bArt2

Hi,

I've got my S2000 2 years now, 80.000 Km.

Since some weeks I noticed it does not run smooth at low speeds especially when the engine is cold.

Driving at constant speed it seems to misfire or something like that, it feels like it slows done for a split second from time to time.

It is not very pronounced (the speed indication does not change) but it does not feel normal, the effect is biggest at low speeds (70-80 Kmh) (2800-3200 Rpm) and with a cold engine.

The performance of the engine feels normal (acceleration)

Could this be a ignition problem or could it also be a mechanical problem.

Lately I had one missed downshift but I am not shure if I did a (big) over Rpm and I had the valve clearance checked 2 months ago.

In the past I had one ignition problem (engine light), there was no ignition on one cylinder, however this problem dissapeared and the reason was not found. (spark plugs were NOT loose).

wanabe

could be several things-
if you want to check something yourself, check the sparkplugs to make sure that they are all properly tightened (i assume from your post that you checked them once so you know how to do it).
if they are tight, take the car to your dealer for new plugs anyway- for the recall.
and have them check your map sensor.
they should be able to find the problem, even if its not one of the above... (b.t.w.- i assume that you are using premium fuel)

cthree

Check your plugs again. One may be fouled or loose. Try some injector cleaner in your next tank of gas. You might also want to have your MAP and O2 sensors and coils checked. If all of that checks out fine then try resetting your ECU. It involves pulling the fuse. You can search and find out how to do this.

cthree

NB:

If you can, post a picture of your spark plugs. That will help us see what they look like and recommend further steps. Check your exhaust. It should be black and sooty but dry. If it's wet or greyish in color, check your plugs again

bArt2

Thanks for the fast reply.

Concerning the sparkplugs, I forgot to mention that I changed them (last week) because they were rather bad but this did not help. (at least they were not lost but they were when my valve clearance was checked 2 months ago).

Today I used a injector cleaning spray but this did not change anything either.

I will go to my dealer end of this week but I am afraid that the mechanics there are not real experts in engines, thats why I am trying to find the problem myself.

I guess bend valves or something like that will not give this kind of problem or am I wrong there?

i'm not able to upload a picture of the plugs at this moment (no hardware )

swells65

What does your air filter look like? Is it clean?

Could be that at low revs there isn't the pressure to suck in air.

Just a thought.