Hard starting when warm

[extower]

Its a 98 Tahoe with a 5.7 Vortec...225k mi, it runs great down the road, until you shut it off and restart a few min later. It bucks and turns over real hard and yesterday wouldnt restart until i let it cool down for a half hr. A friend scanned it last nite but doesnt know what these readings mean...spark adv is 24degrees, long term FT bank 1 is 9.4%, LT FT bank 2 is -3.1%, 02 sens 1-1 & 1-2 is .44 volts, 2-1 & 2-2 is .80 volts, map sens voltage is .6....I`ve owned it for 2 years so not sure about fuel pump, I replaced plugs, wires, cap, rotor and 1 injector 2 years ago...

[MT-2500]

Originally Posted by extower

Its a 98 Tahoe with a 5.7 Vortec...225k mi, it runs great down the road, until you shut it off and restart a few min later. It bucks and turns over real hard and yesterday wouldnt restart until i let it cool down for a half hr. A friend scanned it last nite but doesnt know what these readings mean...spark adv is 24degrees, long term FT bank 1 is 9.4%, LT FT bank 2 is -3.1%, 02 sens 1-1 & 1-2 is .44 volts, 2-1 & 2-2 is .80 volts, map sens voltage is .6....I`ve owned it for 2 years so not sure about fuel pump, I replaced plugs, wires, cap, rotor and 1 injector 2 years ago...

Check fuel pressure and spark to plugs when it is har to start.
Post back pressure readings.

[extower]

My fuel pressure was 58lbs...I was told that was good. We cleared the codes on Friday, read them again on Monday and the scanner said 02 sensor, bank 1 sensor 1....so I`ll start there. I also failed to mention it idles on 7 cylinders when it rains, and clears up under accelaeration, but pretty sure thats unrelated.

[2000CAYukon]

A leaking Fuel Pressure Regulator will also cause a warm hard start condition. This is very common on the Vortec Engines.

//2000CAYukon

[MT-2500]

Originally Posted by extower

My fuel pressure was 58lbs...I was told that was good. We cleared the codes on Friday, read them again on Monday and the scanner said 02 sensor, bank 1 sensor 1....so I`ll start there. I also failed to mention it idles on 7 cylinders when it rains, and clears up under accelaeration, but pretty sure thats unrelated.

Fuel pressure is low.
Specs are 60/66.
You need 63-64 or more for a good start.
Also as said pressure regulator an be bad to.

[extower]

Ok...so just went to replace the o2 sensor and someone mustv cut out the section of pipe and didnt replace the sensor...i only found 3...assuming theres suppose to be one on the crossover towards the driver side...ugh...this is what i get fer buying from an impound lot i guess...might just have to drive it thru winter and scrap it...thanx for the help anyway!!!!

[j cAT]

Originally Posted by extower

Ok...so just went to replace the o2 sensor and someone mustv cut out the section of pipe and didnt replace the sensor...i only found 3...assuming theres suppose to be one on the crossover towards the driver side...ugh...this is what i get fer buying from an impound lot i guess...might just have to drive it thru winter and scrap it...thanx for the help anyway!!!!

hard starting when warm can be the injectors or the fuel regulator are leaking down.

with a pressure gage key on eng off see if the fuel pressure stays up ..if it drops off then find out if injector or regulator is leaking...

injector leak will flood engine and casuse a hard warm start.

could also be the ECT is bad or wires/connector to it ..

O2 missing is no big deal on the down stream side of cat converter.

[extower]

Ok thanx...I have access to a fuel pressure guage...unfortunately the sensor missing is bank 1 sensor 1 which is right off the manifold...and now actually we had some wet weather again, and it acted up so I`m thinkin its related...gonna try new plug wires...AC Delco this time. I very well could have a variety of problems...lol...high miles, only had it 2 years and tryin not to stick a truckload of money in it. I`ve had new vehicles and even with these issues I still would rather have my good ole Chevy than a 500 a month payment...