Loud chirping/whistle under throttle. 92 Rocky

[einTier]

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!

[jav]

checked your fan belts ?

[BundyRumandCoke]

Is this a 1600cc, US Rocky/Feroza? If so, then pull the heat shield off the exhaust manifold, and look for a crack. Well known to produce a whistle under acceleration. Usual remedy is to replace with a set of extractors.

[HeathGQ]

Is this a 1600cc, US Rocky/Feroza? If so, then pull the heat shield off the exhaust manifold, and look for a crack. Well known to produce a whistle under acceleration. Usual remedy is to replace with a set of extractors.

BINGO!!!!!

[SimplyPV]

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!

bingo was the name of a dog... theres no mention of dog here....


exhaust doesnt seem to be the problem. i would suggest checking all your belts like jav suggested. make sure they are not worn/cracked/loose/over tightened. also check your pullies to ensure they are not loose and wobbling on the bearings.

[lay80n]

Is this a 1600cc, US Rocky/Feroza? If so, then pull the heat shield off the exhaust manifold, and look for a crack. Well known to produce a whistle under acceleration. Usual remedy is to replace with a set of extractors.

BINGO!!!!!

Bingo again. 2nd this idea.

Layto....

[BundyRumandCoke]

Yep, I will admit, I didnt bother to read the entire first post. Perhaps my answer is not the answer, but its worth checking that the custom manifold doesnt have a problem, or maybe a leak at the gasket area.

[einTier]

Found the problem. But I can't find the part.

Looking at page 93 in the EFI system shop manual PDF (from warfs.org), I see that I did indeed replace the fuel pump, but not the check valve/silencer assembly on the front. That is what is making the godawful racket.

One problem. Where to find this part?

[SimplyPV]

salvage? something like that likely isnt made OEM...

man thats a tough one! im not finding anything on the parts directory. ive looked at the daihatsu macrocat..... no go. murcod? do you have any ideas as to what the tech. name is for this part?



maybe you could try a salvage yard that has a rocky and see if you can pull one out? then possibily take it in to a parts store and see if theres anything similar. with luck, you might be able to find a toyota part that is close enough'll to where it'll work.

[tufferoza]

my feroza had a horrid whistle, wasnt the manifold at all. was a colapsed baffle in the muffler. new muffler, not annoying whistle.