troy1

Any one got a 3.1L "M" (3100) that hesitates when the engine is cold? after is gets warmed up it goes away. its getting real old The car does not use any oil and does not seem to use any antifreeze.

frstrtdblzr

I have a 97 3.1 with 161000 miles on it and it just started it not to long ago. when i first start it up in the morning it does it and almost dies( it usually does it twice), then it goes away. I just replaced the fuel filter not to long ago at the gas tank so I tried a bottle of fuel injector cleaner, so we'll see if that works

callalilly81

sounds like mine. i am constantly feeding mine injector cleaner. i hear it costs about $100 for chevy to clean them... anyone else heard a price?

fopu

Maybe it's a bad coolant temperature sensor...

frstrtdblzr

I am not saying you are wrong because a temperature sensor is an easy thing to replace if that is it. The thing is I have just racked my brain trying to figure out how it could be the temperature sensor, would you mind explaining how it would cause the car to hesitate. I am what my dad likes to call me and him a shadtree mechanic, but I also like to learn about how this stuff works if I can and if that is it I would be very interested in how that works
Thank you

jeffcoslacker

The ECM uses all the available data sent to it to make a determination of settings for injector pulse, and throttle plate air bypass at idle, effectively taking the place of the choke the a carbed engine had. It has to richen the mixture to make the engine run well when cold. Most times, hesitation and stalling only when cold point to an overly lean condition. Possible causes can be a sensor feeding incorrect info to the ECM regarding air flow and ambient temperature, or an actual mechanical fault with the IAC (idle air control) sticking, allowing too much bypass air, or a gunked up throttle plate that can't close completely due to varnishing, etc.

I would check in this order.

1. Verify correct coolant level.
2. Clean throttle plate with spray cleaner.
3. Check IAC and bore for deposits
4. Check for broken vacuum lines, or other vacuum leaks
5. Clean injectors with the pressurized cleaner that feeds to fuel rail.

Usually, a sensor that is giving false or out-of-range readings will do so not just cold, but all the time, and will generally cause a fault code. So I'd look into the stuff above, and any other possible causes of a lean condition I might have forgotten, and I think you'll find it.

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