M20B25 running problems after swap.

[Moffett76]

I've just completed an engine change on my '88 325i Touring and have some runninbg issues that I need help with. I am missing the sensor that reads from one of the ignition leads and plugs in under the OBD1 plug besdie the crank sensor. I have been told this is a pick up for the rev counter....which strangely still works. What does thispick up do, and where can i source one?...it was lost by a mate who borrowed my leads to troubleshoot his own car. I was pissed as it was bitch to get it slide over the replacment leads i had bought a month previous, neah mind. All else seems to be in place. The car won't idle without throttle when cold ( but will rev ), but will idle fine when warm, but won't rev beyond 2k. I've ordered a new belt and tensioner, but the engine came from a running car with no issues?...no stress was applied to the crank etc. so it is unlikely the timing is out?...is the problem the oick up that I cannot replace?

[Speedtouch]

Have you observed the correct ECU bedding in procedure, i.e., let car idle for at least 10 minutes to enable base idle settings to be learnt, then switch OFF, then go for a drive at varying speeds throughout the rev range.

This gets all the settings into the ECU.

Also, check that the throttle position switch (TPS) is set up correctly.

[Moffett76]

No I have not, though I drove the car 5 miles home from the borrowed shed after the install?, the ECU and loom were left untouched, engine came from a '90 325i...I'll try this, but she was left running for while as I needed to bleed the cooling system. The TPS came untouched from the blown unit, I have the Bently manual and an ex MOD Fluke meter....the TPS shall be investigated!...though I do think it's fine, I need to get that ignition pickup, but I'm not sure what it does?