2001 Chevy Silverado The one no one can Figure out

if you have the plastic style upper intake, most likely is it a bad gasket. this causes a vaccum leak and causes a misfire. check and see if your fuel trims are low like -17%. if so thats your problem. let me know what you find

i had 'misfire' that wasn't a 'misfire'... it was BAD GAS!!!!!!!!!!! here in florida, i've had more than one tank that was CRAPOLA!!!!!!!!!!!!!!!!! i now use Shell[believe me,i have no connection with them, or any of oil company CROOKS!!!]; and i have had no issue with the 'misfire'.
And, like the other chap said, look for VACUUM leaks EVERYWHERE!!![mine had canister line[plastic] that was cracked

so is your problem fixed?

Not yet been trying to look for a vacuum leak none yet

will check the manifold this week

Check the rubber "elbow" that connects the vacuum line at your fuel pressure regulator. My elbow looked fine, but when I pulled it off and inspected closely (by bending back and forth)there were hairline cracks all over.

Will do that today. Have to wait until Tues to check to fuel trim that's when I can get my hands on a tester.

Ok pulled the boot off and there is a crack in it ill change it out today and see if that fixes it. Watch this post and ill let you know.

Nope no help.

That is frustrating since there is no code that is present to give you and idea where to look. Does the problem present itself whether the engine is cold, hot or both? It would be great to determine if it is fuel or spark (could be fpr, tps, ect or csps).

Cold hot it doesnt mater and only 4 cyl's I'm switching #1 with #3 fuel injectors to see if it follows. I wont have access to a tester until Tues. but I'm thinking the 1st guy might be unto something but I figure I might as well do something until then.

OK I tested it out last night and the misfiring stayed on #1 so the switching of the injectors was no help. Now my short term fuel trim bank #1 is about -3.9 to +3 % bank #2 about the same. Long term stays about 8.6 to 9.4% on bank#1 and 5% on bank #2. As I'm going down the road my misses clime at the same time and then drop to low values at the same time then climb again then drop again all at the same time. could that be a crank sensor?

OK I changed the Crank Sensor and that fixed the problem.

Excellent. I'm glad you found it. Too bad you had to go through all the other stuff first to find it.

Thanks I'm an aircraft mechanic and that is usually how it goes isn't it

check your cad. on your exhaust had a 2001 pontiac was doing same thing at50 mph found cad. was pluged