tyy990

Thanks @Wino. I am interested in the signal wires which seem to be 6,5 and 3. 6 and 5 seem to have the same color code which is weird. Do you have any idea how the signal transmission works? E.g. I see 0.42V in VCDS which wire has this voltage?

Does anybody have the pinout of the lambda probe that is between the engine and the catalytic converter? It's a 6 pin connector. I used to get this stuff from cardiagn.com but now it seems to be broken...

Thanks, mate!

LPG ECU on switch. So no power requirements, just voltage has to be there constantly when ignition is on. Is EGR pin 1 a good match?

It's a BBY engine with Magnetti Marelli 4MV ECU. There should be a switched live under bonnet I guess but I fail to find it. Anybody found it before?

Well that's the first engine design of this kind I encounter. How does it suck fresh air in the intake through the oil cap? There is a ventilation hose connecting the valve cover with the intake but it ends way before the throttle body. So, it is the same as outside air to the engine.

It's a BBY engine. I opened the oil cap with the engine running today to check for fumes and blow-by. The moment I did this idle became really rough and the engine started to stall. I closed the cap everything went back to normal. Did this a couple of times and always got the same result. MIL was there on the dashboard, too but haven't had the time to read error codes yet. Is this normal for these engines? I cannot really figure out why that would be happening.

Yep both times. It was saying Adaptation Status OK or something both times and lower and upper voltage limit slightly changed.

Well all in all that was solved by resetting the ECU to factory defaults by writing value 00 to channel 00 in the engine control module. I really can't believe the ECU needs to be reset and cannot figure out but itself something has changed. But that's what really fixed the problem.

There are too many of these topics with no solution given. I'll try to make a difference. The EGR was the problem. Judder started when EGR opened. It disappeared at higher revs but I think the problem remained it just couldn't be felt at higher revs. The EGR was brand new but non-OEM. I got an OEM one and that solved the problem.

Thanks guys!

Information online is quite confusing. Multiple part numbers and manufacturers. Does anybody know what was fitted by Skoda originally on these engines?

It's manual. I tried another MAP sensor from a scrapyard today. No change whatsoever. Cleaned the throttle body, too. Again no change. @Wino I will definitely do the readings with VCDS. EGR has been replaced recently so the chances are low it's bad. Having ruled out EGR and MAP I am thinking along the line of timing belt tensioner. What else could be the root cause? Played with it some more today. On higher gears the RPM range where the problem happens grows. On 5th gear it's there between 1500 an 2200rpm. It is more noticeable when trying to drive in this interval or decelerating through it. When accelerating it's less noticeable. No more CELs, too. Now that is really weird.

The CEL cannot be caused by this though.

It's a 2004 Fabia 1.4 with the BBY engine. It runs and idles perfectly with one exception. Any attempt to drive it at 1500RPM results in really severe engine judder. A tad different RPMs and the problem is gone. If I insist on driving it at 1500RPM I eventually get P1553 Barometric/Manifold pressure signals: Implausible Correlation. Since under normal driving conditions I rarely end up driving at 1500RPM for any significant amount of time, i.e. I either accelerate or decelerate via 1500RPM the problem does not manifest itself and the error goes away after a couple of trips. Now I'd blame it on a faulty MAP sensor but it's a fairly weird way for it to fail. Is there something else that might cause this?

No hijack really. Is not the case in my case though since I get this behavior with the cover removed and throttle open to atmosphere.

Another thing I forgot to mention - the car spent like 8 months partially disassembled waiting for me to find the time to complete the project. Does something on these cars go bad or stuck from sitting around and not being driven?

I disconnected the PCV hose and checked its integrity. I did check all the vacuum hoses on all sides. I haven't blocked the PCV hose yet and that is something I would do. @Wino you mention in another topic a pressure equalizing port on the PCV body. Where is that? Is it where the arrow points here - I mean the PCV used to work just fine before the overhaul but it might have gone bad now by very unlucky coincidence. 0.4 bar is 30% more than 0.3 bar so maybe I really have a vacuum leak. But I really cannot figure out how it comes and goes like that. Or it might be ECU or MAP sensor failure. Argh, that was not really supposed to be that complicated.

It's 2004 Fabia, 1.4 with BBY engine. That all started after a major engine overhaul. I replaced all pistons (one was worn out and made a clanking noise). Other than that noise the car was running fine before the overhaul. So now after I reassembled it and started it it ran perfectly fine for a couple of minutes and then all of a sudden I got a rough idle and the EPC light on followed by the traction control light. Then idle went completely insane fluctuating between 900 and 1200rpm and not reacting at all to the gas pedal. So I double checked the timing, vacuum, cleaned the MAP sensor just in case but there was no change. Then I disconnected the EGR connector while the engine was running and it immediately started running almost fine and reacting to the gas pedal. So I removed the EGR and soaked it for a while in brake fluid. Then I put it back and the car was idling fine. It warmed up then I drove it around the block and it was all fine. Just as I parked it I got the dash lights again and the same errors. So, I blamed it on the EGR and got a new one. After replacing the EGR I got very similar experience. It was running perfectly for a while then I got the dash lights and then it got to its initial state - weird idle and no reaction to the gas pedal. I am really dumbfounded now. I have double checked timing, brake vacuum hose, EVAP hose (blocked that too), PCV hose...nothing. I have VCDS and I have ran adaptation for throttle body and EGR. Nothing changed. It looks like a vacuum leak in a way since when the car seems to run fine idle is at 880rpm (BBY engine so it should be 680) but I really cannot figure out how it get better and worse like that. In general when I manage to trick it into running fine it could idle fine for hours without getting any errors. Errors only emerge while driving. The MAP senor shows 0.4 bar at idle and 0.97 bar with engine off. The latter seams fine but I am not really sure about the former. So there are three questions at this point: 1) What MAP readings do you guys get at idle? Is 0.4 bar normal? 2) Am I missing some possibility for a vacuum leak? 3) Could this be something else?