Rev Limiter

[m.Woody]

HI , i have a problem, sunny day (engine dry), I go to overtake 2 cars on the by-pass , drop to 3rd boot it , zooming past antil 5000 revs and then it was like someone turned off the ignition , so i poped her into 4th, pulling again untill 5000revs ,same again ,into 5th, just managed to pass

this is not the only time it has happened

only happens at full throttle

and only cutts out at 5000 revs

made me look very silly allong side a 16v calibra

i mean who would have thought a 16v calibra faster in a straight line than an Elise ?

HELP !

[chorton_1]

Nothing concrete to add I'm afraid, but if it were me trying to get to the bottom of it....

 

First off, check there are no electrical shorts on all the wiring you can see, and/or that the battery isn't able to move around. It doesn't relate to a 5k limit, but is quick and cheap to check.

 

I would then change a few things on the electrical side as this is the most likely area, due to vibration or because it's near peak torque and therefore loads the electrical system the most. It's also relatively cheap and you can always remove the bits and fit them at the next scheduled service so it's not wasted money.

 

In approximate order:-

Distributor cap and arm (£15)

Plug leads (£20+)

Plugs (should get them for £2->£4 each from a motor factors)

 

After this, see if you can find a diagnostic piece of kit. There are are only two things that are REQUIRED to run an S1..... the throttle position sensor (on the throttle body near the cable) and the crank sensor (down at the crank near the bottom of the engine next to the vertical boot panel). The diagnostic kit will tell you whether these have failed and whether to replace them. It is possible to check the throttle pot with a multimeter, but the crank sensor is difficult.

 

If none of this works then change the coil (approx £50). Changing the coil is awkward for access, but by no means impossible (you need to remove the vertical boot panel near the engine to get access, although it may also be possible from below). If you do it all yourself then the labour cost saving will be enough to cover the cost of the parts (i.e. in the time/cost it has taken the garage to check the bits you will have replaced them for new ones anyway).

 

After that it may be worth seeing if you can post a request to borrow an aftermarket ECU as these will give you more information (when combined with someone who is familiar with it).

 

Good luck!

[Scott_Mac]

It's not a VVC is it?

[m.Woody]

It is a S1 standard everything , no vvc, a mate thought it might be a blocked cat or air filter , i will investigate the air filter

and call a mate with a code reader for the ECU

[Zircon450]

HI , i have a problem, sunny day (engine dry), I go to overtake 2 cars on the by-pass , drop to 3rd boot it , zooming past antil 5000 revs and then it was like someone turned off the ignition , so i poped her into 4th, pulling again untill 5000revs ,same again ,into 5th, just managed to pass

this is not the only time it has happened

only happens at full throttle

and only cutts out at 5000 revs

made me look very silly allong side a 16v calibra 

i mean who would have thought a 16v calibra faster in a straight line than an Elise ?

HELP !

<{POST_SNAPBACK}>

Has this car ever been able to pull past 5k RPM before this event ?

[Steve J]

Does the ECU not have a failsafe mode which restricts the revs to 5k if it detects a misfire or other such problem?

[m.Woody]

Has this car ever been able to pull past 5k RPM before this event ?

<{POST_SNAPBACK}>

It does not do it all the time , just when i want maximum aceleration through the gears (like overtaking), i can go past 5000revs if i use part throttle ,

as i said only happens :

car warmed up ,

full throttle ,

exactly 5000 revs

engine goes dead as if you just turn the ignition off ,change up ok untill 5000 revs again

no pops or bangs .

[chorton_1]

No 5k rev limit on a standard S1 as far as I know, although I could be wrong. The ECU is pretty crude and has no way of detecting misfire etc. Crank sensor failure, throttle pot failure and high rpm are the only things that give a ignition cut that I know of.

 

Not sure what the 'limphome' rev limit is if the throttle sensor goes.

[gerags]

I'll let you know sometime tomorrow.

 

I've got to head up to Nottingham so will give it a blast if the M42/A42 is clear.

[Zircon450]

My GUESS,

 

TPS is kaput, why, cause you've reached the end of the fuel injection map to early, cause the TPS is kaput.

 

Go see Uncle Mike at Horizon and take the pain away, even if I'm way wrong.

[chorton_1]

I agree with the likelihood of the throttle sensor. If its in big trouble a probe with a multimeter will show it (sensor should give a nice and progressive resistance change as you open the throttle). Note that if you disconnect it for any reason you WILL get a diagnostic telling you that the throttle sensor has failed!!

[gerags]

Well it went up to (nearly) 6000 - in 3rd of course

[Scott_Mac]

Does the ECU not have a failsafe mode which restricts the revs to 5k if it detects a misfire or other such problem?

<{POST_SNAPBACK}>

 

The VVC engine does Steve which is why i asked...

[Mark H]

Does sound like a faulty throttle position sensor to me!

[Zircon450]

Does sound like a faulty throttle position sensor to me!

<{POST_SNAPBACK}>

Poor b*stard's from Wales, so Horizon's a bit of a run in retrospect.

 

But if you love your car and want it fixed .. I've said my bit.

 

Mark, if you let another Taffy nip past in a Calibra I'll box your ears when we come Anglesey Trac Mon again