Chrysler Repair: 91 Dodge stalls when cold, coolant temp, lean mixture

Question
Hi, Roland. I have a '91 Dodge Spirit with a 6 cyl. engine and 124k miles. It recently had a major tune up. The problem I've been having lately is that the engine stalls immediately after starting up in the morning. I have to use the accelerator to keep it at an idle until it warms up. Once it does get warmed up it is just fine for the rest of the day. Then, next morning, same problem. It only has this problem when it is cold. If it sits in the sun until the afternoon, it usually starts up just fine. Thanks for your help.

Curt

Answer
Hi Curt,
The problem likely is related to fuel/air mixture not being rich enough when you start the engine from cold. The main sensor is the coolant temp sensor located adjacent to the thermostat housing (the hemispherical fitting that is connected to the top radiator hose). The sensor has 2 wires colored tan/black and black/light blue. If you have an ohmmeter measure the resistance across its terminals when the engine is cold (lift tab on plug gently, then release plug), it should read in the range of 7,000 to 13,000 ohms.
Then as the engine warms up it should drop to 700-1,000 when it reaches full operating temperature. If it is reading below 7,000 ohms when the engine is cold that would make for a too lean mixture.
There are other sensors that have impact too. So do a readout of the engine controller memory for fault codes that it may have noted. Use the ignition key:
"on-off-on-off-on and leave on" doing this in 5 seconds or less. Then watch the check engine light which remains 'on' to begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to verify the counts. Then group the counts into pairs to form the two digit fault codes. A coolant temp sensor fault will be a 22 code. The last code is always 55 (end of readout). Write back with other codes for a translation or go to www.allpar.com/fix/codes.html for a translation. Let me know what the codes are and I can tell you specifically what to do.
Use the 'rate the expert' tab to reach me if I'm maxed out and use the comments section.
Roland
PS: If the car was originally sold in California there would be an exhaust gas recirculation valve which if stuck ajar would also cause a too lean mixture. So check the underhood sticker to see if the vacuum hose diagram shows there to be an "egr valve".