Chibo

Well, I'm pretty far down a path at this point so I figure I should make a thread asking for advice. Pairing down some information here I've got the following history:

Purchased 4/8/2017 with 155k
Valve adjustment .008/.010, AP2 keepers, and retainers on 5/20/2017 with 158.5k
Four new coilpacks (Denso) on 8/15/2017 with 163.8k
New injector o-rings for cylinder 2 injector on 8/18/2017 with 164k
Billman cam chain tensioner on 9/7/2017 with 165k
Ballade Sport oil pan baffle on 10/1/2017 with 165.8k
Koyo radiator on 11/21/2017 with 167.7k
New NGK IFR7G-11KS Spark plugs on 12/2/2017 with 167.9k
Verified valve adjustment .008/.010, valve cover holes punched, and Moroso catch can installed on 12/26/2017
New alternator on 1/7/2018

Now to elaborate a bit. I replaced all four coils because one completely died, I then replaced an injector o-ring because I found it to be leaking and causing a slight idle miss. The car was great after that. My car seemed to burn a fair amount of oil, as I'd seen it at night through headlights when in VTEC on occasion and various people behind me at trackdays had commented that my car puffed smoke coming off the throttle (not full smoke cloud). I also pushed a fair amount of oil through the valve cover during trackdays. I checked oil pretty closely and have never had the car drop out of VTEC.

At some point I began getting what I considered to be more idle vibration than normal, but the car ran fine under power.

At the end of a trackday after the Koyo radiator replacement I started the car up to leave and it was misfiring like it'd dropped an entire cylinder at idle. When revved a little bit it started acting completely normal so I drove it home.
At a trackday in December I had the car stutter for about a second down a straight with a flashing CEL during the first session. No CEL stayed and the car acted completely normal the remainder of the day.

The idle vibration has been getting worse and the exhaust has a puffing noise until it warms up. No smoke. Normal power, puffing usually goes away after the car warms up but the idle still feels rough. I replaced the alternator because the dash oscillated at a stop light last week when I took it out for a night drive, figured maybe the thing was bad and was causing all of my issues. Ended up having a P1399 pending after replacing the alternator, though no CEL has set yet.

Compression tested the car cold today as I'd pulled the injectors to have cleaned expecting the compression test to come back normal, but the compression test came back with 160/200/200/200. I decided to throw the injectors back in, warm the car up (exhaust puffed during this, which then went away after it was warm) and re-tested to get 200/200/210/210.

I'm going to get a leakdown tester tomorrow after work, but does anyone want to spoil my future findings or have any ideas? I'll also note that my car has had a ~+15% fuel correction when logging the OBD2 data. I don't know if this is related, or it's because I have a Greddy Emanage Ultimate piggyback with a Karcepts tune.

Slowcrash_101

I'd go for slightly looser valve clearance and see if that changes anything. If it does then it's likely a valve leakage issue.

3 reasons this engine will burn excessive oil, a cylinder defect, tight torched valves with worn guides, and torched stem seals, or worn piston rings. Our pcv system may contribute to this, but I'm talking about excessive.

All of these could cause misfires, another thing people never consider is that as the timing chain stretches, it throws off valve timing.

Factory narrow band sensor and the fact that we operate with map style fixed tables explains why the cars run "funny" as they get older. Now don't get me wrong the car will still run perfectly fine. They just tend to run richer as it stretches more and more, due to retarded cam timing.(The end result is less power down low and a little more power up top).

Advancing the cam timing would correct this, no replacement necessary.

Worn bearings can also cause more oil consumption due to more oil being flung out of the crankshaft and splattering on the cylinder walls. Although this last one is rare and not usually an issue in these cars.

Chibo

Leakdown came back 10% / 10% / 2% / 2% with the air escaping into the block and nowhere else.

A fellow S2000 owner with a Honda computer tool thing took a look at the car and said it was running really lean judging by the fuel correction (STFT ~15%), so I unhooked my Greddy EMU and the fuel correction dropped down to 1-3% and the car smoothed out at idle immensely.

I'm assuming pulling the pistons/rings and finding a place to have the FRM bores honed will be more expensive than a used motor, assuming the bores are either ovaled or scuffed.
If they aren't scuffed I am assuming that re-ringing them probably won't hold up in the long term.

Anyone have advice? I guess I'm not sure where to go from here other than to save for a spare motor and keep beating on it until the bottom end is toast.

Slowcrash_101

It all depends, if the cylinder walls are ovaled or scuffed up then you'd hone, otherwise I don't think it's necessary at all, the cylinder walls are designed to outlast the rings, so if it's only rings, just toss on new ones with confidence, it's all in the break in.

For the record honing work, won't break the bank, you just have to find the right machine shop. I got mine done for ~$250 + the cost of the stones, the felt pad and the silicon carbide paste. I just talked to the machine shop explained the procedure and it came back fine.

As for the ring pack, get an 06+ ring pack those are the best. Sometimes rebuilding is a viable option, beats $3k for another engine. PM me if you want to have a ring gap discussion.

starchland

Slowcrash_101

Nope, just gap them properly and then break them in. Only need to hone if there's scratches that catch your nail that run the length of the bore.

starchland

Chibo

Nah, carry on. I'm open to a ring slap job, just would like more feedback before planning it.

I think in the mid-term the car is going to get a K24.

Slowcrash_101

You mean why you don't need to hone the cylinders? For one, FRM is porus, it traps oil very well so crosshatching isn't necessary. The most important part of honing FRM is the exposure step.

The liners are actually aluminum but have fiber embedded in them. When you hone FRM, what you are doing is first removing the scratches, then smoothing the surface, then exposing the carbon fiber, by stripping away a layer of aluminum.

The cylinder rings ride on the hard carbon fiber, not the aluminum metal. If the bores are in good shape the fiber is already exposed, installing new rings simply requires you to match the rings to the exposed carbon fiber (ie break in).

I hope that explains why you don't need to hone FRM if the bores are ok.

starchland

If I am interpreting the service manual correctly, light scratches are ok if they can't be felt with a fingernail and don't run the length bore. So I guess some minor bore imperfections will be compensated by new rings is my questions...?