joes sled 2000

I've been experiencing very rough cold starts when the car sits overnight.I go to start it in the morning,i turn the key and let the fuel system pressurize and then i start it.It starts up but it is VERY rough and it stumbles at a VERY low rpm,and then it does its normal 2k cold idle and its ok for the rest of the day.The car has a vortech supercharger and i'm running the iridium ik24s.Also the battery is brand new.The only possibility i can think of is the weather.Its warm during the day and cool at night.Possibly the ecu getting a little confused from the teperature differential?Any ideas?Its been doing this for about 2 weeks now.

xviper

Check the condition and gap of the plugs. Unclip and re-clip the MAP sensor and give it a thump. Reset the ECU. The ECU seems to be easily "fooled" when there is are unusual temperature changes.

joes sled 2000

I already checked the plugs and they look fine.I do remember prior to the s/c install it would have this same symptom from time to time just not this frequently.I shall try the map whack and ecu reset and we shall see if that helps.Thanks xviper for you're response!

xviper

If this is any consolation to you, mine used to do this also at the start of each winter season. Then, after about the 3rd season, it stopped. Each season, it would take about 4 to 5 episodes for the ECU to "learn". I can tell you that on those occasions when I tried to "help" it by working the throttle, it took much longer to learn. By letting it do its thing on its own, it learned much faster.
Funny thing is, since I put my Vortech on, it has never done it again.

yulook

I to have this problem. When I bought the car new, it never happened. But now, it starts, hesitates and will continue. At first I thought my air filter was clogged or I was using bad gas as I would change different brands.

The weather here in Oregon has been cold but who knows.

BroInTheKnow

Hmmmm...the sparkplugs would've been my first guess as well to. Check your charging system as well to as that can lead to hard starts in the morning. The battery maybe new, but if your alternator isn't keeping the charging system up to snuff then your car is pretty much running on your battery.

I don't think an ECU can be "fooled" per say, because if this was the case it could happen to all cars in a way.

Have you happened to change your fuel filter? Sometimes an old fuel filter may contribute to rough starts.

I always look at things on the preventitive maint. side.

Hope this helps and keep us informed.

Wisconsin S2k

The S2000 ECU is not like other cars ECU's. This ECU is different from any other honda.

ol' dood

Cold starting issues such as abnormal idling(roughness) is almost ALWAYS due to an either rich or lean mixture. Yep, too rich and the engine will "lope"(swings up and down in RPM's and usually is accompanied by black exhaust smoke), too lean and the engine will tend to stall as it wants to idle far too low in the RPM range as it warms up to temperature. Maybe your 'cold start' circuit is at fault. This usually points to an exhaust O2 sensor. As your car is an '01, I would consider changing out ALL emission sensors at one time. If I remember correctly, sensor replacement is part of normal maintenance.

xviper

This is not like "all" cars. The ECU on this car has to run a very high output engine. It relies on numerous sensor readings to run the engine. Each sensor has it's high and low values and each one has "acceptable" ranges for its values. If input from different sensors are at opposing extremes at any given time, the ECU tries the best it can to do simple tasks like control idle, both at cold start, at hot start, at cold running, at hot running. Sometimes it tries to do what's best for a given sensor's input but this may be in contradiction with what another sensor may be telling it. So, yes, it can get "confused" in the sense that it tries to do the best job it can given the inputs it has.
Although not exactly "high output" engines, the ECUs for the Viper and for the Vettes do exhibit similar tendencies. I've owned these, too. A "fix" was implemented for the same sort of glitch on my Vette ZR-1. It was a re-programmed EPROM. The software was altered to help the ECU get less "confused" during certain atmospheric and driving parameters. I know this because I had one of the first ZR-1s and GM used it as the ginea pig to try and resolve the problem.
Modern day ECU are "adaptive", so they do "learn". In the same token, they can be "fooled". Air pressure, air temp, humidity, air density will all contribute to how sensors function and what information they send to the ECU.

Wisconsin S2k

[QUOTE=xviper,May 11 2005, 01:08 PM] This is not like "all" cars.