Engine Stalling

[Boomlander]

Hi Folks,

Been having problems with my 2000 Felicia lately.

Car starts and drives without a hitch but when you brake and declutch to turn at a junction or a roundabout or stop at a crossing etc. the revs drop to zero and the engine stops unless I am quick enough to give it a blip on the accelerator (not always possible!)The car fires up immediately on the key and drives fine until the next pull up point!

The local Skoda main dealer advised a new Lambda sensor for £178 so I fitted a new unit for £48 but it only made matters worse with the car hesitating on acceleration and also stalling as before.

I cleaned and replaced the original sensor and would appreciate any advice on what the problem could be caused by.

[adurer]

We can't guess what type of engine is fitted on your car unless you're filling your PROFILE from your account settings.

 

A generic answer would be: fuel starvation (check fuel pressure) or unmetered air (check vacuum leaks).

Edited 15 October, 2013 by adurer

[adurer]

Right. Start simple then go to the next level.

 

1) Assess the cleanliness of air filter, fuel filter, and injectors. Change or clean if necessary.

2) Check for any vacuum leaks between air pressure sensor and intake manifold. Seal any leak.

3) With engine at idle depress rapidly 5-6 times the brake pedal. If the engine stalls, check brake booster.

4) Check fuel pump output pressure. Replace if bad.

5) Check fuel pressure regulator output pressure. Replace if bad.

[Boomlander]

Many thanks, I will start to investigate 

[mycoolbeard]

Funny I have this problem, annoying, but will check this list so hopefully,

Mines a 1998 1.6 Mpi Skoda fun btw

[TeflonTom]

My initial gut reaction would be the internal idle speed controller (which is integral to the throttle housing is failing), or the idle switch contacts are not working properly or the throttle cable is a little too tight and is preventing the idle switch from closing when you release the throttle pedal. again that is also internal to the throttle body housing, either that or the throttle plate and bore needs cleaning so the ecu has reached it's adaption limit for idle speed.

so erm... Yes.. I call throttle body problems.

[mycoolbeard]

Oh forgot to mention, will do it a lot more when it's hot

[adurer]

@Boomlander

It is useful to tell us how the problem started to develop, such as:

 

a) apparently unrelated to anything, just out of the blue

after doing such and such repair

c) after doing such and such maintenance operation

d) after filling gasoline from another vendor

e) after a mechanical shock (pothole, rock, collision, etc.)

f) after an electrical short that blew a fuse

g) after cleaning the engine bay

Edited 19 October, 2013 by adurer

[Boomlander]

The problem began a few months ago and has gradually become more frequent as time goes by.

It does get worse when the engine is up to working temperature and does not occur when starting from cold.

I have used the same petrol supply for over five years and changing fuel brand made no difference.

The only repair I have made was to replace the alternator after the voltage regulator failed in the original unit

and allowed the battery to overcharge and  boil dry. 

[adurer]

When did you clean the throttle body last time?

[Boomlander]

I have not cleaned the throttle body before - would this be done with the carburettor cleaner spray that I use on my Classic car's SU carburettor or is there a better method? 

[TeflonTom]

Yea that's it, get in there with the carb cleaner aerosol and an old toothbrush.

[daverapid]

 No doubt the throttle body needs cleaning/resetting, but first I would start with the more basic stuff. The fuel filter gets missed on services on the Felicia due to it's location...almost every one that I've removed I've been unable to blow through due to it being so old and blocked. Also, check for inlet manifold air leaks, including the gasket and pipes. Czech, erm I mean check the valve clearances too, if they close up [not uncommon] the engine will tend to stall.

[Boomlander]

Thanks guys - got some time off at the end of the week so I will try as many of the suggestions as I can before the car goes to the garage on the 29th! 

[adurer]

Boomlander,
In case you are wondering why there is such a wide array of possible causes for the malfunction of your car, you have to know the symptoms described by you are common for almost every car make and model, including those on carburettor and no ECU. For instance, our local Skoda Felicia Club Polska has this special topic (you might need to register) 59 pages, 1753 replies long dealing almost exclusively with that issue.

 

All those who replied to your original post mentioned correctly one or more parts that usually break. For now we are focused on different ways of fuel starvation, but it is not uncommon to be an electrical problem too, starting from a weak battery up to a bad ECU. One thing is certain though, the local Skoda main dealer can stick the lambda probe in his personal exhaust and return you the money with required apologies. I would be very curious on what ground they decided to advise that.

 

In conclusion, be prepared for a methodical approach and don't buy any new part unless you are presented with strong evidence.

 

PS I advice taking out the throttle body for cleaning. You can assess more thoroughly the status of throttle plate and inlet walls (i.e. pitting). Do not use any metallic tool inside!

Edited 20 October, 2013 by adurer

[TeflonTom]

 

PS I advice taking out the throttle body for cleaning. You can assess more thoroughly the status of throttle plate and inlet walls (i.e. pitting). Do not use any metallic tool inside!

it's not strictly necessary to remove it from the car, but I'm inclined to agree that you can do a more thorough job of it when it's removed from the car, just make sure the ignition is switched OFF before you unplug the throttle body wiring harness connector otherwise it might mean a basic settings and throttle alignment diagnostics procedure to be carried out to get it running properly again, I made the mistake of doing this 250 miles from home once and I regretted it all the way home.

[mycoolbeard]

Well gave my throttle body a good clean and it seems to have helped, so many thanks,one more thing in the list of something new I've learned

Had to have it reset on the computer but no hassle

[adurer]

If you were to rate the before/after engine operation, how would you score it on a 1 to 10 scale?

[mycoolbeard]

Certainly better, can't say there was much of a difference during acceleration but then again it's when idling and declutching that the problem occurs so now that has ceased back to normal I suppose

[Boomlander]

I've narrowed the fault suspects down by a process of elimination and everything seems to be pointing to the Idle Air Control Valve in the throttle body so after a good cleaning the problem should be solved.

 

[adurer]

That is why I asked previously about how the issue developed. That part is very often forgotten by those asking for help, making our task more difficult. When an issue gets worse over a lengthy period, it is either a case of corrosion, dirt, arcing, etc. or a part is close to fail totally due to to wear and tear.

[Boomlander]

Car came back from the garage today - turns out the throttle body is actually worn and will need replacing.

In the meantime the engineer has cleaned and remapped the system so although the idle speed is still a bit erratic at least the engine no longer stalls every time you slow for a junction.

Now looking for a reasonably priced throttle body!

[adurer]

Unless the throttle body valve gouged a groove into the air passage, which I doubt, I don't see what is 'worn'. An erratic idle may happen simply from an old throttle body gasket. I don't know how things go in UK garages, but my trust in our local ones is ZERO. How many miles has your TB? What proof of TB wear did the garage offer?

Edited 30 October, 2013 by adurer

[Boomlander]

The car has done 101,000 miles and the garage told me that they had cleaned and set up the throttle body with diagnostic equipment but due to general wear they could not stabilise the idle speed.

Although the car no longer stalls at junctions the engine speed remains high between gear changes and does not drop when you take your foot off the accelerator pedal, maintaining around 2000rpm.

The engine returns to idle at 1000rpm when you bring the car almost to a standstill by braking while still in gear.

[adurer]

Let's recap a little.

So your car ran well previously (including good idle) except for that stall issue when putting the gear shifter into neutral.

 

After a useless O2 sensor replacement, the garage guys (same jokers?) clean the TB, reset it with VAG-COM then you end up with a 2,000 rpm idle and with a 'general wear' (whatever the hell that is) TB.

 

Is it only me that smells rat?