9 replies to this topic

[Ayrton7]

Hi all,

Got a MPI on 97k which sounds like very loud tapping that comes in at around 3000-4000 rpm, which I have mainly noticed when in 3rd and 4th gear once under load, then it will just hold at a certain rev and is now unable to go over 70mph.

Around 3500 miles ago it had:
Piston rings
Big End Bearings
Head skim
Rebuilt gearbox by Guessworks

Also done a compression test which was all good at 200 200 190 200 PSI (engine at operating temp)

If anyone could suggest on what the problem may be that would be great

Cheers
Ayrton

Edited by Ayrton7, 02 February 2018 - 07:59 PM.

[cal844]

Is it doing it under load(in gear, vehicle moving) or free reving(neutral vehicle stationary)

If you can replicate the fault under free reving, you can listen to areas of the engine to help diagnose

[Ayrton7]

Yes it's only under load, free revving sounds completely normal which is why I'm finding it hard to diagnose

[MIGLIACARS]

Dont keep driving it then it could go bang at any time.

 

Is it sluggish in 1st and 2nd as well.

[Ayrton7]

Dont keep driving it then it could go bang at any time.
 
Is it sluggish in 1st and 2nd as well.

1st and 2nd are like normal, have heard the noise in 2nd once

[Rorf]

200 psi compression is quite high, must be running a high compression ratio. Sounds more like pre detonation so maybe you need to retard the timing until the knock goes away. Not sure how one does that on a MPI.

[carbon]

200psi compression test is about 10:1 - 10.5 compression ratio.

 

I have only experienced severe knock at this rpm once, was due to overadvanced ignition and made a heck of a racket. As MigliaCars says don't drive it hard if it is knocking badly at these rpm, it will wreck the bigends and mains in short order and could also crack the rings.

 

If you're using 95 octane pump fuel I suggest use up the tank of fuel gently and then go to Shell and fill up with V-Power 99 octane. See if this helps.

[Cooperman]

Yes, it does sound like it's over-advanced.

As above, don't drive it far and don't use heavy throttle until you get it re-timed. It might be wise to use 97 RON petrol from now on as well with the CR you appear to have.

[cal844]

Timinh

[Ayrton7]

200psi compression test is about 10:1 - 10.5 compression ratio.

 

I have only experienced severe knock at this rpm once, was due to overadvanced ignition and made a heck of a racket. As MigliaCars says don't drive it hard if it is knocking badly at these rpm, it will wreck the bigends and mains in short order and could also crack the rings.

 

If you're using 95 octane pump fuel I suggest use up the tank of fuel gently and then go to Shell and fill up with V-Power 99 octane. See if this helps.

 

 

Yes, it does sound like it's over-advanced.

As above, don't drive it far and don't use heavy throttle until you get it re-timed. It might be wise to use 97 RON petrol from now on as well with the CR you appear to have.

Have used V-Power and it does seem to have stopped the knocking, power is still not the same as it once used to be but the engine is pretty tired at 97k. Thanks for the advice anyway, hopefully it keeps going for a while longer at least