Hot Start Issue

[Threehz]

It's not the plug by the firewall, that baby will never be plugged in.

Anyhow ('91 318is if it aint obvious), if it's cold out she starts up fine no issues, no issues running, perfect.

If it's hot out (now that we're seeing 90+ degree days), and she has been sitting in the sun for a while. She starts up, but the idle dips way down, back to normal dips back dips back dips maybe 4 to 5 times before staying at normal. She hasn't died out on me, just the painful struggling.

Once she is driving, no issues at all.

She has pulled a CEL before, after driving a while, if I sit idle for more than 10 seconds, a 1222 pops up. However if I run fuel system cleaner, that CEL will go away. When it first showed up, after using fuel system cleaner it went away for about three months, then came about about a month ago, used fuel system cleaner, has been gone since.

For one I hate watching her struggle at start-up, truly pains me, and two I really just want to resolve this issue. Especially before we start seeing our 120 degree days in a couple months.

Anyhow help is very appreciated.

[Dj Buttchug]

lambda control. how many miles on the O2 sensor

[ballarde30]

Idle control valve?

[Threehz]

PO said he replaced the O2 sensor, not sure when or with a used one or what... That's been my underlying prediction since the 1222 popped up.

Just kinda been wondering if a vacuum leak or something minor could be at work.

[av8drvr]

I am experiencing a similar issue, intermittent CEL (1223, CTS) and occasional stumble at start. I believe small cracks in vacuum hoses expanding due to heat and vibrations is my issue. I suspect the same may be the case for you. As someone pointed out to me on another forum, the M42 doesn't have a code for vacuum leak, so it just throws a random one when it nows something is amiss. I initially changed the CTS but the problem is still present. Check all your hoses carefully if you can and grab some ether or propane and see if you can isolate the leak.

[Threehz]

You know expanding hoses makes a lot of sense, I've given my hoses some look-overs and not seen anything real obvious.

I'll have to check out the propane method and see if it works.

[Ryann]

1222 means the DME sees a problem with the fuel mixture, not an issue with the o2 sensor. I think you're on the right track.

[av8drvr]

Just to follow up, I spent the evening with an LED pen light and a very thorough inspection and I found multiple hairline cracks in the lines directly under my intake plenum. I grabbed electrical tape and went to town on the two areas I found, all told about an inch and a half of suspect rubber. Engine responded well at idle so I am going to order new hoses in line with the mess fix, I may use silicone. I am convinced this intermittent issue is temperature/vibration related to small imperceptible cracks in the vacuum side of the M42. Run it to ground and I think you fix this.