Knocking on start until warmup

[ambrosiaB]

there's a new sound in town. checked the oil and trans fluid.... the knocking starts upon starting the car then goes away within a few minutes. also CEL is on with codes 0304 and 1151 both of these from autozone's read vacuum leak as possibility. you know the list they give you. the third code he read off the top of his head about O2 sensor bank 1. anyway. 0304 is cylinder 4 misfire. I changed the spark plugs about a year ago but not the wires. ANYWAY the question I have is would a misfire be caused (eventually) by a vacuum leak and would the knocking from a misfire be THAT obvious?
btw I have been struggling with P1151 for a couple months but after the mechanic did an OBD II read pointed to the MAF sensor. cleaned it. CEL came back on, replaced with junk yard replacement, CEL came on within a couple hours then cleared for atleast a month. then here we are. here's the major kicker I'm BROKE so I'm just figuring out what I'm going to do when I do have money.

 

[ambrosiaB]

some just had the idea it might be a lifter would the knocking go away if it was?
thanks

 

[imp]

some just had the idea it might be a lifter would the knocking go away if it was?
thanks

A hydraulic valve lifter when not functioning properly emits sharp "clicks". A "knock" is a dull, hollow-sounding thud, like a hammer might produce.

"Knocking" upon start-up is commonly found in well-worn engines, resulting from excessive connecting rod bearing clearance(s). Such a knock goes away as soon as oil pressure rises; if it continues longer than a few seconds, eventually going away, the issue is not ignorable for very long.

The years-old "fix" used to be putting in of heavy weight lubricating oil, to "ease" the knocking. Not a great idea, but likely still being done. imp

 

[ambrosiaB]

hmm. i don't know, I will have to listen again tomorrow morning. I didn't even think about describing it as a "click." either way I am totally screwed. anyway thanks man!

 

[ambrosiaB]

http://http://www.oreillyauto.com/site/c/search/Valve+Lifter!s!Tappet/02325/C0146.oap?year=2000&make=Ford&model=Explorer&vi=5015370 is this what I'm looking at? probably not it doesn't cost enough LOL

 

[acschilling]

My 92 OHV has been doing the same thing diligently for the past couple months.now. No matter the temp outside if the engine is cold it'll knock; even in 80+ degrees. Once warmed up, its smooth. I don't have a CEL on though.