Loud chirping/whistle under throttle. 92 Rocky
Posted: Fri Jun 16, 2006 11:02 am
I've got a weird problem that I'm hoping someone can help me chase down.
I've got a really high pitched very fast chirp/whistle noise under throttle. This is independent of vehicle speed but is dependent on load and throttle. It sounds a lot like a tin can full of angry crickets or a six year old girl screeming, "EEEEEEEEEEEEEEEEEEEEEEEE".
Anyway. The noise is absent if I am not on the throttle. It doesn't matter if I'm coasting five kph in a parking lot or 100 down the freeway. It does not matter if the clutch is in or out, four wheel driven engaged or not, which means I can at least isolate the entire drivetrain.
Now, if I engage the throttle, it happens about halfway through the pedal travel. The harder I press, the louder it gets, the higher the pitch goes, and the "faster" it seems to sound. If I'm under load, it will be louder than normal and happen earlier in the throttle. If I'm going up a steep hill, I can usually make it happen with even light throttle application.
The odd thing is, it isn't consistent. Some days it's annoyingly loud, other days it's nearly quiet. I can't seem to figure out a patter, but it almost always seems to do it after sitting overnight.
I tried replacing the fuel pump and fuel filter, as I once had a fuel pump that was going bad sound like this. Well, that wasn't it. I know about the manifold cracking problem, and this doesn't seem to be the problem -- someone custom fabbed a new manifold and exhaust a while back and it seems solid. I just don't know where to go from here, and I'm hoping someone can shed some light on it.
Other than that, I love this truck!
I've got a really high pitched very fast chirp/whistle noise under throttle. This is independent of vehicle speed but is dependent on load and throttle. It sounds a lot like a tin can full of angry crickets or a six year old girl screeming, "EEEEEEEEEEEEEEEEEEEEEEEE".
Anyway. The noise is absent if I am not on the throttle. It doesn't matter if I'm coasting five kph in a parking lot or 100 down the freeway. It does not matter if the clutch is in or out, four wheel driven engaged or not, which means I can at least isolate the entire drivetrain.
Now, if I engage the throttle, it happens about halfway through the pedal travel. The harder I press, the louder it gets, the higher the pitch goes, and the "faster" it seems to sound. If I'm under load, it will be louder than normal and happen earlier in the throttle. If I'm going up a steep hill, I can usually make it happen with even light throttle application.
The odd thing is, it isn't consistent. Some days it's annoyingly loud, other days it's nearly quiet. I can't seem to figure out a patter, but it almost always seems to do it after sitting overnight.
I tried replacing the fuel pump and fuel filter, as I once had a fuel pump that was going bad sound like this. Well, that wasn't it. I know about the manifold cracking problem, and this doesn't seem to be the problem -- someone custom fabbed a new manifold and exhaust a while back and it seems solid. I just don't know where to go from here, and I'm hoping someone can shed some light on it.
Other than that, I love this truck!
