I have a 2003 C5Z 58k miles. Picked it up at 55k, been running like a champ ever since. Recently, I have had a series of issues all come at once.

Hesitation under throttle.
Car cranking over but not starting.
Having to floor the gas pedal to start the car.
Rough idle.
Completely stalling when in gear.


I was leaving the store one afternoon, and on the highway my car started hesitating under throttle. Got it home and the next morning started the car again and it was still hesitating, drove it to the gas station, filled it up and after leaving the gas station that when the hesitation turned into bucking/surging.

Got onto the forum and started looking at issues related. I tried cleaning the MAF Sensor and changing the fuel filter out and checking the spark plugs and wires. No luck.
Tested the fuel pressure, and it held constant around 55PSI for well over 10 mins.

600 miles ago I had the yellow valve springs changed to blue, and new AC DELCO spark plugs.
Two days prior to the bucking issue, I changed out the passenger side front fender, and also the front bumper. Drove fine for about 60 miles.
I believe the form is completely stock aside for the VARAM Intake.

If I even want to get the car out of the driveway I have to keep the RPMS over 2500k to keep it from stalling.
However, there are times when I'll start it up and it'll just idle in neutral just fine.

Also at the same time that the car started bucking the engine temp sensor started spazzing out. The gauge one the cluster panel keeps fluctuating from 100F to 220F. I cannot seem to figure out how that is related.

I pulled the codes and the only code that was there was:
PCM P1115 H C (ENGINE COOL TEMPERATURE- SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE)

PLEASE let me know if you have any ideas to fix this issue.

 

With all the integrated electronics in cars, you may have a bad temp sensor and it is wreaking havoc with the computer. It only takes one bad sensor to throw everything off, when you did the fender and bumper swap you could have knocked a ground or even broke a wire.

 

With the P1115 it’s either a bad ECT sensor or a wiring issue…it’s either an open or short to voltage in the wiring…with an open wire the PCM thinks the engine is cold and “giving it some choke” plainly speaking…most likely why you have to increase the RPM to 2500 to keep the car from stalling…the ECT is a simple 2 wire thermistor which has 5 volts on the signal wire when unplugged and the other wire is a ground….the sensor will pull that 5 volts to ground using the sensor and that is what the PCM is looking at to set the DTC…first follow the ECT wire harness up behind the alternator and then it joins a harness which then goes along side the left fuel rail and wraps around a metal bracket at the back of the fuel rail…chaffing does occur there so pull the harness away from the bracket and look for chaffed wires…if it looks OK remove the harness connector…you should see about -30 or so on the ECT gauge and 5 volts on the yellow wire…you should also remove the sensor and with an ohm meter check the resistance of the sensor in some water at different temperatures…if you get that far we will post the resistance vs. temperature chart for you !!..the pic shows the area of concern at the fuel rail.