juniper_berries
Newbie
Hello!
I'm trying to diagnose a few issues with my 95 C1500 with the 5.7L TBI engine (4spd automatic). It just cracked 300 000 km. For some background, the truck was sitting for several years and I got it for free. It actually started up okay after sitting for a couple years, but didn't make it far and I wound up replacing the entire ignition system (finding that the issue was that the pickup coil on the shaft connecting to the distributor was shot. Unfortunately I don't have a particularly detailed history for the vehicle.
Since I got it in relatively functional condition, it's always had an issue with stalling at idle. This almost always occurs only while in gear, and it will run rough (RPM is not stable, it surges a bit and sometimes drops down to as low as ~400). Trying to turn the wheel at low/no speed will almost always cause it to stall. It usually runs fine while cold, and these issues typically pop up when the engine gets warm (although not exclusively). There are a few other issues as well that may or may not be related:
1) It burns approximately 1L of oil per month. We don't commute with it, just use it for doing grocery runs/etc.
2) I've recently noticed (last month or so) that it has started burning coolant as well.
3) The stalling has been slowly getting more frequent.
4) It makes a knocking-type noise when its cold, particularly during winter. I've read that this is probably a phenomenon called "piston slap" which is common to this type of engine. Goes away when its hot.
5) I'm not 100% confident that I set the distributor position correctly when I was working on the ignition system. I can connect my computer to the OBD1 port with a program that lets me pull engine sensor data, but I couldn't figure out how to get the timing right with that. So I just rotated the distributor cap with the engine running until it sounded like it was running the best. If there is an easy way to determine whether the timing is screwed up with a computer, that might help.
6) The point that prompted me to make this post - I just ran a compression test and found that cylinders 3 and 5 (the driver's side middle cylinders) have low compression, with cylinder 3 being around 130 PSI and cylinder 5 being around 90. The rest were consistently around 150-160 PSI.
Otherwise, I have recently replaced the following with new, reasonable quality parts:
1) Thermostat and water pump (did a coolant flush as well)
2) Fuel pump
3) AC Compressor
4) EGR Valve
5) Ignition system including distributor (cap and shaft), ignition coil, ignition control module, spark plugs, spark plug wires.
My intuition says that the head gasket is on its way out on the driver's side, but I wanted to see if you lovely folks had any insight before I go pulling bits apart. Any advice or guidance would be much appreciated!
I'm trying to diagnose a few issues with my 95 C1500 with the 5.7L TBI engine (4spd automatic). It just cracked 300 000 km. For some background, the truck was sitting for several years and I got it for free. It actually started up okay after sitting for a couple years, but didn't make it far and I wound up replacing the entire ignition system (finding that the issue was that the pickup coil on the shaft connecting to the distributor was shot. Unfortunately I don't have a particularly detailed history for the vehicle.
Since I got it in relatively functional condition, it's always had an issue with stalling at idle. This almost always occurs only while in gear, and it will run rough (RPM is not stable, it surges a bit and sometimes drops down to as low as ~400). Trying to turn the wheel at low/no speed will almost always cause it to stall. It usually runs fine while cold, and these issues typically pop up when the engine gets warm (although not exclusively). There are a few other issues as well that may or may not be related:
1) It burns approximately 1L of oil per month. We don't commute with it, just use it for doing grocery runs/etc.
2) I've recently noticed (last month or so) that it has started burning coolant as well.
3) The stalling has been slowly getting more frequent.
4) It makes a knocking-type noise when its cold, particularly during winter. I've read that this is probably a phenomenon called "piston slap" which is common to this type of engine. Goes away when its hot.
5) I'm not 100% confident that I set the distributor position correctly when I was working on the ignition system. I can connect my computer to the OBD1 port with a program that lets me pull engine sensor data, but I couldn't figure out how to get the timing right with that. So I just rotated the distributor cap with the engine running until it sounded like it was running the best. If there is an easy way to determine whether the timing is screwed up with a computer, that might help.
6) The point that prompted me to make this post - I just ran a compression test and found that cylinders 3 and 5 (the driver's side middle cylinders) have low compression, with cylinder 3 being around 130 PSI and cylinder 5 being around 90. The rest were consistently around 150-160 PSI.
Otherwise, I have recently replaced the following with new, reasonable quality parts:
1) Thermostat and water pump (did a coolant flush as well)
2) Fuel pump
3) AC Compressor
4) EGR Valve
5) Ignition system including distributor (cap and shaft), ignition coil, ignition control module, spark plugs, spark plug wires.
My intuition says that the head gasket is on its way out on the driver's side, but I wanted to see if you lovely folks had any insight before I go pulling bits apart. Any advice or guidance would be much appreciated!