Power delay at 3,900 RPM??

[PikeZ184]

I recently purchased a '93 Manual Trans SHO. The water pump is leaking onto the CPS which I am in the process of replacing. My other problem is that I have a power delay at 3,900 RPM. It pulls good to about 3,800 or 3,900 then there is a small delay and then the power really kicks in at 4,000 RPM.

Has anyone else experienced this? My clutch has a hard pedal, could it be that? It almost feels like it is slipping but at 4K it hits and pulls like it should.

Could it be the CPS not getting a good signal?

The car has 140,000 miles...had the timing belt replaced at 120K and the clutch has not been touched in at least the last 20K.

I am new to the SHO crowd but not new to automotive enthusiast, any help you can provide would be great!

 

[Phoenix]

At 4k rpm , the butterflies opens , the 2nd runners gets a nice boost of air. That's what a variable intake will do. Economy below 4k and power after 4k.

 

[PikeZ184]

Agreed. But why would I have a drop in power right at 3,900 rpm? It pulls fine until that point, it almost sits at that RPM for a few seconds (at WOT) before the butterflies open.

Is there a switch or something that opens the butterflies that could be dirty or seizing a little?

 

[frosho]

They're vacuum operated. Perhaps you have a leak? Though it does sound like they're working right. You can follow the vac lines from the butterflies to the back of the intake to check stuff out if you want.

Mine seems like it has sort of a dead spot for about 1000-1500 rpm before the butterflies open (2.5-3k), so I'm thinking about swapping out the throttle position sensor and/or the mass air sensor to see if that helps any.

 

[itwonder]

The vacuum canister on the back of the intake can develop a hairline crack and leak. Mine did. That affects the butterfly operation. It is also possible somebody switched some of the lines around and the vacuum circuit is not working like it should.

 

[cetroutt]

i too am new and i would check your plug wires and plug wells front and back and see if they're full of oil and make sure that the plug wires are in good shape/getting good connection. i bought a 93 MTX about a month ago and had to do the top 60k on it. it was having problems like your's and after the 60k it cleared up i had about 3 oz of oil in each plug well. also after i finished i thought my clutch was slipping and found out it was the tires. any where above 4000 rpms the tires break loose until i shift. need new tires in the front.

 

[PikeZ184]

Thanks for all of the help guys! I am happy to be a new member of the club.