Timing belt change now popping noise from exhaust

Reticular · Post by **Reticular** » 27 Dec 2020, 08:37

I carried out a timing belt change and subsequently notice a popping noise heard by listening just behind the front wheel and appearing to come from the exhaust just behind the engine. It sounds like unburnt fuel igniting in the down pipe. The noise cannot be noticed from under the bonnet. It is getting louder after a short run. The engine starts easily and seems to run smoothly with good power. The emission control light is on. The problem did not exist before changing the timing belt. I would like to give some fault codes but at present cannot get my Vida Dice kit software running. Could this noise be due to a small error in my timing belt setting or something else.

Post by **SuperHerman** » 27 Dec 2020, 20:26

Yes - my guess is you messed up the VVT hubs and your timing is off. Easy to check - just put the crank shaft at its mark and the cams should be aligned with the marks (take off timing cover).

Reticular · Post by **Reticular** » 28 Dec 2020, 10:03

Your guess is probably right as there was an issue with the VVT unit. On this car the inlet cam shaft is fitted with a VVT. Though it was probably not necessary I used the Laser tool 6558 to set the timing, that's the kit that locks the camshafts by a bar with adaptors fitted to the free end of each shaft.

My difficulty was that in order to fit the locking adaptor to the inlet shaft the reluctor disk for the position sensor must be removed, and later refitted. I'm not quite sure what happened but when tightening the reluctor holding bolt, with the spocket wheel held, the camshaft turns within the VVT unit. The VVT unit fixing bolts were not disturbed.

As a solution I turned the camshaft through 180 degrees hoping this would bring the VVT unit back to alignment, though it sounds as though this was incorrect.

Thanks for your suggestion to check the timing again but what what should I have done to reset the VVT unit after the camshaft had turned within it and its setting lost.

Post by **SuperHerman** » 28 Dec 2020, 11:58

"My difficulty was that in order to fit the locking adaptor to the inlet shaft the reluctor disk for the position sensor must be removed, and later refitted. I'm not quite sure what happened but when tightening the reluctor holding bolt, with the spocket wheel held, the camshaft turns within the VVT unit. The VVT unit fixing bolts were not disturbed. "

This does not sound right. If I recall the reluctor should fit only one way correctly - so it is in a fixed position. This is put on after the timing is set.

The VVT should not rotate, other than the amount of play used to adjust the cams. Meaning it should not rotate around and around. The VVT is press fit by a torx bolt under the oil seal cover plug. This is torqued to a fairly high torque. Did you take this bolt out? If so that is where your problem is. You say "bolts" with an "s" - which is the cam timing gear.

Could you clarify?

Reticular · Post by **Reticular** » 28 Dec 2020, 14:24

As you say, the sensor reluctor rotor has two pegs (one round and one cut at 45degrees) that locate with the slot and 45 degree cut out on the end of the camshaft, ensuring positive location. The problem came with tightening the bolt that holds it on.

It is difficult to tighten the fixing bolt into the camshaft end by reacting against the sprocket because the VVT unit prevents the use of a simple sprocket holding tool. At that stage the new belt was already fitted and I was reluctant to rely on the belt alone to hold against my tightening torque. I cannot recollect how I came to notice it, but found the camshaft was able to move via the VVT in relation to the sprocket, and seemed to have no internal return spring or other self resetting ability. That's why I rotated it a complete turn in the vain hope it would re-ajust itself.

The torx bolt in the center of the VVT unit was not released nor the VVT unit removed or dismantled in any way, and for this reason I'd hoped to avoid having to reset it (as described in the Haynes manual) but perhaps this must be gone through ?

Post by **SuperHerman** » 28 Dec 2020, 21:50

Have you reviewed this post? Read through it and this post and then review again what follows below.

viewtopic.php?t=77183

Are you saying the VVT hub has no forward or backward end point?

Can you remove the plastic VVT hub plug and make sure the internal torx screw is properly torqued?