75mph shudder whoa wtf?

[Mike1992]

I was cruising up to the dsm meet yesterday, driving normally up and down these huge hills. All off a sudden going up a steep hill at around 75mph in 5th my car starts to shudder and feels like its losing power, so I downshift into forth and its doing the same thing. I get over the top the hill and cruise up another hill and its doing this shiddering again, i get off on the next exit and pull over. My engine seems to be shuddering at idle, i turn it off and look under the hood, hmm nothing abnormal looking, so i fire it up looking over the engine nothing abnormal. WTF I hop back in and the car doesnt does have another incident the whole way for the next 100 miles. Anyone have a clue what this coulda been? Im clueless

It seemed like it started shuddering above 4k and if i let off the gas it would stop shuddering, so im guessing its engine related rather than anything else, but am clueless to why it did this. i've never had a problem with the car before input is needed.

Also note the engine has been running normally after that happened.

 

[luv2rallye]

Perhaps a spark plug temporarily got something clogged between it's electrodes preventing it from firing? Pull the plugs and make sure they're ok.

 

[Mike1992]

The plugs are NGK copper's and only 5,000 miles old. Theyre cheap enough, Ill just go spend $4 to see if that fixes it, thanks for your input.

 

[Ryans99OZ]

this might sound kinda dumb but did u check ur tire pressure?

 

[Mike1992]

Just checked the tire pressure 32 up front and 35 in the rear. Any more idea's?

I never got a check engine light either.

 

[Mike1992]

I think I may have figured it out, the vaccum line coming off the intake manifold and running to the FPR came off. Would you think this would cause the problem?

 

[jott5555]

possiably a vac leak that comes and goes.. ive seen em

 

[Mike1992]

The shudder returned today for about 10 seconds right after I started the car. Weird thing is I had some crazy loud lifter tapping as it shuddered this time, and as soon as the lifter tap stopped the shudder stopped. Im starting to get worried guys

Maybe it wasn't lifter tap after all, maybe something else was tapping anyone got any clues to make it tap and shudder at the same time, maybe timing belt related?