I'm not completely sure how you would check the injectors, i would guess pull the fuel rail out with the injector still in, turn the key to the on position, place some paper towel underneath an injector, and then apply voltage by some means to the individual injector to see if you get fuel, and then repeat for all the injectors. Thats really my best guess.

 

You're running the old lifters from your killed motor?! That took some *****.

I would consider also the 02 sensor wiring like they stated in the other post. BUT, if it were that, they would throw a code as well, haha.

You do need to check your LTFT's, or have a wideband in there.

 

Well, I just didn't think anything would be wrong with them!! Oh well!!!

 

Is there any way to test a coil? Do coils either work or not? I have a very uneven burn across 8 cylinders. I have a carbureted LS-1, 650 Mighty Demon, MSD / Edlebrock combo package.

 

I'm having the same problem on my engine, except the 2 dead cyl are next to each other and move with the coil packs it seems

 

anyone have any new ideas here yet?

 

i would lean toward injectors. they are almost as easy to move as the coil packs. i am having a misfire problem with my ta, also. i have it narrowed down to cyl. #7, but swapping coils didn't fix it, swapping plug wires didn't fix it, swapping plugs didn't fix it, however, swapping injectors HELPED IT OUT, but did not completely get rid of the misfire, now it just misfires LESS, but on the same cyl.

 

Some coils will fail or become intermittant due to engine heat and sometimes increased dwell (tuning here).

I had two MSD coils that would fail after getting warmed up.

Easiest way to tell was by brute force.

When the engine started to miss, I would stop and pull a plug wire (coil side) and start the car and look for a spark to jump across.

I replaced one and then a few days later the same problem occured. WTF?

The *** kicker was that it ended up being another coil!

MSD stood behind the product though.

 

Mine are not firing at all except at high rpm or extreme low rpm, but like I said the problem follows the coil packs so it shouldn't be a tuning issue. But it also doesn't seem to be the coils themselves.

Everything else on the car is done...this is the only thing standing between me and driving my car for the first time since June. Bleh.

I guess I'm going to try to find someone with a truck and pull a set of coils, perhaps its the harness.

 

Swapping a set of coil paks should be duck soup.

good luck.

 

I just can't find a v8 chevy 99+ who is willing to come out here for 10 minutes

You think in this area where everyone has at least 4 ******* trucks I could come across one someone could do without for a few minutes to test the theory

 

You need several things:

• clean fouled plugs;
• gap all plugs to 0.040" and inspect for damage.
• check that all plug wires are in the same good condition.
• check fuel pressure key-on-engine-off, if it's not holding steady then some injectors may be leaking (the passenger side ones...!).
• using a "block tester kit" check for presence of combustion gases in coolant while motor runs.

Goto a shop that uses a lab oscilloscope to diagnose driveability problems (if they look at you "huh...?" then go elsewhere)...

Get the shop to capture the following waveforms (in separate captures):

1. crank sensor voltage (use trigger probe on #1 for firing order reference)... non-uniform amplitude may be a problem.
2. injector voltages (at injector) and current (thru fuses INJ1 and INJ2... they will know how)... might be hard, but do all 8... the waveforms will show if the injectors are opening/closing.
3. coil secondary voltages, might be hard, but do all 8 (if these look bad, also do primary voltages)... the waveforms will show the kV and duration.
4. starter current (with fuel disabled)... this is a "relative compression test"... (use trigger probe on #1 for firing order reference).
5. not necessary but might as well also look at cam sensor voltage wrt crank sensor voltage to make sure it's correct.

They should be able to look at those waveforms and determine your problem.


When the rotating mass and/or crank sensor is changed, a CASE relearn is required... the PCM uses the relearn info in the misfire detection algorithms (this is what the GM service manual says)... I don't know if this may/maynot cause detectable misfires if not done.

 

swapped for a set of coils from a friends truck, car fired right off

Not a problem since, so I'm getting another set from the scrap yard tomorrow and chalking it up to bad wiring inside the coil harness

I'm excited as **** right now

 

Good for you!

 

Well, I finally found out what the problem was: plugged catalytic converter on the passenger side. I pulled the Y-pipe off, fired the car up and there was no flow at all. Remove the cat, gutted the interior, re-installed and fired it up again. Success!!

This was without-a-doubt, the most frustrating problem I've ever had with a car!! I'm just glad I finally could figure it out!!