Hello guys and gals,

I have an annoying problem with my 2007 Fabia with the 1.4 16v BBZ petrol engine, which may or may not indicate major problems. 

When starting out from cold (in a subtropical climate where I live and is rarely under 30°c, mind you) and warming up (between 70° and 90° indicated water temp), my car judders at throttle, and hesitates on his own. I'll explain: when going, say, 30 MPH at 4th gear and with the throttle just barely pressed, it feels as if I were pumping it, it goes back and forth, not violently but still noticeably to the point that my passengers ask what's wrong. Other than that the throttle response is pretty good when fully warmed up and no hesitation is noticeable at any point in the rev range.

I've cleaned and adapted the throttle body in hopes it would solve the problem. No dice. I've cleaned the MAP (which was pretty gummed up), still no luck. As part of routine mainteinance spark plugs have been upgraded to iridium NGKs, injectors have been recently serviced, fuel filter with built-in pressure regulator replaced, ECT sensor replaced, fuel pump replaced (it used to cut off at rather inconvenient times) and all consumables (air filter/oil/etc) are serviced every 7500 km. 


I have a little question as well. There are 4 bar fuel pressure regulators as well as 3 bar ones. I wonder if my car came with a 3 bar regulator originally or if changing from a 4 bar to a 3 bar would make any difference. A 4 bar was the one installed in the car when I bought it but it was a rather shabby one, so I replaced it with a Mahle unit, but I still have my doubts about the correct pressure values.

Thank you in advance

Regards, 


Juan.
 

I strongly suspect a blocked EGR circuit combined with vacuum leaks is to blame for the kangaroo throttle.

@sepulchrave I disconnected the EGR to see what would happen. Nothing at all... I expected an EPC warning or any warning whatsoever. The car behaves normally. The pipe going to the brake servo seems fine, i still need to do the 'soapy water' test, though. I know the EGR valve has been replaced in the past and I'm not surprised if it's the culprit, since our "premium" fuel is just 91 RON. Maybe the EGR pipe is due for a cleaning...

 

Now, what do you reckon about the fuel pressure regulator question? I'm genuinely intrigued. 

24 minutes ago, juanse_2691 said:

@sepulchrave I disconnected the EGR to see what would happen. Nothing at all... I expected an EPC warning or any warning whatsoever. The car behaves normally. The pipe going to the brake servo seems fine, i still need to do the 'soapy water' test, though. I know the EGR valve has been replaced in the past and I'm not surprised if it's the culprit, since our "premium" fuel is just 91 RON. Maybe the EGR pipe is due for a cleaning...

 

Now, what do you reckon about the fuel pressure regulator question? I'm genuinely intrigued. 

 

Fuel pressure regulator either works or it doesn't, I'm not clear why you replaced the old 3 bar unit for a new 4 bar unit, put the old one back on.

15 minutes ago, sepulchrave said:

 

Fuel pressure regulator either works or it doesn't, I'm not clear why you replaced the old 3 bar unit for a new 4 bar unit, put the old one back on.

I guess I didn't explain myself well. The old fuel filter was a generic, off-brand unit which was rated 4.5 bar. I guess a previous owner thought it was fine as it fit. I know OEM regulators for this engine come in 4 and 3 bar forms so I put a 4 bar, as it was readily available, but I wonder if the 3 bar is the correct one. Is there any way to confirm what's the correct fuel filter by chassis number/VIN? The online ETKA catalogs say nothing and there's conflicting information online.

If you get the full car data via erWin  or a helpful Skoda dealer you should find a PR code of either 1A1 if it was built with a 3 bar regulator or 1A3 if 4 bar. My Polo with BBY has 3 bar, but I don't think that helps much.

Edited 8 June, 20196 yr by Wino
Correction

Thank you very much @Wino. I wonder if the PR code is also present at the data sticker near the spare wheel. 

Maybe, if you are lucky.

3 hours ago, Wino said:

Maybe, if you are lucky.

Turns out I'm not. Oh well. Thank you all the same. 

Well, it has been interesting. I unplugged the EGR valve electrical connector yesterday. As I mentioned in an earlier post, nothing happened at all. The car was warm so I just let it rest overnight. 

Today I started the car in the morning, it started normally, and went for a drive. 

The car is soft as silk 🤔 No hesitation, no coughing, no pulsing. The transition from cold to warm is barely noticeable. Apart from a tiny bit of harshness when changing gears (the revs drop a little bit faster now) I notice nothing. Will test with a full tank of gas to check for differences in fuel economy, throttle response etc. 

I'll reset the ECU when I hit the 120k KM mark and see what happens. No check engine lights so far. 

Oh by the way, vacuum leaks are discarded now, except if they are caused by the EGR, in which case a good cleaning and VCDS adaptation would make a difference. I'll clean the EGR valve and piping as last resource before disabling it just like that.

If nothing happens and no fault codes/lights are present with it disconnected from the power supply I'll consider an EGR delete. An EGR valve is a very expensive piece of machinery where I live (450+ EUR, without labor) which doesn't compensate if it breaks often (it was replaced at the dealer 4 years ago) by the quality of fuels we have in this 4th world country I live in. 91RON (max octane rating fuel available) on an 98+RON engine is no good and introducing soot back to the intake only makes things worse. Were our politicians worried about tailpipe emmissions they would require oil companies to improve their quality of fuel. I think a simple EGR delete won't hurt the environment much, all things considered 🤷‍♂️


 

You can't delete the EGR system because you can't reprogram the ECU, you would have permanent fault codes and warning lights and the engine would not run well at all.

 

Simply disconnect the EGR valve to delete it, it will not open and you can see how it negatively affects running and fuel consumption.

6 hours ago, juanse_2691 said:

Well, it has been interesting. I unplugged the EGR valve electrical connector yesterday. As I mentioned in an earlier post, nothing happened at all. The car was warm so I just let it rest overnight. 

Today I started the car in the morning, it started normally, and went for a drive. 

The car is soft as silk 🤔 No hesitation, no coughing, no pulsing. The transition from cold to warm is barely noticeable. Apart from a tiny bit of harshness when changing gears (the revs drop a little bit faster now) I notice nothing. Will test with a full tank of gas to check for differences in fuel economy, throttle response etc. 

I'll reset the ECU when I hit the 120k KM mark and see what happens. No check engine lights so far. 

Oh by the way, vacuum leaks are discarded now, except if they are caused by the EGR, in which case a good cleaning and VCDS adaptation would make a difference. I'll clean the EGR valve and piping as last resource before disabling it just like that.

If nothing happens and no fault codes/lights are present with it disconnected from the power supply I'll consider an EGR delete. An EGR valve is a very expensive piece of machinery where I live (450+ EUR, without labor) which doesn't compensate if it breaks often (it was replaced at the dealer 4 years ago) by the quality of fuels we have in this 4th world country I live in. 91RON (max octane rating fuel available) on an 98+RON engine is no good and introducing soot back to the intake only makes things worse. Were our politicians worried about tailpipe emmissions they would require oil companies to improve their quality of fuel. I think a simple EGR delete won't hurt the environment much, all things considered 🤷‍♂️


 

 

I think you will get fault codes and after a while these will give you the 'emissions' warning light, but I can't say that I'm sure about that, because I haven't tried it myself.

If you can clear the codes with equipment you already have, then that shouldn't be much of a problem.

Good to hear that you've got the car running better.

 

 

3 hours ago, sepulchrave said:

You can't delete the EGR system because you can't reprogram the ECU, you would have permanent fault codes and warning lights and the engine would not run well at all.

 

Simply disconnect the EGR valve to delete it, it will not open and you can see how it negatively affects running and fuel consumption.

That's the weird thing I'm talking about. It's disconnected and it's running better so far...

4 minutes ago, juanse_2691 said:

That's the weird thing I'm talking about. It's disconnected and it's running better so far...

 

That's not weird, that tells you that either the valve is faulty or the pipework is blocked.

 

If you have VCDS you can try running the EGR adaptation routine, if it adapts then the valve is ok, if not the valve has failed, either way you should clean the system out thoroughly.

I unplugged mine at lunchtime, just out of curiosity. No fault lights on the way back to the office, but will give it a fault scan when I find my cable. Didn't notice any driving difference.

I probably won't leave it that way , just experimenting.

My ECU didn't tell me about a completely dead post-cat lambda sensor a while back, at least not with a warning light (just a fault code when I happened to do a scan for another reason), so I'm not sure what will happen.

 

 

 

Yup, I'm doing it just for experimentation as well. 

 

Will give the EGR a good cleaning and adaptation, along with a 3 bar fuel pressure regulator at the next service. Thank you all for bearing with me. I will update as I go. 

If you PM me your VIN, I could probably look up the fuel pressure regulator PR code mentioned earlier, as I'm expecting to be on erWin myself in the next few days. I wonder if @Tech1e knows which engines used 4-bar regs?

 

 

I think AUB and BBZ have a 4 bar FPR, I recall my AUB had the original fuel filter with a separate FPR clipped into the end and I had to replace the whole assembly with the later type with a built in FPR, this was a 4 bar unit and the car ran perfectly subsequently.

This post suggests (if I'm reading it right) that @indars had a 3 bar in his BBZ?

https://www.briskoda.net/forums/topic/226713-fuel-filter-for-14-16v-which-one/

 

I think on balance it's probably irrelevant since the OPs car is now running well with the EGR valve disconnected, whatever FPR he's fitted is clearly compatible.

Well, with the previous 4.5 bar it also ran "right", I've seen these engines only get picky (throw "rich condition" codes) after 6 bar regulators (!) so if a 3 bar regulator is what came with the car, so be it.

3 hours ago, Wino said:

If you PM me your VIN, I could probably look up the fuel pressure regulator PR code mentioned earlier, as I'm expecting to be on erWin myself in the next few days. I wonder if @Tech1e knows which engines used 4-bar regs?

 

 

PM sent, thank you very much!

PM received. 

I've done about 6 short journeys now with disconnected EGR and still no fault lights.  Two codes though when scanned just now, unsurprisingly.  Place your bets on how long 'til I see a fault light...

 

 

On 10/06/2019 at 17:48, Wino said:

This post suggests (if I'm reading it right) that @indars had a 3 bar in his BBZ?

https://www.briskoda.net/forums/topic/226713-fuel-filter-for-14-16v-which-one/

 

 

Yes. When warranty was over, I made maintenance by myself > and old=OE filter was 6Q0201051B (3 bar, with integrated pressure regulator).

Made in PRC- just like Knecht filter, which I used afterwards every 60k km.

Excellent to know that @Wino. I have a 200 mile trip coming on the next few days, I'll have a look at how the car behaves. Thank you. 

And thank you too @indars for joining in. I'll make sure to replace the filter for the correct one at the next service.