Performance change after cam belt replacement?

[Julian Edgar]

Hi, my 1.9 TDI Roomster was going very well - bigger intercooler, straight-through rear muffler, custom intake, custom ECU reflash on dyno. (It's the PD engine.)

Then I got the cambelt changed at 105,000km.

The performance now seems stronger at the top end but much more sluggish at low/mid revs. The performance at 1500 - 2500 rpm now is back to being like a standard car - on the dyno mine was previously about 20 per cent stronger than standard at these revs.

After the new cambelt the idle is also now a little rougher and fuel economy seems a little worse.

Any ideas?

[Transporter]

Re-check the camshaft and crankshaft timing make sure that it was not moved by a tooth and the timing belt is correctly tensioned. If it was done properly performance shouldn't change.

[brad]

one tooth out?

[Julian Edgar]

I didn't do the cam belt change. The company that did it suggests that 'one tooth out' would result in a radical change in performance. Is this true on these engines?

[Jarred]

Aren't PD engines interference engines?

I know what the other guys are saying, but can't imagine that it'd be running very well (if at all) if it was one tooth out.

I don't have any evidence to back that up though, and I'm not about to go change my cambelt to find out.

Did you do it yourself, or at a workshop. Either way, checking the timing would probably be a good idea, as I think scanning the car would be. Might have a sensor that's unplugged, or something that's un related to the cambelt change has gone rye. Just spit balling though.

[Transporter]

one tooth out?

Never heard of?

[ST33VI]

If it is only a very slight change perhaps the old belt was a bit stretched, and now that it has a new belt the tune u had may b a tad bit off. If it is a substantial change it may very well b a tooth out, although usually low end suffers more then high end.
First thing to do is check cam & crank timing are correct and if they are maybe u need to retune.

[Preen59]

I'd suggest that maybe the cam timing is a tooth retarded.

Engines will run 1-2 teeth out usually, as long as there is enough piston to valve clearance.

[brad]

I didn't do the cam belt change. The company that did it suggests that 'one tooth out' would result in a radical change in performance. Is this true on these engines?

I've deliberately done "one tooth out" on other engines in a tightwads attempt to make it go faster (it moved the powerband and didn't really work). I've also managed about 3 or 4 teeth out (because I'm a crap engine mechanic) & the car would still run.

If they refuse to double check the timing marks then you should be able to check it yourself fairly easily.

[brad]

Never heard of?

As in the timing marks aren't lined up / mistimed. Not actually missing a tooth or anything like that.

[gldgti]

No No No No No.

Preen is right - as long as there is enough clearance - and there isnt.

As Jarred said, you can't just go "1 tooth out" on these diesel engines. The valves and pistons WILL hit each other. Changing the belt involves using locking tools for the camshaft to ensure its in exactly the right position and furthermore, the cam sprocket is adjusted on its taper to allow for the difference in belt stretch between the old belt and the new one. Herein lies the possibility for the cam to be less than one tooth out and still work. There of course is a margin to work within, and its feasible that you could notice it.

Please don't anyone put their diesel engine 1 tooth out and lunch you engine.

[Julian Edgar]

So, as a result of my complaint, when the cam timing is re-checked by the company that did it, the marks should line up exactly? And if they don't, there is sufficient adjustment in the taper to ensure they do?

(The performance curve has clearly been moved upwards, and the fuel economy in cruise is also clearly worse than it was previously - have now done a lot more kilometres.)

[brad]

Please don't anyone put their diesel engine 1 tooth out and lunch you engine.

I don't think anyone was suggesting the engine should be mis-timed deliberately. I certainly wasn't. What I was saying is that 1 tooth out is a distinct possibility.

[brad]

So, as a result of my complaint, when the cam timing is re-checked by the company that did it, the marks should line up exactly? And if they don't, there is sufficient adjustment in the taper to ensure they do?

(The performance curve has clearly been moved upwards, and the fuel economy in cruise is also clearly worse than it was previously - have now done a lot more kilometres.)

They should line up IAW whatever the manual says. It will be quite specific & there will be pictures for them to look at.

This any help?

[Transporter]

I don't think anyone was suggesting the engine should be mis-timed deliberately. I certainly wasn't. What I was saying is that 1 tooth out is a distinct possibility.

Me neither, and certainly the slots in the cam gear are wide enough, so they could move by 1 tooth on the cam without the pistons hitting the valves. It would be interesting to know what reason they will give.