Have a 2006 GMC envoy Denali with 130000 miles that is occasionally blowing out a cloud on smoke while driving down the road. My mechanic told me I would need to replace the pcv valve and said I could continue to drive for a little while without doing harm. The last time I drove it, it started running extremely rough and tried to cut off on me. So I carried to my mechanic and he replaced the pcv valve and also said there was a build up of oil under the intake manifold or cover?? from over-pressure from pcv?? and had to take it off and clean out. Well I got it back yesterday and drove for about 15 minutes and saw a cloud of smoke come out the back end again. This is about the 5th time my mechanic has had my truck to work on it in the past 6 months. We have replaced at least 2 spark plugs that were cracked and I am not even sure what else has been done to it recently. It seems I get it back and within a month it is running rough/skipping again or losing power and engine lights come on. I also notice occasionally that there is a slight surge in power as I'm driving. Please offer advise on these truck problems.
What is the fault code you receive when the engine light comes on?
If you do not know try to retreive the engine trouble codes and post them here.
SOURCE: 2005 SIERRA 1500 CHECK ENGINE LIGHT ON (STEADY)
Sound like it could be the purge valve, it is located between the cab and the box on the drivers side, it has a plug and a hose going to it. It has a small foam filter in it which must be removed, cleaned, dried and then reinstalled.
It happened to me.
I don't remember if I had to remove the neg. post off the battery for a minute or so to reset the fault code.
SOURCE: 2006 Envoy fuel sensor failure
the sending unit for the gas gauge is in the fuel tank and part of the fule pump module, it is not sold seperately. price around $350.00, 2 hours labor to install the part. see photo
SOURCE: low oil pressure 93 GMC P/U w/350 motor w/205,000 miles gauge
While engine is running, open the cover where you add oil to engine and see if you see a good flow of oil, if good flow, could be as easy as replacing oil sending sensor. got to realize that if poor maintenance history your engine may not be building enough pressure at iddle to move your hydraulic operated valves, only when you rev it up it will pump enough to run smooth. if running engine too long, you may cause more damage to other engine components such as crankshaft and cam shaft bearings. if you can spare a few bucks, have a good mechanic check your oil pressure with a mechanical gauge. another cheap option is to replace oil pump. last resort if you love your truck as much as we do,replace engine or rebuild it. At 205,000 this is a normal symptom, other than timing chain problems, most engines don't make it that far. hope this helps!
SOURCE: 95 GMC Sierra 4x4 350 5.7 rough idle problem
It sounds like a MAP sensor going bad. MAP is short for manifold absolute pressure sensor, it senses the manifold pressure and applies the right amount of gas with the right amount of ignition timing so the car runs and performs well if this does not work properly. It throws off the whole loop cycle for the computer, which in turn makes it run badly and get poor fuel economy. It can causes the engine to have a lack of power, combined with a loss of fuel economy. Poor take offs and sometimes an occasional stalling may occur if the MAP sensor is faulty and sending the wrong signals to the ECM.
Hope this helps and thank you for using Fixya.
Here is a link that my help you in the future.
http://www.troublecodes.net/GM/
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