can anyone shed any light on this problem its drivin me mad

[TOMMO69TOMMO 0]

right i have a 97 golf vr6 has been running sweet until the other day when all of a sudden it began to hold back at 3000 rpm. the symptoms:

idles fine and runs fine up to 3000 rpm then holds back and get a loud induction roar (engine is standard including air box)

exhaust gets red hot and the gases from back box are red hot

fuel comsumption is averaging 17 mpg

car sounds like its pinking 3000rpm and over

everything points to timing being out but all the mechanics say they have never heard of vr6 timing chain jumping (is this right or is there something else that would cause it)

been on vag.com faults found

00668 supply voltage terminal 30

signal too low-intermittent

00533 idle speed regulation

adaption limit(add)exceeded-intermittent

would these cause these problems????

also been on rolling road and run 133bhp with major torque and power loss at 3000 rpm and above but running fine below 3000 rpm

any input would be appreciated grately as this has baffled many mechanics including the guy at bosch specialist center

[silverline 0]

cat? im sure you would know if the chain had slipped?!

[TOMMO69TOMMO 0]

thanks for the response but the cat has been checked and is fine

[Dave Lea 4]

cat or exhaust baffle partly blocked try removeing o2 sensor from cat and see if it reves better

[Dave Lea 4]

how did they test the cat

[TOMMO69TOMMO 0]

cat was checked visualy and also on a emmisions test and also checked back pressure by replacing o2 sensor with pressure guage

[Dave Lea 4]

what have u tested up to now

[cadguy77 0]

Are you getting any unusual noise from the engine?

[TOMMO69TOMMO 0]

exhaust system and cat checked been on autodiagnosis running test everything seems to be giving right readings had new maf fitted all faults cleared adaptions reset removed and cleaned cam sensor (hall sensor) fuel pressure test new fuel filter

[TOMMO69TOMMO 0]

Are you getting any unusual noise from the engine?

the only difference in engine noise is 3000 revs and above there is alot of induction noise (like its fitted with cone filter) and there isnt the nice vr6 growl from the exhaust that i usually get at 3000revs

[Dave Lea 4]

poss crank sensor prob check if havent

[FishWick 21]

A duff MAF and/or cam sensor can cause what you've described.

[silverline 0]

would the ecu pick up a fault in the emissions ie if the car was running lean? i read a post on another site that an engine running lean can exceed its normal running temp quite considerably and in extreme cases cause piston meltdown!!

not saying that your engine is going to melt but if it was running lean that could cause temps to exceed their norm.

[TOMMO69TOMMO 0]

Thanks for the info the maf has been changed the other day, fitted new cam sensor and one of the temperature senders (the engine control one) were fitted today didnt make any difference as for running lean what would cause this all of a sudden the temp gauge in car is still reading normal but exhaust and exhaust gases are unusually hot

[FishWick 21]

Could be the fuel pump getting tired and not supplying enough motion potion at the top end. You seem to have done everything else, so I'd look there next. I take it it's not had any head work at all recently? Just thinking if the cam timing is a tooth out you'll lose a lot of power and it will run hot.

[TOMMO69TOMMO 0]

have had the fuel pressure tested was 2.5bar the bosch technician said the same thing about it looking like timing was out 1 tooth but the head hasnt been touched it just happened one day while giving it some stick round roundabout

[jaysVR6 2]

Try cleaning your throttle body, I have had this problem intermittentley (only on two occasions) and it's stopped. I've had a word with a mechanic at a local dealer and the throttle bodies get carbonised with age and need cleaning after a while. This is only a guess and I hope it works as I want to stop it happening to. Same symptoms as you, loads of induction no revs and then after a couple of mins she's on song again, it's deffo not mechanical mate if it was it wouildn't run properly full stop.

[Buzzark 0]

have had the fuel pressure tested was 2.5bar the bosch technician said the same thing about it looking like timing was out 1 tooth but the head hasnt been touched it just happened one day while giving it some stick round roundabout

Perhaps what you felt or heard at the time happened is relevant? I assume it was something sudden?

[kilokilla 0]

i have had similar problems to this with vrs and 16v try inspecting all your breather and air intake hoses if they have a small split or are not sealing properly they can cause these sort of problems.

[TOMMO69TOMMO 0]

thanks for all the advice i have had all the air intake pipes off and checked thoroughly no splits or leaks the only thing i do know is when it happened the lifters got very noisey for a couple of minutes then stopped tappin

[Buzzark 0]

Giving stick on roundabout + hydraulic followers going noisey = oil starvation. Hopefully it's just the top end.

Not sure what that does on a VR6 engine, but you may have seized one of the followers or damaged it so it's not pumping up enough to push the valve open fully.

One cylinder (or more) out will cause the lambda sensor to send a false (not really false - it's reading what it's given) and the ECU will try to compensate. Sounds like you've got one cylinder running rich and it's leaning them all off to achieve a balanced oxygen level. That leads to 5 cylinders running lean, pinking, overheated exhaust and impending engine death. x)

Checking that would probably be visible by inspecting the plugs. 5 will look overheated, 1 would look normal or sooted.

(If it's just one cylinder)

Otherwise, a compression test may highlight some variance but chances are the springs are holding it closed OK, it's just not opening to fill correctly on an inlet or exhausting fully.

[TOMMO69TOMMO 0]

thanks for all the info after spending a small fortune on bits i didnt need the problem was found the hyraulic adjuster on the timing chain lost oil pressure allowing the chain to go slack and jump a tooth putting the timing out slightly its now fixed and back on the road and running sweet !lol !lol !lol !lol

[Buzzark 0]

I was party right, but overly gloomy in my prediction! Lost pressure but only the tensioner is very lucky.

I had no idea they had hydraulic adjusters.

Most of my knowledge is gained elsewhere... Since I bought my car yesterday, it's time to start reading up on the VR6 unit me thinks.