Thoughts on a lumpy idle

[Nick91]

Hey guys!

I could use some thoughts for a fix for my 325i. It has a lumpy idle which sounds like it's had a mild cam installed. It seems to run fine whenever not idling. I've tried the following without finding the culprit:
-Had the injectors professionally cleaned
-Replaced the intake boot with a new one
-Replaced the Vacuum hose from the valve cover to the throttle body
-Ignition leads, distributor cap and rotor, spark plugs and coil has been replaced with new original parts.
-Spraying engine-starter on all of the hoses and caps whilst listening for a change in idle with no luck
-The TPS is clicking and I've checked the resistance
-Blue temp sensor has been checked at the ECU plug with a multimeter
-ICV has been cleaned
-O2 sensor is new
-AFM looks fine, no binding.
-Replaced intake manifold gaskets
-Replaced throttle body gasket
-Removed carbon canister and replaced with a rubber cap on the throttle body
-Replaced the o-rings on the metal crankcase breather pipe
-Ran a can of Bell-add "engine cleaner" through the intake
-Adjusted the valves

Is there something I missed?

Cheers!

[Grrrmachine]

Run your eye through this:

http://www.e30zone.net/e30zonewiki/inde ... ake#Idling

[Nick91]

Run your eye through this:

http://www.e30zone.net/e30zonewiki/inde ... ake#Idling

Already did several times

[Grrrmachine]

Ahh ok, cos you make no mention of checking the Blue Temp Sensor, which is the FIRST thing to check for a bad M20 idle. Secondly, just because the TPS is clicking doesn't mean it's good, so you need a multimeter on both of these bits to make sure they're working as they ought to. Doing that does mean getting access to the ECU, so you'll have to get the kick panel out of the drivers footwell.

If they're alright, then you can get the tools out and remove the throttle body to check the status of the rubber bung.

[Nick91]

Ahh ok, cos you make no mention of checking the Blue Temp Sensor, which is the FIRST thing to check for a bad M20 idle. Secondly, just because the TPS is clicking doesn't mean it's good, so you need a multimeter on both of these bits to make sure they're working as they ought to. Doing that does mean getting access to the ECU, so you'll have to get the kick panel out of the drivers footwell.

If they're alright, then you can get the tools out and remove the throttle body to check the status of the rubber bung.

Point taken! Is it easier to do the test from the ECU? I always thought you'd need to do it directly from the sensor itself.

[Grrrmachine]

It's essential you do it from the ECU, because you need to check not only the sensor but the wiring as well. The procedure, as always, is in the Wiki

[Nick91]

It's essential you do it from the ECU, because you need to check not only the sensor but the wiring as well. The procedure, as always, is in the Wiki

I actually read it in the wiki the minut after I posted the last post Well thanks anyway for reminding me about those things, I'll get hold off a multimeter and see if I can figure it out

[Brianmoooore]

The rubber bung (assuming your car doesn't have a cat. in the exhaust, and all the other associated equipment) is on the underside of the throttle body, almost touching the throttle position switch.

[Nick91]

The rubber bung (assuming your car doesn't have a cat. in the exhaust, and all the other associated equipment) is on the underside of the throttle body, almost touching the throttle position switch.

My car used to have a cat, but I removed it in order for me to fit the BTB 6-Branch an scorpion system. What difference does it make?

[Brianmoooore]

If it has emissions equipment the connection onto the throttle body, where the bung fits, will be in use - connected by a hose to a solenoid valve, and then onto a large cannister that is part of the fuel tank vent system.
Strangely enough, the very last thing I did, about half an hour ago, was to remove this cannister and valve from one of my cabs that I am putting on the road on June 1st, and block off the connection to the throttle body. They are not MOT testable, and take up valuable under bonnet space.

[Nick91]

I've now bought a multimeter and had both the TPS and the blue temp sensor checked and they're perfectly fine. The reading on the ECU plug is the same as from the sensor. The carbon canister system is working as well so I've ruled that one out too. The AFM seems fine too. I ran a can of engine cleaner through the intake as I read it could be due to a carbon build up on the inside and the engine did run better, however the misfire/lumpy idle remains. Today I'll try adjusting the valves even though it hasn't been too long. Any other ideas for me to check out?

[Andyboy]

325i's can have a ragged idle (but not a misfire) if the exhaust clearances are set to the specified 10 thou - reset them to 12 thou and see what that does.

What's the fuel economy like?

[Nick91]

325i's can have a ragged idle (but not a misfire) if the exhaust clearances are set to the specified 10 thou - reset them to 12 thou and see what that does.

What's the fuel economy like?

I've heard about setting them to 9 thou instead and 12 thou only when it's warmed up. Isn't that a bit risky or is it just me?

The fuel economy seems alright, though I just found out that my coding plug is the wrong one so it'll be a bit underrated. It ran 21 MPG with a heavy foot the last time I checked, but the speedo is always showing 5 mph too much, so I'm not sure what that equals to.

[Andyboy]

I've heard about setting them to 9 thou instead and 12 thou only when it's warmed up. Isn't that a bit risky or is it just me?

They should be done stone cold to 10 thou but some 325i's benefit from 12 thou exhausts to improve the idle. Some do them with the engine hot but you have to be quick as a hot engine loses heat quickly with the cam cover off. By the time you've got to the last valve, the engine could have cooled enough to result in the last clearances to be different to the first. Do them cold and this doesn't happen.
Try doing it like this, stone cold, 10 thou inlets and 12 thou exhaust.

[Nick91]

bump

[Nick91]

What spark plugs are you using? and what gap are they set to?

I'm using Bosch WR8LC+ Supers as recommended by Pelican Parts and they were fitted only a couple of thousand miles ago. The gap is just as they were set from the factory(0.8mm I believe?)

[e30topless]

valve clearances are very important to the M20 to make it smooth, Bosch plugs are crap,

I highly reccomend NGK BPR6ES,

you say the AFM looks fine have you tested it ? whats the CO level ?

[Rav335uk]

valve clearances are very important to the M20 to make it smooth, Bosch plugs are crap,

I highly reccomend NGK BPR6ES,

you say the AFM looks fine have you tested it ? whats the CO level ?

What about LIDL plugs

[Nick91]

valve clearances are very important to the M20 to make it smooth, Bosch plugs are crap,

I highly reccomend NGK BPR6ES,

you say the AFM looks fine have you tested it ? whats the CO level ?

The valve clearances were set to factory spec just last week.

How do I test the AFM? I didn't think it was possible to do anything but a visual inspection on these.
I haven't got a CO2-gauge at this point so I can't tell you. What could the CO2 level tell me? Wouldn't the O2 sensor keep all O2 out of the exhaust at all times?

[Nick91]

Bump