Flat spot in low revs and slight increase in tappet noise

[matth76 0]

Hi

I've just had a new stainless steel exhaust manifold fitted today to my golf vr6 and had new head gasket and tensioners kit fitted (the kit includes all timing chains). The stainless steel 6 branch looks amazing.

 

I have a couple of questions though which have resulted from my journey home:

 

I have noticed the 'usual' vr6 tappet noise is just a bit noisier than normal (although only if I have the window open and I'm not travelling) but it is absolutely fine travelling along - smooth and quiet as usual, although the VR6 noise does drown out everything else. I've been told this kind of tappet noise is pretty normal by Stealth, and a few other companies. Should it be slightly more noticable after just having had the timing chains and head gasket done?

 

One other thing I noticed today was a big flat spot / no decent power between 1k and 2k revs. After that the needle dives for the red line and I get a surge of power - it's almost as though I have a turbo and I have a bit of lag! The 6 branch manifold certainly increases top end torque. I have been told that the flat spot is likely due to the ECU relearning the fuel air mixtures but I have been driving for two hours on the way home from garage and the flat spot is still there (will it normally take longer than two hours for the ECU to sort things out?). I was told my car was originally overfuelling and this has been rectified by the garage. Could it be perhaps that now the overfuelling has been rectified my car will not feel as quick as it used to in the low down revs? Could it be my MAF sensor that is faulty? The garage did say my original "lamda" sensor was on it's way out so they fitted a second hand one. Could the lamda sensor they fitted be faulty? Either way I am taking it back in 500 miles time for an oil change and to resolve any problems for free. Any input or comments from here though will be really useful so I can ask the right questions when I go back after xmas.

 

Could the flat spot be a normal after effect after having a new head gasket fitted? It is a standard head gasket that was fitted. The garage did re-align my throttle body by the way as well as it wasn't correct before. They did a fault check with my car while it was in and there were no faults - although a faulty MAF won't necessarily show up which is why I think it could be possibly this.

 

The ECU was reset while it was with them but should I do it again myself by disconnecting the battery - would this possibly resolve my flat spot problem? If so, what is the procedure to reset the ECU?

 

Thanks for any help guys.

 

Cheers

Matt

[Supercharged 2]

I've just had a new stainless steel exhaust manifold fitted today to my golf vr6 and had new head gasket and tensioners kit fitted (the kit includes all timing chains). The stainless steel 6 branch looks amazing.

 

Jesus - did that actually get done in a day - alot of work there, must have cost a bit!!

 

Tappet noise - can't really think of any reason it would be louder usless it's just being amplified by the SS manifold... did the oil get changed and if so what did they use (thinner oils may cause tappets to become noisy)

 

Half your engine has been taken apart today so you really need to get it on VAGCOM to have a look and check everything is responding and go thru the basic settings...

[matth76 0]

I've just had a new stainless steel exhaust manifold fitted today to my golf vr6 and had new head gasket and tensioners kit fitted (the kit includes all timing chains). The stainless steel 6 branch looks amazing.

 

Jesus - did that actually get done in a day - alot of work there, must have cost a bit!!

 

Tappet noise - can't really think of any reason it would be louder usless it's just being amplified by the SS manifold... did the oil get changed and if so what did they use (thinner oils may cause tappets to become noisy)

 

Half your engine has been taken apart today so you really need to get it on VAGCOM to have a look and check everything is responding and go thru the basic settings...

 

No I 'received' it today sorry. They've had it since Tuesday. They did all the fault checks with VAG com and the only faults were related to the throttle body alignment and lamda which were both sorted out and no other faults were present. Could my MAF sensor cause a flat spot (a faulty MAF sensor may well not show up on VAG COM)?

 

The oil they use is 10w40 and semi-synthetic. They said this was better than the Syntha Silva from VW because it has an anti-gunge additive. They did do a complete oil change when they changed the head gasket etc. They said the oil should in fact quieten down the usual tappet noise although maybe it takes a bit of time ??

 

Would a simple ECU reset solve the flat spot?

 

Thanks for any help.

[matth76 0]

I let my engine warm up fully for a good twenty minutes or more before I went over 3000 revs. Do you think it's bad to rev the engine high after having the chains and head gasket done? I was told no run in period is required and the engine could be treated as normal as long as it is fully warmed up which I am always very careful to do.

[Trig 0]

Engine shouldn't require a run-in period after the chains and clutch have been done. In general though you should avoid taking the car over 3000 until the oil has warmed up. :)

[matth76 0]

Engine shouldn't require a run-in period after the chains and clutch have been done. In general though you should avoid taking the car over 3000 until the oil has warmed up. :)

 

Thanks.. thats cool then because I'm always very careful to let the oil warm up to around 88/90 degrees or at least 15 minutes.

 

Any idea what might be causing the flat spot or increase in tappet noise?

 

I'm having a new head put on in 6 months which will include new tappets / valve guide etc. I can only assume the slight increase in tappet noise must be down to the different kind of oil they have used.

[matth76 0]

Ok..I took my car for a drive today - the tappet noise is fine - slightly tappety as it used to be maybe even slightly quieter (so nothing really to worry about here) - not sure why it was noisier yesterday. The new manifold does tick too when it gets hot and also emphasises any engine sounds - not sure.

 

But the car does seem to have lost power in total I suspect... and there is a clear flat spot early on in the rev range, mainly between 1-3k revs. What could cause all of this? The top end power doesn't feel quite as strong as it used to, although it does remain smooth which is good. I'm concerned about the flat spot though.

 

I was told by a couple of companies and some members on here that a 6 branch should increase mid range torque. I seem to have lost some to be honest. I don't think it is the 6 branch causing my problem as others with a similar 6 branch haven't lost any power - I assume the MAF sensor maybe something to do with this... what does anyone think? I was told the garage reset the ecu (normal practice) when they did all the chains and head gasket etc, so I shouldn't have to reset the ecu again.

 

What about cam timing: how can I or a garage tell if the cam timing is out of sync? Is this easy to diagnose and fix? Would incorrect cam timing cause a slight loss in power?

 

To recap, I had the following done to my car:

Fitted new chains/ tensioners.

Fitted new standard head gasket.

Fitted 6 branch exhaust manifold.

Also realigned throttle body.

Also fitted second hand lamda sensor.

Reduced the fuelling level (as car was over-fuelling).

 

They did a VAG COM fault check and found the throttle body alignment to be incorrect so fixed this (fault disappeared). VAG COM also showed up the original lamda sensor as being faulty so the garage fitted a second hand lamda sensor (fault disappeared). They also corrected my fuelling as my car was overfuelling. This was corrected and fault disappeared. No other faults remained on VAG COM after this.

 

A faulty maf sensor may not appear on VAG COM... could this therefore be the culprit? Not sure why it would suddenly fail after the work was carried out. My car did drive really well before. Could any of the work carried out above cause slight loss in power?

 

Thanks again for any help.

Matt

[dr_mat 0]

"Corrected the fuelling" - how did they do this? The VR6 has a fully managed ECU...

[Trig 0]

Reduced the fuelling level (as car was over-fuelling).

 

Took some of his fuel out?!

[Supercharged 2]

LOL!

[Kevin Bacon 5]

But the car does seem to have lost power in total I suspect... and there is a clear flat spot early on in the rev range, mainly between 1-3k revs.

 

Assuming everything else is OK, the altered flow characteristics of the new manifold could be causing that....either that or the cam timing could be a tooth out on one of the banks, or both.

 

It's similar with the Schrick inlet, you get everything below 4000 and then it flattens off.

[matth76 0]

Ok - an update: I went back to Storm today and they were really helpful - they did another VAG COM check and found out my cam sensor was faulty. Storm put a new one in for me for free and now it drives fine. It is still very very slightly lacking in the low revs but is certainly better than it was yesterday. How easy is it to check and fix cam timing - would it take a good few hours?

 

I took it for a test drive with one of the guys and it certainly seemed much better and pulled stronger in the low revs with the new cam sensor (and the VAG COM fault disappeared with the new cam sensor). It's hard to tell whether the exhaust manifold is going to take away some of my lower rev power (if there is any loss it is only fractional). There certainly is more power top end now with the new 6 branch. They did say the cam timing was double checked when they did it and turned the engine over before the inlet manifold was put back on. By the way they only did the top timing chain and tensioners - not the lower chain as that apparently never needs doing and uses totally different tensioners.

 

I asked them is there an 'easy' way for them to check the cam timing again and they said it can only be done manually and it would be a lengthy process. They would do that for me if necessary for free of course but it seems much better than it was yesterday for sure - from 2.5k revs it starts pulling hard and pulls harder now with the 6 branch. I do know a VR6 as standard lacks grunt below this so I'm assuming it's back to normal. My fuelling was reduced (as my car was overfuelling) so this and the new exhaust manifold could account for slight shift in power towards the top end. And the faulty cam sensor seems to have been the cause of my problems yesterday. What does everyone think? Anyone had similar problems with a cam sensor and found it to be fine after it was fixed?

 

Cheers for any help / comments.

Matt

[Supercharged 2]

A faulty CPS will make it feel 30bhp down...

[Trig 0]

I still don't get the whole 'Overfueling thing', as dr_mat said, it is fully managed by the ECU. My car is overfueling but that is because my ECU is knackered, was there a problem with you lambda probe?

[matth76 0]

Thanks for your replies. Yes I had a problem with my lamda (showed up on VAG COM) which I assume also showed up the over fuelling fault. They replaced the lamda sensor and the fault was corrected. They also realigned my throttle body. There is a tiny bit of slack in the throttle cable but this was checked by them too and it is fine.

 

What is a CPS - is that a cam sensor? My car certainly did seem far more powerful today than yesterday - there does seem to be more power now in the top half of the rev range (quite a fair bit - be good to put it on the rr sometime) but that is due I assume to the 6 branch exhaust manifold. There's certainly no problem with my maf (air flow) sensor and ignition timing as that was all checked today as well on VAG COM. Would a 6 branch exhaust manifold make it feel very very slightly less powerful in the lower revs but more powerful higher up? It all seems to be fixed with the new cam sensor and I think the only difference in driveability in the lower revs (if any) is due to the 6 branch. I'm sure if the cam timing was out (even by a notch) there would still be a fair lack of power?

 

Storm were really helpful and certainly offered (naturally for free) to check and fix any cam timing problems if I had any further problems - but to be honest fitting the new cam sensor seems to have fixed it. Would a rolling road show up any cam timing problems (even if it was slightly out)? As I was thinking of having a rolling road session at Stealth in the new year now I've had the 6 branch fitted.

 

Thanks again for all your comments.

[Supercharged 2]

Yep, without the CPS signal you loose the sequential injection...

[matth76 0]

Cool thanks. The cam sensor does seem to have been the cause of my problem. (what does the 'p' in cps stand for... is it cam 'position' sensor?) My car now pulls fine from 2-2.5k revs onwards. Above 3k revs it pulls like a train and you can hear the air flow through the stainless manifold. It's slightly sluggish below 2k revs but am I right in assuming this is down to the new freeflowing 6 branch exhaust manifold shifting power towards the top end power band? Is it really worth getting them to open the engine up and check the timing again? They did manually turn the engine over before putting the inlet mani back on after they did the chains - they seem to know exactly what they're doing. If my car is pulling fine from 2-2.5k revs onwards does this mean the cam timing is ok?

 

What would be the symptoms if the cam timing was out even by just one notch? Can a rolling road session highlight if cam timing was not correct?

[Kevin Bacon 5]

So they only changed the upper chain and tensioner pad? What about the guide rails? Now that is weird. The gearbox has to come off to change either of the two chains and the upper tensioner. I've never seen any garage leave the bottom chain and tensioner in place and just change the upper ones. That's a false economy and as I said ages ago, you should have stuck a new clutch in aswell to save on repeat labour.

 

The VR will run OK a tooth out on one bank with a drop in power, but if a tooth out on both banks you will notice quite a big lack of power. If the timing is advanced, you'll get more torque low down and nothing at the top. If the timing is retarded, the reverse....

[andy 0]

Putting the engine back together a tooth out is unforgivable in my opinion. Its just not on, and it would be bl**dy amatuerish too. I've done two in my driveway now, the first without a manual even, and still got the timing right. You check, check and check again. Spin the engine over 4 revolutions and check all the timing marks line up again etc etc. If it transpires they've reassembled it a tooth out I'd seriously consider taking it somewhere else next time.

[matth76 0]

They did take the gearbox out to do the upper chain and all tensioners. They replaced everything to do with the upper chain including all guide rails. It was a complete head gasket and tensioners kit. They did a good job.

 

I would have gone for a new clutch and also flywheel but funds were stretched to the limit (with xmas etc).

 

The car seems fine now to be honest and I think they did a good job. It pulls fine from 2k onwards in any gear. Slightly hesitant around 1-1.5k but then it always was. The cam sensor was definitely the culprit for my flat spot.

 

Thanks for your help guys.

[Kevin Bacon 5]

Cool, glad you're happy.

 

The VR is not at it's best in that rpm range anyway, so I shouldn't worry about it.