leaman griffin

2002 5.3L LS in a 1998 tahoe.

I have had a bad misfire from day one.... took my plugs off the ecm and checked continuity on all of the injector and coil wires... turned out 2 of my injectors were plugged into the wrong place. luckily they were pins not used... Inj 3 was plugged into the inj 2 pin and inj 2 was plugged into a dead pin. So I got that fixed and it ran ALOT smoother... Cleared the codes and drove it down the street and back... still hesitating and it died on me in my driveway.. Pulled the new codes... p0300 random misfire....

So here is what i did.

Checked each injector to make sure it was in the correct pin on the ecm.

#1 C1 - 36
#2 C1 - 4
#3 C1 - 3
#4 C1 - 44
#5 C1 - 76
#6 C1 - 37
#7 C1 - 43
#8 C1 - 77

checked +V to each injector.
checked resistance of each injector 12.9 - 13.0 across the board..
checked signal wire for each coil to ecm. All are correct.

#1 C2 - 26
#2 C2 - 67
#3 C2 - 69
#4 C2 - 27
#5 C2 - 68
#6 C2 - 28
#7 C2 - 29
#8 C2 - 66

Checked 12V to each coil.
Checked ground to each coil
Then I found something interesting... Cylinders 7 and 4 seem to be the problem..
My headers are new and I let it run through a small heat cycle and the tubes off of those cylinders are still glossy paint where as all the other cylinders are turning colors due to heat...after shutting off i could touch those header tubes without burning my finger..

So I checked resistance of those two coils from the output to the ground terminal...
I got 5400ohms for both which I hear is a normal reading..

So I tested my fuel pump.. Hooked up a gauge and got 52 psi at idle and no drop in psi at all during revving...

Fuel filter is new..
Plug wires are new...
I checked the plugs the other day and found 1 wet plug on the cylinder with the mis wired injector.. Replaced it..


Update... I also replaced all 8 plugs and no improvement. Moved plug wires around to see if the dead cylinders followed but nope still the same..

Moved coils to different cylinders... no change.

Removed and cleaned all of my injectors. swapped the injectors on the 2 bad cylinders with injectors from 2 good cylinders... no change.

I am stuck.... I have limited funds to throw money at it for now so I am trying to go over everything.......

MontecarloDrag

iTrader: (3)

OK, you ruled out injectors, plugs, coils and cables.
Next step is to make sure those 2 cylinders are actually getting spark and fuel. Even if all components are good it doesn't mean the cylinder is getting fuel and spark.

Unplug both spark plug wires (from the plug), insert a spare spark plug into the cable and make contact with any grounded metal, have somebody start the engine while you watch the plug. If you get no spark then you have a wiring problem or a bad PCM

If all cylinders have spark, then test for fuel. You need to check injector pulse. Buy a injector signal tester, they are very cheap. Plug it to the injector harness and let the engine idle. The tester should light
If you get no injector pulse you have a wiring problem or the PCM has faulty injector drivers.

If both tests check ok, then you have a mechanical problem. Do a compression test and valvetrain inspection. You may find damaged valves, bent pushrods, worn camshaft lobes, broken piston rings, etc.

Old Geezer

iTrader: (3)

"Removed and cleaned all of my injectors".
What method did you use to clean them??
Did the 02 engine sit for some time, b4 the swap was completed, and the engine started?

leaman griffin

Thanks I will try that tomorrow... as far as the engine sitting...

I bought the engine from a performance shop that specializes in LS swaps.. they keep 5.3L engines in stock... not sure how long it was sitting before I aquired it however i had it a month and a half before starting it..

leaman griffin

I tested for spark.... all is good on both cylinders... so i think i can officially rule out coils, plugs, wires.... I will test the injectors with a noid light tomorrow and also do a comp test..

S8ER95Z

iTrader: (3)

This may not help but I had an issue with this code and a CASE learn was required. Mine was due to an engine change but if you have changed out certain sensors it might be needed. I'm not an expert but it resolved my issue.

SES light would flash around 3500rpm but I did not feel a change in the way the engine was running, the light seemed cosmetic. Good luck!

http://www.hptuners.com/help/index.h...cmcontrols.htm

Special VCM Controls
CASE Learn: To use the CASE learn function please follow these steps:

• Ensure the engine is at normal operating temperature (ECT > ~65C).
• Put the vehicle into park (auto) or neutral (manual).
• Turn off all accessories and A/C.
• Turn the vehicle off.
• Apply the parking brake.
• Press the brake pedal. Keep the brake pedal depressed during the entire procedure. REQUIRED for successful test completion
• Start the vehicle and let it idle.
• Press Begin.
• Gradually rev the vehicle to fuel cutoff (around 4000-5000 RPM's) over a period of about 4 seconds. When fuel cuts out, immediately release the throttle.
• Allow the engine to come back to an idle.
• Turn the ignition off for at least 15 seconds. This step is required for the VCM to store the newly learned configuration.

1FastBrick

iTrader: (16)

Let us know what you find when you verify the injectors are getting a signal from the PCM with a noid light.

Old Geezer

iTrader: (3)

Post #3...haven't seen your reply.
If that engine set for an extended period, and the injs are gummed up, checking the circuitry w/ a noid will only tell you the power is good.
I clean injs for the local JY. His engines sit for long periods...Many are so bad, the injs are junk...

MontecarloDrag

iTrader: (3)

He swapped injectors from a running cylinder to the dead ones and didn't help

leaman griffin

yes... i cleaned them by hooking them to a battery while feeding pressurized carb cleaner into them... all 8 sprayed fine... a few had gunk in the top cavity that i cleaned out, but i would have to say they arent clogged due to switching cylinders with them and the problem not following..

truckdoug

iTrader: (25)

did you run a compression test? if this was happening on a carb'd car I'd look at valve seals.

good luck with it

leaman griffin

I got the noid tester and a compression tester... Here is where it gets confusing... Noid light shows a perfect signal to both injectors... Compression test is 150ish on both cylinders....

LSX Power Tuning

iTrader: (4)

Do a leakdown test on those cylinders. I bought a LS1 one time that had been sitting and apparently it got water in it at some point and #1 cylinder had a valve that a little piece rusted off and it flagged as a miss fire. It took a good while to figure that out because everything tested good all the time.

leaman griffin

my only concern is i can run the engine and hold the header tube the whole time on those 2 cylinders..... even if i had a small leak in compression it would still combust and bee too hot to touch on the header. and it idles so bad i cant even put it in gear..

S8ER95Z

iTrader: (3)

You have confirmed spark and fuel in those cylinders?

leaman griffin

yes.... mulltiple times and in multiple ways... I do have some insight though...

I bought the engine from a shop and they also sold me an ecm... however the ecm wasnt from the same engine... Do I need a crank relearn performed?

MontecarloDrag

iTrader: (3)

Yes, if the PCM is from another car a case relearn is needed.
However, the only consequence of not doing it is misfires, it won't cause 2 completely dead cylinders.

It's very puzzling that you have fuel, compression and spark and the cylinders won't fire. Now you need to check for air, intake may be plugged or a valve may not be opening, so fresh air is not getting into the cylinder.

Does your PCM have the correct tune? It may be from a V6 engine or something different. The injectors may be opening out of sync or the spark may be happening out of time. I mean, you can see the spark and the noid tester shows injector pulse, but they may be out of whack

truckdoug

iTrader: (25)

and you swapped injectors around? (i know I read you swapped coils/plugs/wires around up there)

dang thats hella weird.

leakdown is next atmo.

strange things are afoot at the circle K

truckdoug

iTrader: (25)

damn that is something i would have never thought of

leaman griffin

it seems like it is firing when the cylinder is down causing the fuel/air to blow out the exhaust port.... like its firing when a port is open and the air movement causes it to not ignite.... only thing i can think of.. if it was a v6 tune wouldnt the pinout be different? or wouldnt i have no signal on 2 of the cylinders coils and injectors?