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My first attempt at tuning had a mishap, need some reassurance / wisdom

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Well after watching hours of videos (which have been great) I had the confidence to try and fix slight things that had been bothering me with my tune that that my tuner left me with. My main goal for the course was to be translate all the chinese in my Hondata s300 into something I understood and I think that’s been pretty successful. This is also my first forum post anywhere ever so I hope I’m not about to get flamed for not following forum rules correctly or something.

So here’s the scoop:

I just wanted to fix my idle, it’s been a little too high, and I wanted to verify my base timing which turned out to be off by 1 degree which I fixed.

Car is a 95 Civic EJ1 with a b18c1 I put in over the last year, did the majority of the work myself, have had this car since I was 16 (original owner), I’m 41 now and this is the car project I always wanted to do since I’ve been toying with this car for 25 years and now trying to make that transition from wrench turner to tuner. I’ve got a mild Skunk2 stage 1 tuner series cam in it and their intake manifold and some upgraded valve springs to go with it. CAI, 4-1 headers and some other less relevant stuff. Injectors are 290cc prelude injectors which are only 50cc more than stock. Motor has about 3k miles ok it since rebuild.

So the mishap... the ignition lead for cylinder number 2 was tight against the socket wrench when I loosened and tightened the distributor to set my timing. The ignition lead fell off the distributor somewhere down the road. I’m pretty sure it happened on my first speed bump because that’s when things got weird though I’ll be re-checking my timing to be sure.

So immediately after that speed bump immediately smelled a mild but noticable burning smell which think was my cat heating up from the extra fuel pouring into it. Kept going (dumb). Went down the freeway one exit and noticed on a pull that I had a sudden power loss. I think this is when the lead fell completely off, may have had partial contact before. Pulled off next exit (about 1 mile) car not running so good, vibrating a lot, I’m wondering how advancing timing 1 degree and getting my idle lower could have done this (which of course was not the reason). Drive the mile back home. Found the problem!

Now my worries are about bore wash since that spark plug was obviously not firing the whole time. (Maybe total 2.5 miles). During this stint I did do 2 wot pulls, neither went redline because things got funky and the 2nd one was hardly a pull but it wasn’t cruise. I also figure I may have taken some miles off my cat as that didn’t smell too good until I plugged the lead back in. Not too worried about the cat though. How worried should I be about bore wash? I did a leakdown test and everything seemed ok, 8-10% when cold (on all cylinders). I figure when I do it hot later should be less than that and I think that’s not bad for cold, and all the cylinders match. Cylinder #2 looked notably cleaner than the others looking through the spark plug hole, fuel had some sort of cleaning effect on the top.

My other question is I want to understand the strange things I saw with my AFR during the situation on my wideband that seem counter intuitive to me. I would have thought that the wideband would be reading ultra rich given all of cylinder #2 fuel was going straight through however it was quite the opposite. At idle (after the lead fell off) it just started reading leaner and leaner. At a point it was idling at 16:1 and sometimes 17:1. Same on light load / cruise. Once we got to that stage I’m driving as slowly and carefully as I can of course except for this strange phenomemom that it seemes the more throttle I gave it the better the AFRs. So I got it home by giving it a bit more load (kept it around 4,500 rpm) and this kept the afr’s at 14.7. I did run a red light on the way home because it was not kind to my afrs to stop. So how does that make sense that a cylinder where the injector is still firing but the spark plug is not would result in a lean condition at the o2 sensor? Only theory I can come up with is that in my case the o2 is installed into the inlet side of the cat and I presume the cat was getting quite hot and perhaps combusting the extra fuel at the o2 sensor until I gave it enough load that a) it was pushing the exhaust through faster and b) under normal circumstances under that load I’ve got a slightly richer target lambda and that little extra fuel added up to counter the situation. That’s just my best theory. The spark plugs had some white crusties on the base rings which hasn’t been there before (all spark plugs).

Hopefully someome above my pay grade can chime in here and shed some light.

As it was a short distance, and the rings were already bedded in, you shouldn't have a problem with the bore wash - might be something to keep an eye on later, just to be sure.

The reason you were getting a lean condition is because the lambda is an oxygen sensor, it measures the amount of oxygen in the exhaust gasses. Since it's normally placed between the manifold and the cat', it was measuring the unused oxygen from the mis-firing cylinder.

The cat' may have been damaged, causing a loss of power, as it was oxidising the unburned fuel and that puts a LOT of heat into it - that can result in it physically distorting and blocking the passages the gasses normally flow through. Something else to bear in mind.

Overall, I expect you to be fine in future - and you've learned something.

To me you do not to worry about bore wash at all as the engine was not ran long enough to suffer from it.

Your WBO was displaying lean mixture instead of reach because it measures residual oxygen not fuel. As oxygen was not consumed in cylinder 2 WBO was reading it as lean mixture...

Many many thanks guys! So far have to say HPA is worth it’s weight in gold. Makes perfect sense now why the lean reading (seems obvious now). Just for the knowledge, at how long of a runtime would you start to be concearned with bore wash? I figure the answer is an opinion piece and may vary from person to person. The guy that originally tuned my car a while back claimed bore wash is myth and had some story about how he had some massive injectors on a 1k hp race car where something went wrong and the injectors stuck open on a race. He fixed whatever caused that and was back on the track with no ill effects. That was his story as to why his opinion was it’s a myth. I’m guessing it’s not so much a myth but moreso unlikely.

I'd be seriously considering a new 'tuner'.

The reasons I wouldn't be too concerned about your case are - the rings and bore were already well run in, that the rings would have been lightly loaded because there wasn't the combustion gasses loading them, the engine was run like that for a short time and, strange as it sounds, most fuels actually have some lubrication value.

Thanks for that Gord. A quick update, I pulled the cat, it looks pretty much like it did when I installed it new and the car drives like it did prior to the mishap. You guys were spot on.

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