1991 z32 upper engine knock

[eryx18]

ok so i have a z32 that i picked up really recently. Ill start by giving you all abit of history of the car. (i apologize for the long post)

1991 300zx 2+0 NA Slicktop 5spd Manual
bought at 67k (According to odometer) Not sure if thats accurate or not.
I traded my 94 cbr 600 and $200 for it.

When i first purchased the car, it would not idle unless it was warm. so after reading forums and using the search button quite extensively, i discovered that it was a maf problem. I swapped it out, and it ran like it was trying to hop the border to mexico. I proceeded to do a full tune up, oil change, plugs, cables and coils.

Now fastforward to friday night, this is where the trouble begins. After hitting taco bell, me and a buddy of mine stopped outside a mates band bractice to wait for him. I decided to go inside while he stayed inside the car on the phone and blasting my stereo. About 10min later, i hear a loud rev and squeling tires. When i came out this Jack **s of a friend was fishtailing on the street trying to impress some random girls. (last time i leave my keys in my car) So after cursing and yelling and slapping this guy across the face , we decided to go home. (Hes been my best friend since i was 3, so i forgave him ive know he's an idiot. but freinds are friends and he offered to pay for repairs.)

So on my drive home after dropping him off i noticed this knock, which sounds exactly like a woodpecker coming from the top-front-left of my engine. When you face it from the front of the car. I thought it was a lifter at first, but my oil level was perfect and so was the pressure.

Here are the symptoms ive recorded since the issue began.

My tps is giving me code 43 and wont let me rev past 2k rpms. when i unplug The tps it reves fine but knocks.
The knock kicks in ONLY at 2100rpms and higher never below or at idle
My car wont idle ( i think this is the bad tps)
there is no power loss whatsoever just the knock.
when the car is cold and i turn it on the oil pressure is at 90psi
when it warms up the oil pressure is at 30psi at idle and 60 while driving.

Im at a loss of what it could be at the moment, i can drive with no knock with my tps plugged in but i can rev past 2k which i know is the tps fault but i dont want to pull it at risk of damaging the internal engine. And this is defenitly from the top end of the motor. Any ideas? bent valves? bent cams? ect? im going to be pulling the head apart today to inspect it.

any help is appreciated

[nissanfreak12]

Code 43 is fuel pressure. Check the FPR, unhook the vacuum line, does the idle change? Try and get a pressure tester see what the pressure is at.

The knock could be VTC springs. VTC kicks on I think at about 2300 rpms, they like to make noise when the spring is weak.

[eryx18]

Thanks for the quick response ill check the fuel pressure when im out of work. And as for the VTC would pulling the vtc solenoid silence the noise? so as to tell me thats where the issue lies?

[nissanfreak12]

It should, I hope someone can verify it does. Doesn't hurt to give it a shot, it won't hurt the engine to not run the VTC, just won't have the same power. Its a grey plug in the back of the engine, VTC runs off intake cam, you should be able to see the solenoid, just follow the wire to the connector.

[t.mcginley.jr]

You can remove the VTC's from the back of the intake cames, but you would need to plug up the hole where it goes with a half moon plug like the exhaust sides have. But you will lose a bunch of power like nissanfreak said. You're better off just replacing the VTC springs inside the intake cam gears, much easier to do and it will actually fix the problem. You can get JWT heavy duty ones (stronger than OEM springs) for around $26/pair I believe.

[eryx18]

I pulled the vtcs andthe noise didnt go away. So I started taking the rest apart first I figured it would be a good time for a timing belt change. After pulling the cover I noticed the belt was moving back and forth on the gears. So I pulled the pullies and what I noticed is the auto tensioner isnt hitting the metal pin even though it's fully extended. I have to push it back slghtly to touch the pin. If I rock it back and forth it makes the same sound as the knock ive been hearing. Is it supposed to move like this or is a bad tensioner likely my problem?

[t.mcginley.jr]

Yeah sounds like a busted autotensioner and belt slap will make noises like that. Good thing you caught it before any damage occurred