"Help!" -- 1992 300zx NA won't rev past 5k rpm

[mundilfar]

Hello,
Since I am new to the NICO forums, I am going to provide a bit of background. I am a college student and love to work on cars. I purchased a 1992 300zx na with no motor 2 years ago and have finally got some time and money to fix her up. I purchased a 1994 j30 vg30de motor from the junkyard and have since got the car running.

Here is the problem I am running into:
The car starts up and idles ,after warming up to operating temperature, between 900-1000 rpm (according to the gauge). Once warmed up I can rev the engine to redline. However, once driving the vehicle down the road in first gear can only hit ~5k rpm. In second gear I can only hit ~4.5k rpm. And in third it goes down once again to about ~4k rpm.
This issue is intermittent. I cleaned the MAF sensor with electrical parts cleaner, the disc on the CAS with electrical parts cleaner, and cleaned the terminals on the throttle position sensor and found that I was able to accelerate to ~7k rpm in first gear. Then in second gear I was only able to reach a maximum of ~6.5k rpm. However, after a drive I found that the issue became worse and I was only able to rev up to ~5k rpm(in first).

Troubleshooting:
-the oil on the highflow intake from Z1motorports may be causing issues with the Mass Airflow sensor (my guess). However, I have since cleaned the mass airflow sensor again and it did not allow me to rev past 5k rpm. I also tested the MAF sensor with a multimeter:

Voltages on MAF harness:
Terminal E (positive 12V) and Terminal C (ground) was ~14 V (engine on) and ~12 V (engine off)
Terminal E (positive 12V) and Terminal D (ground) was ~14 V (engine on) and ~12 V (engine off)
Terminal B (positive 12V) and Terminal C (ground) was ~0.22 V (engine on) and ~0.434 V (engine off)

This appears to be out of spec according to vicman from the twinturbo technical forums.

-replaced the throttle position sensor with a used TPS and cleaned the terminals on the harness with screwdriver and electrical parts cleaner. However, this did not do anything to change the issue.

-skimmed through 1992 300zx FSM for any related issues but skimming through it did not find any. (did not look very hard, google is faster)

-visibly checked harness on MAF and did not find any corrosion.

-visibly checked harness in engine bay to see any breaks or cuts. Did not see any.

-I have not checked the fuel pressure. I will check the fuel pressure this week (hopefully).

-Will be checking the crank angle sensor with a timing light sometime this week as well.

Conclusion:
It appears to me that the car is running lean. From what I have done so far the MAF may have gone out on me. However, I have not encountered this problem before and don't want to spend over $200 on a MAF if I don't have to. I am posting here to see if anyone on here has had a similar issue and could offer some knowledge so that I may identify the problem.

[elecfus]

MAF cleaner is purified water
electrical parts cleaner is degreaser. you sprayed degreaser on your MAF. he's dead jim.

[mundilfar]

I would also like to add that there was no CEL when I encountered this problem.

I solved the problem. Solution:

Purchased new oem MAF from Z1.

Tested new MAF sensor:

Voltages on MAF harness:
Terminal E (positive 12V) and Terminal C (ground) was ~14 V (engine on) and ~12 V (engine off)
Terminal E (positive 12V) and Terminal D (ground) was ~14 V (engine on) and ~12 V (engine off)
Terminal B (positive 12V) and Terminal C (ground) was ~1.5 V (engine on) and ~0.44 V (engine off)

Also, looking at the safety data sheet for the MAF sensor cleaner. It is definitely not purified water. And the safety data sheet for the electronic cleaner has many of the same ingredients as the MAF sensor cleaner. I did make a mistake in saying in my first post that I used electronic parts cleaner to clean the MAF sensor.

The car is over 20 years old... things go bad. I hope this helps someone who runs into this problem in the future.