Don't know if anyone has dealt with or seen this before, however my tickover is unpredictable. Sometimes it's what I would expect (around 900rpm) and then others it's a good deal higher (2000). If the tickover is at the higher of these speeds, a flick of the throttle pedal sorts it and it settles back down to 900. Thinking it might have been a sticking throttle cable, I disconnected it, cleaned it, put a small amount of lube into the sleeve, etc and it's not made any difference. To be honest, the spring is so strong on the throttle, I don't know how the cable could stick unless it was seriously frayed.
It's not just that the engine revs too high when coming to a stop, but on deceleration and off the throttle, the car kangaroos as it comes to a stop, when it's in that 'high tickover mode'.
Any ideas/suggestions?

 

Common Problems

Idle / Hesitation / Kangerooing / Misfire Problems

I see a lot of posts on this, and get a lot of PM's about these type of problems so I thought maybe making this a sticky thread would filter some of the problems out.

As idle / hesitation / kangerooing / misfire problems and misfires seem to be a common problem on the S2000, and indeed on most cars, I thought I would construct a thread to aid people in diagnosing their problems.

Aside from an actual problems listed below, these type of problems can just be a passing phase. Your ECU has to cope with changing ambient temps and pressures, and can simply be adjusting. If your problem persists or gets worse then read on....

All this info is based on MY00-05 cars - the 06 has some differences in its setup which im not clued up on (drive by wire throttle etc)

Idle and hesitation / kangeroo problems can be caused by the following:
Loose throttle cable
Failed or failing MAP sensor
Failed or failing O2 / lambda sensor
Air leaks (on the vacuum side)
Blocked throttle lines
Dirty throttle butterfly
Blocked air filter
ISCV / AIC (idle speed control valve) misbehaving
One person (simon prelude) also had a seized aircon pulley which cause a bad idle on his

Hesitation / Kangeroo!
This is a common complaint. You have been driving the car a while, you stop at a junction waiting to pull out, you see your chance, boot the throttle and not a lot happens Frustrating at best, dangerous at worst if you roll out in front of someone!

It has been said that the car will kangeroo becuase of the light flywheel - I dont subscribe to that view. No car ive ever owned does it this bad, and the ECU should easily be able to cope with the flywheel weight. The kangerooing I believe is to be ether IAT (intake air temp) or MAP (manifold absolute pressure) heatsoak. I have some logs from my PLX when the car was kangerooing and there was basically no fuel going in, and some very screwy readings from both sensors.

In my case I bought a new MAP sensor and it was fine again, while others have cured it with intake snorkels and cooling mods. An intake snorkle is a good idea anyway as it ensures the airbox only takes air from outside the engine bay.

Some people decide to live with it by revving the car before pulling away, which effectively allows the engine to gulp a lot of warm air and clear the problem.

Misfires are slightly different but can have some similar causes (more often than not its the MAP sensor if above 6000 rpm):
Failed or failing MAP sensor
Blocked injectors
Damaged coil packs
Worn or damaged spark plugs
Valve clearances
Damaged Crank Position Sensor
Corroded ECU wires - this has been found on a number of cars and isnt easy to detect or fix!
Failed or failing O2 or lambda sensor
Air leaks (on the vacuum side)

One thing to note regarding misfire codes is that they can be diagnosed quite nicely by doing the following. If you have an error code on cylinder 1 and 3, then you can find out if its a coil pack by swapping them around (noting where you put them!) and see if the fault follows it. Valve clearance issues and blocked injectors seem to be the main culprit of misfire codes....

There are many others faults which can crop up, but these tend to be the main ones. This guide should either identify one of these problems as a cause, but if not then at least you have narrowed it down and post up what issues you have!

Ok now how to check what is causing the problem, to be checked in this order.... If your car is hesitating, idling badly or misfiring, then the following should be checked, and if you still get stuck then post up - but it would be helpful to check these first!

 

Cleaning the throttle body is the best place to start.

 

Thanks for the responses. The car runs absolutely fine in all other respects, so I think most of the things above aren't causes of my problem, which is only on tickover and intermittent, fixed with a flick of the throttle pedal. Think I'll try cleaning the throttle body in the first instance but I've not removed those parts before. Will I need any replacement gaskets before I start?

 

It's the most common cause of poor idle a lot of folk tend to clean it in situ which can't be done as the gum and crud is on the rear side of the butterfly so it has to be removed to do the job correctly and while your at it you may as well do the idle control valve as well

 

Thanks again and I'm going to try that, although as I said I don't have poor idle as such. The idle is very smooth. It's just either normal or way too high. I suspect the butterfly doesn't close consistently, probably the result of a buildup of deposits.

will I need any replacement gaskets to do this?

 

if it's normal one time then high another and settles after a blip then it's classed as poor idle and classic symptoms for a sticky throttle butterfly caused by build up of crud as you suggested, as for a new gasket you won't know till you remove it i haven't damaged one yet but i always keep a sheet of gasket paper as back up for these situations just in case i have to make one so if your careful you should be ok if your not sure then give si at Hendy a shout and get one just in case

 

I use my fingers to jam the flap open, Matron...

That way I can blast/wipe both sides and clean the carbon ring off the ridge. It's uncomfortable to painful, but I get better.

Just be careful not to go too mad and hydro-lock the engine with spray.

 

yep, or a brick on the accelerator pedal and a suitable size, soft bottle cleaning brush if you like your fingers intact I'd go for an idle control valve clean while I'm at it too