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2004 Tahoe Help!!


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Dwebb76
Novice

Jun 6, 2016, 3:31 PM

Post #1 of 11 (1134 views)
2004 Tahoe Help!! Sign In

Hi, I just bought a 2004 Chevy Tahoe, 4.8l, V8,with 202k and some change on it. Or is throwing a random misfire and a cylinder 6 misfire code. Replaced plugs & wires and #6 coil. Injectors are all firing. Checked for vacuum leaks and replaced Mass air flow sensor. Doesnt want to go over 30. Trans shifts fine.


kev2
Veteran
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Jun 6, 2016, 3:44 PM

Post #2 of 11 (1130 views)
Re: 2004 Tahoe Help!! Sign In

tell us the code numbers.
I am assuming you do NOT have a scanner - correct?
check fuel pressure- post the PSI reading. Then with KOEO observe pressure drop
MIght want to do a compression test esp #6 and adjacent cylinders.
Plugs - use ONLY AC Delco or expect a misfire. how does #6 plug look WET,black, dry, tan?
do you have a vacuum gauge to check for excess exhaust back pressure?


Add a can/bottle of 'seafoam' or 'techron' fuel system cleaner


Discretesignals
Ultimate Carjunky / Moderator
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Jun 6, 2016, 3:54 PM

Post #3 of 11 (1121 views)
Re: 2004 Tahoe Help!! Sign In

Why would you buy a truck with that kind of mileage that has a bunch of misfire issues? I say do a compression test first to be sure you don't have any mechanical issues.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jun 6, 2016, 3:55 PM)


Dwebb76
Novice

Jun 6, 2016, 4:11 PM

Post #4 of 11 (1116 views)
Re: 2004 Tahoe Help!! Sign In

Codes are po301 & po600


Dwebb76
Novice

Jun 6, 2016, 4:14 PM

Post #5 of 11 (1113 views)
Re: 2004 Tahoe Help!! Sign In

Did not have misfire issues when bought. Did a tune up & issues came up. Originally thought it needed a transmission, but it was just a filter/fluid issue.


Discretesignals
Ultimate Carjunky / Moderator
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Jun 6, 2016, 4:18 PM

Post #6 of 11 (1109 views)
Re: 2004 Tahoe Help!! Sign In

You sure that is a P0600? You should still perform a compression test just to see what kind of shape the engine is in.

Does the engine feel like it is bogging out when it won't go over 30 or is the engine revving up, but the transmission isn't shifting to the next gear? What was wrong with the transmission that the fluid/filter change corrected?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jun 6, 2016, 4:22 PM)


Dwebb76
Novice

Jun 6, 2016, 4:22 PM

Post #7 of 11 (1104 views)
Re: 2004 Tahoe Help!! Sign In

Yes, positive. I bought cheap plugs...will redo those. And compression test next. What should compression be at?


kev2
Veteran
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Jun 6, 2016, 4:23 PM

Post #8 of 11 (1103 views)
Re: 2004 Tahoe Help!! Sign In

no issue before your 'tune up" so recheck your work...
Are you sure of P0600 ?
those codes do not indicate cylinder #6 -
P0301 is cylinder #1
P0600? IDK confirm


Dwebb76
Novice

Jun 6, 2016, 4:26 PM

Post #9 of 11 (1103 views)
Re: 2004 Tahoe Help!! Sign In

Yes it is bogging badly. No engine rev or shifting issues. That's what previous owner thought was issue, decided to check filter and fluid before changing transmission out. All service records came with vehicle, I am 3rd owner.


Dwebb76
Novice

Jun 6, 2016, 4:31 PM

Post #10 of 11 (1098 views)
Re: 2004 Tahoe Help!! Sign In

Will check again, and change plugs. And let you know. Just racking my brain trying to get it running right. Thanks for the help, I'll get back to you when I get those things checked out.


Discretesignals
Ultimate Carjunky / Moderator
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Jun 6, 2016, 4:36 PM

Post #11 of 11 (1096 views)
Re: 2004 Tahoe Help!! Sign In


Quote
The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi).


There really is no specification for a pressure reading. The main thing is that cylinder pressures are consistent. Be sure your battery is fully charged and the throttle is wide open when you do your test. You will need to disable spark and fuel. Probably easiest way is to bypass the starter relay by jumping 87 to 30 in the relay cavity with the ignition off.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jun 6, 2016, 4:37 PM)






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