So I finally got the Z running again after letting it sit all winter with the motor pulled.

This was happening before I pulled the motor last fall.

At any steady speed between 1-70 mph I get a hesitation. Kind of feels like the engine can't decide if the throttle is open or closed. On my boost gauge it is usually between 15-20 vacuum when this problem is occurring. I can give a little throttle and slowly accelerate and it quits acting up. Also if I get up to 80 mph and cruise there it does not occur and the vacuum is sitting at 10.

I have checked all the vacuum lines and there are no leaks and they are all ran right.

Everything I have replaced in the past year/5k miles:

Oil/filter
Fuel filter
Fuel injectors (from old style to new)
Spark plugs w/ correct plugs
Motor mounts
Turbo's
ECU chip
Dual intake set up
PTU (from old style to new)
Exhaust

Car runs great at idle and acceleration. Just not at a steady cruising speed.

This is an N/A to TT swap vehicle btw.

As I write this I'm starting to suspect the TPS. If anyone has any ideas or leads it would be greatly appreciated.

 

Is it idling well? I have a similar problem but my idle's all over the place so I feel like when I finally get looking into it I'll find the issue(s).

 

Idles and accelerates perfect. Just stumbles around at cruising speed.

Feels like I let off the gas and hit it again real fast repeatedly.

 

You might want to Deoxit all you connector, make sure everything is good and clean. Also doing a star ground setup on your car could very well fix your problem. An intermittent connection or poor ground van cause all kinds of problems. here's a quote from fricfrac on how to do a star ground,

The ECU and the sensors, however, are their own single system so you should go from the battery to the ECU then from the same point at the ECU to the plenum where most of the sensors are. That will prevent ground loops.

There's other posts in the forums and pics too, but you are basically eliminating the use of the body and frame as a ground, steel is far inferior conducting electricity, factor in corrosion and it starts to fail.

 

That kind of doesn't make much sense considering there are 4 grounds on the plenum already plus the body ground.

 

So today it started having an idling issue. Staying anywhere from 1500-2000 rpm. Also noticed bluish black smoke coming from the passenger side exhaust. Funny thing is if I unhook one of the vacuum lines from the fuel purge canister it will idle down and quit smoking. Any ideas?