Hi, i have a LS1 Chev and the 4 rear Cyls wont fire, have replaced Plugs , leads and the coil packs seem to be ok, can you help?

Plugs from left to right:

1-2-3-4


Coil Connections from front of engine bay to rear firewall of engine bay


3 - Rear coil pack, rear post
2 - Rear coil pack, front post

4 - Front coil pack, rear post
1 - Front coil pack, front post


Firing Order 1-3-4-2

Bad coil pack cyl 1&3 work off same segment

3.7 V6, mileage?

most likely the HV wires bad.

then bad coil pack.

did you check spark directly at the coil pack?

i use 2 known good HV wires to do that and 2 good test spark plugs.

both plugs grounded to engine (shell)

that is how you test any wasted spark coil pack. 3 coil pack.

if that fails the FSM shows, unplugging it and check the coil resistances. if wrong the pack is bad,

keep in mind the res. can read ok and coil be bad ,due to internal insulation break down (internal shorts)

if thats ok. the resistance , make sure the wires are not (primary)

to the coil (the low voltage connnector)

if that is ok, its mostly likely a bad coil, (pray not bad PCM)

if tool-less? start with cheap parts , work to expensive. (guessing)





now wasted spark 101.

if one line opens , both spark plugs die. no spark

the wasted spark is wired in SERIES. ( like Christmas lights)

the magic cuts cost of 6 coil\'s.

so if the HV wires are say, cheap , carbon wire and open

you lose, both spark plugs. use MAG wire and end this issues.

get some nice NGK mag wire or Bosch Mag wires.

you can see i hate carbon wire. for good causes.

(carbon string wire)

mag wires is real wire that is coil spun and is inductive. it

has the correct impedance but is not a resistor its and inductor.

and lasts the longest , and worth every penny.

The firing order is 1-2-3-4-5-6
Cyl #1 is front left when looking at engine front to back
left coil pack connects to cyls. 5-2
center coil pack connects to cyls. 3-6
right coil pack connects to cyls. 4-1
It doesn't matter which connector on the coil you use just that the cylinder is connected to the proper coil pack (the coil fires both plugs at the same time, twice per each full 4 stroke cycle)
1998 Chevrolet Lumina
3.1 liter V-6 VIN "M"

I would say its the coil. A crank or cam sensor could cause one cylinder to miss, or go completely dead, but I doubt it would affect two cylinders. And you would get a code for either sensor.

may be a bad module it is under the coils I think 3 and 6 are on the same coil so that would make both cyls not fire

if one of the plugs is fouled neither plug will fire

hi from uk i assume you have done all the above work correctly? and the leads from coils are correct firing order 1 3 4 2 ? CAMBELTtiming set correctly etc as you say this has happened since cyl head renewed and miss fire is on Nos 1+2 cyl's this normally suggest now after all work u have done and assume compressions are ok ? i had such a fault on a customers mini some years ago who had done exact type of job as you described this fault turned out to be the inlet manifold gasket had split between cyls inlet ports and resulted in missfire on 2 cyls adjoining on removal of manifold the gasket had been damaged whilst reassembling new gasket cured missfire which had caused weak mixtur on both cyls ie on induction more air being drawn via cracked gasket on each cyl and as your engine if injection same problem?? might be worth checking?? hope this throws some light on the problem?

have you checked that the points in the distributer are set ok and havent closed or burnt,as this is what makes the coil spark the ht lead to the distributer cap to the rotor arm then to the plug leads.
hope this helps

have you changed the ignition wires? perhaps firing order crossed? if not coil pack or ignition wires faulty how do you know it is not "FIREING" on 1 & 4 have you tested it with a spark tester tool???