Rough idle 325i

Post Mon Sep 24, 2018 6:21 pm

I have face lift 325 which has developed a very lumpy idle ,
It's become difficult to start from cold with on occasion a heavy smell of petrol . The car sounds heavy if that makes sense although quick it seems to have dropped in acceleration
Items replaced so far:
New plugs
rotor arm and cap
New AFM ,
Refurbished injectors , new fuel pump ,
New blue thermostat sensor,
New TPS (Lucus made not Bosch ) this is the item which I think maybe the cause although the mpg according to the OBC has improved from 17 to 29 mph and the idle is correct at 700 rpm the car just doesn't feel right since I've replaced the TPS , I followed an online guide in how to reinstall and reset the TPS and all seemed well for about a day but it's gradually got to the stage I find it today
Any suggestions gratefully received

Post Mon Sep 24, 2018 9:11 pm

try cleaning the icv.
check on here wiki, how to test the tps. its basically a switch fully open at idle, closed part throttle.
fully open second switch at w.o.t.

Post Mon Sep 24, 2018 10:39 pm

arrisbmw wrote:try cleaning the icv.
check on here wiki, how to test the tps. its basically a switch fully open at idle, closed part throttle.
fully open second switch at w.o.t.

Done both, testing the resistance at idle and at three quarter throttle open , both times the switch operated/clicked , the ICV is clean and isn't stuck at any point .I could try a known good throttle body which maybe my next move , but a £10 a go for a OEM gasket (Dealer robbery at its finest ) and due to the fact that the TPS fitted is brand new I'm hoping it's something simple

Post Mon Sep 24, 2018 11:18 pm

iirc 325i some have a idle control module , 2 inch by 2 inch box by the ecu, its know as a vodo box. that takes all the input from various sensors, tps , crank sensor, blue temp sensor , temp sensor in a.fm to name a few, and then chucks out the output to the i.c.v. don,t know what year motor though.

or more likely you got a vacuum leak somewhere on the inlet side.
,
what your servo working like ? . reason i ask cause when i had a vacuum leak once i found and fixed it .my brakes were 30 % better , needed less foot power.

Post Mon Sep 24, 2018 11:22 pm

can,t see its the throttle body , unless its badly cracked, do the revs rise if you spray carb cleaner around it.
do at your own risk and have a fire extinguisher near.

Post Mon Sep 24, 2018 11:29 pm

you could have a problem with fuel pressure , check fuel pressure regulator.

1st check remove rubber tube to it ,no petrol should be coming out or smell of it.

Post Mon Sep 24, 2018 11:35 pm

seems sstrange : I followed an online guide in how to reinstall and reset the TPS and all seemed well for about a day : i,d be tempted to, test clean out and refit the bosch one.

Post Tue Sep 25, 2018 8:54 am

arrisbmw wrote:seems sstrange : I followed an online guide in how to reinstall and reset the TPS and all seemed well for about a day : i,d be tempted to, test clean out and refit the bosch one.

That might be my next move but the switch didn't operate when I tested it at WOT ,
I may replace the vacuum hoses from the rocker cover and ICV first

Post Tue Sep 25, 2018 8:54 am

arrisbmw wrote:seems sstrange : I followed an online guide in how to reinstall and reset the TPS and all seemed well for about a day : i,d be tempted to, test clean out and refit the bosch one.

That might be my next move but the switch didn't operate when I tested it at WOT ,
I may replace the vacuum hoses from the rocker cover and ICV first

Post Tue Sep 25, 2018 2:52 pm

its proably just full of oil. open it up and clean out with carb spray.
they recommend making a small hole in it so the oil can drain out.

" That might be my next move but the switch didn't operate when I tested it at WOT " , that won,t effect the idle.
iirc that switch fires all injectors together. rather than in 2 banks of 3.

defo worth checking the line ( vacuum )