Car stumbles/stalls on cold start, what the F is it?

[91 318is]

First off, I've searched on a few boards to see if this is a common problem, everyone seems to say it's the vacuum hoses under the intake. I took care of that last year and replace every gasket that I took off, still have this problem. When you first start it up, for some reason, it idles at about 600, and almost everytime, it will stumble, sometimes it will catch itself and come back up, sometimes it stalls. I checked the plugs, change the coolant sensor for the ECU, and changed all the gaskets on the intake and bypassed all the vacuum hoses.

Anyone have any ideas? I'm thinking it might be the AFM, anyway I can confirm this? I would hate to drop $250+ for a new AFM and it not be the problem.

Thanks

[wolfgangstbd]

you can test your AFM by hooking a multimeter positive lead up to it at either the grey/white wire or the yellow/white wire(more sure its this one) behind the rubber boot on the connector then the other lead to ground. it should read a voltage scale like .75 at idle and 4 volts at WOT im pretty sure. a graphing meter is best but look for any sudden drops in voltage while snapping the throttle and opening it slowly

[91 318is]

you can test your AFM by hooking a multimeter positive lead up to it at either the grey/white wire or the yellow/white wire(more sure its this one) behind the rubber boot on the connector then the other lead to ground. it should read a voltage scale like .75 at idle and 4 volts at WOT im pretty sure. a graphing meter is best but look for any sudden drops in voltage while snapping the throttle and opening it slowly

thanks, I'll give it a shot.

Did the stomp test and came up with nothing, only code I got was 1444 which means "no fault codes".

What about the ICV or Fuel delivery problem?

Sometimes under load when acclerating, the car will buck until it gets higher in the RPM band.

[wolfgangstbd]

i had a fuel delivery problem it was just my fuel pump but a shopped fixed it b/c i ddont have any fuel pressure tools haha. just unplug you icv when the cars running if it still runs like shit its prob. stuck. happens to me if you just hit it it might wirk. but theyre really easy to cleanjust remove and clean with carb cleaner and install. try it might help

[91 318is]

i had a fuel delivery problem it was just my fuel pump but a shopped fixed it b/c i ddont have any fuel pressure tools haha. just unplug you icv when the cars running if it still runs like shit its prob. stuck. happens to me if you just hit it it might wirk. but theyre really easy to cleanjust remove and clean with carb cleaner and install. try it might help

well I cleaned it last night and the idle dropped down to 1k when fully warm, so it helped a little bit. When I unplugged it while it was running at NOT, the started surging from 1k to about 1500. I'm going to try and check the resistance of the ICV when it's cold to see what happens.

I'm also going to get some NPT nipples to make a T so I can use my existing fuel pressure gauge and test the pressure. I found a M42 manual online which will help me troubleshoot some.

[Cobra Jet]

Stating the obvious, but when is the last time you changed your fuel filter and what filter are you using?

Another sensor that would screw around w/ idle or drivability would be the temp sensor that is located in the head, right above the oil can on the driver side (blue connector). If this sensor is going bad, it's going to mess w/ idle & drivability.

One more thing to note - a failing crank positioning sensor will cause drivability issues as well - hard starting, idle fluctuations, sputtering, stalling and possible no starts when hot or cold. A failed CPS will NOT create a stored code within the M42 175DME. There is an actual code # for such a failure, however, in multiple instances (including my own CPS failure), for whatever reasons unknown to many, when performing the stomp test, you will never get an error code for a failed CPS... I'm not sure if this is a programming logic error within the DME, a problem w/ that failure not being picked up properly by the DME, etc... In every single instance of someone having a failed CPS, the DME always spits back a "1444", which means no stored fault codes... So, don't take it for "fact" that there are truly no stored codes IF the CPS is failing. If your CPS is original or has high miles on it, do pull the plug and perform a test on it w/ it on the car and one w/ it off the car... If your resistance level results are higher or lower than the Bentley specs - replace it, as those are signs of a faulty CPS.

m42club.com has tons of threads on idle/no start tech...

[91 318is]

Stating the obvious, but when is the last time you changed your fuel filter and what filter are you using?

Another sensor that would screw around w/ idle or drivability would be the temp sensor that is located in the head, right above the oil can on the driver side (blue connector). If this sensor is going bad, it's going to mess w/ idle & drivability.

One more thing to note - a failing crank positioning sensor will cause drivability issues as well - hard starting, idle fluctuations, sputtering, stalling and possible no starts when hot or cold. A failed CPS will NOT create a stored code within the M42 175DME. There is an actual code # for such a failure, however, in multiple instances (including my own CPS failure), for whatever reasons unknown to many, when performing the stomp test, you will never get an error code for a failed CPS... I'm not sure if this is a programming logic error within the DME, a problem w/ that failure not being picked up properly by the DME, etc... In every single instance of someone having a failed CPS, the DME always spits back a "1444", which means no stored fault codes... So, don't take it for "fact" that there are truly no stored codes IF the CPS is failing. If your CPS is original or has high miles on it, do pull the plug and perform a test on it w/ it on the car and one w/ it off the car... If your resistance level results are higher or lower than the Bentley specs - replace it, as those are signs of a faulty CPS.

m42club.com has tons of threads on idle/no start tech...

Changed both the fuel filter and temp sensor for the DME. I checked the ICV today and when it's cold and warm, it still reads 8.5 ohms, bentley calls for 40 ohms. Here's the thing though, another guy at work has an 318 so I checked his to compare, it was also 8.5 ohms. Next step is to check fuel pressure, TPS, then move to the o2 sensor.

[Cobra Jet]

check the CPS resistance values...