2003 with 4.8. idle surge and stall when cold.

[kenman1717]

i have a 2003 silverado with a 4.8 engine. i bought the truck in the summer of 2010. no problems in the winter of 2010. ran great all year in 2011, then my block heater shorted out in the winter of 2011, so i wasn't able to plug the truck in.

we get some cold nights up her in alberta, but anything below -10c the truck would idle surge and stall, would do this about 4 times in a row then it would just surge a few times but stay running.

had a buddy thats a gm driveability tech take the truck and do a tone of updates for the throttle body and to correct idle surge and some other driveability related stuff. i cleaned the maf, map and tps as well as the throttle plates. replaced plugs, wires, air filter and fuel filter. all this and it was still doing it, but it had to be really cold to stall.

wasn't able to replace the block heater till this summer. but now that its getting colder and dropping below -10c at night the truck is starting to idle surge when i start it up in the morning.

anyone have any ideas of what i can do to correct this. i will be plugging the truck in soon, probably within the next month. if the block is warm it won't surge. i realize this is a temporary solution, but i really would like to fix this.

[j cAT]

the ECT should be replaced. also check the fuel pressure. should be 53-57 psi engine running.

with cold temps you need more fuel.

you may also have dirty injectors.

the throttle body would not cause a poor cold start/run ONLY.

the throttle body would effect normal engine temp operation if it were with problems. the TAC would cause reduced power if defective.

the IAC would control idle rpm . this would be after the engine as warmed.

with the engine @15 deg f and lower the IAC would be not controling idle.

the ECT would report a temp that would cause the PCM to increase fuel to the engine [rich mixture] until the ECT reports a higher temp.

The block heater is heating the engine to hide these defects.

I have had operation well below your -10 deg C with none of those start run issues.

what synthetic oil viscosity do you use ? In your location 0-30wt or 5-30wt is what you should be using.

[kenman1717]

Originally Posted by j cAT

the ECT should be replaced. also check the fuel pressure. should be 53-57 psi engine running.

with cold temps you need more fuel.

you may also have dirty injectors.

the throttle body would not cause a poor cold start/run ONLY.

the throttle body would effect normal engine temp operation if it were with problems. the TAC would cause reduced power if defective.

the IAC would control idle rpm . this would be after the engine as warmed.

with the engine @15 deg f and lower the IAC would be not controling idle.

the ECT would report a temp that would cause the PCM to increase fuel to the engine [rich mixture] until the ECT reports a higher temp.

The block heater is heating the engine to hide these defects.

I have had operation well below your -10 deg C with none of those start run issues.

what synthetic oil viscosity do you use ? In your location 0-30wt or 5-30wt is what you should be using.

i will try replacing the ect. fuel pressure has been checked a few times and its within specs.

i run injector cleaner through every couple of tanks of gas.

it has been suggested to me it may be carbon build up on the intake valves. i have some of that cleaner that gm uses to remove carbon from the cylinders on the newer trucks for the oil consumption, i was told its also an injector cleaner. haven't actually removed anything to try to get that onto the intake valves yet.

the first winter i had this truck, i forgot to plug it in a few times and it got to like -30c and it fired right up and ran great, but not the second winter.

i only run regular 5w30, i don't normally use synthetic oil.

[j cAT]

I would use synthetic engine oil. In cold temps where you live you will see very quickly how fast the engine cranks when is -20 deg f .

I would also replace the transmission fluid to dexronVI. this is a synthetic fluid now recommended by GM. not dexron III, which is no longer an approved fluid for transmissions. you will see faster shifting at the very cold temps and save on fuel.

The ECT is a problem with going out of CAL. as they get older.

at warm temps this may not show its error.

some have had wiring and connector issues.

If the sensor fails in a way that reports -40degf the engine will be very hard to start and run . this is a failure which does occur often.