My boyfriend's 2004 GMC Sierra 2500HD 6.0 litre gas engine truck has been idling really high and when were driving down the road it doesn't seem to have any power, then suddenly the power kicks in and the truck runs kinda normal, we have a bully dog system in the truck and it doesn't say anything is wrong with the truck, and sometimes when we are driving it will quit but will restart immediately, the truck also has a 6 inch suspension lift in it also, can someone help? We have been thinking about maybe replacing the computer but want to know other things to check before we have to spend a fortune on a computer.
Are you saying the check engine light is not on, and there are no trouble codes stored ?
When the check engine light comes on he uses the bully dog system to see what wrongs and it didn't have any codes, and sometimes he does check without the engine light being on to see if there are any codes and there aren't any
there are codes sometimes when the light is on, and when it is always has MAF Sensor code and already replaced MAF Sensor with new part, and sometimes when lights on also 2 System to lean codes and when he clears codes nothing changes, and once in awhile it wont shift into overdrive and he scans it with bullydog scanner and it brings only the MAF Sensor code and when he clears code it instantly shifts into overdrive and also roughly 8 months ago it burned out a new altenator that was less than a year old then replaced with used one from other truck and it worked. For long time now its only running between 12-13 volts charge
I should tell you replacing a component only fixes a problem about 50% of the time. A code is only a guide for the mechanic for what to check. The MAF code could be caused by a wiring problem or something in the fresh air intake. The sensor may be reading correctly but the computer does not like the data. Same thing with the O2 sensors. If another sensor makes the computer lean out the injectors, the O2 sensors will read the mixture is too lean, which it may well be. You usually need the shop manual to get the testing procedures for each code.
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SOURCE: 1996 gmc sierra 4.3l fuel injection
It sounds like a fuel contamination problem or fuel filter/pump problem. Did the problem start after a recent fuel fill, if not, has the fuel filter been changed at any time, if so, check fuel pressure. Pressure should be 30 to 40 pounds.
Let me know.
Regards,
SOURCE: 2004 GMC Sierra High Oil Pressure
if it is electrical oil pressure sensor I would start there. The best way to see if you have a major problem is to use a mechanical oil pressure tester. Take off the oil pressure sensor and put the mechanical tester on. The tester should come with a Gage. If it comes within your trucks oil pressure range than all is fine and replace the sending unit and see if that don't help your problem.If the tester runs high then the oil pump is bad or your cam-bearings could be the problem. But with cam-bearings you would usually get a low reading.
SOURCE: My 1993 chevy 1500 Silverado truck suddenly quits
I put a new fuel pump, fuel filter, and a fuel pump relay and the fuel pump is still not coming on. I am not getting any fuel. Can you please tell me what it might be.
SOURCE: 1991 isuzu pup idle problem
Before you do anything check the coolant level,not just the reservoir but the radiator(check it when the engine is cold!).
SOURCE: When I start my 2000 GMC Sierra the gear shift
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