hi all.driving my 2001 5.4 harley f150 toady i was braking to stop at a red light when the truck done a quick rev on its own which made the truck shoot forward ,luckily i had the brakes on.please help

 

if the ac was running you probally had a surge, if not then you might want to check and make sure that your camshaft position sensor is in nice and tight. i had a similar problem with my mustang and it was due to the sensor being lose

 

hi mate ,thanks for the advice .sad to say that here in the uk we dont get to use our ac that much ,so ill look into the cam sensor .thanks very much for your time.darren

 

hi mate ,is the cam position sensor the same as the throttle position sensor thanks darren

 

No. The TPS senses the throttle position and the CPS senses the camshaft position, there are 2 of them I believe.

Might this have something to do with your PCV issues?

Could be a problem with your IAC popping open?

 

look for the power stearing resevor (sp?) there is a little black thing on the front cover right behind it thats the sensor.

 

sounds like the IAC to me

 

hi mate ,thanks for your advice.where shall i start.i have codes po171 po174 ,changed pcv valve,but im waiting for the plastic tube and elbow to arive.spent ££££££ on diagnostics but no joy.ive been told to replace the maf,iac .when the pcv kit comes ill put it on and take it from there.thanks darren

 

That's the best idea, otherwise you may just be chasing your tail.

 

Pull your floor mat back, away from the gas pedal.

 

the same thig just happened to me i replaced the TPS and all was good

 

Heres what happens allot - There's a port right behind the IAC stemming from the your PVC valve. when you hit your brakes, that may have created extra suction and/or flow within the TB - specially if the check-valve sticks on the booster . Too much pressure on that weak 90 degree elbow can cause it to split.

The IAC then has more air than it knows what to do with. If this happened once all of the sudden , that would be my guess as to what went on. The more air the higher it will rev into the RPM's.

Your codes usually mean you have a leak in the PVC or VAC system as others have pointed out and it's usually in that elbow .

This one in the back by the firewall. -