3 questions. 1 thread. Boost solenoid. Rattle. Cracking noise


Active Member
Ok. First question. How does the computer control the wastegate solenoid? Does it simply close and allow pressure to build up in the wastegate until boost reaches the point you set with the actuator, and then open to bleed off pressure at lower boost? Or does it cycle in pulses. Question basically is, does it simply crack open and close, or does it pulse to give better control of the boost curve?
I used to have this slight rattling sound coming from my engine when it warmed up. Never could track it down. Totally sounds like a piece of tin rattling against something in pulses about 2 seconds long, but pretty erratic. Imagine if the torque converter cover was loose and rattling around pretty loud, but its not coming from there. Not a valvetrain knock or anything like that. I thought it was a loose heat deflector on a header, or the A/C clutch spring thing rattling around. But lately, this rattle has gotten really bad, and is worst when the engine is cold. When its warmed up, its practically gone. Ive taken a hose and listened all over the engine. Its usually easy to track a noise down and know what it is, especially from a guy working on hot rods for over 20 years who used to be an engine builder, but this one stumps me. It seems like the noise is most pronounced under the intake manifold...but sometimes sounds like the front of the motor. Hard to say with so many noises under the hood, but it definetely seems to be more under the intake than anywhere. What the hell is under the intake that could rattle like this? Maybe there is an oil deflector/pan thing rattling around or something? But why would the noise diminish when it warms up? Not sure what gasket is on there. The intake gaskets look paper thin, so I wouldnt think they used the stock pan. Ever had a noise like this? Is it possible to have a timing chain or chain/tensioner that sounds like this, and the noise is throwing itself to different parts of the motor? The motor allegedly had been rebuilt 4000 miles before I bought it, although it looked pretty crappy for a new motor, so who knows.
Final stupid question. Ive always had this crackling/fast popping sound from under my hood when I go WOT. Ive fixed all the exhaust leaks, and all the vacuum leaks. The tune is good. It sounds like the turbo is cutting the air up and throwing pulses through the intake tube (it sounds like that, even though "cutting it up" sounds ridiculous, I know). The intake tube does make alot of noise, being an aluminum piece. The car pulls hard and is not misfiring from what I can tell. Ive replaced the ignition module and everything you can think of.
Does this sound like a bad timing chain/gear problem? Like maybe my cam timing is really thrown off and the crackling is the combustion popping slightly into the intake? I dont get any intake backfires, even with alky spraying. It doesnt matter what I do to the tune. Its always there when getting deep into the throttle and always has been. The closer I get to WOT, the worse it is Ive pulled my valve covers off and checked play in all my rockers when the valves are closed. Ive cranked it and all the valves are opening. I wonder if I can get a good enough look at the chain by pulling the cam sensor out, and maybe stick a rod in there and check for chain slop.
Thanks in advance.
Well, there is a tensioner on the chain, and pulling the cam sensor out you will only be able to see the top cam gear... so no need to pull the cam sensor.

I chased a rattle for over a year, sounds exactly like a tin can tink tink tink tink, i would rev the motor and the noise would go away, bring it back to idle and tink tink tink friggin drove me nuts.....
If you have a atr downpipe, the one that looks just like a THDP then its the flapper rattling against the exhaust housing. Everything worked fine, just drove me nuts!!!
There is a heat shield next to the starter that could be rattling, that or the heat shield right below the breather on the pass side valve cover.

Well I did have the valve covers off a few weeks ago, and that little piece by the breather wasnt loose. I have a stock DP, but the bushing for the flapper is pretty worn out. But, I have the wastegate arm pulled pretty tight, so I wouldnt think thats it. My rattle goes away when I rev it up also, but the noise seems to totally be coming from under the intake. Wonder if some genius left a wrech under the intake. I actually had a friend who lost a pair of dikes. I pulled his intake off to do a head swap on his chevelle, and lo and behold, there they were with the plastic from the handles melted away. This was the same guy who had a dart thrown at his head by another friend of mine, and it stuck right in his head and was dangling there. He wondered why everyone was laughing, and we told him the dart was stuck in his head. He said "shut up dude. No its not!" He sat there for about 5 minutes before he realized he had a dart sticking in his skull. Not the brightest lamp in the house.
Is there anything under the intake that could rattle around? Doesnt the stock intake gasket use a pan?
So theres a heat shield next to the starter? Ive had that TC cover off several times and never noticed it. Ill have to take a look. But that rattle definetely seems to be coming from right under the plenum lid.
Would a cracked rocker shaft sound like this? I didnt notice this, but maybe they're hard to see sometimes?
Well, i doubt it, but you could try and take the wastegate arm off and see if the noise goes away?
There is a shield above the starter, it has 2 bolts and they go into the block.
Stock gasket does have a valley pan...

as mentioned valley pan on the intake gasket. also could be the cam sensor or the tensioner on the timing chain - do not use a tensioner on the double roller timing set.

let us know if you figure it out