I get a lot of black smoke when I try to pass or take off fast from a stop. its so bad that at night when I take of hard when someone is behind me the smoke blocks out their lights.
is this because it runs rich (btw '94 Z)?
and I'm certain the cats are shot so would removing them show any gain to anythng?

 

Sounds like its running EXTREMELY rich in power enrichement (PE) mode. At least if its black smoke. If its actually blue smoke, then it may be a serious oil problem. Do you have any scan software that would allow you to data log the PCM while this is happening?

 

well it holds oil well it was my wife's car she gave it to me. she told me its had this problem for a while. the has been rebuilt withing the last 80k she tells me.
and I have nothing comeputer-wise for it. haven't the money for such equip. is there any remedy it could try.
btw I decided to clean the TB earlier and notice everything is black from the air cleaner to inside the intake as far as I could see. could this be a result of the extremely rich condition?

 

No. The crankcase evacuation system pulls oil mist/droplets into the throttle body and it bakes on the interior of the intake. Unfortunately this is completely normal.

Is it any better (less black smoke) when you first start it versus a minute or more after it's been started?

Pull the vacuum line off of the Fuel Pressure regulator and see if any fuel/gasoline is present. (This is to check if the diaphram in the FPR is ruptured)

 

when its sitting idle after I start it, the smoke isn't too noticable. and it tends to idle high (1200 rpm) for a few minutes ( say 7) then drop down to about 700rpm. its mostly noticable when I try to take off slightly hard nothing to much. But the amount increases with more throttle. it stops after it shifts and drops engine speed to about 1800. when its cruising its not too bad. just when I trying to tap into the power I know it has.
Is there anything I can do to test and possibly find/fix the problem? I don't have to money to buy any logging software right now though.
I'm not to familar with my Z yet so where is the vac. hose for the FPR located?

 

If you're standing if front of the car, the vacuum source is about 2/3 of the way to the back of the intake manifold on the side. There are two vacuum nipples there. One is providing vacuum to the Fuel Pressure regulator, the other feeds a vacuum source to the Heater/Air conditioning controls to control opening/closing of the 'blend' doors within the Air Boxes. The other end of the vacuum tube is on the FPR that is behind the intake on the right hand side. THe 2 fuel lines that emanate out of the drivers side fender go to two tubes on the Fuel rails. One of those is going directly to the FPR.

Here's a great picture from Shoebox's site. There is a ton of great info on Shoebox's site for a variety of questions.
http://shbox.com/1/fp_reg.jpg

 

there is no fuel in the FPR vac line.
thnx for the explaination. found it immediatly.
so if its not the fpr what else could it be?

 

It could be a dirty injector or injectors but I'm still suspecting the FPR since it's the modulation of throttle that introduces the Black smoke which is obviously too much gas.
It 'could' be that your O2 sensors are reading falsely and making the PCM think you're running Lean when you're really not. So if the O2's are lying and saying it's lean, the PCM starts pushing the BL (Block Learns) to 160(the maximum value the PCM allows) so it's adding a ton of fuel. Now this is at steady/moderate throttle. Once you press the gas pedal to a certain degree, the PCM goes into PE mode (power enrichment) for acceleration and adds even more fuel above the already rich (if this is the problem anyway).
To test this, disconnect the MAF connector. This will keep the PCM from going into closed loop. You will get an SES/Check Engine light but that will be related to the disconnected MAF. Afterwards, drive it around a little bit and see if the Black Smoke is still present. If it is, go ahead and reconnect the MAF sensor. Speaking of MAF, Have you ported it? (don't). Have you cleaned it with the spray MAF cleaner?(do). If the black smoke isn't present, then it's probably the O2 sensors.

If the cats weren't clogged before, they probably are by now with all that fuel. I would gut them(drill hole, plunge a screwdriver in it and rotate (rotate over and over) until the 'brick' is broken up, then insert a large enough sheet metal screw to cover the hole)

 

ok I juat took it for a spin with the MAF disconneted i first pushed it, I saw some black smoke. but It felt like I had more power than before. I'm still getting black smoke. but it doesn't seem to be AS much. and I managed to turn the tires for the first time on dry cement since I got the car.
so now what? lol
if it is the O2 sensors what's would the price be on those?
but are there any other little tricks I could try?
and does it hurt to leave the MAF disconnected for a while?

 

These cars have several redundancies built into their PCMs so that if one method of fueling the car fails due to one sensor, it can run off a default. You can disconnect the MAF, it will run Open loop. You can disconnect the O2 sensors, it will run in Open Loop. You can disconnect both and it will still run in Open Loop.
O2 sensors are available for as little as $3x.xx each but you have to look around. Autozone has them as do most of the other franchise parts stores.
I wish there were some way you could try a new FPR w/o having to buy it, just so you could eliminate that possibility. It's just that, in the absence of an SES (when the MAF is connected) I sure have a tendency to think it's something the PCM can't report which would be something like a mechanical failure of the FPR. I just bought one for my car last month at O'Reillys.
http://www.oreillyauto.com/EW3/Displ...ycleCount=1003

 

I could just buy it and if it doesn't solve it I could take it back...
but right now I just moved into a new place and am really strecthed for cash so it may be a while.
about how much do you think it running rich like this lowers my mpg?

 

I would more worry about the damage to the rings since the extra gas washes away some of the thin oil film the rings normally slide against. Commonly called "washing out the rings". If you must/have to drive it, I would try to stay out of the 'black cloud' mode as much as possible till you get whatever is going on resolved.

 

ok I can do that.
thanks for the help.
I'm going to have it plugged into a computer. so I can cross out everything else before I replace the FPR.

 

What was the problem? i was just going thru old stuff and was intrested.

 

I had a similar problem until I had the intake manifold gasket replaced.(Check your #8 spark plug and if it looks all gunked up,that could be the problem( hope this helps.)