Acceleration hesitation

[loz1971]

HI,
I hope someone out there can help me as i'm starting to pull my hair out, and i don't have enough left!!.

About a week ago, my 406 2.0 16v developed a fault, where, upon acceleration the engine will feel like it is mis-firing for a while and then eventually accelerate as it should. when cruising along the car runs perfectly, and will still reach speeds of 120 on the german 'barns when i'm over there, but as soon as i slow down and have to accelerate starts jumping again, it seems especially bad in second gear.
So far i have replaced all the coolant sensors, all the sensors on the inlet manifold,all the injectors,the fuel filter,the coil pack, all the fan relays, the cooling E.C.U. and all the spark plug rubbers. the spark plugs were only changed just before christmas so i have left them alone.

If anybody can help i will be really, really really greatful.

[jameslxdt]

does it happen at about 2800rpm or anything below 3000rpm?

[mikey s]

replace the lambda sensor mate. had this happen on a couple of different makes.

[philg]

Exact same problem started with me today. Floor the pedal... wait about a second... then the car will start to accelerate. very noticible in second gear.

I had just refitted the tps sensor last night. Had cracked it open to bend the contacts hoping it would mend my ever so slightly irratic idle. it didnt. Wonder could this be the cause somehow.

Whilst searching through past threads its seems that a map sensor COULD solve the problem, at £29.... but you say you've already changed the sensor on the manifold so thats me stumped.

[loz1971]

does it happen at about 2800rpm or anything below 3000rpm?

Hi,
yes it does happen at about those revs, once it's up and going its fine, pulling as normal in fifth gear at high speeds.

[loz1971]

Exact same problem started with me today. Floor the pedal... wait about a second... then the car will start to accelerate. very noticible in second gear.

I had just refitted the tps sensor last night. Had cracked it open to bend the contacts hoping it would mend my ever so slightly irratic idle. it didnt. Wonder could this be the cause somehow.

Whilst searching through past threads its seems that a map sensor COULD solve the problem, at £29.... but you say you've already changed the sensor on the manifold so thats me stumped.

My 406 has NEVER had a smooth tick-over. it went back to the supplying dealer 3 or 4 times for them to sort it out, but in the end they told me it was just normal for all 406's to do it!

[loz1971]

replace the lambda sensor mate. had this happen on a couple of different makes.

Hi,
Thanks for the help, i think i'll try to get a good sensor of another car to try first. I've already spent a fortune and my bank manager will probably torch my car if i spend out on a new lambda sensor. I'll try it this weekend.

[loz1971]

Hi all,
Many thanks for all your advice, i really appreciate it. i will be trying the lambda sensor route this weekend, but not with a new sensor, im not made of money! I'll let you know what happens.
I did read an article given to me by a friend that says Peugeot knew there was a problem with the early cars but didn't perform a recall. It says that there is a chip in the E.C.U. that needs replacing to sort out the readings from the lambda sensor which cures the lumpy tick-over, hesitation and flat spots. I doubt that they will perform this swap for free anymore but i will also be finding out if-

A: this story is true and

B: if they will still change the chip

Again i will let you know, unless any of you already know otherwise.
Thanks again for all your help

[mupp]

Exact same problem started with me today. Floor the pedal... wait about a second... then the car will start to accelerate. very noticible in second gear.

wow my W reg 1.8 petrol has always done this ( 2nd gear being by far the worst ). I had assumed it was a case of They All Do That Sir

[jameslxdt]

Hi all,
Many thanks for all your advice, i really appreciate it. i will be trying the lambda sensor route this weekend, but not with a new sensor, im not made of money! I'll let you know what happens.

if your car is a D8 (pre 99) then you can just disconnect the sensor, if all is well then leave it like this till the mot, then change it, the engine management is soo crap and insensitive it wont see this as a fault

[robconnors1977]

Yes - if i remember from my peugeot days there was a problem with 1.8 16v engines having flat spots in second gear, but from what i can remember a download was available and this cured the fault.

[philmeboots]

I get exactly the same when cold pulling away in the morning - only noticed it in second gear! Give it a bit of welly and it seems to go away

I'm starting to wonder if I've got a cursed 406 (I thought all French cars were cursed TBH!!!)