JoeHeff

Without fail, within 20 seconds or so of engine start, you can hear a popping sound coming from somewhere in the engine bay. It is a loud, short pop, like the sound you would hear if a significant electrical arc blew a relay or large fuse. The tricky thing is, it only happens once each time the truck is started, and if I shut the engine off and wait at least a few minutes and start it back up, it does it again without fail! I am not sure how long this has been happening, I only noticed it because I had the truck in my friend's garage, which amplified the sound (plus he was standing in front of the truck and heard it). We noticed it just before doing a plug/wire/coil change. Before today's ignition tuneup, it was displaying typical ignition system-related symptoms... occasional missing and what not. Now, all those symptoms are gone, the truck runs smooth again! But I can't figure out what this popping noise is.

Other than the fact that it sounds like some sort of electrical related pop, nothing else points to electrical... If it was a relay or fuse, I would think it would just pop once and whatever sub system is involved would symply not work until the relay/fuse was replaced. Or, if it is an electrical problem such as arcing without blowing a relay/fuse, I would expect the noise to continue as the truck runs.

I am thinking some accessory that only operates during/shortly after a cold start? This truck is new to me, so I'm not very familiar with it. Is there something like a secondary air injection pump or something similar that only operates when the engine is first fired up? Any help would be appreciated.

w0lvez

Try disconnecting the Tube from the intake going to the Driver Side Valve Cover. Temporary install a plug or plastic to prevent vacuum leak before starting e engine. You can also try compress air or blow the tube going to the valve cover.