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Worrying engine sound

A few months after having my engine rebuilt I started hearing a sort of "off-tone" in from my engine. Its between 3-4K and sounds like something is loose or catching inside. My car sounds different before and after, which I thought was to do with the cam (standard) which made the engine a lot sweeter at top end.

What Im concerned about is that Ive not had it retuned since the rebuild as it was tuned a couple of moths before going in, will it need doing again? Another thing is I got one of those ecotek things and thought that might be causing it, although Im not really sure. After reading an ecotek post, Im just hoping its not running lean... infact it might be the other way. Does a rebuild need a retune and what could possibly be casuing this differance in engine tone?
  Skoda Fabia vRS

have you done an oil change since the rebuild

also if you had a new cam was it bedded in properly, i might be wrong but it was my understanding you had to bed them in

also regardin the ecotek, if urs is an RT then make sure the vacuum servo is central or its only going to feed cylinders one and two

Oil has been changed and I the cam was fine when it was rebuilt, Im pretty sure they kept it, even so it shouldve run in by now.

I have no idea about a vaccuum servo. Does it need setting up dya think?

ps Its a 1991 RT
  Skoda Fabia vRS

the ecotek does need tuning, but i very much doubt its causing your problems, its very easy to turn it off so check

Its not the ecotek that needs tuning, Ive done that. Im concerned that my mixture being off is causing the sound, because its not been setup by a krypton tuner since the rebuild. Would an off mixture affect my engine like this?
  172 sport,

if you had a full rebuild and the garage didnt retune it then yes it will need to be retuned as everything will be out as you have more compression now , could this noise be pinking wrong c/o wrong timing will cause this , was it fully rebuilt ie pistons, rings, rods, mains, shells etc or just part done???


before we get too carried away lol.......

be a bit more specific on the noise or sound - ie - describe it in detail.

off load, under load, straight line, cornering, hot, cold, with passengers, without, etc etc


I cant really describe the noise but it happens beween 3000-4000rpm and matches the timing of the engine (as if its a constant, in beat with the engine kind of thing), but it only ever makes it in this range. Either side of these points seems fine, but my engine was a bit knacked before it went in, so the mixture might be off, but because It was knacked when I got it I might not realise. I think theyll have setup it up, but I dont know how "roughly" they did it, whether it was done by ear or hooked up to a computer...

When I had it rebuilt they just did the top end, stuff like valves etc, they also did a full belt and gasket change.

Dont know if it makes it when its cold because I wait for it to warm up before winding it up that high, and it doesnt matter if its up hill/down hill or weighed down with a car full, it makes it all the time.

It had to be rebuilt because it had somehow got a crack in the inlet manifold which had leaked air in and burnt away a few valves (nice!), while he was in he said he "rebuilt the top half"

Thats the extent of my knowledge.
  172 sport,

would have thought they d retuned it after all that work so probably count that out is it a high milage / well thrashed engine

if it dont vary on uphill or down, its unlikelt to be load dependent, therefore, unlikely to be engine internals where load donates knock usually.

So, might be exhaust resonannce..

exhaust touching main body.

Heat shields. (rubbing)

Not the top of the engine as this is at half engine speed..

Not the drive shafts or otherwise same as above..

so, more likely the exhaust or bottom pully area..

Could even be engine mounts causing contact when not intended...

Dont sound like engine problems directly though.


Im sure the mounts are okay, because one onf htme was a bit dodgy and I had to have it redone, just a fortnight ago, its still doing it. If its not causing any damage then its no problem I guess. I just dont remember it making that sound before the rebuild.

It sounds like an internal thing and not so much a rattle, the exhaust is unlikely as Ive had all that checked last week and Im constantly underneath it if i do hear a rattle from it.

Cheers for your help