Hi

Under firm acceleration from lowish revs (1500 – 2500 ish) the car stumbles momentarily a few times.  A bit like a 2 stroke "nipping up".

 

It's more than a simple misfire as the car jolts each time.

 

It did this on the drive home from the garage on a Hill and continues to do it.

No engine light.

Garage has suggested running their diagnostics but of course it won't be under load. Will this even show up on diags.

 

AI seems to think its something wrong during fitting of the VVT or oil tube .

Part fitted was ULPTK164AF priced at £164 on ebay which the garage charged at £268. This is a full kit with sprockets and oil pump chain.

Your advice please.

Total bill was £730.

You do not mention what engine the car has. Did you ever use that fuel that you asked about in other threads, from the petrol / diesel misfueling.?

1 minute ago, Evolution13 said:

You do not mention what engine the car has. Did you ever use that fuel that you asked about in other threads, from the petrol / diesel misfueling.?

CBZB

CBZB doesn't have variable valve timing, if that's what you mean by VVT.

Garage need to check timing correlation with correct locking tools.

You probably can see fault codes in engine ECU if cam timing is far enough wrong relative to crank.

Whereabouts are you?

What year is the car?

That's AI for you re VVT.

So timing out is your guess?

If so, it's an interference engine so might suffer damage.

Seems to run OK at higher revs, maybe a bit down on power.

2014

Devizes

Seems likely, given recent work, yes.

Please check for typos in the timing kit number you wrote, google struggling...

https://www.ebay.co.uk/sch/i.html?_nkw=TK164AF+timing+chain+kit&_sacat=0&_from=R40&_trksid=m570.l1313&_odkw=ULPTK164AF+timing+chain+kit+&_osacat=0

So you'd expect these symptoms with timing out?

AI is now saying it sounds like an ECU cut because it senses something is amiss.

get a vcds and look for timing chain deviation and all other parameter related, in that way you will know for sure what is going on, probably even just listening at it wile idling can tell if something is wrong

will do, thanks

you're welcome :)

little AI but you will get a point

This engine features what is known as a "floating" camshaft sprocket. This means the sprocket does not have a keyway, dowel pin, or slot to lock it into a fixed position on the shaft. As long as the center bolt is loose, the sprocket can rotate freely 360 degrees around the camshaft.

The factory procedure for setting the engine to TDC (timing alignment) looks exactly like this:

1. Locking the engine:

   • The crankshaft is set to Top Dead Center (TDC) and locked using a special timing pin screwed into the engine block.

   • The camshaft is locked from the rear end (near the vacuum pump) using a specialized flat alignment plate tool to keep it perfectly horizontal.

2. Installing the chain with loose bolts: The new chain and guides are mounted onto the engine. At this point, the center bolt of the camshaft sprocket must be loose. This allows the sprocket to rotate independently and adapt to the teeth of the chain as it's being installed, without moving the actual camshaft, which remains firmly locked by the tool.

3. Activating the tensioner: The pin is pulled from the new hydraulic chain tensioner so it can extend and fully tension the chain. Only when the tensioner takes up all the slack does everything sit in its ideal position.

4. Torquing down at true zero: While both the crankshaft and camshaft are still 100% locked in place, and the chain is fully tensioned, the mechanic must use a counter-hold tool on the sprocket and torque the new camshaft center bolt to the exact factory specification (torque plus angle).

Where did the mechanic most likely make a mistake?

If the mechanic did not loosen the sprocket bolt when installing the new chain, or if they torqued the bolt down without using a proper counter-hold tool (relying solely on the locking tools inside the engine block/head to resist the tightening force), the locking tools flexed or bent slightly under the heavy pressure. At the exact moment the bolt was torqued, the sprocket "pulled" the camshaft a degree or two out of alignment.

The result is exactly what you are experiencing—an engine that seems to run, but suffers from "incorrect timing" under load because the ECU detects a mismatch between the crankshaft sensor and the camshaft sensor.

---

We went for a test drive with Diags running, all timing parameters were good. Cylinder 4 is cutting out occasionally under load. I will fit new plugs and see if its fixed.

Bizarre coincidence it started immediately after fitting timing chain kit.

Thanks to all who contributed.

nteresting

interesting