LS1ROPER

iTrader: (21)

Cranked my new 408 project couple of weeks ago sounded as if it had a miss, really didn't think to much was trying to finish up everything to get it road worthy. Anyway finished anything this afternoon took it around the block it has a very bad miss. After looking everything over we noticed the two rear headers tubes were a different color than the other 6 the drive side rear tube was cool to the touch shortly after we turned off engine. We took the drive side rear spark plug out it looks brand new the other 3 on that side looked liked they have been used. I also took an old plug put in rear spark plug wire while a buddy turn the ignition there was spark so I know it is getting fire.
Now the computer was sent off to a sponsor to get a break in tune on it. Also my fuel injectors were bought used from a board member everything has gone so smooth up to this point any ideas way the back 2 cylinders are running cold or not getting any fuel?

blk00ss

iTrader: (66)

Are you throwing any codes? One time I forgot to plug up the #4 injector and it made both #4 and #3 not fire. So go over all your connections and make sure your plugins are all secured. Also you can try swapping plug wires. Also you can pull your coil packs and look up in where your plug wire connects. It should be a nice copper color. If it is discolored it's a sign of a bad coil pack or plug wire.

CalSpeedPerformance

iTrader: (64)

Start with simple diagnosis.

Swap the spark plugs and wires from those two cylinders to 2 good cylinders and see if there is a change.

Next swap coil packs same way...test.

Then swap fuel injectors from two good cylinders...test..

If the problem moves to another cylinder at any point, then youve found your problem.

After also check the wiring to the injector/coil plugs and make sure you dont have a pulled wire out of the connector. Test the injector plug in with a noid tester to see its firing. . Check spark plug wire for spark.

LS1ROPER

iTrader: (21)

Ok I've checked injector plug with noid light,, light flashes, swap'd coil packs still same result; have not changed the fuel injectors yet. Is there a posibility taht something could have been done on the breakin tune with the computer

CalSpeedPerformance

iTrader: (64)

Well if you have fuel and spark, you should have non-misfiring cylinder.

Check everything on that list. Also do a compression & leakdown test on those cylinders

blk00ss

iTrader: (66)

Yeah it's possible you have some bent valves. But I'm still banking on a bad plug or something electrical.

LS1ROPER

iTrader: (21)

I think something Electrical also just have to run it down. Dont think bent valve everything is new from Intake to Oil Pan except for "dyno time only" fuel injectors, not that means anything but just throwing that out there. When I get off this morning will chnage the fuel injectors around see what that does. Again is it posible that something not put in or left on the breakin/strart up tune Just tring to rule everything out.

blk00ss

iTrader: (66)

No its nothing in the tune.

TomM

iTrader: (56)

Had the same problem on start up. Did all the things you did, swapped coil packs, wires, plugs etc......it was a bad injector, had already changed it once.......
Didn't have a light, just plugged an old spark plug on to the wire and grounded it. It was firing, but not enough to heat the cylinder as there was no fuel........sounds like an injector....


T,

LS1ROPER

iTrader: (21)

Yes it is the injector pulled the 2 injectors over the cylinders that were not firing fuel gushed out of fuel rails had trash on top of both injectors cleaned them 1 is working fine now, the other still is not working guess I have to get another injector! Thanks Guys for your replys