Hey guys, I just replaced the valve cover gaskets, coil packs, spark plugs + wires. Now I hear this sound at very low RPMs and especially loud when I blip the throttle. Seems to get louder near the exhaust manifold/SAI plumbing. I did have to loosen the SAI nuts and bend the pipes down to get to the valve cover - but im 99% sure I did not crack the tube. Anyone heard something similar on their truck and already diagnosed it?



https://www.youtube.com/watch?v=9yJEuSCPNko

 

That sounds like a knock or a bad tick
hope it’s not

what coolant temps are you running at

 

Temps are fine, 194 max idling in the garage and revving the engine.

 

Sounds like an exhaust leak to me. Stick a leaf blower or similar in the tailpipe and spray soapy water around the manifold. I’ve had leaks at the manifold/head and the y-pipe gaskets in the past.

 

i have a very similar sound after doing the head gaskets on mine. i never heard the engine run before i did them so i don't know if the noise developed then, but i'm pretty sure that it's not a knock or a tick.
the noise was initially there only once the engine was warm, but it has been getting worse to the point where now i can hear it when the engine starts, rather than only after it has run for a while. it's more evident under load and when revving the engine.
i've never had an sai engine before so i don't know many details about that system, but the noise seems to come from the little cannister things on the sai pipes on both sides.
i initially thought it was an exhaust leak. i've re-torqued the manifold bolts but that didn't help. i also considered head gasket leak but there don't appear to be any issues with the engine running.

 

What I'll try today after work is tightening up any SAI connections (including the can on top). Maybe disconnecting the SAI pump, evap purge can, etc. And testing. I'll report back any findings.

 

Are you talking about a low frequency burble noise or the clicking noise? Exhaust leaks will be more evident when the engine is cool if they are small. Vacuum leak can sound like a tick at all temps and sound stronger under load. Make sure all the vacuum lines in the SAI system and cruise control are good. Low frequency noise can happen when the solenoid that controls the SAI valves sticks causing exhaust to flow back through the SAI system. The fix for that is a new solenoid, cheap. Hope this helps, good luck!

 

It's the *tack tack tack* sound when I blip the throttle. It sounds like someone is slapping their finger on a sheet of 8.5x11 paper, increases frequency with RPM. I'll definitely look into those SAI recommendations though - thanks!! I'm thinking about just unplugging power to the system and seeing what behavior changes.

 

That sounds like a vacuum leak to me, check around the ends of all the SAI hoses/plastic nipples, and at the hose barb on the throttle body, passenger side, the one toward the firewall. I had the vacuum leak at the throttle body where the plastic barb was loose in its threaded hole. Tighten that too much and it will break. Can be solved with Best4x4's PCV mod. Also had a split end on the vacuum line going into the cruise control diaphragm once, similar noise.

 

Fixed it... my own stupid fault (as per usual). Didn't tighten up the SAI bolt to the head enough. It was leaking air through the threads I am sure...

Here's a video for comparison:

Thanks for all the help guys!