Alright here is the deal I have been dealing with this problem, and I need to get it fixed so that I can drive my Z and put my truck in the shop. The car is running waaaay rich like the exhaust fumes are strong and it is smoking like a freight train. The car idles a little rough but not real bad. When you try to drive the car it is really rough running like it is shuddering. I have replaced the EGR valve that was stuck that helped but didn't fix it. I also adjust the IAC, TPS, and clean the throttle body out a little while it was off for the EGR. The TPS might need replacing because the chiltons manual said it should be .525 + or- .075 volts and mine would only go down to .656. The motor is a .030 over L98 with ZZ4 cam other than a little cosmetic work it is stock. If anyone can help me it would be much appreciated.

 

I'd check the fuel system before going any further, including engine off (apply 12v to the ALDL terminal G,) and idle fuel pressure. Injectors would be the next step.

I'm guessing you cleaned the TB first, set IAC second, and TPS last. In order to properly set the TPS, the minimum air rate must be checked before adjusting the the TPS voltage.

For my 88' Z28 the Minimum air rate is 450-500rpm in neutral, or 500-600 in drive using the following prosedure, and the TPS voltage is .54±.04.
NOTE: I always compress the IAC spring before step 1 to insure that it's actually working.

Normal operating idle speed is controlled by the ECM through the Idle Speed Control motor and isn't adjustable. The minimum air rate (I prefer to call this the base idle speed.) is adjusted as follows.

Minimum Air Rate & TPS[list=1][*]Jumper the ALDL terminals A&B, turn ignition on, leave engine off.[*]Wait 45 seconds for IAC to fully extend, with the ignition still on disconnect the IAC connector.[*]Disconnect the distributor set timing connector.[*]Start the engine, and allow engine to achieve "Closed Loop" operation. [*]Remove jumper from ALDL terminals A&B.[*]Adjust idle speed to specifications with the throttle stop screw.[*]Turn ignition off and reconnect IAC connector.[*]Adjust TPS voltage with the ignition "ON" and whatever method you have to read the voltage. Adjust the TPS sensor to correct voltage specification, tighten the screws, and recheck voltage reading to verify voltage reading has changed.[*]Start engine and check for proper idle.[*]Reconnect the distributor set timing connector.[/list=1]

 

Is there a way to test the injectors?

 

and should I replace the TPS since the voltage will not drop below .656 ?

 

Using a noid light will only verify ECM injector signal not the injector itself.
Testing injector coil resistance 14-16ohms will not insure injector is flowing.

Copied this from one of my other post and editted it.

Stock injectors are designed to give you at least 50,000 miles. If your injectors are stock, and you have more than 50,000 miles on them then you've already gotten your money's worth.

The following isn't the best way to do it, but it won't cost you any thing except your time. If you're experiencing idle hunt, or stalls this would be a good time to clean the plemum and Throttle Body expecially the EGR passages, do the Minimum Air(IAC)/TPS adjustment procedures in that order after cleaning.

I would pull the plenum off, raise the fuel rails up, put a large jar under each pair of injectors (wide enough to center each injector to allow you to see the spray pattern,) and with the coil to distributor spark wire removed (don't disable the Dizzy because the ECM will disable the injector pulse) disconnect one injector of each pair, crank the engine for exactly 30 seconds, and compare the amount of fuel each injector flowed, then do this to the others, and again compare them all. Do this again only to look at the conical spray pattern, and inspect the fuel for contamination (like water, if the fuel is rusty colored, and or has a milky substance air is getting into your gas tank) if there's no abnormal flow patterns, or flowrates then the injectors are OK, be sure to get a second opinion.

 

check the vac hose going to the FPR and make sure there's no gas in it. you might have a hole in the diaphram causeing extra gas to get dumped into the plenum.