1996 5.7 Vortec Yukon 4WD, 245K original miles.
Doesn't want to start when cold (if it sits out overnight, 50° or colder temps).
I'm the original owner. We weren't using it much, then we totalled the other car.
So I bought parts and did some preventive maintenance to make it reliable:
New water pump, coolant flush, all new coolant and heater hoses.
Removed fan clutch, installed Windstar e-Fan, controlled by temp sensor in lower radiator hose tee, works great.
Tranny flush, drop pan, change filter.
Oil and filter, chassis lube.
New wix fuel filter (only 8K miles on old filter and delphi fuel pump).
New sensors - IAT, MAP, TPS, IAC.
New PCV valve and tube and grommet and vacuum fitting at manifold.
Cleaned MAF sensor.
Cleaned throttle body.
New spark plugs and cables and new Ign coil.
New CKP sensor.
New aluminum body distributor with new CPS. I used DashCommand to set cam retard value with rpm at 1100 on warm engine. Then I got misfire codes at high rpm, so I did the [warm engine-neutral gear-parking brake on-rev over 4K for 30 seconds] thing for relearning crank. It seemed to work, no more codes.
New headlamps and running lights fixtures with two relays switched by the green and tan wires for direct power feed to headlamps, plus a diode between the green and tan for 4-High mod.
New tires.
The engine is strong, gets 17mpg on the highway at 70mph, sounds good, feels good, starts with one crank when cool or warm, and there are no codes.
But if you let it sit out all night in cold weather, it doesn't want to start or idle.
It hunts and stumbles and idles rough and shakes the car.
After several attempts, it eventually find itself and then it runs fine.
I can't say whether it was doing this before the PM work, because it was garage kept in a climate-controlled garage.
We didn't discover it until we started using it and sometimes leaving it out in the cold.
I tested fuel pressure on warm engine: 60psi with engine-off key-on. 52psi while idling. If you turn off the engine, the pressure actually climbs to 56psi and holds there for 2 minutes before it starts dropping very slowly and i got bored and quit watching after 5 minutes, it was still over 50psi.
I changed the intake manifold gasket at 100K, but i've never changed the oem spider.
I have checked for vacuum leaks with spray water, spray starter fluid, propane, and just listening. I can't find any vac leaks.
Got any ideas?
Thx.
Doesn't want to start when cold (if it sits out overnight, 50° or colder temps).
I'm the original owner. We weren't using it much, then we totalled the other car.
So I bought parts and did some preventive maintenance to make it reliable:
New water pump, coolant flush, all new coolant and heater hoses.
Removed fan clutch, installed Windstar e-Fan, controlled by temp sensor in lower radiator hose tee, works great.
Tranny flush, drop pan, change filter.
Oil and filter, chassis lube.
New wix fuel filter (only 8K miles on old filter and delphi fuel pump).
New sensors - IAT, MAP, TPS, IAC.
New PCV valve and tube and grommet and vacuum fitting at manifold.
Cleaned MAF sensor.
Cleaned throttle body.
New spark plugs and cables and new Ign coil.
New CKP sensor.
New aluminum body distributor with new CPS. I used DashCommand to set cam retard value with rpm at 1100 on warm engine. Then I got misfire codes at high rpm, so I did the [warm engine-neutral gear-parking brake on-rev over 4K for 30 seconds] thing for relearning crank. It seemed to work, no more codes.
New headlamps and running lights fixtures with two relays switched by the green and tan wires for direct power feed to headlamps, plus a diode between the green and tan for 4-High mod.
New tires.
The engine is strong, gets 17mpg on the highway at 70mph, sounds good, feels good, starts with one crank when cool or warm, and there are no codes.
But if you let it sit out all night in cold weather, it doesn't want to start or idle.
It hunts and stumbles and idles rough and shakes the car.
After several attempts, it eventually find itself and then it runs fine.
I can't say whether it was doing this before the PM work, because it was garage kept in a climate-controlled garage.
We didn't discover it until we started using it and sometimes leaving it out in the cold.
I tested fuel pressure on warm engine: 60psi with engine-off key-on. 52psi while idling. If you turn off the engine, the pressure actually climbs to 56psi and holds there for 2 minutes before it starts dropping very slowly and i got bored and quit watching after 5 minutes, it was still over 50psi.
I changed the intake manifold gasket at 100K, but i've never changed the oem spider.
I have checked for vacuum leaks with spray water, spray starter fluid, propane, and just listening. I can't find any vac leaks.
Got any ideas?
Thx.