Loss of midrange in TT

[malc350]

In the past couple of days my TT seems to have lost some midrange response (1,000-2500 rpm). I can't think what it can be. I've had a good look for vacuum or exhaust leaks but would have thought I'd hear that sort of problem.

Only seems to be a bit unresponsive at revs mentioned above on a light throttle. If I hit the pedal the car still flies - in fact it just seems quicker lately when I really get on it! (cold winter air maybe?)

Anyone got any ideas? There's no "stuttering" or misfiring or rough running, tickover is perfect. It just feels like it needs more effort to get the part-throttle performance.

Since I've owned the car (I've covered 9,000 miles) it's had: new plugs and plug wires, distributor cap and rotor, fuel filter, air filter cleaned (K&N), occasional fuel system cleaner, ignition timing just checked. Runs on 95 unleaded, no cats.

Thanks in advance.

 

[SurfnSun]

You won't be able to hear a vacuum leak, you'll need to test that with a gauge.

 

[malc350]

Surf, would I have to connect the gauge to the intake manifold somehow? Would I have to test it under load (driving?)

I suspected the fuel pump at first but figure that would affect the car even more when I punch the throttle?

 

[SurfnSun]

yea you can pull the vacuum lines off the rear on the plenum and put the gauge on them. Test both lines.

 

[SurfnSun]

sorry Malc I didnt quite answer your question fully.

You don't need to have the car running to test the vacuum. Just pull each of the vacuum lines from the rear passenger side of the plenum and hook it to the vac pump. Pump it up to about 10lbs and watch for leak down.

 

[malc350]

Cheers Surf

Funny tonight I was talking to a mate who has a ZR1 which is just in the process of being stroked to 368 inches by Geoff Jeal.

He had a vacuum leak on his Z and said it's easy to know if you have a vacuum problem on the King because the vacuum pump runs for ever!

Strangely I went out in my car a couple of nights ago and didn't notice the problem (it was raining though so I took it REAL easy!)

I'm going to change a couple of ignition components as a matter of course (coil, module) and I've had a real close look to see if I can spot anything.

There's a lot of wires and vacuum lines that disappear into the unknown on a B2K...

 

[SurfnSun]

Malc, the ZR1 has a completely different vacuum system than the b2k. I would go ahead and check it anyway. Takes about 5 mins or 15 if you check the microfueler too. Will give piece of mind