borrone821

iTrader: (3)

Folks,
I have a cammed LQ9 w/243 heads stuffed in my 02 WS6... chasing down a miss on the driver's side.
At first I was convinced I was screwing up the tuning since I'm new to tuning, but now I'm sure there's something electrical or mechanical.

I've pulled all the plugs and regapped them. I've tested each coil and wire with a spark plug tester from Harbor Freight.
Question: Do coils fail hard, or do they degrade and if they degrade, is there a way to tell?

If I have a faulty/stuck injector, wouldn't there be a code for that? If not, how can i test them?

I'm 99% sure the valvetrain is good; no metal on metal sounds or anything like that, but it's clearly a miss on the driver's side.
I was looking for a different issue a while back and had the cover off bumping the starter, so i know the valvetrain looks decent and the rockers are doing what they're supposed to.
Pulling a wire at the coil pack just makes it arc back to the coil and doesn't change the idle somehow.

Any help would be greatly appreciated.
thanks
Jim

Full Power

You can disable injectors, one at a time and see if the idle speed drops evenly, per cylinder to isolate the miss.
There are defective NEW IN BOX Spark plugs on occasion.
Lot of counterfeit knock-offs in the supply chain.
Once you isolate cylinderr mis-fire, replace spark plug with a GOOD one, ie a spark plug that DOES fire other cylinders.
Swap coil(s) similar.
Look for ignition coil wires chafed/ rubbed through and contacting coil mount bracket, heard of that causing trouble.

borrone821

iTrader: (3)

Thank Full Power. I know I have spark getting to the plugs, but obviously can't tell if those are firing.... not sure if the spark is enough nor how to tell but that doesn't sound like what i should be chasing.

Shouldn't I be getting codes coming up on particular cylinders to reflect what I'm hearing and feeling?

the_merv

iTrader: (88)

Stuck open Injector you'll have a Plug covered in gas when you take it out. That or it won't look like the others will. Running lean it'll be really white.

borrone821

iTrader: (3)

Yeah getting none of that, nor white plugs either.
I swapped all 4 driver side plugs with 4 older plugs just to test it out and it's exactly the same.
So looks like spark isn't the issue.

How do I check the injectors?
I was only able to pull the front 2 injector connectors; neither felt like there was discernible difference in idle.
Do I need to pull the entire fuel rail off and/or essentially take off the entire intake?

I can't believe spark wasn't a problem

CattleAc

iTrader: (7)

Do you know which cylinder is actually missing?

borrone821

iTrader: (3)

no, that's what i can't figure out... i'm not getting any codes, but it's a pretty clear miss, and when you open the hood, it's 100% from the drivers side.. haven't gotten a mechanics' stethoscope or anything yet but that may be the next step.
Already checked entire spark path including replacing all plugs, so gotta be air or fuel, right?
I might just take off the entire intake the make sure the gaskets are all good, plus it's easier to get the fuel rail off there

the_merv

iTrader: (88)

I'd pull a Valve Cover and look at the Valve Train. Intake side with the Lifter collapsed will do the same.

borrone821

iTrader: (3)

I did that earlier this week.. valve cover off, jumped the starter relay. All the rocker movements looked good and smooth. Nothing stuck or any jagged movements.. i felt the rocker movements up top and everything was operating smoothly.

the_merv

iTrader: (88)

Have you moved a Coil?

CattleAc

iTrader: (7)

If you don't have anything else, buy or borrow an IR heat gun and check each exhaust port on all the cylinders. You have to get a definitive answer on which cylinder is missing then go from there. Otherwise your just pi$$ing in the wind.

LS1Formulation

iTrader: (13)

Do you have a P0300 misfire code? And if so, can your scanner do misfire counts? I was able to use my scanner to determine what cylinders were misfiring in my '06 Silverado, but I'm not sure if an '02 PCM has that capability.

borrone821

iTrader: (3)

No P0300.
I do have an IR gun and have no clue how I didn't thnk of shooting the exhaust.

Car is cammed and I'm still working through tuning. Everyone on HPtuners told me misfire counts are useless when you cam a car (but happy to be convinced otherwise)

borrone821

iTrader: (3)

Alright, so shooting the laser is harder than i thought. am i going right above the exhuast manifold connection to the head? Exhaust itself wildly fluctuates no matter how close to the head.

What delta values tell me there is an issue?

I'm getting to the point where i'm just gonna pull the entire intake and fuel rails off tonight, i'm so frustrated. Spark path looks good and any changes I make (coils, wires, plugs) do nothing to help remediate the issue.

I'm thinking fuel is next; if not there, it's gonna be in the valvetrain, even though when bumping the starter with the valve cover off, everything looked good

LS1Formulation

iTrader: (13)

Don't pull the intake yet. Do a compression test first. If you don't have a compression tester, you can do a loan a tool at any of the big box auto parts stores. Without knowing for sure that every cylinder is putting in the same amount of work, you'll be chasing your tail trying to figure it out. Many years ago I had an '82 Z-28 that had a miss but no codes. No matter what I did, I couldn't figure it out. Did a compression test and one cylinder was about 80 PSI lower than the rest. Tore the engine down and one connecting rod had bent so badly that the piston was around 1/4" below deck. Never made a sound either, and from all appearances, it had happened early on in the car's life. You just never know.

borrone821

iTrader: (3)

I assume a leakdown tester would be just as good, yes? I have one of those and may be able to get to it tonight

borrone821

iTrader: (3)

Alright, kids were watching olympics so i snuck to the garage for a bit.

Only did the driver's side.
Cylinders 1 and 7 were perfect. With my HF testing, they were in the "set" setting, is lower than "low" compression.
Cylinder 3s and 5 I need help with.
In both cases, as I built up pressure, it started going, then went back to zero. Heard a "whoosh"
cylinder 5 built up the pressure by itself and as I increased to 100psi, it got to that "set" setting, which is perfect.
On Cylinder 3, i had to go back to zero and build it back up, then it got to that "set" setting.
What is going on here?

the_merv

iTrader: (88)

You pull the Rockers to close the Valves?

borrone821

iTrader: (3)

no, went to what i thought was TDC based on manually turning crank and watching pressure rise and fall, but didn't touch valvetrain at all. I'm sure could've been a litte off TDC

The fact that it held completely and showed near-zero loss is great, but i want to know what i did wrong on 3 and 5.
I know I did a leakdown test when the engine was out of the car and it was fine. didn't know if install and 500 miles changed anything.

CattleAc

iTrader: (7)

3-5...head gasket out between them...???