Saxo Boy

I have been having an intermittent problem with my 2003 S2000. First the details.

Engine: F20c
Miles: 27,400
Service History: FHSH, serviced last week
Mods: T1-R single exit exhaust with T1-R test pipe running anti-foulers to avoid CEL. Spoon snorkel into original airbox. K&N filter in place of stock filter.

The problem: Basically every now and then (i.e. intermittently) my idle goes to pot on approach to lights/roundabout/etc. When I drop into neutral and the revs drop they drop right down to about 2 illuminated bars and the car shakes before either recovering back to normal or cutting out. This can be really bad and can last for up to a few minutes in traffic. Usually when the car is playing up like this it is VERY jerky in the lower gears and feels like it has the mother of all heat soak issues. There seems to be no pattern to it doing this - it just decides to play up and I have to manually hold the idle, whilst braking and operating the clutch - no fun at all!

At its recent service I mentioned the problem and they checked the valve clearances (part of the 27k service anyway) and found them to be out. They said this was the cause, adjusted them and the car ran silky smooth and free from problems for a few days but then the problem returned and it as bad or worse and still intermittent.

I just took a Honda tech out and typically the thing would not play up at all. We discussed the possibilities and he suggested that it might be a back pressure problem. I currently run the T1-R without the bung and with no cat in place. He believes that as it approaches idle the backpressure isn't sufficient and the revs drop too low. As a course of action we have agreed I'll run the car with the bung in and see if that makes any difference. If not then I'll put the standard cat back in and try that. Both the bung and the cat will add some back pressure back into the system.

My questions today are:

1. Can any T1-R on an F20c owners confirm if they have had this or a similar problem?
2. Does a lack of back pressure sound like a plausible cause of my problem?
3. Can anyone otherwise suggest what the problem might be?


Many thanks in advance

Paper Lawyer

Kenny, I never had any problem with the T1-R on the car when it was catted or for the short period (1000 miles?) that it was decatted. I doubt the back pressure is a problem as there are many owners with T1-R exhausts and bigger in the US and I've never seen a problem reported.

shaolin

put your cat back and see how your car runs..

the o2 sensor ready might be off now due to it isn't running the same way it use to be and your computer wasn't set up that way. that's why people toon their ecu, etc.

icethug81

I don't think exhaust have anything to do with it since I have the same problem but my car is totally stock.

After going through different threads on the forum, I found few suggestions since there are manay owners with similar problems....

1. MAP Sensor: some owners reported changing map sensor solved the problems while some other still suffered same problems even after changing it...
2. IAT Sensor: honda tech. usually suggest IAT Sensor is the problem or also it could be Throttle Position Sensor.
3. Fuel Injector/Fuel Cleaner: getting rid of deposits on fuel injector or water in the fuel also could solve the problem.
4. Tightening the throttle cable: too much slack in the cable could cause the rough idle but it rarely solve these kind of problem but it definitely good to check once in a while. (1/2" to 1/4" slack is recommended)
5. Throttle Body Cleaning: some believe this could cure the problem but I really doubt it.....probably temporary solution.
6. Cam Chain Auto Tensioner: some have reported malfunctioning auto tensioner has caused a rough idle but you can actually hear it when auto tensioner is not working......
7. ECU: this is only for MY00 & MY01....there are reports of 00 & 01 Owners, upgrading to '02s or '03s ECU solved the problem and also improved their cars' performance.

I hope this helps~

p.s. I'm getting a new MAP Sensor this week and I'll let you know the result after testing out a bit.

xviper

This situation has been reported on every model year of S2000. It is not a problem unless it starts to do it all the time or if it completely stalls. It is simply the nature of this engine and the way the ECU controls it, that "once in a while", if the conditions are right, you will experience this phenomenon. Not all cars will exhibit this but many do. The ECU is getting all sorts of signals from all sorts of sensors and depending upon the driving situation and the environmental factors at the time, it will do this.
The worst thing you can do is to "help it" by giving it gas to keep it from dipping down in rpm. This will only confuse the ECU some more and the problem will persist even longer. Let it nearly die so that it can learn to compensate.
Now, if you have a car that doesn't learn in spite of NOT helping it, then you can look at things like "freshening up" the contacts of the MAP wiring harness by unclipping it and wiggling it vigorously back on. Then secure it with something like a zip tie. This is what Honda did as a TSB for some MAP issues. Once you do this, an ECU reset won't hurt anything either. But, DON'T do anything until you've determined that it will not learn on its own.
Doing a valve clearance check or replacing the MAP sensor for this situation may not have any relevence and you're just wasting your time and money. Next thing you know, some tech someplace will be replacing your fuel pump, injectors and spark plugs because he hasn't clued in yet that this is NOT a real "problem".

Saxo Boy

It usually stalls these days if I don't catch it. Perhaps I should try a cleaning process (injectors, throttle body, etc), a reset and a 'don't catch' policy if it does it again.

xviper

As hard as it is to do, I suggest you don't "catch it". Let it stall. Then start it up with NO throttle input till it fires up and the idle is secure.
Mine did this from the very first week I got the car new. It did it every year at the same time each year for the first 3 years. I let it die each time and restarted. In the 4th and 5th year, it has not done it.
"Catching it" may only prevent it from ever learning.

ps. Also, sometimes, running the air conditioning can put just enough load on the engine at these low rpms that it will stall. Again, let it stall. It may very well learn on its own.

Saxo Boy

Interesting - what time of year? Here in Scotland it has been doing it over the winter period. Generally it is cold to the tune of 10 degrees C to -10 degrees C. Part of me is curious to see if it will improve/go away as we move into spring. Were the symptoms on your car pretty much identical to mines. Apparantly random, revs drop right down, shudders but then usually picks up after 10-15s and sits fine after that.

xviper

Mine used to happen each year in the transition from fall to winter when the temps begin to approach freezing. You shouldn't have to wait till spring for it to clear itself up, assuming you aren't "helping" it. It should figure itself out after about 1/2 dozen episodes. If it doesn't and you haven't been helping it, then you may have a real electronic or mechanical problem.

icethug81

I just replaced MAP Sensor w/ New Updated one last night. As I started to drive idle got worse than before and finally stalled, but after that there's no more problem with idle anymore. In fact, engine feels more smooth and quite than before. (it could be just my imagination) but it solved the idle problems for me. I guess my MAP sensor was messed up and prevented ECU from 'learning' or feeding wrong info. It only costed me around $50 and I think it's a worth a try. It is cheaper than doing valve job. Hope this help~