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Discussion Starter #1
Hi all,

I fired up my RSR today for the first time in around 2 months. When I started it up I expected it to be a bit tappy until the heads filled with oil but 5 mins later it was still tapping and getting worse so I shut it off. Checked the basics (oil, plug leads etc.) and all seemed fine. Fired it up again and this time it seemed a little worse, the EFI was picking up the revs constantly from idle. I revved it up and it backfired a little but kept running, then when I pressed the throttle again it bogged down and wouldn't rev up so I shut it off again. I didn't really have time to investigate any further but it sounds like a valve related issue :mad:

Heres a video of the problem, if anybody has any ideas I'd appreciate hearing them. It's a bit of a pain to take the rocker covers off as I'll have to take the engine out (The minari subframe is a little tight on the 16v, or some I'm told).

Minari RSR Alfa 1.7 16v 33 Boxer Tapping noise - YouTube

Please let me know if anybody has any ideas!

Thanks!
 
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sounds remarkably like the 33 16V i have on stands at the moment.
that turned out to have 4 bent exhaust valves on the drivers side head....

only way to tell is basic checks, find which cylinders aren't working and check all things like spark and fuel injection (if you're not running carbs) but compression test & more accurately cylinder leak test will give the answers.

access is limited on the 33, had to drop the engine down below the chassis rails to get the compression tester in the plug holes, so may be more of an issue on the minari....
 

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Discussion Starter #3
I seriously hope it isn't bent exhaust valves! That'll be depressing considering I only just got the car with an (apparently) rebuilt engine.

Why would the valves have bent? I don't think the cam belt has slipped, the car hasn't been driven for some time and was fine the last time it was run. Oh dear, looks like I'll have to get the compression tester out on Saturday :(
 
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I seriously hope it isn't bent exhaust valves! That'll be depressing considering I only just got the car with an (apparently) rebuilt engine.

Why would the valves have bent? I don't think the cam belt has slipped, the car hasn't been driven for some time and was fine the last time it was run. Oh dear, looks like I'll have to get the compression tester out on Saturday :(
hope it's not as serious as that, but mine did sound similar although for a glimmer of hope mine struggled to tick over....

does yours sound like all 4 are running? pull off plug leads individually to see if it kills that clyinder (at the cap to be easier as the plugs are burried) or unplug each injector in turn to see which cyls are working, or not...

mine looked like this with the head off. exhaust cam is rotated so all valves should be closed.....:D

 

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Well, I can only hear one "tap" in every four bangs, so whatever the problem is, it should only be affecting one cylinder, hopefully.

My single-cam engine used to tap quietly on one side due to a lack of oil from the centre oil feed (because the cam carrier gasket was leaking), but this sound could be made by a leaking exhaust manifold gasket.

One way of checking where noise is coming from on an engine is to use a length of hose against one ear, move the other end around the engine until the noise is loudest. I know it seems a bit silly, but it does work!

Fingers crossed it is nothing more serious, my honest opinion is that the engine would barely be able to start or run if you had dropped all the valves on one bank, so I reckon it is probably something less catastrophic :thumbs:

Lauren
 
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Fingers crossed it is nothing more serious, my honest opinion is that the engine would barely be able to start or run if you had dropped all the valves on one bank, so I reckon it is probably something less catastrophic :thumbs:

Lauren
mine did!!

although i agree lauren, i can't understand how it did!

even ticked over on the 2 cyls...
 

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If you take one cambelt off a 16v 33 motor (or more likely, one breaks), it will not only idle ok (if a bit shakey) but you can drive the thing without too much trouble. Assuming valves and pistons didn't interfere with each other too much...
 

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mine did!!

although i agree lauren, i can't understand how it did!

even ticked over on the 2 cyls...
If you take one cambelt off a 16v 33 motor (or more likely, one breaks), it will not only idle ok (if a bit shakey) but you can drive the thing without too much trouble. Assuming valves and pistons didn't interfere with each other too much...
Well, I never knew that! I guess the odd firing order makes the engine more likely to run on one cylinder bank, and the extra capacity helps to keep everything ticking over. Probably very similar to one of those new-fangled twin-cylinder engines!

OK, so dropped valves go back on the list of potential faults (gulp).

Lauren
 

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Discussion Starter #9
Ok, so I had a bit of a play today.

First thing I did was to tighten the exhaust bolts up on the drivers side cylinder bank. A friend had mentioned that the noise sounded like a blowing exhaust and I think he may have been right, one of the nuts was quite loose on the stud.

So after tightening them up I fired the car up, she started first time and no more tapping noise was audible (as far as I could tell), however after about 10 seconds she backfired a little, then again and then quite a loud one so I decided to kill the engine. I don't like engines backfiring, it always worries me!

So I had a little google and found a forum in reference to a 145 with a similar backfiring from cold issue. It was suggested that a malfunctioning coolant sensor may have something to do with this (maybe the ECU thinks the engine is hotter then it is?) so I think I'm going to change that because the temp gauge in the car is also reading wrong (it seems to think the engine is at 60c when it's cold, but it's a 3rd party gauge and I'm yet to look if it uses the standard sensor). I also wondered if the MAF had something to do it or perhaps the Lambda sensor, does anybody have any ideas?

As always, advice is appreciated! :D
 

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Interesting…..!

Sounds like we have some similar issues. I started another (similar) thread to try and solve my similar problem.

Will spend some time investigating tomorrow (if my hangover clears in time!) and see if I can come up with somethings to suggest. I may swap over the water temperature sensor as a start, although my gauge reads normally but does not get above about 60 degrees - but I think that may be because there may be no thermostat in the system as it was a race car!
 

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First thing I did was to tighten the exhaust bolts up on the drivers side cylinder bank. I fired the car up, she started first time and no more tapping noise was audible
Yessss! Get in there :thumbs:

So that's the tapping noise sorted, well done. Backfiring does sound like a lean mixture, which as you say could be due to the coolant temperature sender, but I don't know owt about EFI engines, so that is as far as I can go. Sounds like you are on the right track though!

Lauren
 

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Discussion Starter #12
Ok, so I THINK I have a spare coolant sensor. Hopefully I'll get it fitted tomorrow!

I think the MAF might have been a bit damp, as I took it off and kept it in the house for a bit and there was a bit of moisture in it.

So, all being well I'm hoping I'll be able to make some progress tomorrow!
 
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