I own a 2000 chevy 1500 Z71 with 105,000 miles. I service this truck like the NASA people do the shuttles. For the last 4 months, the check engine light comes on when traveling long distances (300 miles) at high speed (70mph).
My mechanic checked out the problem initially by telling me that it could be a fuel pump. His computer read the codes and that a few of my cylinders are misfiring...ie one misfired 55,000 times, another 30,000 times and another 5000 times. I've held off replacing the fuel pump due to the high cost with the idea that it may not be the problem at all. He resets it every time and when driving locally it does not come on at all for up to one month. Then when I take another long trip it comes on after about 100 miles. Now with the light off, the engine starts but stalls and it is getting worse where I cannot drive it without going through this every time. Seems that once the engine is warmed up it will stay running but the tachometer goes up and down at idle while at a traffic light. I may get it started again but as soon as I put it in drive it stalls or nearly stalls. Any ideas?

 

welcome to the forum. The random misfire code doesn't really help without the saved freeze frame data. Now that the problem is less intermittent, the mechanic should be able to hang a scan tool and monitor what's going on while in the problem state. If he gives you some vague "could be a fuel pump" diagnostic again, you'll probably want to find a new shop.

 

I forgot to mention: My mechanic told me that even if the check engine light goes off, the codes should still be there when he hooks up his computer. He questions the worthiness of the truck computer that it could be the culprit. What do you think in conjunction with what I initially stated? Thanks

 

He's expecting to see DTC records in the PCM history store but not seeing one? So, the PCM "could be the culprit," is that it? Is he giving you "let's throw a new PCM in and see if it fixes it" kind of diagnostic? Since we aren't talking small change in neither the fuel pump nor PCM, I think you should get a second opinion.

 

What is up with all the could be s? The likely hood of a failed computer is ALMOST none. If the fuel pump was bad the problem would be almost constant. Is your engine a 5.7 or 5.3? How about tune up parts? Plugs, wires, dis cap and rotor (if applicable) fuel filter etc.... If it is a 5.7 could be a problem with the fuel injection (very common failure). Seems like a such a far jump for an easy problem. Take it to someone else he does not have a clue.

 

Thank all of you for the help. Truck is acting real crazy still and wondering what my next move will be.

 

So the check engine light only came on after traveling for longer distances and at cruising speeds meaning the engine was at operating temperature and in closed loop. Now the light is off, but the engine is running rough until the engine is warmed up again. That along with the misfire codes makes me think it is EGR related. The valve may just be stuck open and not closing when it should.

The guy you took it to wasn't able to pull up an stored codes? What were the code numbers?