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Joe
Joe, ASE Certified Technician
Category: Chevy
Satisfied Customers: 7251
Experience:  ASE, electronics, Marine inboards and electronics, automotive drivability, all around repair tech,
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my 2000 chevy truck with a 5.3 is hard starting after warm.

Customer Question

my 2000 chevy truck with a 5.3 is hard starting after warm. when cool it starts right up. I changed the fuel filter, pvc valve and the fuel pump runs. Any idea what may be the problem?
Submitted: 7 years ago.
Category: Chevy
Expert:  Joe replied 7 years ago.

Hello,

 

If it has a tach on the dash when you try to start does it move at all?

 

Thanks,

Joe

Customer: replied 7 years ago.

I JUST STARTED THE RPM FLUTUATES FROM 0 - 1000 RPM ROUGH THEN IT WILL RUN SMOOTH AFTER I PUSH GAS PEDDLE. TURNS OVER FINE JUST STRUGGLES TO START WHEN WARM. WHEN I START IN MORNING AFTER SITTING ALL NIGHT FOR THE FIRST TIME IT STARTS RIGHT UP WITH OUT ANY HESITATION.

Customer: replied 7 years ago.
DID YOU GET MY LAST EMAIL?
Expert:  Joe replied 7 years ago.
yes it just came through give me just a sec please
Expert:  Joe replied 7 years ago.

I really need it not to start, I need to know when it will not start if the tach moves at all when trying to start, the reason I ask this is sometimes when a crank sensor fails it only fails when hot and the tach will usually not move at all if that is what is bad.

 

That is the easiest test.

 

If the rpm's are jumping all over when you start then try tapping on the 2 sensors lightly with your fingers and see if anything changes if not, then grab a screwdriver and use the plastic end of it and lightly tap on them and see if anything changes?

Customer: replied 7 years ago.

WHERE IS THE TWO SENSORS LOCATED THAT YOU WANT ME TO TAP?

Expert:  Joe replied 7 years ago.
Sorry I thought I mentioned that they are the only two located on the throttle body, tap lightly I do not want you do damage them, the plastic one is the one you need to go lighter on it is the tps throttle position sensor, the other is the iac idle air control valve.
Customer: replied 7 years ago.
I JUST TAPPED ON IT AND START AND STOPPED SEVERAL TIMES IT STARTED FINE. IF THIS WORKS WHICH ONE SHOULD BE REPLACED? HOW CAN I CONTACT YOU TOMORROW, I'M LEAVING IN 5MIN.?
Expert:  Joe replied 7 years ago.

so you tapped on one of them and it made it die/stall? if so which one?

 

if that is the case then it needs to be replaced.

 

the one that changes how it runs.

 

just save one of these emails and reply back when you are ready, sometimes the question will close if you take too long but that would be like 22hrs from the last reply you or I send I believe.

Customer: replied 7 years ago.
NO IT DIDN'T DIE IT JUST STARTED NORMAL!
Expert:  Joe replied 7 years ago.

Oh, was it not starting again and then it started after tapping?

 

what you will need to do to confirm is get it not to start and only tap one then try to start if no go try the other. I do not want much tapping on the tps sensor if possible it is electronic.

Customer: replied 7 years ago.
still doing it happened everytime i turned off last night after running a short distance (3) times. It still starts like it did, hesitates terrible/idles very rough an will sometime die while starting other times it will work its self out after a few seconds. If i apply a little gas it will eventually run smooth and idle smooth after a several seconds. I noticed that the rpm guages all work when starting even if it hesitates starting. Tapping the sensors while running had no effect on idle. Turns over fine. Also as usual it started right up this morning, with out any hesitation but it sat for 9 hrs. Any more ideas?
Expert:  Joe replied 7 years ago.
Ok, can you now get a fuel pressure reading for me during that problem?
Customer: replied 7 years ago.
I DON'T HAVE A PRESSURE GUAGE!
Expert:  Joe replied 7 years ago.
only other thing for now is check for missfires with a scan tool or a timing light, if no missfires then going to have to have the fuel pressure tested.