Hi everyone.

I'm hoping some of you may be able to help me with a problem I have. I have seen it in some earlier topics, but never with a sollution.

Last spring I bought a Fabia 1,4 16V with motor code BBY.

From the beginning I've had the same intermittent problem, but it seems to be getting more frequent. Most of the time the car runs fine.

Problem: Sometimes after a long drive, when I stop at red light the idle speed drops from the normal 800-900 rpm, down to half. The engine goes roughly alternating a little up and down in rpm, and the engine studders. The EPC light comes on. I turn of the engine, and start it again, and then the engine runs smoothly. EPC-light stays on.

This is the main problem.

I have read out DTCs many times and each time I get another set of DTCs.

The trouble code it signals now is:

17961 (P1553) : Unknown trouble code (I've found this on the net: (Barometric / Manifold Pressure Signals: Implausible Correlation))

What I have done so far (based on earlier DTCs):

Changed brake pedal switch (16955 (P0571)

Cleaned throttle body and aligned it afterwards (It was really messy) (17956 (P1545))

Changed the G28 sensor (Crank sensor) (16705 (P0321))

Other info: The previous owner has retrofittet original cruise control. The engine uses a bit too much engine oil.

Questions:

Have any of you had the same problem and do you know what is causing it?

Could it theoreticaly be a problem with the retrofittet cruise control (which works perfectly)?

Is there any sonsor that could cause this problem?

I am thinking that my next move would be to clean the EGR-system with valve. Can any of you tell me which specific parts and hoses ect. to clean, and if it is not to difficult to do?

What would your next move be?

Thanks in advance. I really hope somebody knows some answers, so I won't loose any more hair over this :-)

The EGR valve sounds like it's failing, they're £50 for a pattern part so just replace it.

Make sure you run it on super unleaded, not the cheap stuff and thrash it more often to help reduce oil consumption.

By "thrashing" do you mean that I should drive the engine to the red area in the rpm.-meter?

How does this help lower oil consumption? Forgive me for being ignorant :-) Thanks for your reply!

By "thrashing" do you mean that I should drive the engine to the red area in the rpm.-meter?

How does this help lower oil consumption? Forgive me for being ignorant :-) Thanks for your reply!

Peak power is about 5500 RPM, so no point in revving it past that point, change down earlier too.

By revving the engine past peak torque to peak power you are dramatically increasing cylinder pressures and this forces the piston rings out harder against the cylinder walls which improves the seal, it also clears out the cat, EGR and exhaust system.

I disconnected the EGR valve and the connecting pipe and cleaned both, though they were not clogged up with dirt.

Sadly it did not help and the same intermittent error is back.

The DTC is 17961 (P1553) - Barometric / Manifold Pressure Signals: Implausible Correlation

Am thinking about changing the MAP-sensor as this is the sensor measuring the pressure in the intake manifold. I have already cleaned the throttle body.

But if the MAP-sensor was faulty would this not give a DTC that the sensor is out of order. Is it possible that the MAP-sensor gives this (above mentioned) intermittent error, that only occurs when the motor is hot and idling?

Thanks in advance :-)

I had a 16v 1.4 (but the earlier version)... peak torque is around 4500rpm.

Someone once told me that engines benefit form periods of peak torque being produced.. I'd have to confirm it as well because by the time I came to sell the car the engine had got sweeter rather than rougher and seemed to get more and more eager while I owned it.. Almost like it had been waiting to be worn in for the previous 40k that the original owner had only ever gone back and forth from the supermarket.

This doesn't specifically help with your fault, but I'm just agreeing with the previous post recommending a thrash. It doesn't have to mean lighting up the tyres.. just some spirited motorway driving

I had a 16v 1.4 (but the earlier version)... peak torque is around 4500rpm.

Someone once told me that engines benefit form periods of peak torque being produced.. I'd have to confirm it as well because by the time I came to sell the car the engine had got sweeter rather than rougher and seemed to get more and more eager while I owned it.. Almost like it had been waiting to be worn in for the previous 40k that the original owner had only ever gone back and forth from the supermarket.

This doesn't specifically help with your fault, but I'm just agreeing with the previous post recommending a thrash. It doesn't have to mean lighting up the tyres.. just some spirited motorway driving

Absolutely, get that engine buzzing between 4000 and 5500 rpm. My oil consumption has dropped dramatically from nearly a litre every 250 miles to almost zero now, this in the space of about 3000 miles of mixed and often 'spirited' driving on super unleaded.

I really cannot recommend replacing that EGR valve highly enough, it isn't that it gets gunged up, it's that the solenoids efficiency is affected by age and constant heat cycling. Also replace your plugs, leads, coilpack if required and definitely replace the temperature sensor on the thermostat housing, then reset the ECU and you'll be good to go.

There's no free fix, you'll have to buy parts, but you can buy 'em cheap on ebay and they'll be fine. Ignore the fault codes, they're usually red herrings.

Absolutely, get that engine buzzing between 4000 and 5500 rpm. My oil consumption has dropped dramatically from nearly a litre every 250 miles to almost zero now, this in the space of about 3000 miles of mixed and often 'spirited' driving on super unleaded.

I really cannot recommend replacing that EGR valve highly enough, it isn't that it gets gunged up, it's that the solenoids efficiency is affected by age and constant heat cycling. Also replace your plugs, leads, coilpack if required and definitely replace the temperature sensor on the thermostat housing, then reset the ECU and you'll be good to go.

There's no free fix, you'll have to buy parts, but you can buy 'em cheap on ebay and they'll be fine. Ignore the fault codes, they're usually red herrings.

I took up the advice some time back and now i'm driving like a mad man, many times a drive up to 5000 rpm. I hope it helps - I'll let time tell me :-)

Sepulchrave: Just to understand you correctly, you think it is a good idea to replace the EGR-valve with a new one? You were not referring to blocking the EGR valve out?

And thank you guys for the advice.

Cleaned the MAP sensor today. It was rather messy. I'll let you know if it helps

Yes, replace that EGR valve. Do NOT attempt an EGR delete, the engine will run much worse.

just to conclude what was causing the initial problem with the rough idling, it was caused by a very dirty MAP-sensor. I changed it and the problem has gone away. Very easy. Just unplug and put in the new sensor. 

Italian tuning is the way to go and although I dont really work on these vehicles. 9times out of 10 . When a vehicle is dripping down and idling funny. Is because of the map sensor. Also 9 times of 10 its not broken. Its just gummed up with oily sludge. A good clean in parts bath or with brake cleaner sorts it