Problem with rev flat spot on E34 518i

[topcat72]

i have a 1992 UK E34 518i manual, just over 100k miles. it runs perfectly until i get the revs just above 4000. as soon as the needle passes the 4k mark, the engine seems to suddenly loose all its power. i can keep my foot down and watch the needle rise, but there doesnt seem to be a corresponding increase in power from the engine.

if i change up a gear, the engine revs drop to suit the new gear and there is a pause of maybe half a second to a second before the power returns.

its as though there is some kind of limiter in place preventing the engine from outputting any more power as the revs increase.

does anybody have any ideas?

[Jon K]

clutch?

[topcat72]

clutch?


im ruling nothing out, but the clutch shows no other signs of slippage or shudder or excessive travel or any of the normal symptons of wear. it can be driven pretty hard and shows no sign of slipping.

[DaveVoorhis]

its as though there is some kind of limiter in place preventing the engine from outputting any more power as the revs increase.
The limiter *is* the engine. The 518i is about the most staggeringly underpowered car ever unleashed, er, slowly oozed out by BMW.

Actually, if the revs are slowly climbing but the vehicle speed is not, the clutch is slipping. If the vehicle speed increases (slowly) corresponding to the increase in revs, then I'd start by checking the usual suspects: Fuel filter, air filter, plugs, ignition leads, distributor cap, rotor, weak fuel pump, etc. The rev limiter should only cut in at red line.