problem of 406 after ignition

jonasy · Post by **jonasy** » 21 Jul 2007, 18:25

re: 406 2.0auto gasoline (VIN:VF3**************[VIN obfuscated, can be read by forum staff])
70,000KM

Even now at summer morning, after the first ignition, RPM cannot get up to normal 1300, at most 1100, then start to wobble for 10sec. and then it goes up to 1300(or step on the gas).
or, under a little lower temperature(20c), after ignition, the engine strongly wobbles, then flameout.(if give a step on the pedal before flameout, or restart after flameout, everything seems normal)
besides, I found, for each time of ignition, the rpm is always a bit lower than normal.(for example, when the engine is not cold enough, rpm should be 1000 while ignition, then it is aournd 900, then wobbles, after a little while, up to 1000)
I have cleaned fuel pump, injectors,changed new fuel filter and spark plug.

Your kind help would be high appreciated.

AndersDK · Post by **AndersDK** » 21 Jul 2007, 20:07

Whats the model year of this 2.0L Peugeot ?

Post by **CitroJim** » 21 Jul 2007, 21:47

My first thought here is a problem with the MAP sensor, most likely the pipe from the inlet manifold leading to it letting in air and upsetting the mixture as a result. Quite a common problem. You can often hear a hissing noise indicating an air leak.

This problem can be caused by inlet manifold air leaks anywhere from the throttle body onwards.

Another cause can be the Coolant Temperature Sensor not sending the right signal to the ECU telling the engine it is cold and thus needs a rich mixture.

Does the car run better when it has warmed up?

jonasy · Post by **jonasy** » 22 Jul 2007, 02:48

AndersDK wrote:Whats the model year of this 2.0L Peugeot ?

from the VIN, 2001, i think.

jonasy · Post by **jonasy** » 22 Jul 2007, 02:51

citrojim wrote:My first thought here is a problem with the MAP sensor, most likely the pipe from the inlet manifold leading to it letting in air and upsetting the mixture as a result. Quite a common problem. You can often hear a hissing noise indicating an air leak.

This problem can be caused by inlet manifold air leaks anywhere from the throttle body onwards.

Another cause can be the Coolant Temperature Sensor not sending the right signal to the ECU telling the engine it is cold and thus needs a rich mixture.

Does the car run better when it has warmed up?

yes, it seems normally after warm up.
"from the throttle body onwards"? or backwards?

Post by **CitroJim** » 22 Jul 2007, 07:56

jonasy wrote:yes, it seems normally after warm up.
"from the throttle body onwards"? or backwards?

Air leaks between the throttle body and the engine are the most fatal to a MAP-based system. Check the inlet manifiold gasket for leaks by spraying WD-40 on the joint and looking for it being sucked in and also check every pipe going off themanifold, not forgetting the brake servo.

Given that it is OK once it is warmed, the Coolant Temperature Sensor is worth a check. Check its connections first as they can corrode from small coolant leaks.

jonasy · Post by **jonasy** » 22 Jul 2007, 14:50

citrojim wrote:
jonasy wrote:yes, it seems normally after warm up.
"from the throttle body onwards"? or backwards?
Air leaks between the throttle body and the engine are the most fatal to a MAP-based system. Check the inlet manifiold gasket for leaks by spraying WD-40 on the joint and looking for it being sucked in and also check every pipe going off themanifold, not forgetting the brake servo.

Given that it is OK once it is warmed, the Coolant Temperature Sensor is worth a check. Check its connections first as they can corrode from small coolant leaks.

thanx a lot, ill check them.

jonasy · Post by **jonasy** » 25 Jul 2007, 13:32

today checked possible problem of air leak, it seems ok, please ignore this possibility.

please note: for every ignition, the idle speed is always a little lower than the level it should be, then wobbleds, after a while, goes up to normal idle speed.

hcloh · Post by **hcloh** » 06 Aug 2007, 14:49

If it happens occassionally and you have changed everything else.. then the MAP sensor is on the way out too.

It happended to a friend of mine a coupled of weeks ago and after changing it the idle problem just dissappeared.

jonasy · Post by **jonasy** » 06 Aug 2007, 19:36

hcloh wrote:If it happens occassionally and you have changed everything else.. then the MAP sensor is on the way out too.

It happended to a friend of mine a coupled of weeks ago and after changing it the idle problem just dissappeared.

it happens after all the long-time ignitions.(several hours or one night ,or engine turns ignition off under lower temperature.)