Help with a 2003 GM

[Mike]

My brother has a 2003 GM with 153k miles and he says that he feels a hesitation at light acceleration when starting from a complete stop. He says he also feels the same hesitation at around 70 MPH. He recently had his plugs (Platinum) changed. I gave him a few ideas as to what might be wrong. He's not a mechanic or anything. He said his mechanic can't do anything till the check engine light comes on. I thought my/his best bet was to ask the experts on MM.net. Any and all ideas would help. Thanks in advance :D

[vtwoodsman]

Contributors: Timing Advance (computer), Fuel Injectors (dirty fuel system), piss poor E10 fuel.

[WI Fordguy]

Did this start right after the plug change?

[Mike]

Contributors: Timing Advance (computer), Fuel Injectors (dirty fuel system), piss poor E10 fuel.

Thanks....I'll let him know to look into this :D


Did this start right after the plug change?

Tried getting a hold of him last night with no luck. Once I do, I'll ask him and post up :D

[mcgyver59]

Have him do a WOT run from 0-90. It will give the pcm enough time to flash the engine light if a coil is bad. <<<<<<< This is an honest test.

[justbob]

My money is on a coil. I've replaced several on CV's & GM's. What years had the notorious intake manifold cracks?

Sent from my Ally using Tapatalk

[justbob]

Have him do a WOT run from 0-90. It will give the pcm enough time to flash the engine light if a coil is bad. <<<<<<< This is an honest test.

^Beat me to it^

Sent from my Ally using Tapatalk

[Jesse]

What years had the notorious intake manifold cracks?

Sent from my Ally using Tapatalk
'03 was supposed to be the year that problem was eliminated. Man I hope so!

[RF Overlord]

My money is on a coil. Agreed.
What years had the notorious intake manifold cracks?I believe the cracked manifold issue was resolved in 2001.

[gdmjoe]

In addition to the possibility of a COP, consider the following ... run some fuel injector cleaner thru a couple tanks of fuel.
Seafoam thru the PCV hose. *In addition to cleaning the cylinder head components, should also help remove any build-up in the throttle body adapter.
check the throttle body plate for carbon build-up.
you mention platinum spark plugs ... Were they double platinum ? *Recommend.The thought behind the above is to start with some low-dollar / easy fixes before throwing parts at it.
.

[TFB]

Clean the MAF, common problem on high mileage 4.6s...

Manifold problem was fixed in '01...

[Mike]

Thanks for all the ideas so far guys :beer: Still haven't gotten a hold of him but I'll pass all the suggestions on to him and let you know. COP's were my first thought as well. And thought of the MAF cleaning as well.

[Mike]

Did this start right after the plug change?

Problem started after the plugs were changed. His mechanic said if computer says it's running rich in reality it's running lean and visa verse not sure how true that is??????:confused:

[TFB]

Problem started after the plugs were changed. His mechanic said if computer says it's running rich in reality it's running lean and visa verse not sure how true that is??????:confused:

Clean the MAF, when dirty the PCM see the info as too rich and leans out the A/F ratio...

[Chevyguy]

Agreed.I believe the cracked manifold issue was resolved in 2001.

Late 2001 models got the new manifold. My 2001 Vic was a October 2000 build and had the all Nylon intake (which never failed in 195K miles I have it as a spare still)