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225 AMU noisy engine, cam chain tensioner?

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225 AMU noisy engine, cam chain tensioner?

 
Old 03-19-2019, 04:05 PM
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Default 225 AMU noisy engine, cam chain tensioner?

I'll try to make this as short as possible....

I've got a 2001 TT quattro turbo AMU. I've been chasing coolant leaks for a while. I've replaced temperature sensors and o-rings, oil cooler hoses, and the oil cooler itself. Suddenly the check engine light is telling me I've got misfires in cylinder 2. The engine is running rough. I'm seeing coolant under the cylinder 2 area. I think that is from the thermostat o-ring or I fear I've run too hot too long and torn the head gasket around 2 or warped the head.

The quickest thing to do right now is to replace the coil on cylinder 2. Reset and get CEL and misfire in 2 again. Replaced all the spark plugs and I'm noticing the wiring harness connectors are really wonky. A few have broken locking tabs for a long time now and number 1 and number 2 are actually broken inside. The inner piece seems to have broken away from the outer shell. I bet this is the misfire problem. I need to replace all these connectors some day.

While I've got so much stuff removed from the top of the engine I go ahead and pressure test the combustion chambers o.k. I replace the thermostat and o-ring and pressure test the coolant system O.K. I put it all back together and really focus on the connector to the number 2 coil so I get it pushed on as far as it will go. It really doesn't fit nicely so I'm worried about it.

This entire process has been dragged out over several months of free time. The car has been sitting outside through the freezing winter. Battery dead. I jump start it and it runs rough. Starts up right away, but runs rough and really noisy. I drove it around briefly. It lacks power. Check engine light does not come on. Good for now. I think the connector is the problem and really shoving it on there hard is the immediate fix, but now after sitting for months it is making a lot of noise. Online I read that this could be the cam chain tensioner. I think that would throw off the timing enough to lose power, correct? I checked the alignment of the crankshaft, outer exhaust cam gear and flywheel -- all right on. But could it be the tensioner inside causing a slight synchronization issue between the two cams and the rough running and loss of power?

I take everything off the top again and remove the valve cover expecting to see some sort of loose and sloppy chain in there, but it is tight. I have a valve cover gasket set and a new tensioner. The one on the car actually seems tighter than the new one in my hands. I can easily compress the new one and I can press down on the one in the car a little bit. The chain seems tight at least while the engine is not running.

My guess was that freezing cold and old age have finally ruined the tensioner.

And this is my question... how do I know if the tensioner is bad? And also can it be replaced without removing the cams and the chain? It looks like it is really wedged in there like the cams and the chain need to come out in order to remove and replace the tensioner.

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Old 03-22-2019, 06:53 AM
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Originally Posted by Dave-2001 View Post
I'll try to make this as short as possible....

I've got a 2001 TT quattro turbo AMU. I've been chasing coolant leaks for a while. I've replaced temperature sensors and o-rings, oil cooler hoses, and the oil cooler itself. Suddenly the check engine light is telling me I've got misfires in cylinder 2. The engine is running rough. I'm seeing coolant under the cylinder 2 area. I think that is from the thermostat o-ring or I fear I've run too hot too long and torn the head gasket around 2 or warped the head.

The quickest thing to do right now is to replace the coil on cylinder 2. Reset and get CEL and misfire in 2 again. Replaced all the spark plugs and I'm noticing the wiring harness connectors are really wonky. A few have broken locking tabs for a long time now and number 1 and number 2 are actually broken inside. The inner piece seems to have broken away from the outer shell. I bet this is the misfire problem. I need to replace all these connectors some day.

While I've got so much stuff removed from the top of the engine I go ahead and pressure test the combustion chambers o.k. I replace the thermostat and o-ring and pressure test the coolant system O.K. I put it all back together and really focus on the connector to the number 2 coil so I get it pushed on as far as it will go. It really doesn't fit nicely so I'm worried about it.

This entire process has been dragged out over several months of free time. The car has been sitting outside through the freezing winter. Battery dead. I jump start it and it runs rough. Starts up right away, but runs rough and really noisy. I drove it around briefly. It lacks power. Check engine light does not come on. Good for now. I think the connector is the problem and really shoving it on there hard is the immediate fix, but now after sitting for months it is making a lot of noise. Online I read that this could be the cam chain tensioner. I think that would throw off the timing enough to lose power, correct? I checked the alignment of the crankshaft, outer exhaust cam gear and flywheel -- all right on. But could it be the tensioner inside causing a slight synchronization issue between the two cams and the rough running and loss of power?

I take everything off the top again and remove the valve cover expecting to see some sort of loose and sloppy chain in there, but it is tight. I have a valve cover gasket set and a new tensioner. The one on the car actually seems tighter than the new one in my hands. I can easily compress the new one and I can press down on the one in the car a little bit. The chain seems tight at least while the engine is not running.

My guess was that freezing cold and old age have finally ruined the tensioner.

And this is my question... how do I know if the tensioner is bad? And also can it be replaced without removing the cams and the chain? It looks like it is really wedged in there like the cams and the chain need to come out in order to remove and replace the tensioner.
FWIW I haven't seen many cases of bad tensioners on the TT. As far as I know mine is original and I'm going on 18 years/195k miles with no abnormal noises. That being said, there have been a few instances so I think it's worth investigating. It won't be possible now that the valve cover is off but a video of the noise would have been helpful in this situation.

I doubt you'll be able to tell if the tensioner is bad just by feeling it while it's on the car. I do agree that it's strange that the new one feels "softer" but without seeing it for myself it's hard to tell. If it's brand new then there's no reason the tensioner should be bad out of the box. Make sure you have a new tensioner gasket!

Rough running and loss of power can be related to many things. Could be a vacuum leak, but the misfire is most certainly coil-related, or in your case connector-related. All of my coil connectors broke when I had to replace my coils last year. The solution for me was to find someone who sold the connectors as pigtails (not Audi) and use a set of tiny connector tools to remove those pigtails. This leaves just the plastic/rubber seals in place. Break off the old connectors with a pair of needlenose pliers. This shouldn't be hard at all since they are old and brittle, but be careful not to damage the actual metal contacts. The contacts just slide into the back of the new plastic connectors and seat with a tiny click. Voila, you have brand new connectors without any soldering/splicing/etc. There is a DIY thread floating around with this process, I'll see if I can find it for you. Project took me 20 minutes max.

Do you have VCDS? Even though the CEL never came on, the ECU will often store codes if it's running poorly. Finding out if it has any would be worthwhile in this situation.
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