94 z32 multiple problems after engine rebuild

[Benjammin]

Im desperate for some help with my z, im having multiple issues after doing an engine rebuild and im not really sure what could be the problem so any help would be greatly appreciated. Ok so about a year ago an injector went out and was causing it to sputter, so after replacing it i ran it for half an hour then shut it off and when i tried to start it again it seemed locked up. Turns out something happened when changing the injector causing fuel to leak and hydro locking the engine and bent a rod. I decided to rebuild so i bought a aftermarket rebuild kit with rings, std bearings, and gaskets. I sent the heads the crank and the pistons with rods to a machine shop and had everything tested and the heads were ported polished and shaved, the machinist said everything was good so i assembled the engine and put it in the car. I also made some modifications like headers, a luk performance clutch, i did an egr delete, tb coolant removal and removed the catalytic converters and because i wasn't replacing the injectors i sent them to be ultrasonic cleaned. When i first started it everything seemed ok, good oil pressure, firing on all 6, but the injectors were ticking louder than normal and it had a knock from the top end. Now since ive done the rebuild ive put about 50 miles on it and ive already had to replace 2 of the injectors. Ive changed the oil 3 times now running valvoline vr1 10w 30. It still knocks but only after its warm and its not very loud at idle only past 2k rpms. On top of that its only getting around 5 miles to the the gallon. Ive checked almost everything i can think of so if anybody could help i woukd really appreciate it. Thanks

[t.mcginley.jr]

Are you sure its knocking and not ticking from the lifters?

As for the crappy mileage your O2 sensors could be shot from the bad injectors fouling it up. Thus the ECU thinks your running lean or rich and it's throwing extra fuel into the engine. When you put the headers of did you replace the O2's?

Problems with the injectors can also be caused by the CAS or PTU being faulty. Have you checked for codes yet?

[Benjammin]

Actually i thought it was the lifters ticking at first but i can hear the lifters tick when i first start it and they sound different, its actually more of a knock than a tick. And no i didnt replace the o2 sensors although i did clean them. And i checked the codes after the rebuild and i got 2 codes, one was fuel injector circuit which i think was 51 and then the other was exhaust gas temp sensor, 35 i think. But i checked it again a couple days ago and got 55, no problems. Do you know how to check the ptu or cas?

[t.mcginley.jr]

So if you just rebuild the bottom end you shouldn't be having rod knock. Did the machine shop cut the crank or just polish it?

As for the CAS you take the three bolts out holding it in and when you rotate it by hand you should hear each injector click as it goes around. There's a sticky thread at the very top of this forum that says "Dead Cylinder? Can't figure out why? Read Me! (S2 PTU Test)" for testing the PTU.

[Benjammin]

Yea thats what i figured and if it was a bearing i would have oil pressure issues, and the crank was just polished. I tried adjusting the cas to see if that would help but it didn't help the knock, ill check the ptu today.

[H1tman]

Well a rod knock is very recognizable.
It sounds to me like your timing belt skipped a tooth or your cam gears are shot.
I have seen both instances cause the same symptoms you describe.

[Benjammin]

Actually there was a guy who was helping me do the build and hes the one that put the belt on, so do you think if he did install it a couple teeth off itll cause it to knock like this?, and do you think it could have caused it to bend a valve or anything? Also i can hear some serious noises coming from the vtc gears like a rattle about the same time it starts to knock.

[t.mcginley.jr]

Did he remember to put the springs in the intake cam gears? Or maybe they are just worn out so every time the cam rotates it has enough play to move back and fourth a little. Usually a rod knock is pretty loud

[Benjammin]

Yea there in there, they probably do need to be replaced anyways so ill try that this weekend, but ill post a video tomorrow so you can hear it for yourself and tell me what you think, also if it was a rod knock it would knock when cold too right?

[t.mcginley.jr]

yeah rod knock happens all the time and gets louder the higher you rev. JWT sells heavy duty vtc springs which might help, they aren't that expensive either I think like $20-30 for the pair

[Benjammin]

Alright ill check out those springs and see if they help. But here's a video of it knocking.
https://www.youtube.com/watch?v=re7ArK7 ... ata_player

[Ziggy1621]

Videos are always funky, but it almost sounds like a stuck lifter. You used plenty of assembly lube?

Also, if your friend did the timing, I'd always double check it to make sure

[H1tman]

Double check your buddy put the belt on correctly. If the noise continues check your vtc gears. You can take the belt off and with an wrench hold the gear still and try to turn the gear with your hand, if it spins while the bolt holding it isnt moving that means its bad.

[Benjammin]

Ziggy i think i used enough assembly lube and ive tried putting different additives for lifters and tried different oils but nothing seems to help but do you think if the lifter is just bad it could cause it to knock like that? Ane yea im going to make sure the belts on right and buy a timing light to check it. And thanks hitman ill check the gears but if they are bad would i have to replace them or can they be repaired?

[Ziggy1621]

Did you have your valve springs checked?

[Benjammin]

Yea i had everything on the heads checked at the machine shop.

[nissanfreak12]

Did you use the old lifters or put new ones in? If you used old lifters, how did you store them while engine was being built? It could just be a really bad collapsed lifter. Have you tried using thicker oil, like 20w-50? It could take a few hundred miles to fill the lifter with the oil.

To answer your question, yes, a collapsed lifter will sound like that. That is just way too fast to be a rod knock, they usually knock at half that speed. A knock will also be more at the bottom of the car, not at the top like that.

[t.mcginley.jr]

Did you use the old lifters or put new ones in? If you used old lifters, how did you store them while engine was being built? It could just be a really bad collapsed lifter. Have you tried using thicker oil, like 20w-50? It could take a few hundred miles to fill the lifter with the oil.

To answer your question, yes, a collapsed lifter will sound like that. That is just way too fast to be a rod knock, they usually knock at half that speed. A knock will also be more at the bottom of the car, not at the top like that.

+1, the FSM says to keep the lifters upright while they're out, having them on their side or upside down will "deflate" them so to speak. If it's a stuck lifter, you can use Marvel Mystery Oil for ~100 miles and then change the oil, people have had good results this way.

[Benjammin]

I used the old ones and yea i made sure they were upright and didn't get turned over while they were out although they weren't stored in oil or anything and i made sure to keep them in order as well. But the car also set for about a year with no oil circulation on top of the time they were out of the engine so they might just need to build pressure so ill try some marvel but what would explain the bad gas mileage? And since i switched to synthetic i noticed a small oil leak near the rear main seal, u know of a easy fix without dropping the transmission or oil pan?

[Ziggy1621]

Nothing that would be permanent

[Benjammin]

Oh ok thanks. So what do you guys think about the bad gas mileage?

[t.mcginley.jr]

I thought I posted but I guess it didn't submit. The crappy gas mileage is usually caused by running lean, from faulty injectors or bad O2 sensors. And there's really no easy way to fix the RMS, if it started leaking when you put synthetic in then it's past due to be replaced anyway

[nissanfreak12]

What is crappy mileage to you? I would not worry about mileage until after you break in your motor, at least 500 miles. Just remember, nothing is properly seated yet, so things could be off. If mileage is still bad after, then look at what t.mcginley said.

RMS, yeah, should have replaced that with engine out, if you did, either it was installed a little at an angle, no lube on the gasket itself that joins to the crank, or its just being a butt. I had one stop leaking after a few hundred miles. Sure its not the oil pan gasket? Was the rear seal used? Installed with sealant on the edge/corners?

[nissanfreak12]

I used the old ones and yea i made sure they were upright and didn't get turned over while they were out although they weren't stored in oil or anything and i made sure to keep them in order as well. But the car also set for about a year with no oil circulation on top of the time they were out of the engine so they might just need to build pressure so ill try some marvel but what would explain the bad gas mileage?

This will definitely cause your noise, give them time to build pressure, marvel does good. Z1 makes stuff to clean them out. I used about a half a quart of ATF, that worked miracles. Even using a thicker oil will build build up pressure, it will just take some time.

[Benjammin]

Thanks for all the help guys. Yea i replaced every seal and gasket in the engine and transmission so its new, and i used silicone on the corners, but yea it could be coming from the oil pan its just coming from the back so it could be either. And the mileage is around 5-6 mpg, so i was wondering if the problems are related. So is there a way to determine if it is the lifters or not?

[t.mcginley.jr]

Despite the noise does it run crappy? If it runs normally then I would say the lifters aren't affecting your mileage. 5-6 mpg is pretty crappy though, even on a fresh build

[Benjammin]

No it runs great. At first it would hesitate and have really slow throttle response but i think that was because the denso plugs that were in it but i have ngks now and its fine. It has good response no hesitation and plenty of power. Do you think the injector's could be causing problems cause two have already went bad since the build and i sent them off to a guy to be cleaned but didn't replace them. If there's something wrong with injectors could it cause these problems? Also i forgot to mention there's a real strong gas smell from the exhaust when running as well.

[nissanfreak12]

It sounds like one or a few of the injectors might be stuck open or sticking open. 5-6 mpg is way bad, even for a fresh build as stated by t.mcginley

[Benjammin]

Yea that was the problem in the first place, thats actually what hydro locked my engine, so do you think if that were the case it could be causing the knock if its not the lifters?

[nissanfreak12]

Injectors can get loud, but not as loud as lifters. Did you replace your injectors with the build?