90 300sl Hard to start when temperature is 50 or bellow

[Blablabloom]

I am rooky here and need some help. My 90 300sl is hard to start when parked overnight and temperature is bellow 50 degrees. It take me a few minutes to finally get it to iddle at very low rpm. If i press more gas it stalls. I have to let it warm up for a few minutes before i can drive it.
I have a non original o2 sensor on the car that I am replacing with an OEM in the next couple of days. will that make any difference? what ese to check?, temperature sensor? cold start injector? or pther?
Pls help...weather is getting colder and it is a real problem...

Thanks
Blablabloom
90 300sl

[aam]

Originally Posted by Blablabloom

I am rooky here and need some help. My 90 300sl is hard to start when parked overnight and temperature is bellow 50 degrees. It take me a few minutes to finally get it to iddle at very low rpm. If i press more gas it stalls. I have to let it warm up for a few minutes before i can drive it.
I have a non original o2 sensor on the car that I am replacing with an OEM in the next couple of days. will that make any difference? what ese to check?, temperature sensor? cold start injector? or pther?
Pls help...weather is getting colder and it is a real problem...

Thanks
Blablabloom
90 300sl

Check first for vacuum leaks.
2) Clean with carburetor cleaner the electronic idle speed control valve.
To test it pull the connector out, your rpm should jump to about 1500rpm.
If not thats your problem
I don't think is your sensor.

[ScottinSoCal]

Originally Posted by Blablabloom

I have a non original o2 sensor on the car that I am replacing with an OEM in the next couple of days. will that make any difference? what ese to check?, temperature sensor? cold start injector? or pther?

Your O2 sensor wouldn't have anything to do with it, your computer ignores it until it's up to operating temperature. I'd look at temperature sensors and your cold start injector.

[Blablabloom]

Thanks guys, i will check all of this this weekend and post the results...thanks again
Blablabloom
90 300SL

[ctaylor738]

Sounds like the coolant temp sensor to me.

[Blablabloom]

I have checked the idle speed control valve and disconnected the plug to it...no change in idle speed.
I have also discovered that the thermostat has been removed. The car takes forever to warm up and the temp guage barely reaches 80 degrees after driving for a while. I have checked the resistance reading on the coolant temp sensor and it was at 2.2kohm when the car was cold....55 degrees or so ambiant temperature. would the lack of thermostat create that issue or they are seperate? I am ordering a thermostat but should i order an idle speed valve too???

Thanks guys for all your input..much appreciated

[ScottinSoCal]

Originally Posted by Blablabloom

I have also discovered that the thermostat has been removed. The car takes forever to warm up and the temp guage barely reaches 80 degrees after driving for a while.

Without a properly operating thermostat your car would be running cold most of the time. That will lead to excessive carbon buildup and all kinds of weird operation. My 75 had the thermostat gutted by some well-intentioned nitwit. After replacing it and driving the crap out of the car for a couple of weeks (long freeway drives at speeds the police would be unhappy with) most of the strangeness disappeared. After I took out the aux air valve and cleaned it, the rest of it cleared up.

[ctaylor738]

2.2k ohm sounds about right for 55 degrees, but check it with the engine warmed up, once you get a thermostat in it. Once you install the thermostat, you may see a great improvement since the FI control unit is currently very confused.

A new O2 sensor and a mixture adjustment via the on/off ratio is always a good idea.

Check to see if you are getting voltage to the ICV before replacing it. You check it by pulling the connector back just enough to get the meter's leads on the ICV's pins.

[Blablabloom]

thanks guys, I have ordered all the electrical ignition components and will replace them by the weekend, Also a new thermostat, and cleaned all 3 water sensors, new coolant etc... will keep you posted....

[aam]

Try with water first in case you have to replace the sensor.