revs up to 7000rpm by itself on my 1.6 auto please help :(

[modman]

Hi everyone I'm new to this site and have bought I cracking 2005 1.6cc allure auto. It has been going fine and then, when I'm drive along the revs will suddenly go up to 7000rpm and thrust the car forward it's quite freaky. It does the same when I put it into reverse. I have change the following new coil pack new Bosch plugs, new cat and full exhaust system. Can anyone please help me shed some light on this so I can get back on the road asap safely thanks Ian

[Capncol]

Does it do it with no input at all from you, or does it carry on accelerating when you back off the throttle? When does it happen? (cold/hot engine) Any warnng lghts? Does it drop back itself? How long does it do it for and how often? What are the gears dong while all ths is going on? change up/down/ lose drive?

[GrandadMonkey]

Throttle pedal potentiometer. Make sure electrical connections are clean and secure. If they are then I think you'll need a replacement throttle pedal something like this:

http://www.ebay.co.uk/itm/Peugeot-206-F ... 27d48b5d6e

However I also believe that they need to be calibrated to the car so personally I would entrust the job to a reputable Peugeot specialist.

[Capncol]

Ron they are an easy DIY calibration, but throttle pedal shouldn't do that as they have 2 circuits that have to agree with each other or else ecu drops into limp and put MIL on. Having said that, I wouldn't completely rule it out.

[GrandadMonkey]

Ok Col. You're more of a techie than I am so, modman, perhaps you'll answer Col's questions so that he can help you to home in on the fault.

I'll sit back and learn.

[modman]

Thank you for your response. My 206cc is a 2005 1.6 16v auto NFU engine. to answer your questions. It will do it without me touching the throttle panel when I put it into drive or reverse. It revs up so i cover the brake pedal until it dies down usual within seconds. Other times I will be driving alone at a steady speed ease of the throttle and then it will Rev up so I then press the brake as not to hit the car in front. When reversing I can be going along and then yet again it will Rev up so again I press the brake and it will die back down.

The gears when driving forward will drop down as if you have planted the accelerator to the floor and the kick down have kicked in. In reverse it just speeds up very quickly as one on reverse gear.

I would say it is mainly when the engine is warm or hot and getting more and more often I have noticed it more when slowing down in forward gear if it helps.

Tick over is bang on. So I don't know what it could be. A friend at work said it may have an air leak and that's sucking in to much air and then the engine management will think it's running too lean so increase the fuel intake. Could he be right and would it be worth changing the intake manifold gasket and throttle body gasket and injector seals?
I did have the anti-pollution come up and the engine manage light but put that down to the old cat that was on it. As now new one it on along with the new exhuast it do not come on any more and the garage plug it in to check codes and it can up with running lean on high bank load 1. So I changed spark plugs and coil pack for an original peugeot one as patten part on before they check the air mass señsor and cleaned the throttle body and reset the engine management light. It has not come back on since.

Thank again for all your help and advice I am very greatful.
Regards Ian

[Capncol]

That would be a massive air leak to make it rev like that so I would think unlikely unless other symptoms.
To check it, have the car fully warmed up and with it idling in park & handbrake on (have an assistant ready to switch off) and gently but firmly try and move the inlet manifold by pulling and pushing backward and forward. Then do the same with throttle body.
You should not get any change in rpm or sounds.
If you can hear it start hissing there is a crack or air leak in the system.

To check throttle pedal output, idealy you need a code reader with live data.
If not you can do it with a digital multimeter. If you have one, I can explain how.
But basically you have a 5V feed to the APP (Pedal position sensor) and you should get 2 different voltages out. One voltage is half the other, and as you open the throttle, the output voltages will go up in synch with throttle position, but still one voltage being half the other (this is the cross check for the ECU)
If one circuit failed, it would run on the other one on limited power for safety as there is no cross check (limp)
You would also get a fault code such as P1120 to P1126 / P1135 or P1214 to P1217/ P1223/ P1224

As an example P1135 (Pedal position sensor circuit A Intermittent) car would use circuit B
P1214 is the opposite (Pedal position sensor B circuit Intermittent) and car would use circuit A

Given the extremely high RPM, I would be looking at a possible ECU fault. If you can get a pro code reader or PP2000 that will read live data , I can tell you what to look for and this would give the best diagnosis.

[modman]

Thanks col I will have a try with the air leak thing at the weekend when I can get my daughter to be my assistant. And will have a word with the fitters at work to see if they can pop round with the car reader machine and see what comes up. I have orders a airtime manifold and throttle body some new injectors and new breather pipes and intake gasket. May not need it but at least I know they are new. I will let you know if anything helps or changes and post the results if it is still like it I will be picking your brains some more.
Cheers Ian