zawahra

Hey guys!

Recently my 90 300zx NA has been acting up.

On a cold start, the idle is rough jumping from 1500 rpm and dipping below 500 rpm and then begins to stabilize around 1000 rpm. The tranny shifts hard and delayed especially 1st to 2nd. When the car warms the transmission shifts smoothly. When I first shift into reverse or to drive the rpms dips so low that the car will often stall (only when its cold) so I have to press the gas pedal right away to avoid that. On the highway I'll be moderately accelerating to get to 110 km/hr and it'll sometimes just downshift (Usually at about 80 km/hr.)

I did a ECU diagnostics test and got the error 53 [Exhaust Gas (O2) Sensor Circuit (Right)] I have no check engine light on even though code 53 is supposed to toggle it.

I took a voltmeter to my battery and I am getting a steady 14v (I had alternator issues in the past)

I am thinking it could be a vacuum leak, EGR valve malfunction, a dirty throttle body, or corroded wire(s) ? I am really no expert.

A little background. This is the 5th summer I own this car and I had the engine replaced and transmission rebuilt summer of 2012 because the engine had a crank problem and the transmission was finished (Shifting badly even when warm) at 200,000kms. I only drive this car during the summer months, so I barely put 7000 km on it since. I also checked the transmission fluid and its bright red and clear with no metal filings or dirt. It isn't sticky either.

You guys are my only real hope. I would really appreciate your input, the summer is flying by!

Kenny Z

PredatorZ

I think you almost answered your own question, so you are on the right path, not sure if the auto trans is connected to vacuum, but the engine stumbling sure could be. I would check the EGR, they are cheap. Vacuum lines can crack, get brittle with age, or just come loose, easiest way to fix a cracked end is just cut it off back to pliable rubber. Corroded connections are always an issue, but the fact that it goes away when warm, might be your Cylinder head temp sensor, or thermal time, if z32's have one. I could crack open a z32 fsm and research the problem if it persists, PM if you get stuck and Ill do some research.
You did the right thing checking your trans fluid, that sounded good, one point of caution, if your car ever over heats, have the trans fluid changed asap.

zawahra

Hey thanks for the reply!

I forgot to mention that the rough idling and tranny hard shifting happened simultaneously. I have no problem at all with the transmission before that.

I took a propane tank to the main intakes and couldn't spot the leak.I tried to take a look at the z32 fsm for a vacuum diagram but the diagrams in general are soo hard on the eyes my nose started to bleed (Jokes) but I did find a nice vacuum line diagram on google and I'll give it another go with the propane. If all fails I'll find a garage with a smoke machine.

I also think it might be the EGR but apparently I have to pull the engine to check or replace it. You would think the ECU would give me an EGR error code. When you say the EGR is cheap, you mean cheap to replace or cheap that in that they break easily?

The car has never overheated yet. If it did why change the fluid?

I apologize for my novice questions in advance.

Kenny Z