So just had my truck in the shop last week and the mechanic told me the plenum was still good with 130k miles... I do however have a Hughes fix kit in the mail now.

So I am driving over the mountain pass near me yesterday and I noticed the truck was lacking a bit more power than usual. When the trans downshifts (after a switch back starting to climb) the motor hits 3000rpm under load (sounds like its working harder than normal) I get a loud almost squealing noise.

Now I know pinging has been discribed as dropping a can a marbles into the tub or something similar, but can it resemble a squealing brake pad or belt? Sounds like its coming directly from under the hood. My belt is good and my brakes are new.

I should add that once I got down from the pass (11,000ft or so) to the freeway (7-8000 ft) my power had returned and i could not replicate the incident even at 3-4500 rpm. Ohh and upon start up i get a rough idle for about 10 seconds then smooths out. Cat is new, o2's are new

 

So, how was your mechanic able to determine that your plenum gasket was still good ?. With 130k miles on the engine I highly doubt that it is. I see you have a Hughes plenum kit ordered, I would also suggest that you replace the timing chain at the same time. The stock timing chain is junk and known to stretch and wear out. A good double roller timing chain is recommended.


At a 11000 feet the air is pretty thin so you will lose some power at that altitude, but get it back when you drop back down to a lower altitude.

 

Did he take off the throttle body to check for pooling oil in back of intake?
Checking for vacuum in the crankcase will only reveal a major gasket failure. Mine passed the vacuum test but started using more oil at around 87,000 miles. The plenum gasket was intact but very brittle and oil was still pooled in the back my intake, so it was getting past the gasket somehow. Don't know what the squealing could have been about on your truck. Maybe it didn't like descending to fast. A loud whistling can be from leaking front crank seal.

 

That is definitely not ping. You have a bearing or belt going bad.

 

Had a mechanic put the cat on because i didn't have a tool to cut my rusted bolts at the flange, I asked him to also check the plenum gasket. He said that because the engine runs fine and he didn't see any pooling only oil that he says came from the PCV valve that it's good. I ordered the hughes kit because the milage on the truck is arguable due to a broken guage cluster over several months, But Guessing between 120-130k. From what i read here it will need done soon, parts were only $120 so atleast i have it when its in need.

Belt looks in good shape, It did cross my mind that a bearing could be going out....

 

i have 225k miles on my truck plenum gasket was never changed and is still good this truck was my dads i just got it off him. not the one in my sig

 

Could pull the belt and spin/check all the pulleys for play or roughness.

 

Could you be hearing a high pitched whistle like noise? I haven't yet found a vacuum leak but have noticed that if I floor it I'll hear a high pitched whistle until I let off the accelerator a little...

 

it is a high pitch kinda wistle nosie but it has a high and a low point in the tone so thats why i thought maybe ping.

So while spining the bearings it should be consistant and smooth? I'll check when i get the truck back home tomorrow