Hard to start when cold. . . ive herd it runs rich when first staring because of the tbi system. what i herd is the coolent sensor on the left side of the block tell the pcm or pcu to give a hotter spark when starting cold to compinsate for the way the cold fuel ignites or what not. any ways is this sensor called someting else. . . i tried to buy it to replace it but they gave me the one on the top of the engine near the thermostate instead wich i belive is just for the temp gage

check the ECT sw. it is the one that looks like a temp. sw by the thermostat housing and not the one on the side of the head. The ECT sw. tells the cpu what the temp conditions are and how much fuel to feed to the tbi. In addition, you might want to check the idle air control on the side of the tbi if when cold the truck will not idle. After truck heats up iac doesn't do anything.

MAF sensors can cause the engine to run rough, have no power, etc. I had a Blazer that didn't run right on start up. It would backfire and run rough until it warmed up, but still never ran good. MAF stands for mass air flow and if it tells the computer the wrong airflow, the computer will mis-judge the amount of fuel to add. On the other hand, if it won't start at all it could be the fuel!

Change the temp sensor on the left side of the engine also change the thermostat at the same time if possible flush the coolent system.I have a 2000 chevy silverado 1500 5.3 with 435,700 miles same engine 2nd ****** im having the same problem an i beelieve mine is from straight coolent insted of 50/50 mixture.Hope this works for you if so im glad i could help,also ive done all thework to my truck except for the ****** change and i put a new one in at 314500.

Try the idle air control valve, and the throttle position sensor

try the temp sensor by the thermostat housing,make sure its not broken when you unplug it,ohm sensor itself when warmed up,and when cold

I am going to guess at the easiest first .
I will attempt to explain my reasoning without going into it so far as to bore anyone...

Coolent tempreture sensor ;
When the car is cold it starts fine , as it warms up (coolent temp sensor) the ECM is signaled to decrese the rich fuel mixture (choke).

Test coolent sensor for variences in reading with an ohm meter to verify the sensors condition.


Plugged fuel filter;
Cold start , fuel is sedentary allowing particles to settle (paired with the enrichened fuel mixture of cold start), Then when warmed the particles are clogging the filter and the fuel enrichment of the cold start is no longer helping the starving condition...

Its hard to diagnose with what little information you have provided.
If you are ghetting a code , take it to the nearest AutoZone and get a free diagnostic done.

Oxygen sensor. They tend to fail by sending the engine computer a steady lean reading. the computer then runs the TBI rich in order to compensate for the false lean condition.

Also, the Engine Coolant Temperature sensor. If it fails and shows the engine to be ice cold when it is really warm, the computer will schedule lots of fuel.

Intake Air Temperature sensor. same result as ECT above. Computer sees nothing but cold dense air all the time and schedules more fuel.

Yes...timing. Adjust the distributor...back it off a little and set the timing....also check your carb setting for rich/lean mix....air mix will cause this also.

What have you done to the system to cause this or were you trying to adjust something?

coolent temp sensor to pcm . the truck thinks it cold and its riching the fuel mixture . its a cheap part . i would have a good shop with a good scaner check it fist but thats up to you

I recommend you check the fuel pressure regulator diaphragm for proper installation and tears. Did you get a new one with your rebuild kit?