Shops, Barns, Varmints, and Trucks - What have I over looked

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What have I over looked

Printed From: Unofficial Allis
Category: Other Topics
Forum Name: Shops, Barns, Varmints, and Trucks
Forum Description: anything you want to talk about except politics
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=204054
Printed Date: 14 Nov 2024 at 2:15am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: What have I over looked

Posted By: bobkyllo
Subject: What have I over looked
Date Posted: 08 Nov 2024 at 12:58am

Customer brings in a 2004 chevy avalanche 5.3 liter said check engine light is in. I scan it and get a random misfire along with a mass air flow sensor under reporting. I also took it for a drive. During the drive I notice the check engine light to flash.

Told the customer my feelings. He wants to do plugs and wires seeing as it has 180k on the vehicle. And he wanted the mass air flow.

I do the work. Start it ag still misses. This time no flashing light and no mass air flow code.

Look farther into this random miss and my monitor on the scanner is going nuts for cylinder 2 and 7. Quick easy and no cost I move cylinder 2 coil to number 3 I belive. No help.

Doing some thinking what can cause this. Intake gaskets-- but long and short fuel show nearly prefect. Injectors-- again trims show good and during a balance test the 2 that missed performed just as good as ones that were not suspect.

Last before I gave up tonight I did a cam crank relearn. Tomorrow I'll go drive it.

Have I over looked anything or does anything come to your guys mind.

Replies:

Posted By: jaybmiller
Date Posted: 08 Nov 2024 at 6:30am

off the top of my head....

hmm. 20 year old..

disconnect 'computer' connectors ,clean and reseat at least 3-4 times

inspect(remove/clean/reattach) ALL possible ground wires between engine and 'computer'

check wires on the 'coils' for chews,almost breaks,cuts.

have no idea HOW the computer decides 'misfire on #2'.... but I suspect 'bad' wires/connectors OR maybe the injector ? Coil could be fine, but inj not spraying right ??

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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)

Never burn your bridges, unless you can walk on water

Posted By: Lars(wi)
Date Posted: 08 Nov 2024 at 6:50am

Hydraulic lifters? Maybe a couple getting weak/worn out. Lobe or two worn down on camshaft.
Owner probably was not diligent enough on oil changes.

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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.

Posted By: Les Kerf
Date Posted: 08 Nov 2024 at 7:33am

My 98 Isuzu Trooper did a similar missfire due to a bad intake manifold gasket. Replacing spark plugs didn't help.

Posted By: steve(ill)
Date Posted: 08 Nov 2024 at 7:53am

never had a chevy.. but 2001 and 2002 F150 with 5.4 and 2006 with 4.6 .... EVERY missfire i had was due to a COIL, bad INJECTOR , or the electrical plug/ bent wire on them..

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Like them all, but love the "B"s.

Posted By: steve(ill)
Date Posted: 08 Nov 2024 at 8:01am

i did an ON LINE SEARCH for "2004 chevy 5.3 missfire" ... and normally its coils or injectors... when those are changed and no help, it seems the problem goes to the Lifters wearing out.. Several posts on that Known problem .

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Like them all, but love the "B"s.

Posted By: Alberta Phil
Date Posted: 08 Nov 2024 at 9:24am

I have an '05 Saturn Vue and had a similar problem with the V6. My mechanic buddy checked it out and it was showing a miss on #5 and intermittent on #2. He swapped plugs and coils around and no difference. He said it had probably never had a valve adjustment, so got my OK to do it. That fixed it, but with a $1000 bill as half the engine has to be taken apart and re-assembled. 6 hours labor!

Posted By: Hubert (Ga)engine7
Date Posted: 08 Nov 2024 at 3:34pm

Presently I have a similar problem with my 99 F150 with 5.4, check engine light illuminating then later intermittently flashing, showing misfiring on #3. I’m thinking bad computer/connection or grounding issues. Let us know what you find.

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Just an old country boy saved by the grace of God.

Posted By: DaveKamp
Date Posted: 10 Nov 2024 at 9:33pm

If you move electricals around, and nothing changes, it isn't the electricals.

2 and 7 are at the complete opposite corners. IF they share an intake runner, I'd venture a guess that there's a crack in the intake manifold... is it plastic?

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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.