty good B4 I re-gapped the plugs,just had a slight miss.

Edited March 28, 2012 by Gunboat

[GtpKo]

I once had a brand new coil pack give me a misfire when the casing cracked a bit on install(put it on a bit too tight). Just a thought.

 

And my next thought was faulty wiring related to those 2 cylinders.

[Galaxie500XL]

I'm a little confused...since the DIS system sends spark to two plugs, and the firing order is 1-2-3-4-5-6, a single coil wouldn't cause a misfire on those two adjacent plugs, since each of them would be fired by a different coil.

 

Going left to right, the first coil fires 1-4, the middle coil fires 3-6, and the righmost coil 2-5.

 

In other words, a SINGLE bad coil would cause misfing pairs on OPPOSITE sides of the engine...for example, if the leftmost coil is failing, you should have a pair of misifires on cylinders 1 and 4, which are on the opposite sides of the engine.

 

Adjacent misfires would more than likely be either miswired coils, or something the two cylinders have in common---for instance, a leak at either the plenum gasket, or the LIM gasket on that side of the engine.

 

However, I could see how it would be VERY easy to have the plug wire for 6 on the rightmost coil, and the plug wire for 4 on the center coil, which would create exactly the symptom you describe...please don't ask me how I know how easy that would be to do..

Edited March 28, 2012 by Galaxie500XL

[94 olds vert]

I have done. I accidently mixed up my wires when doing the plugs&wires. Gave me a nice little miss fire and was very easy to correct.

 

However, I could see how it would be VERY easy to have the plug wire for 6 on the rightmost coil, and the plug wire for 4 on the center coil, which would create exactly the symptom you describe...please don't ask me how I know how easy that would be to do..

[Gunboat]

ok,the wires are new,they will fire a plug if you pull it out and ground it,it doesn't make any difference if I pull the wire when I pull the wire off the plug no difference in the way the thing runs..it seems like I have broken a injector wire,but I can't see any breaks.was running good until the plug regap...I have swapped injectors thinking that I might have damages one.but it seems to be pointing to the fact thaqt the injectors aren't getting a firing pulse...guess I'm going to have to do the light bulb trick and see if the wire is sending a pulse to those injectors..if that doesn't work,guess that I'll be back here posting what the results were ,thanks guys

[Addicted To Boost]

Check the resistance of your coils.

[ricklovin93]

really sounds like you mixed up the wires, its a very easy thing to do, i did it when i changed the plugs on the olds (which to date is the hardest thing i have ever had to do to the car, what a pain in the ass)