Intermittent Engine Rattle

[ThomasT56]

Hello everyone, I have built myself a 2.3 turbo from a NA engine, and I'm having some issues, there's a lot I've done so I'll list it here.

-The main issue is a rattle sound with a cylinder dropping out of play intermittently. It happens after 10- 15psi of boost is made.

-Engine decided after my first week of driving, and my first time turning it up to 15 psi from 7, to make a loud rattle/knock and not run. I proceeded to tear the entire engine apart, finding almost nothing wrong. In the head it seemed like a valve spring was spinning somehow.

-Put it back together, didn't run (vacuum went to 15inhg and it sounded horrible). I then tore the head off and used my other head I had from my old engine. Boom she runs, no sounds, good vacuum.

-Took it for a few drives, had some boost issues but ran great. Fixed boost issues (new turbo) put a 10psi spring in it (had a 15 before, I believe other turbo was shitting out) . Now still made 15 psi, pulled like a freight train, actually pushed through the clutch in 3rd gear. On the 6th pull (not WOT about 3/4), boom the same knocking and rattling came back and it ran like crap (as in down a cylinder). I limped it the 0.5 mile home and it intermittently ran good with little sounds, then the bad sound comes back and it runs awful. I parked it and you can still hear a slight sound but still idled fine.

-Im going to put a 5psi spring in it and hope it lowers the boost, I don't need a racecar, but I'm wondering what the hell that knock/rattle is, and why it comes and goes.

-Do I need upgraded valve springs? I've heard that somehow rockers can come out and slip back in. On that drive home the rattle was absolutely insane, sounded like the engine was falling apart, then it goes away and runs fine.

-I can't find anyone with this problem, its an 8plug head that was rebuilt 5k miles ago. And now it's got the same exact knock the other head had.

I apparently can't upload a MP4 or a mp3, I wish I could.

 

[franklin2]

You need to run the very best highest octane fuel you can buy. If you have some old stuff in it that has been sitting around for a few months, run it out on lower boost, put the good stuff in it, and try again.

You may end up running a water injection system on it if you want to run that much boost. Or put a boost timing controller on it. The factory turbo engines had lower compression pistons that also helped this problem.

 

[ThomasT56]

I just filled it with a tank of 93 last weekend, I'm going to lower the boost, I wasn't shooting for 15 anyway. I just hope that sound doesn't come back, or if anyone had a similar thing happen. It runs great until the noise happens, and it happened after the pull, not during. I'm gonna lower the boost and try again next weekend, since tomorrow is snow. Thanks for the input.

 

[scotts90ranger]

What pistons are you running? stock cast or forged turbo? I'm running stock turbo forged 8:1 and run 14-15psi on a ported single plug head and on premium (around here it's 91, hard to even find 92) it doesn't ping or do anything dumb...

I would do a leak down test to see if the valves are working... if it leaned out it could have melted a valve but then it wouldn't start working right again... what engine control system are you running?

 

[ThomasT56]

They're forged pistons, I built the motor myself. They're not turbo pistons, they have a NA compression ratio still but they're forged. I'm using a mega squirt standalone ECU, its not that it's pinging under power, it's a mechanical issue. When the sound comes the vacuum goes to absolute crap like a valve is stuck open or something. The sound happens after the pull, during the pull it feels awesome with no sounds, AFRs were 10.0:1. While goes down my road I was barley on the throttle when the sound comes and goes. Its definitely not a melted valve, the other head I took a part had no signs of major damage, and it ran worse than this current head.