p0300 Tried almost everything....

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Apr 15, 2014 | 07:58 PM

#21

leaman griffin

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montecarlo... i think i have ruled out airflow because I have cranked the engine with both valve covers off and watched the valvesprings function correctly...

Apr 15, 2014 | 07:59 PM

#22

leaman griffin

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also i can hear sucking through my intake when the truck is "idling" haha..

Apr 16, 2014 | 05:13 AM

#23

sicksspeed

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From: bayville n.j.

And I assume you verified that there isn't a over fuel condition as in pull those plugs and they are not soaked. How about ruptured fuel pressure regulator diaphragm. Just passing thoughts.

Apr 16, 2014 | 07:41 AM

#24

leaman griffin

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yes i checked the regulator.... seems to be fine.. not leaking through to my vacuum hose. as far as the overfuel, hard to tell because my plugs seem a little black but not soaked... which could be caused by multiple problems like firing at the wrong time and the air movement in the cylinder is blowing out the spark....

Apr 16, 2014 | 07:42 AM

#25

leaman griffin

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thank you everyone for all of the suggestions....

Apr 16, 2014 | 08:24 AM

#26

sicksspeed

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From: bayville n.j.

Here is another way to check compression, cylinder sealing. Hook up compresion gauge like normal and fire the motor up. Preasure will be lower than regular test but you can watch it under normal conditions and release the preasure repeatedly and watch it build then swap to a good cylinder and watch how it acts. I found a problem this way before that regular compresion test missed but a leak down test was also was questioned.

Apr 16, 2014 | 08:36 AM

#27

Iam Broke

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Since the PCM was from a different engine ect. verify the correct firing order in the tune if you haven't.

Apr 16, 2014 | 09:37 AM

#28

S8ER95Z

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From: NC

Can you post up the tune file?

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May 19, 2014 | 04:49 PM

#29

Old Geezer

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"Any thoughts before I start pouring money into the car. "

Maybe, start your own thread??

May 19, 2014 | 06:14 PM

#30

aknovaman

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From: Hog Back, KS

Pm me your email and I can send you a config to use with hp tuners to see exactly which cylinders are mis- firing. It's pretty easy.

May 20, 2014 | 12:15 AM

#31

CattleAc

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From: Dakota Territory

Quote:

Originally Posted by leaman griffin

2002 5.3L LS in a 1998 tahoe.

Quote:

Originally Posted by leaman griffin

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..

I have to ask...did you change intake manifold??? Gaskets???

Every 1999-2006 5.3L I had come through the shop this winter with any kind of mileage on them needed intake gaskets...

Lots of P0300 codes, lean codes, poor idle, high idle.

May 20, 2014 | 08:15 AM

#32

S8ER95Z

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Quote:

Originally Posted by Old Geezer

"Any thoughts before I start pouring money into the car. "

Maybe, start your own thread??

Wrong thread? Did I miss a post?

May 20, 2014 | 08:49 PM

#33

1FastBrick

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From: JunkYard

Quote:

Originally Posted by S8ER95Z

Wrong thread? Did I miss a post?

You did. There was another post above but it was deleted by the user.

Since Old Geezer didn't quote it properly in his reply, it can't be seen.

The part in parentheses is part of the quote from the deleted post.

May 21, 2014 | 06:02 AM

#34

S8ER95Z

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From: NC

That makes way more sense...I even searched the page to make sure I wasn't going crazy. haha thanks!

Jun 4, 2014 | 10:56 PM

#35

NJ 666

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Quote:

Originally Posted by Iam Broke

Since the PCM was from a different engine ect. verify the correct firing order in the tune if you haven't.

Was thinking this reading the thread. Maybe those 2 cylinders are firing on the exhaust stroke Maybe the coils are wired to the ECM incorrectly. .

Jun 10, 2014 | 08:32 PM

#36

joecar

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From: So.Cal.

Looks like you should obtain a wiring diagram and verify the correctness of all the wires/connectors.

Jun 13, 2014 | 12:09 PM

#37

95wannabe

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Quote:

Originally Posted by leaman griffin

Then I found something interesting... Cylinders 7 and 4 seem to be the problem.........

Quote:

Originally Posted by MontecarloDrag

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

Soon as read your original post, I thought of the 4/7 firing order swap from SBC days. I'm not familiar with tuning software...do you tell the PCM what the firing order is?
If old school SBC guy put it in, it may be why 2 & 3 were wrong also. If memory serves...didn't the LS firing order swap 4/7 & 2/3 from SBC firing order?

Last edited by 95wannabe; Jun 13, 2014 at 12:22 PM.