Engine problems following cambelt change on 1.4 16V (AUB)

[karospondent]

I recently fitted new cambelts, tensioners and a waterpump to yy 2002 85,000 mile Fabia 1.4 16v. We've had this car from new and I did the last belt change 6 years ago so it was overdue. The car was running fine with no warning lights on before I started the job. I used a home made cam locking tool to do the job and when I'd finished it was reluctant to fire up and idled very roughly. Furthermore, the EPC, Traction Control and Engine Management lights remained on. I suspected incorrect cam timing and when I checked it the alignment of the various holes on the cam wheels didn't look exactly right so I took both belts off, checked that the crank was at TDC, adjusted the position of the cam wheels slightly and refitted the belt. I checked the postion of the cam shaft locking tool holes and all looked good. I restarted the engine and it started easily but the same warning  lights stayed on and it was idling roughly. I took it for a short drive and it seemed to perform as normal. However, if the revs dropped to idle sometimes it would not respond to the throttle at all and was just stuck at idle. Restarting it several times would get it working again but then it wold do the same thing at low revs or at higher revs. It also feels it is misfiring occasionally underload at low revs.

 

For what its worth my generic OBD reader shows the following errors:

 

Current faults:

 

C3000 - Chassis

P0170 - Powertrain - Fuel Trim (Bank 1)

 

Pending Faults

 

P0172 - Powertrain - System too rich (Bank 1)

C3200 - Chassis

 

Thinking that incorrect cam timing may have bent a valve I checked the commpressions and all four cylinders were within a pound or two of 220 psi (15 bar). The Haynes manual gives the minimum acceptable compression as 7 bar, so there doesn't seem to be any damage.

 

I've disconnected the battery, the throttle body and the ECU and left it for 40 minutes before reconnecting them but it has not made any difference.

 

I've considered checking the cam timings with my dial gauge but I can't find any timing information for this engine and with the camcarrier and cam cover being one unit i can't see how you can get a dial gauge onto the tappet buckets to measure the lift.

 

In desparation I've booked it into my local independent garage, who are good guys, but they can't look at it until next Tuesday. In the meantime does anyone have any constructive suggestions as to what else I could try. It's all very frustrating, especially when i did the last belt change with no problems at all.

[sepulchrave]

You haven't re-adapted the throttle body, it's lost its settings.

[karospondent]

OK, I have disconnected the throttle body so it will need re-adapting. I did follow two different processes for doing htis that I'd read about on this forum but neither appeared to have any effect. Maybe the instructions were incorrect or is it only possible to do this using the full version of VCDS/VAG-COM?

 

Also. it was exhibiting the same symptoms directly after the cambelt change, which did not involve disconnectiong the throttle.

 

Thanks for your response.

[sepulchrave]

You need a registered version of VCDS to do it, although you should clear all the codes anyway and see what comes back.

[karospondent]

A VCDS reset sounds promising and my local garage does have full VCDS, but I still don't understand why the throttle needed resetting if all I'd done was change the cambelts. Is it possible that the cam timing being slightly out would have resulted in the ECU forgetting the throttle settings? I can see that it will need resetting now after having disconnected the throttle but will that resolve the symptoms that I was experiencing before disconecting the throttle? Sorry, but I'm a bit of an old school amateur mechanic and electronics in cars are a bit alien to me!

[sepulchrave]

Stop overthinking this and follow the magic footprints, get all the codes cleared and the TB re-adapted, then see where you stand.

[karospondent]

Codes cleared just now. Not possible to do a DIY VCDS TB re-adaption but I've run it and all the original errors have come back with an extra one:

 

P01016 - Powertrain - Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance problem

 

Unless anyone else has a brilliant idea I'm going to have to leave it till the garage can look at it next Tuesday. I'll post the result!

[Breezy_Pete]

If you were to narrow down your location a bit, someone with VCDS near you might offer to help. I'd be happy to have a go if you're anywhere near me?

[karospondent]

I'm in Coulsdon, Surrey (tel: 07956 22241) and will offer a terrifying pax ride in my Messerschmitt KR200 (bubble-car not fighter plane!) or my faster but rather less exciting Lotus Elise S1 to anyone willing to come round to my place and use their VCDS to work its magic on the old Skoda. Unfortunately, I'm away from early Friday morning until next Monday evening so it would need to be done either tomorrow or Thursday evening.

[sepulchrave]

Your generic OBD reader is missing a ton of stuff and it's not clearing everything, they're crap TBH which is why everyone on here uses VCDS, it's $99 for a licenced version and the lead is only a tenner or so.

[karospondent]

OK, here's the result of my Fabia's visit to the local garage. Embarrasingly they found that the exhaust cam timing was two notches out. The inlet cam timing was fine. They reset the exhaust cam timing and it ran beautifully and all the warning lights went out and have stayed out. They didn't need to use VCDS for any reset work despite me having disconnected the wiring to both the ECU and throttle body to try and reset things. They only charged an hour's labour as i hadn't refitted the wheel arch liner, undertray or cambelt covers so they could get the belts on and off pdq.

 

So next time i do this job i am going to carefully mark the cam wheel positions at TDC using strategically placed dabs of white paint.

[Breezy_Pete]

Thanks for posting this explanation of what was wrong.

Glad you got it fixed for a good price.