2002 400fse will idle but won't rev!

[Jake_mci]

Hey all, I have a 2002 400 fse, it's a little bit slow to start, and once it does start it will idle but not continuously, will stall after 5 or 10 seconds, and if you try and rev it at all while its idling the engine stalls straight away every time!!! Any help or ideas would be great!!! Cheers!!

 

[fastisbetter]

hows the spark plug look? black, white, tan? Maybe a little history, when were the valve clearances checked? did this happen all of a sudden or get worse after a while