Weird stalling problem on my I30. Dies between cold and warm but runs when warm!

[dr-rjp]

Before I begin, I want to say that I did a thorough search of the posts, and my problem is not covered in any of them.

This is very weird. Usually, when someone's car dies, it's either when cold or when warm. My car dies IN BETWEEN cold and warm.

For example, it will start fine when engine is stone cold. After letting it idle for two minutes, the engine dies and takes anywhere from 30 seconds to 1 minute of continuous cranking to get it restarted - at which point gobs of smoke and what smells like unburned gas gets blown out of the tailpipe.

Car initially threw an EGR system code. Like P0400 or P1400.

The other reason why this is weird is when I get right on the highway after starting the car and getting it it up to speed, it runs OK. When the engine reaches operating temp, it also runs fine without stalling - even when sitting at a dead stop.

I can also restart it without incident IF the engine is still warm. Let it cool off too much and hasta la vista, baby, it won't restart without continuous cranklng.

I had the EGR solenoid and valve replaced along with cleaning out the EGR tube. (I mean that I sure hope the mechanic actually performed the work he said he did).

IT DID NOT HELP AT ALL.

Now, according to him, it is throwing a bad MAF code. I'm going to confirm it tomorrow at AutoZone, but it seems unlikely to me.

If the MAF is bad, then why would it work when the engine has warmed to operating temp or when the car is going above 35 mph?

Logically speaking, there is a high air flow across the MAF's hot wire when the car is cruising at speed versus no air flow when the car is at a dead stop or a reduced flow when going slower than 30mph.

But, if the MAF is really bad, then what other components would it affect between when the engine is cold and when it is warm?

The only sensors that I know are offline when the engine is cold are the O2 sensors. What else changes as the engine temperature changes from cold to warm AND/OR the air flow/engine speed? The IAT?

Before I do anything else, I'll wait for some suggestions from you - which will be greatly appreiciated.

[loystock]

Better get a free scan from Autozone. But your mechanic may be right. An internal failure in the MAF sensor (cold solder or cracked board) could be the cause of the problem (assuming the EGR problem has been fixed). With the engine running, try tapping the MAF sensor (close to the connector) and listen for any change in engine response.

[MattB]

My first thoughts would be either the MAF sensor or a dirty IAC valve. Both can cause the symptoms you describe.

[infinitidude123]

have the mass airflow sensor checked out. The coolant temp sensor can cause fuel air mixture problems if it is bad. which could cause problems starting.