Chevy truck diagnose ...

hunterdan

hunterdan

Well-Known Member
Joined
Apr 13, 2009
Location
Morganton,NC
I have a 2003 chevy 1500 4x4 with the 4.8. It is running rough and throwing multiple codes. Codes are for
multiple missfires
lean on bank 1 and 2 of cat
mass air flow

Any idea as to what could cause all this?

Had a local shop pull the codes and he basically threw out the mass air flow sensor as the culprit. He tapped it with a wrench and nothing changed with idle so he claimed it was probably not the problem...I dunno

Idles real rough when cold and gets better when warm but still has issues at stop lights with bucking and jumping. Seems to idle to low...almost to the point of shutting off. On hwy it runs normally with less pwr through all ranges.

Thanks
 
I have a 01 6 liter that does the same. The colder it is the worse it is. Have to use throttle to keep it running during warm up in sub freezing weather. Diagnosis was bad intake gasket per GM service bulletin. Runs fine when fine when warm so I’ll keep driving like is for a while. I’ll stay tuned to see how you resolve your problem !
 
Depending on the particular mass air code, it may be the mass air sensor though.. I have seen dirty airflow sensors cause that.. usually after a k&n over oiled filter.
 
My 03 Denali 6.0 is doing similar things. Randomly throwing those codes, among others. I know I need to do the manifold gaskets, probably needed them for years, but it's not eating that much coolant. Never thought the faults could be related to that! I thought it was probably funk in the bulkhead connector, and cleaning it would probably help.
 
Clean the idle air control motor and put new intake gaskets on it. It's running lean enough to cause a misfire and it can see that it's sucking air in after the MAF and throwing a code for that too. There's a nice set of metal framed intake gaskets that will last wayyy longer than the standard plastic framed ones.

LS intakes don't have coolant running through them...just a small tube through the throttle body.

You'r talking less than 100 bucks and a few hours for the job if you do it yourself. Just do it.
 
Croatan_Kid said:
Clean the idle air control motor and put new intake gaskets on it. It's running lean enough to cause a misfire and it can see that it's sucking air in after the MAF and throwing a code for that too. There's a nice set of metal framed intake gaskets that will last wayyy longer than the standard plastic framed ones.

LS intakes don't have coolant running through them...just a small tube through the throttle body.

You'r talking less than 100 bucks and a few hours for the job if you do it yourself. Just do it.
Click to expand...

This!!
I have fixed a bunch of these just like he said.
 
Thanks for all the responses. The reason I'm thinking it is something else is because I have sprayed carb cleaner around entire intake and top of engine with no change. I've done it when cold and idling erratically and when it's hot. I or the mechanic can't find any leaks.

Someone suggested a fuel pump could be going bad which could cause all the same symptoms ...Is that a possibility? Anybody know what the dealer would charge to diagnose it? I just hate to throw parts and guesses at it. Other than the local dealer no garages around here are great at diagnosing.
 
It's intake gaskets. My sisters Tahoe just had the same exact codes. New intake gaskets fixed it. It doesn't take much of a leak to make it throw the codes. My Tahoe is doing the same thing. Just haven't had the time to do mine yet. Its not a bad job to do at all. I would recommend putting a new oil PSi sending unit on while you have the intake off.
 
If you think it's the fuel pump, hit the Schrader valve and see if you have fuel pressure at the fuel rails.
 
moldman05 said:
I have a 01 6 liter that does the same. The colder it is the worse it is. Have to use throttle to keep it running during warm up in sub freezing weather. Diagnosis was bad intake gasket per GM service bulletin. Runs fine when fine when warm so I’ll keep driving like is for a while. I’ll stay tuned to see how you resolve your problem !
Click to expand...

Id advise fixing this sooner than later, you're setting yourself up for either sucking a or cracking a valve, that make the intake gasket job REALLY cheap in comparison
 
Easy enough to check fuel pressure. Put a gauge on it. My vote is on intake gaskets. Another possibility is dirty injectors. Most likely it's the intake gaskets.
 
First cold start up since changing intake gaskets on 6.0 Suburban. It idles smooth as silk now. Thanks for the advice
 
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