Enigine knock - help!

[NigelC]

Right, where to start?!

The car is a '98 VVTI TT6.

In the last few weeks engine developed minor pinking or engine knock under acceleration from low revs, especially in high gears, i.e. pulling from 30mph in 4th.

Car was booked in for mods anyway so hopefully they would of sorted it out.

On way to get the mods done, det became more noticeable, making me glad that upgrades were about to be done.

Following mods were then fitted:

New colder plugs
Walbro pump
Lower CW CAT removal pipe
FCD
Megan Racing CAT back exhaust

A fault crack was found on the MAF sensor, and that has been replaced too.

The car still has pinking, det, knocking, call it what you like!

Anyone with any ideas as to what might cause this? Any and all help gladly accepted!

[Martin F]

Be careful, engine knock, det and pinking can be many different things depending on what term you use.

Sounds quite a severe problem, how did it come about ?

Are there any strange noises at idle ?

Without further info the first thing i'd check would be the ignition timing and cam timing. One of these may well lead to narrowing down the problem further.

[NigelC]

Morning Martin!

I first noticed it when I had to fill the car with normal unleaded. Didn't think much of it, just filled it up with Optimax as soon as I could get to a suitable garage.

Car runs on Optimax all the time now.

I'll get the timing checked ASAP and post results.

[NigelC]

Sorry, forgot to mention that it idles perfectly.

[Martin F]

Would I be right in saying you have been through that tank of petrol now or are you still using it ?

It could of been a very bad batch of petrol, but it would have had to of been pretty bad to cause those sorts of problems. Also once it has passed through car should recover fine on new fuel.

[NigelC]

Yeah, tank been refilled many a time since with Optimax.

To describe the sound it is a quietish rattle sounding low and at the front of the car. Almost like stones in a can being shaken.

Paul Whiffin has agreed that is is Det

[Martin F]

Shouldn't really be detonation at that sort of load.

Best to go with the timing checks as I suggested should show up something.

[NigelC]

Cheers mate, I'll let you know the results.

What would cause the timing to be out? Cambelt issue, ECU problem?http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/sad.gif

[Martin F]

Yep, cam belt could of jumped a tooth or you could have a sensor fault which is causing the ignition timing to be off.

It's really a case of checking to see if the basics are all working correctly and then going from there. I guess it could be a spark plug problem so who ever checks the timing may want to pull them out and take a quick look at the plugs as well. The colour and condition can sometimes be quite informative as well.

[NigelC]

Thanks again, I'll pass it on. Plugs are brand new, and were changed to try and cure the probs, so that should rule them out...

[Martin F]

Quote[/b] (NigelC @ Aug. 24 2004,11:31)]Plugs are brand new, and were changed to try and cure the probs, so that should rule them out...
But still pull them if time and chance allows as if you pulled them and they were all a good colour apart from one it would narrow your problem down to an issue with a single cylinder.

Then you could start looking at the injector, running compression test on that cylinder etc.

Good Luck

[NigelC]

See where you are going... I'll pass it on!

[NigelC]

CAM timing was spot on. Timing gun going on it today...

[Martin F]

Hmmm if the ignition timing turns out to be OK as well i'd try checking for any ECU fault codes.

Think IIRC your car is an OBDII one which means you'll need to find somebody with the appropriate scan tool

[NigelC]

hi Guys,

Forgot to update this thread with the resolution.

Well, the car is sorted. Big thanks Paul Whiffin and the boys at Thor.

Turns out the knock was on the car probably due to a combination of the following:

broken MAP sensor
standard fuel pump
dodgy fuel filter

Those were the problems before the tuning started (but unknown at that point).

Tuning involved:
Lower decat
Megan Racing exhaust
FCD
Cold Plugs

After the tune up, the knock got worst, and the parts above were change for new or uprated parts. Knock remained...

Ended up with Thor for a rather long session, and net result was:

The HKS FCD was causing the knock.

An unexpected culprit to say the least!

My advice to all is if you are trying to find a fault, don't forget to check your new parts even if they were added after the fault, as sods law says it's there staring you in your face!

Once again, big thanks to Paul.

[Martin F]

Thats good news, do you know if any fault codes were thrown at all ?


Are you coming to the meet at the end of the month Nigel ?

[Nathan]

Quote[/b] (NigelC @ Sep. 20 2004,14:47)]The HKS FCD was causing the knock.
....but was it still doing it's job ie I presume the car wasn't fuel cutting as you didn't mention that in your initial post.

It's highly odd that the FCD was doing it's job yet in some way it was 'faulty'.

In short, the HKS FCD can quite easily cause problems with det (due to lack of fuel) if it's not set right.....any idea what number it was set at (dial on top)?

[Whifbitz]

Channel 9 mate, it wasn't hitting fuel cut as the boost/ignition was being retarded as there was so much knock!
It wasn't just this causing the problem as the car was detting before the FCD was fitted.

[Nathan]

lol......Channel 9.......the Fast Show.....

So the FCD wasn't the problem then, it was merely aggravating a stiuation that was already there, which is perfectly normal bearing in mind that even on Channel 9 the FCD may well be having an effect on fuelling.

Glad we cleared that up then..... http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif