issues on new m52 install.

[nickso]

having a few issues on my m52 and was wondering if anyone had any ideas. m50 manifold is fitted.

1) it backfires on overrun. not big bangs but lots of little pops. i've not worked it out yet but fuel economy is looking vastly different from when it was in the e36 touring which i drove for a year before conversion. willnz suggested checking the throttle cable was shutting the intake butterfly properly, i put a brand new cable on as the one i had was a bodge and its set correctly now, i also changed the TPS for a spare. no effect. is there any chance my shit exhaust is causing an issue? i used the 325 one mated to the downpipes as a stopgap to a bespoke number in the winter.

2) whats the idle speed supposed to be? when its cold it sits at 600ish except every so often it drops as if to stall but catches itself and returns to 600rpm. when its hot it hunts around a lot more. when on overrun from a lot of revs it will have a lot of trouble getting to an idle and it often stalls if i put the clutch in above 1k rpm. if i feather the revs down to 6-700 whilst moving in gear it still hunts around but hasn't stalled yet. double checked for air leaks and there's nothing obvious. i kept the crankcase breather system but i'm considering binning it now. would it matter if the ICV was backwards? i don't remember which way round it was on the e36.

[DanThe]

ICV has an arrow on it to tell you which way it should go, I had a similar cutting out thing when pulling up to junctions with my 2.8 and put it down to the light weight flywheel, that didnt have the oil separator valve and didnt have any idle issues apart from that

[nickso]

which way does it go though dan? arrow to under the inlet or to the inlet boot?

if the flywheel is the problem i'll be putting the DM fly back on as its a pain in the arse. can't see why it would be though as its ok when cold.

think i'm going to remove the seperator and see what happens. whats best to do with the tube from the rocker cover? straight down to the sump or back into the inlet?

[DanThe]

Arrow to the inlet manifold, I doubt your problem is with the flywheel
Cam cover vent to intake boot, make sure you blank off the drain tube

[nickso]

ok. i think from memory the ICV is backwards then.

drain tube? the one that i skillfully bodged onto my dipstick?