L47/Aurora 4.0L powered Fiero.


Usually something dumb.


It was. There’s a little four-wire harness that runs down to the crankshaft position sensors and the camshaft position sensor. I decided to torque the intake manifold down on top of that. Took a good solid 5 miles before it shorted enough to kill the ignition. Hah. Runs great now.

…except for that knock-like noise it started making. Jesus, I can’t win.


Well details!?


About what, the knock-like noise it just started making? Not sure what it is. Hoping it’s not a rod, but it could be. Seems to only make the noise above 2K and under load. No noise at idle. Frequency of the knock varies with RPM. As soon as I get into 5th gear steady RPM cruising; no noise. Oil pressure seems fine, never drops below 10lbs. I’ll have to head over and spend some time listening to it tomorrow or Thursday I guess. Well, I got almost 600 miles out of it…


Jesus man…what a pain…


Fuck cars. This is the motto you should adopt. Your life will be simpler, things will make more sense, you will have less stress in your life if you just say fuck cars


this. swearing and hating inanimate objects is my personal therapy as well.


So, I should work on the Triumph instead? Good call.

I’ll head over tonight or tomorrow to fuck with it. I’m not convinced it’s internal to the motor. No noise at idle. The only time I heard a bad rod bearing, it sounded like a bag of hammers getting swung around at idle and only got worse with RPM. This isn’t nearly as noisy. It’s barely even audible most of the time. It’s most prevalent in a 5-4 downshift situation where I just stay on the gas enough to maintain speed or speed up slowly, but not floor it. I spent literally zero minutes diagnosing it after I got it back to the shop. I was definitely done with it for the night. Could be as simple as an issue with balancer, water pump belt tensioner or even the trans. I can pull the pan without yanking the motor if the first two things are fine to check the rod caps.

I’ve got another week of vacation coming up.


Sometimes you get so excited and concerned over the car running perfect you start to believe that there are problems when there aren’t. You should get a second opinion from a motor-head friend to validate your concerns.


Yea, I’ll get my dad and my buddy Steve to take a listen as well. It’s definitely a new noise that wasn’t there before this whole starter fiasco. I’m not sure what it is, but it was loud/concerning enough to stop me from driving the thing more than a few miles last night. Like I said, it could be as simple as a shot balancer or water pump idler. Just need to spend some time and trace the noise out.


Maybe you’re starter motor isn’t fully disengaged??


I’ve had water pumps and ac compressors make funny noises that sounded like death… But i really doubt your issue is a rod or rod bearing. Possibly main bearing but I doubt it’s rods. What does your oil pressure gauge look like at idle?


I’m pretty seriously doubting a rod bearing as well. I wasn’t beating on it and I’ve been good about warming it up. Pressure is right around 10 pounds on the gauge at idle. Sometimes it lopes at idle a bit and when it does that, the needle moves around. If the RPM is relatively consistent, so is oil pressure. I put ~7 quarts of Rotella 10W40 in there a few weeks ago when I put the motor back in, so it’s got plenty of ZDDP and it’s good oil.


That’s pretty marginal oil pressure with 10w40. When you are at 5000 rpm what does it read? Fwiw, my last Honda build was 35psi+ at idle warm on 10w30, the going up to 80psi at 6500+rpm. At minimum you should see 10 psi oil pressure for every 1000rpm of engine speed…


I was worried about that a while ago as well and believe it or not, the users manual [and a group of Northstar engineers] states that HOT oil pressure can be as low as 5PSI at idle with the 10w30 recommended. I’d also say the 10PSI for 1K rpm increments is accurate here. I’ve got 30-40 pounds at 2K-3K rpm cruising and it only goes up from there. AT 5K, it’s around 50-60PSI. I mean, if anything happened to a bearing because of oil starvation/high RPM, it very likely happened before the starter swap. You don’t spin bearings when you’re being nice to it. I’m going to try and get over there in a bit to do some investigating.


I fixed some shit. Found this when I got there, so that’s where I started.


So, I re-torqued the balancer because it was somewhat loose. Okay, that explains the oil leak and possibly the slightly low oil pressure. Then I found the other little bastard. Right behind the balancer there’s a dust cover for the front main seal. That little fucker was loose and rattling around. I’m 98% sure that was my noise. That rattling on top of the front cover echoing into the cavernous timing chamber. I got some Ultra Black, glued it to the front cover and I’ll let it cure overnight. If that was my noise I’ll bring it up to Cars & Coffee on Sunday. That’s my birthday, as well. Still runs like a champ.


Hopefully that fixed the issue!


Still should have torched it. I’ll bring you a can of gas and some matches for your birthday


It didn’t and I haven’t touched it since. It’s not the water pump or idler and it’s not the alternator. There’s not much else externally that could be making bad noises. I don’t know what it is, but it can’t be good. Guess the next step is to pull the valve covers and check the valvetrain. If everything checks out okay there, the motor comes out and I get to go motor shopping or rebuild parts shopping, I guess. Not super likely to happen before winter.

On another note, I found three ECM grounds that I had somehow missed when I built the harness. I haven’t verified with HPTuners, but I wonder if that fixed the sensor issues I was having before. Maybe I’ll head over tomorrow afternoon and fuck with it some more.


I am dropping off a birthday present for you.


I’m guessing it’s flammable? Just do me a solid. Keep it away from this guy. I don’t hate this one yet.