tritium_pie

My '03 s2k has been having an intermittently "lumpy" idle where maybe once every 20-30 seconds it sounds like it's hesitating, or the firing is ever-so-slightly off, typically when the engine is still cold, but also a bit even after it is fully warmed up. It also happens in 1st gear, wherein I give it the usual amount of gas to accelerate slowly and for just a fraction of a second it feels like it's going to stall, so I have to give it a touch more gas. Once I'm moving well, the issue goes away in all gears. And I feel absolutely no issues when accelerating hard and going into VTEC.

This has been happening since early January.

I did do the "MAP whack" a couple times, but that hasn't fixed it. And I do still have the original MY03 MAP sensor and am aware of https://www.s2ki.com/stor/library/TSB/a04-073/index.htm... but this doesn't feel the same as previously when the MAP sensor was acting up. (Previously when the MAP sensor was being flaky, I was on the highway and tried to accelerate and the engine hesitated and lost power... that felt different from the above symptoms.)

At first I thought maybe I had accidentally put in gas with low octane, so there was some pre-detonation and the engine was having to sometimes retard the firing? I added more 91 octane and it seemed to have helped slightly, but I'm not sure.

It might also be the MAP acting up, just in a different manner than previously, because this really started happening when the weather changed to be colder and rainy.

Does anyone have any ideas?

Thanks!!

windhund116

Status of air filter & spark plugs?


Thanks!

s2000Junky

When was the last time you checked the valve adjustment? Do you burn any oil and If so, how much have you logged? Spark plug condition would be the first and easiest thing to check for signs of abnormal firing conditions or contamination. No CEL I assume?

UberDuper

That's how my problems started out and it got progressively worse to the point I just wouldn't drive it. It only happened to me after driving for a while.
After doing a bunch of stuff that made no difference at all, I finally sent my injectors off to be cleaned and replaced what had appeared to be perfectly fine spark plugs ~300 miles prior when I did the valve spring retainer swap. When I pulled the plugs this time, two showed signs of running rich.

I'm not declaring victory yet, but it's run great for the last ~150 miles.

Soviet

I have found to have a similar issue on my AP1 on cold starts. Will accelerate in first gear and it feels like there was a misfire because the power will stutter. Only happens at low RPMs. For now I've just driven with it since it doesn't bother me too much and no codes have come up yet. In for updates though.

tritium_pie

Original spark plugs from factory, I guess probably due as well (I honestly don't know lifespan of spark plugs).

Replaced air filter at 80k miles, car currently has 97k miles, so probably due soon as well, though I checked it yesterday and it wasn't that bad.

tritium_pie

Have never checked valves, and oil burn has been consistent since day 1. I would assume (perhaps wrongly?) that valve issues would be consistent across all revs and all gears?

No CEL.

tritium_pie

Thanks everyone for the feedback!

Here's the first actions I'm going to take:
* Replace spark plugs. https://www.s2ki.com/s2000/topic/765...ug-change-diy/
* Replace engine air filter
* Get the updated MAP sensor (Bought it from hardtopguy, not too expensive: https://www.hardtopguy.com/store/pro...5&cat=0&page=1)

I'm hoping I can avoid having a valve job done as I'm sure that's $$$$.

Slowcrash_101

First rule when working on these cars, 70% of the time you're better off doing the work yourself. Valve adjustments aren't hard, not even tricky if you have the right feeler gauges, just time consuming. Compared to a Porsche engine, ours is a cake walk.

The main takeaway is the right drag means you can still slide the feeler gauge but you feel resistance while doing so. If you have to fight it to slide it around, it's too tight, if you have zero resistance, it's too loose. The right drag is the same as putting your finger on wood surface and rubbing it back and forth. I know it's a little subjective, but that's as close as I can get to describing what you're feeling for.

tritium_pie

Thanks for the feedback. I might consider doing the valve adjustments myself if it comes to that. And I think your description for correct resistance is pretty good.