Vehicle is a '98 K2500 with 5.7L (350). I just finished up replacing the
intake manifold gasket. Upon initial startup, I get a loud metalic popping
sound. Almost like something was left in the vicinity of the belt. Not
rythmic, though. It was one of the first things I heard the instant the
engine caught and ran. I shut it down and looked at the belt and pulleys for
any sign of anything caught or somehow in the way. Didn't find or see
anything. Checked over the connections and all seem OK.
Engine is also misfiring and the Service Engine Soon light is on and
constant. I figure that this one is caused by moving the spark plug wires
and getting a misfire from this.
Could the popping sound be the cat trying to burn raw gas from the misfire?
This truck has 2 cats. To me it would seem to need some time for the cat to
heat up before this could happen. The popping sound, more like a banging
sound, starts as soon as the truck is running. I haven't run it for long,
just in case. :-)
Some online sources say a vacuum leak could cause this. Other than the brake
booster line, what other vacuum lines should I look for? I don't remember
unhooking any, but my clumsy fingers and arms seem to find places under the
hood I didn't know existed. :-0 I might have accidentally knocked something
off. I'm going over it with a fine tooth comb to check, but will use any and
all ideas and suggestions.
If you need any more info, please let me know.
Any help you wish to offer is greatly appreciated. Thanks.