Mi Trying To Kill Me

[Chris_Mi 6]

Hi all (a long but amusing story) - questions at the end!

 

After deciding that I am going to pull my Mi on Jenvies (Omex 600) to bits to build a minter, it has grown a mind of its own and is hell bent on killing me.

Last night, on the M42 at rush hour, travelling about 50mph, the car in front starts to brake, so I ease of the throttle to begin to slow down.

 

The 205 decides overwise though, jamming on the revs and rapidly speeding up, even though the accelorator pedal is fully released. As I rapidly increase in velocity, the only way to prevent me from crashing is to brake quite hard - all the while, the car is trying its best to get upto top speed.

 

As I'm stuck in the fast lane with cars all round, this is a pretty dangerous situation - so in all, I end up braking hard for the best part of 0.5km while I figure what to do. When a gap appeared, I stuck it into neutral and free wheeled across to the hard shoulder. It this point the car is in a frenzy of revving its nuts off and I think about 7500rpm was hit for at least 40 seconds.

 

On the hard shoulder I turned the ignition off, opened the bonnet and checked the throttle cable and linkages on the bodies - the cable adjustment was fine, and the linkage/butterflies in the spindles were not sticking - all the butterflies opened and closed as they should when manually moving the linkages.

 

Puzzled, I got back in the car and turned the ignition on - the car sat there happy as larry idling away at 1000 as per normal. Drove home and the car feels significantly less responsive (like you have to really boot it to get anywhere), and it sounds like the engine is doing 500 rpm more than what it actually is doing.

 

So - any ideas. My initial thought is that the OMEX 600 ECU has reset itself somehow - has anyone else experienced this?

Also, does anyone know what part sents the signal for throttle opening to the ECU? And where is this located?

 

Many thanks

Chris

[Anthony 1,000]

The TPS on the (usually passenger) end of the throttle bodies tells the ECU the throttle position.

 

However, even if this failed and told the ECU it was at full throttle when it wasn't, with the throttle shut it should have just bogged down and flooded thanks to being starved of air.

 

Sure the throttle wasn't somehow sticking on the bonnet (or cable caught on the bonnet, bonnet stay etc) hence the issue went away when you opened the bonnet on the hard shoulder? If it happens again, just switch off the ignition with it in gear and it will slow down with a degree of engine braking, plus normal braking as required.

[kyepan 291]

i had this exact same problem on my mi with standard throttles, the radiator cowel had been cut to fit the manifold, the rad was being pushed back by air resistance or hard acceleration and jamming the throttle open.

 

i would guess that you have a similar problem, perhaps the insulation on the underside of the body jammed the linkage open, and as a result, when you opened the bonnet it snapped back, looking fine on inspection.

 

take off the grill and look at how much clearance you have between the bonnet and linkages, then factor in air resistance pushing down the bonnet.. etc etc.

 

it sounds solvable.

[[L'e$kro] 2]

If it happens again, just switch off the ignition with it in gear and it will slow down with a degree of engine braking, plus normal braking as required.

...But don't completely turn off the key as you'll end locking the steering

 

I agree with Anthony's theory: even with a TPS issue the engine would't rev with throttle bodies closed.

Can you check if you don't have any vacuum leaks (servo pickup, inlet manifold not tighten, idle valve etc)

Nicolas

[Baz 421]

' date='Mar 9 2010, 12:47 PM' post='1050610']

...But don't completely turn off the key as you'll end locking the steering

 

Even with the key turned all the way 'off', with the key still in the ignition the steering lock *shouldn't* engage!

[kate205gti 4]

mine did something similar when it was mi16 on TBs running emerald ECU - turned out to be a blue sensor on the side of the block

[Chris_Mi 6]

Thanks Guys (and Gals),

 

I'n not too sure it is vacuum etc related - as it is on Jenvey's!

I'll have a look for catching throttle linkage, but it has never occurred before, and I think there is sufficient clearance all around. Also the throttle pedal definately moved back up to the non-acceleration position which it presumably wouldn't if the linkage was stuck.

 

I'll have a look at the sensors as I think these might be the likely culprit, although I do have a suspicion about the map being reset because it just doesn't ssem quite right now - unless I destroyed the block whilst redlining!

[sideways danny 0]

the map can't be "reset" on the 600. You've probably had massive amounts of valve bounce by letting it rev without load for so long

 

my bet is something's come loose.

[petert 554]

Heat? Causing the shaft to bind in the aluminium body?

 

That's one of the problems with sensing load via TPS. Lots of fuel can be applied for a small load.

[kate205gti 4]

http://forum.205gtidrivers.com/index.php?s...c=56218&hl= found my original thread lol does sound familiar? def worth checking one of the wires into the blue ecu temp sensor hasnt come loose