What went wrong :( (timing chain)

Hi guys, Greetings from the UK.

I recently replaced the the timing chain on my beater car and something obviously went very wrong however I cannot figure out what. I am hoping you guys may have some ideas.

So for my POS I have a 2005 toyota yaris, echo I believe you call them in the USA. Its been running like c**p for a while. Low power (even worse than when it’s running properly haha) rough idle and a rattle coming from the engine.

I suspected this may be the timing chain however I wanted to make sure. I did a dry compression test in each cylinder and all were between 150-160 which I thought was alright for its age and mileage (130k). There were no misfires so I assumed the timing must be messed up.

I am a fairly experienced DIY but I have never done a timing chain before, but first time for everything right.

I removed the valve cover and the chain was loose as f**k, upon inspection it seemed the exhaust cam had slipped a tooth which explains why the engine was running like total c**p.

I proceeded to remove all the pullies and other gubbins so I could remove the timing cover and access the timing chain, I rotated the engine so that cylinder 1 was at TDC and as suspected, the inlet cam was a TDC but the exhaust cam was 1 tooth out. Upon looking closer it was obvious the tensioner had failed.

I replaced the chain, tensioner and guides. When I put the chain on I checked that the gold links in the chain lined up with the timing marks on the sprockets, I also checked this after releasing the new tensioner. Additionally I verified cycl one was at TDC and the lobes on both cams were pointing outwards for cyl 1. I rotated the engine 4 or 5 times by hand and all seemed perfect.

I then put everything back together, once again checking before I put the valve cover on that cyl one was TDC and the timing marks were TDC on the cams and the lobes pointing outwards.

I reconnected the battery and tried to start it. It cranked a few times and then I heard that dreaded metal on metal sounds. S**T.

I dismantled everything again and all the timing marks still line up at TDC but the crank will only rotate 180° then jams. It will not rotate either way.

I am aware this means most likely a piston has hit a valve and the engine will need to be stripped down or scrapped but I was so careful to make sure the timing was correct and even referenced the haynes manual to make sure.

I know nothing will save the engine but I just wand to know where I might have gone wrong/ what could cause this. Any help would be much appreciated.

Thanks Wez

Topic

[Jeffrey VoightParticipant]

You say number 1 was TDC. Was it TDC on the compression stroke or exhaust stroke?

[Wesley PowellParticipant]

Yes I’m sure. I think maybe there was some tension or slack in the chain somewhere when I first turned it and the crankshaft may have slipped a tooth or two and I’ve not noticed.

Guess I’ll have to take the head off and see what the damage is

[Jeffrey VoightParticipant]

I’m asking which TDC it was on. Compression or exhaust. It is one or the other. Which one is it?

[Wesley PowellParticipant]

I’m sure compression but I never rotated the crank with the chain off anyway. I only moved the cam slightly. Unless I made a massive screw up and and it somehow rotated…

[Wesley PowellParticipant]

Wait.. If I put the crankshaft positioning sensor sprocket on backwards could it mess the ignition timing up and cause this to happen?

[Jeffrey VoightParticipant]

I wouldn’t think so. It is only a signal generator. It wouldn’t cause pistons and valves to collide.

[Wesley PowellParticipant]

The engine does have variable valve timing though

[Author]

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