Since the weather started cooling off this fall I've noticed that when I go up a hill without downshifting, I'm getting a rather loud rattling that I think is a spark knock. At the same time this started it also started stalling when I put it in gear if I don't let it run for a minute or so to warm up. anyone else experience this or have any ideas about what could be causing it?

 

My first thought would be bad gas. But if it's been doing it since fall, then something else. Do you have a tuner in it? Does it give you any codes? I think I would have taken it to the dealer by now, but maybe see what they say?

 

yeah, gas is out. The truck is all stock, no engine light has ever come on, which is why I haven't taken it to the dealer because they'll probably tell me there is nothing they can do if it doesn't have the check engine light on. The only thing I could think that they might do is a reflash???? But I don't know.

 

can they duplicate this during a test drve
Bad knock sensor?

I would get this checked, not good IMHO.

 

Well, just because curiosity was getting the best of me, I put 91 octane without ethanol in and no more problems. Strange that I've been running regular 87 w/10% ethanol since day one with no problems and all of a sudden this. I'll go back to regular after this tank to see what happens. I'll update then.

 

In the past i have seen faulty egr valves on all makes and models cause that type of problem(pinging)if stuck closed.egr lowers combustion chamber temps and computer will probibly only retard the timing so far.If stuck full open at low rpms it acts as vacuum leak and could give a stall problem or high idle.Probibly should set a code though for egr position.If it is intermittent maybe the computer does not see it long enough to set code.Something to think about if you have a scanner and want to check it out yourself