Sudden acceleration


tkswan
02-25-2011, 10:57 AM
What would be some of the root causes of sudden acceleration? I know the RPM's should fluctuate slightly when the compressor kicks in and out as well as and other engine functions. But something is causing a random spike in RPM's.

For example: at a red light if you aren't holding the brake tightly, it will try to lunge forward; and at curb idle (transmission in park) the RPM's will rev up like it does when you start the engine for the first time on a cold day.

joegr
02-25-2011, 02:57 PM
It's important to know the year of your LS. It would be good to know if it is V6 or V8.

For example, the 2002 LS has a mechanical throttle and an IAC. The 2003 has an electronic throttle and no IAC.

tkswan
02-25-2011, 03:29 PM
Well, I didn't say because its actually my sisters 03 Navigator and I wanted general opinions. The navigator forum is dead most of the time, whenever i post a question on that site it never gets a reply, and I know the navigators are just a problem plagued as the LSs'.

This forum is loaded with good expert advice. :) Sorry for breaking the rules...

joegr
02-25-2011, 05:17 PM
Well, I didn't say because its actually my sisters 03 Navigator and I wanted general opinions. The navigator forum is dead most of the time, whenever i post a question on that site it never gets a reply, and I know the navigators are just a problem plagued as the LSs'.

This forum is loaded with good expert advice. :) Sorry for breaking the rules...

I don't know those as well, but I would guess that the Idle Air Bypass Valve (aka IAC) would be a good first suspect. (I believe, but am not certain, that the 03 Navigator was still a mechanical throttle. If I am wrong on that, then there would be no IAC to suspect and you'll have to look elsewhere.)

olopezm
02-25-2011, 06:42 PM
What about a bad MAF sensor? If it's dirty and the air being sensed is different than the actual air the RPM's will keep going up and down.

Best regards,

Oscar.

shorod
02-25-2011, 07:58 PM
How much are the rpms jumping? Is it only happening when at a stop with the foot on the brake or does it also happen to some degree when driving down the road? When the transmission is in park and the engine speed increases, does it stay high or is it just a momentary spike? Does it only happen when the engine is up to temperature?

-Rod

danielsatur
03-01-2011, 04:17 PM
Symptoms of a sticky TPS, or throttle plate.

Is this Lincoln using a drive-by-wire system with a electronic throttle body, or is it cable driven?

If cable driven, clean both sides of throttle plate on your throttle body.

Caution - On a drive-by-wire system, you don't want to mess up the calibration by forcing the throttle plate open.
The key is ON with engine off , need an assistant to hold the accelerator pedal down while you clean the throttle plate.

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