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Q: car runs great when engine is cold but dies when engine is warm

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I can start the car with no problem and it runs get until the engine warms up. I can even drive it around my parking lot 3 or 4 times but when the engine warms up and I put it in gear, it dies. I can restart the engine but when I put it in gear & take my foot off the clutch, it dies. My friend replaced the sparks, air filter, put in a new water pump last year... Most recently he cleaned the mass air intake & that's when this major problem started. I was having a little issue with the idle before he cleaned the air intake but after he cleaned it is when the dying when warm started. What's wrong with my baby?

My car has 84000 miles.
My car has a manual transmission.

A: This sounds like there is a problem with th...

This sounds like there is a problem with the MAF (mass airflow) sensor. When your vehicle is cold, the PCM (Powertrain Control Module) is in what is known as open loop. Open loop is a preprogrammed program put in place for warm up. Closed loop is when the PCM begins using the sensors to adjust fuel ratio. The primary sensor the PCM uses to make decisions is the MAF. I’m leaning toward three possible problems here. The MAF may have been damaged during cleaning, the connector may have a bent pin from disconnecting and reconnecting its connector or the boot that connects the MAF to the throttle body has developed an air leak.

Before condemning the MAF, make sure there isn’t any unmetered air entering the motor after the MAF. This will confuse the PCM and things just won’t work correctly. Unmetered air is what we call it when there is a leak between the MAF and the throttle body.

Of course, make sure the MAF has been plugged in. If it is, disconnect the connector and inspect the pins. It is fairly common for the small electrical pins in all sensors to get bent over when reconnecting their connector.

It is very easy to damage sensors in the area of the throttle body when cleaning it. Carburetor cleaner can damage sensors. The one I am particularly worried about is the IAC valve. These can stick and cause many different idle control issues.

If this isn’t of any help to you, I recommend having a certified technician, such as one from YourMechanic, diagnose your stalling condition for an accurate repair.

Good luck!

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