Rb26 Cefiro changed battery now dull knock bottom end

[26cefiroguy]

Hey guys,

I know the title doesn't make much sense but to keep it short I received my 1991 cefiro rb26 swapped and it had a Prius battery. I'm assuming this was so the dealer didn't have to swap terminals but the car would have random times where it didn't want to start.  Prius battery CCA's are not in spec so I decided to change the battery to a 51RPLT. I used what the parts store had and the list of battery's wasn't available.   I am under the impression that it shouldn't matter. However after I started it with this battery a dull knock had started.   I drove it a short distance and it would go away with revs but come back at idle.    I did notice the idle rpm is ~1100 before the battery change it was at ~900. Obviously there's alot to support the battery change as the issue. Would there be anything else that would cause this?

 

Deeper information

Engine was swapped 6k km ago. R32 26 stripped the oil pump so I'm pretty familiar with metal on metal noise. R33 26 is in now, has been good for the 6k kms with the other battery.  Spark plugs, water pump, oil pump, hks timing belt, theremostat all changed with the r33 engine. Supposed to have around 40k km on it. No shavings in the oil, oil level good doesn't burn any, temps are always cool. We did have a stint with bad coil packs idk if the ones we swapped were good but our problem with miss fires did go away. It's had 3 oil changes only with oem filters. I was so worried about doing everything right seems I may have still not done enough. Pretty heartbreaking. Ecu appears to be a stock 26 ecu. Car does pop a flame every once in a while but I equated that to the aftermarket exhaust.

I am gonna try and get the Prius battery again but idk if I can trust another RB if the bottom end is out. Just alittle too convenient that it came with the battery change. Gonna check spark plugs and ohm read coil packs and lastly a compression test if all else fails.

 

Any ideas or trouble shooting I can do would help.

[GTSBoy]

I can't see it being the battery or the process of changing the battery as the cause.

I would suggest getting it up on a hoist and listening to the engine with a stethoscope, to try to find what this knock is and where it is.

The only ECU related thing that could have happened is that removing power from the ECU will clear some learned trims. But that really shouldn't affect anything that would lead to an engine noise, or change in idle rpm.

Some people claim there is no such thing as a coincidence. I'm pretty sure that there are coincidences. This could be one.

[joshuaho96]

I would not trust any used engine with "40k km mileage" without opening it up and measuring everything and inspecting for damage in critical regions and a major overhaul. Your battery can't cause a bottom-end knock. RBs in general seem to attract a lot of questionable mechanics at least in the US that are used to doing sloppy work. There's a reason why YouTubers are able to buy two cars with RB26s that snap a cam and start crank walking an engine that is not known for such issues. Any new car design within the last 20 years is going to be even more sensitive to improper maintenance/repair than an R-chassis.

Use a stethoscope or something similar to narrow down where the noise is coming from. If you know it's from the bottom-end shut it down and stop doing damage to the engine. If you've spun a bearing every second the engine runs raises the risk that it's beyond saving. Don't waste your time buying a new battery to see if that changes anything. The only way it could be the battery is if you somehow flipped the terminals and destroyed the electronics but it somehow still barely runs.

I know this is tough to hear but unfortunately this is just how it goes with cars.