1.8T Shutting down after driving a while

[Pravs]

I have a '06 1.8T which is giving me nightmares these days. Its done 80k miles - engine code AUM.

 

A few weeks ago on a particularly hot day the car started to loose power after being driven for 20 miles or so. It would loose power (not shut down) and in a few second would pick up again and drive normal for a minute or so before loosing power again. Since the past few weeks its been to 3 different garages including Skoda authorized dealer but the problem remains unresolved. I was first asked to change the fuel pump. Did that and it didnt solve a thing. Next in line was injector cleaning and fuel filter change. No change. Now Skoda is asking me to change TB and all hoses. No one has an explanation of why this is happening.

 

As of today it will drive fine for 20-25 miles and then start loosing power. If continue to be driven then it will start shutting down. Starts with a single crank after shutting down but will shut down again in a few seconds. If I shut it down for 10-15 minutes then it will again drive fine for 15-20 miles before doing those things all over again. On a cooler day it will drive for longer before behaving like that. Other symptoms are it has a bit of an erratic idle (not too much though) and takes 2 cranks to start (the battery is fine). The coolant temp stays at 90 throughout so no over heating. No warning lights have come up either.

 

Seriously lost as to what might be wrong. Any help and suggestions would be welcome.

Edited 1 July, 2014 by Pravs

[BrownBarge]

Coolant temp sensor maybe? Just a guess though. Sounds temp related

[David 8]

A possibility is the brake light switch.

 

I got a feeling brownbarge has beaten me to it !!

[David 8]

Haa ha not quite lol

[Bobmonga]

I was thinking brake light switch too until the stalling part.

I believe the brake light switch will only cause loss of power.

[Pravs]

The coolant temp climbs to 90 and stays there so I am guessing that isnt the culprit. What's brake light switch got to do with it? And where should i be looking?

 

Plus it starts stalling after lossing power a few times. If its an open road and I keep on driving then the loosing power bit continues. The moment I slow down or have to stop at a light then the engine stalls. Also if I keep the engine running while standing still then it shuts down after 35-40 mins. And will then keep on shutting down if I restart it. So probably not brake light switch related either coz it does it even when standing still.

 

I keep on feeling that its something electrical. The engine fan was changed a few weeks ago before this problem happened. Post which one of the wires on the top of the battery fuse box (which houses 3 fuses and has 4-5 thick wires going into it) also got burnt. Those are leading met o belive that it might be electrical. However neither Skoda (who scanned the car with VAG COM) nor the other two garages (who also plugged in a high end scanner from Launch while testing the car) I have taken the car to are saying that it might be anything electrical. 

Edited 1 July, 2014 by Pravs

[AndyRG]

I would be checking the battery fuse box.. I had a problem with mine heating up and melting the box and wires.. i could feel mine getting extremely hot within a few minutes of starting the car.

so worth having a closer look

[Pravs]

The fuse box on top of battery was found to be ok.

Have an update. Although its even crazier. 

 

The garage where the car is right now is telling me that there is something wrong with the valves and they will have to open the engine head!!!!! I am beginning to freak out a bit now coz that is dangerous territory. Apparently they swapped a few parts like camshaft sensor and hoses that might have caused this issue with another 1.8T but the problem remains. Can someone please help wrt wether or not valves can be causing such a problem? I have to get back to them by tomorrow morning - either give them a go ahead to open the head or take my car back. The garage is run by 2 guys who used to work for Skoda for many years and I dont have any outright reason to mistrust them.

 

Any other smaller things that I can possibly test out before opening the engine head?  

Edited 1 July, 2014 by Pravs

[Silver Bullet]

This is a new one to me, having rebuilt / tuned a few engines myself (not Skoda's), im puzzled about the statement "something wrong with the valves".

They / you can, without taking the head off :-

Do a compression test (when engine cold then when warmed up), replace spark plugs ( have been known to break down under load and cause misfiring plus maybe wrong gaps), hydraulic tappets functioning (noisey), valves sticking (misfire and loss of power), check for a leaking head head gasket (blown or head warped), dip into the coolant with tool and check for exhaust gasses (or do visual check, remove cap with engine cold, start and check for bubbles in water, check for mayo deposits in coolant tank and under oil filler cap). check all hoses are clamped tight and not leaking when warmed up. Check inlet / outlet mainfold bolts are tight, no leaks around injectors.

 

Finally, keep a list of what has been checked (sounds like this will be an elimination exercise, could be one or more probs contributing). Replace if you can cheaper parts plugs, any suspect hoses / hose clamps, check all electrical connectors wiring etc before moving onto major engine strip down as a last resort.

 

I think a major clue is it seems to be heat related, keep us posted.

 

Good Luck

[BrownBarge]

Could it be the battery or its charging system? If either is weak its only a matter of time before theres not enough electricity to power the electrics that are needed to run the engine, coilpacks, sensors, fuel pump etc... If youve had the fusebox on the battery replaced i would start there was work your way towards the alternator, check its charging correctly and that the battery isnt forked too. Could also try a battery from another car to test that theory. Its sound electrical to me, not mechanical

[KenONeill]

Are you getting lots of warning lights for things like low charge, engine management, anti-lock brake system failure and traction control (including ESP) failure, and maybe losing the stereo and/or seeing the headlights dimming? If not, it may well not be a battery/alternator problem.

 

As to the idea of "something wrong with the valves", I'm thinking more of the tappets than the valves themselves. This is a hydraulic tappet engine, and your symptoms are a bit like tappet pump taken to extremes. So how sure are you about the service schedule having been kept, since this is most likely to be caused by old sudgy engine oil?

 

Alternatively, and this is the most heat-related idea, the coil packs and/or spark plugs could be breaking down at high temperatures and under load, but I'd expect a trained mechanic to consider that.

[DGW]

You say the coolant temperature reading is correct but have you checked the temperature signal being sent to the engine ECU is also correct? I am assuming that your car has a dual temperature sender in which case if it is faulty the two temperature signals could be very different.

[rwbaldwin]

You can get problems like this when the camshaft adjuster is malfunctioning and this would affect the valve timing. If the screen is blocked OR the pickup in the sump is blocked you wouldn't always get a fault logged.

[SONICtheONE]

I would say it sounds like a sensor breaking down when hot, I had a 1.8 20v non turbo do this once, turned out to be the crankshaft sensor.  All the times it did it, the fault was only logged twice.

[Pravs]

Spark plugs and coils were replaced 3-4 months ago at the dealer and have again been checked and found to be working fine.

The battery isn't forked out either coz when the car stalls it starts at one crank. Plus the battery isn't too old either. Also when it stalls all electricals in the car like stereo etc work fine.

Like I said - there have been no light whatsoever on the dash till now. Not even once.

Which sensor sends the temp reading to ECU? And where is it located? In fact this was one if my first theories that ECU is getting higher temp reading and forcing the engine to shut. But then it doesn't explain the loss in power.

The camshaft sensor was swapped with another 1.8t and the problem remained.

If I had to put my money on something I would probably put it on electricals but the car was inspected at the dealer by an electrician and he ruled out any electrical issue.

To say that I am lost would be a huge understatement.

[niceyellow vrs]

I know there is no light on the dash but when it was scanned, were any codes logged at all? Not all codes will put the light on.

[Pravs]

When the car was scanned at the dealer I was told that vagcom showed a TB fault. They don't let you on the workshop floor here so I could not see for myself. Outside with the Launch scanner it didn't throw any code even when the car was stalling while the scanner was plugged in.

[rwbaldwin]

When the car was scanned at the dealer I was told that vagcom showed a TB fault. They don't let you on the workshop floor here so I could not see for myself. Outside with the Launch scanner it didn't throw any code even when the car was stalling while the scanner was plugged in.

The throttle body probably needs a good clean. There is a 'how to' thread. The secret is to do it without removing the connector.

[mluton]

Temp sender does 2 jobs, sorry if this is mentioned already but last week but I had an MOT fail for emissions and my temp gauge was at 90, but on logging it was only 69. So new temp sender and all was well.

Yours could be the opposite and the ecu might cut off the engine if it exceeds 120 sending the wrong values.

A maybe ???????

Sent from my iPhone using Tapatalk

[Pravs]

The throttle body probably needs a good clean. There is a 'how to' thread. The secret is to do it without removing the connector.

 

TB was cleaned last week according to the guide in here. It anyway was pretty clean to begin with.

[KenONeill]

As mluton implies, but doesn't actually say, the engine temperature sensor has 2 separate outputs, one to the guage and one to the EMS, and it's not unknown for the one to fail whilst the other works fine.

[Pravs]

Can that also result in power loss? If the temp sensor sends a high reading then the ECU should just cut the engine off .. not cause it to loose power? 

[BrownBarge]

I dont think it will shut the engine off unless your stationary. No good blasting along at 70mph and suddenly having your engine cut off

[OJazem]

Did you find any solution for this? I have the same problem on my Skoda Octavia, but when the engine goes off I get the battery light on dash. I have tested the battery and it is operating very well.

[Manjunath]

If your car is diesel version. Please check if petrol mistakenly filled on fuel tank. It could cause this problem.