V6 wouldn't rev!

I just got back from picking up my little sister from a trip. I drove the 5 minutes to the coach drop off fine, pulled in fine and stopped the car.
It started back up fine and I went to pull away but it wouldn't rev, at all.

It didn't judder or anything, the engine was smooth but there was nothing when I put the throttle down. I looked at the dash and the injector warning light had come on.

I pulled back in and restarted the car and tried again and this time it revved normally, the injector warning light went out about a minute down the road and it worked fine the whole way home.

What would cause this?

hi mot i am having the same problem i think it could be down to the maf sensor or the lambda sensor.did the light come on when you hit a bump?

Nope, I pulled in smoothly and it was fine, when I started up the problem occurred.

Right I have an error code:

p1120
Failed Component Code: Throttle valve pedal plausibility or Throttle valve pedal spring control or Throttle valve actuator protection
Fault Symptom: Signal Not Plausible
Warning Lamp Status: Warning Lamp Illuminated
Fault Test State: Test not complete for this error.
Fault Code Storage State: Error Not Present at time of request
Event Count: 64 count
Filter Count: 0 count

I had this once a few months back, started the engine and revs just didnt seem right (no warning lights), turned it off and on again and it was normal again. I thought it most likely to be the throttle position sensor on the pedal.

Last week the MAF failed completely. Was driving pretty hard along the road when the engine completely lost power, coasted to the road side and the engine cut out. Alfa dealer picked it up and turns out its the MAF had failed.

Well i've gone out and about halfway to my mates the throttle took on a mind of its own. It was idling at 1500 and randomly rising to 3000. Any ideas?could someone post the throttle reset procedure in this thread, as i am on my mobile and its really difficult to navigate this site. Cheers.

m0t - its a throttle problem for sure, not MAF or lambda. Mine seems to throw a fit like this about once a month - I assume the car is female

Symptoms can be:

Driving on a bumpy road, hit particularly vicious bump, injector light comes on, car will not rev properly, feels like massive turbo lag, but is normal-ish after 4k rpm.

If I turn the car off and back on again, the light goes out, but the idle is at 1500, slowly rises to 3000, if I touch the throttle the injector light immediately comes on, the idle drops back down to 800 and it won't rev again. But other times, I turn the car off and back on, and its fine, light on but it goes out after a mile or so.

I think its a loose/corroded connection somewhere that temporarily throws the ECU a signal out of range.

Ive been playing today:

Unpluggeed maf, no difference
Unplugged Lambda, No difference
Check alfa diag and at idle throttle is reported as 30% open, unplug throttle and it idles perfect.
Throttle is making a whiny noise at idle as well, like it is trying to close but can't (sounds like a straining motor) so I am assuming its borked because it thinks it is open more than it is and is trying to close (so the ecu thinks its open more than it is and it wont run right)

Do a throttle reset then:

insert key
turn to MAR
wait 90 seconds
Turn off
(wait 90 seconds - this might be wrong)
turn on and leave to idle
DO NOT TOUCH THE PEDDLE DURING THIS PROCEDURE

Tried it several times, doesn't make a difference

Maybe its the motor that opens and closes the throttle, it might be on its last legs, or maybe it just has a bit of corrosion on the contacts. Have you tried unplugging it and giving it some electrical spray on the pins?

Aye, tried that made no difference

This is an awkward nut to crack.. Next thing I can suggest is to take your car somewhere and swap the throttle body over and see if it cures it. Ned at AutoLusso will have a load, Bedfordshire isn't too far away from you.. This will prove whether or not its a throttle problem or something else.

I have just ordered another throttle body - I don't have time this week to take it anywhere as I need the car for wednesday (going away), If it turns out not to be the problem then I'll just flog it on ebay.

Would appear to be the fault though due to the noise its making and the fact it ran properly unplugged.

Hang on - you unplugged the throttle? What does that do? Prevent the throttle valve from moving at all?!

Originally Posted by Pud237

Hang on - you unplugged the throttle? What does that do? Prevent the throttle valve from moving at all?!

The throttle valve is always open at an idle position, as the v6 has no bypass so in its default position it lets the correct amount of air in to allow the car to idle properly (It doesn't move when you turn it on).

If the throttle is unplugged then the car doesn't know where the throttle is, and in this case once it was unplugged it ran rock steady at 800rpm indicating that whatever the throttle pot is telling the ecu is screwing it up rather than the position of the throttle itself.

Not sure if that indicates a problem with the throttle pot or position sensor, or if its a motor problem on the throttle itself..

Throttle pot.

I did the one thing that seems to be advised against, I took the thing apart.

Took it apart resoldered the connections to the pot, plugged it back in and bobs your uncle it now works fine.

Hopefully I can get a refund on the one I ordered...