Hey guys, this is my first post since I just recently purchased a 1990 z32 n/a. I got it for a steal, but I'm working on bringing it back to life and I've got big plans for it (and a decent budget ). My problem is the car starts up and runs, but it is loading up really bad, and when I tap the throttle it barely wants to rev. I changed the battery and added new spark plugs (the last ones were toasted), but I think that it's either something with the fuel or intake systems. If anybody can help me on where to get started I would appreciate it!

 

Sounds like timing. I had an issue like that with my 280...P.o.s Distrubitor...Car would jump timing everytime I got on it, causing the car to stall, and I'd look like a jackass pushing my old car through the nieghborhood.

 

agreed, check timing and injectors.
also pull your plugs if you haven't already.
they might tell you what the car's been thru already.

 

I have a '90 2+2 (N/A - of course). I just went thru the same thing with mine. This is what I would recommend in this order.
1. First, remove the battery terminal for about 10 minutes and then reconnect. This resets the computer (ECU). The computer will then reset itself from the sensors' feedback to compensate for any modifications that were made to the vehicle before you owned it. (Do this after you change anything to ensure that the computer compensates for changes made to the car.)
2. While the car is running, disconnect the single wire that goes to the water temperature sensor that goes to the ECU. There are tweo sensors on the thermostat pipe. The ECU one only has one wire (the other has 2 which goes to your gauge). The RPM of the engine should change, and the condenser fan may come on, so be prepared. Replace if RPM doesn't change (about $21.00). If RPM changes, go to 3.
3. Change the fuel pressure regulator. The fuel pressure regulator drops the pressure down. If its bad, you'll run rich. It was about $40.00. If can measure the fuel pressure downsteam of the regulator, if you have access to the right equipment. I didn't. Replacing fuel pressure regulator doesn't change anything, go to 4.
4. Replace the 02 sensors (about $80.00 ea. and a pain to replace).
I checked my timing, change the plugs, changed the ECU temperature sensor, changed the fuel pressure regulator, and until I changed the O2 sensors, mine still ran rich. Once I finished all of this, I couldn't believe the difference! It was like getting a whole new car!
I started off with the least expensive items and easiest to change first. In my case, I believe that it was the O2 sensors all along, but I never truely know now!
Good Luck! Been there - Done that!

 

^^^ 2nd ^^^ I would also add to check for vaccum leaks which will cause some of the same problems. If you got a old car at a REALLY good price, I would start with a very thorough tune-up. If you don't know when the T-belt was last changed, that is #1.

 

I did replace my timing belt as well, though it was because of an overheating problem. When I changed the water pump, you're into the engine so far to get the Water pump, you just as well change the timing belt too! Since I didn't know the history of this car, I changed the thermostat, water pump, timing belt & tensioner while I had the car torn down. This was done before I attached the running rich issue.

 

This is not correct, the single wire sensor goes to the temperature gauge inside of the dash on the instrument panel. The two wire sensor or the sensor that is on the left as you are looking at both sensors from the front of the car, the outer cap should be yellow. This is the sensor that is controlling the ECM.

The temperature sensing unit employs a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in responce to the temperature rise. (which can only be employed by having a two wire sensor)

 

It's not likely you're fuel pressure regulator either. They very rarely fail.

Replace air and fuel filters.

Clean you Throttle bodies and IACV.

Is the ECU throwing out any fault codes?

How old is the gas that's in the car?

I'd recommend using Sea Foam through the intake and in your gas tank.

O2 sensors are a good suggestion.

Are there any mods that have made to the car?

 

Kind of off topic, but...Can someone clarify..What the hell is seafoam?

 

https://www.zdriver.com/forum/showthread.php?t=10058

 

Thanks for all the input guys!! The car currently has a Stillen intake system, and a Greddy Evo cat-back system. I thought that maybe it was something with the fuel pressure regulator, but the oxygen sensors seem like they might be the culprit due to your responses. I'll let you know what happens

 

remembe the fuel injectors..do a quick resistance reading....10-14 ohms is spec.