ok I have an 02 5.3l gmc sierra 4x4 Extracab. Starts rough in morning on cold mornings. I am getting codes 171 and 174 also randomm misfire all cylinders and recently but 1 time only a code 420. is it the cats or the leaking manifold, or the o2 sensors or MAF or MAP. I also read about a notice about a loose ground on the back of the intake? any help would be appreciated. I have purchaces MAF cleaner and cleaned the sensor, It was time so I put in new plugs. Where should I go from here. I have a code reader and have cleared them each time but did I read somewhere that I may need to go to a shop and have the comp reset or some such? Thanks in advance.
Country: United StatesMake: GMModel: SierraYear: 2002Engine: 5.3l non flex
New plugs, cleaned Maf, reset codes.
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.
Those codes are almost always set due to a plugged fuel filter or weak fuel pump. When did you change them last?
Hmm I have not. Being that it only happens on cold mornings and I seem to have no lag problems it would suggest to me that it is the filter. What do you think?
The fitler is the best place to start, if the fuel system proves fine then I would look at the intake manifold gaskets.
Yeah i have the ladies going to get me a can of starting fluid as we speak so that was going to be my first choice since its cold and I have not started it this morning . Where do these leaks on the mani usualy occur, or where do you suggest to first try spraying?
THey may be hard to find, but between the ports and the head. It may be that the gasket is old and collapsed and leaking but when hot it seals. THey are hard to find but easy to fix.
Ok I will start there. Saw the price of cats and was waahhhh! So am hoping that its the filter. How long would you say is the r&r of the mani gaskets? I am both self taught and had some schooling. I do 95% of all my own work and am quite proficient?
mani, about an hour.
I doubt cats, if it was you would feel a lack of power when passing and get a flashing check engine light.
ok ! Thanks the girls will be back in acouple hours. If I ned to ask some more questions of you whats the process to get back in touch with you, or will I be rerouted to you since we have spoken before?
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Ok thanks I'll get back to you with what I find. Thanks again!
GM Grand Master Technician 2007. 11 years experience.