I have an '82 Chevy half ton with a factory 305. It runs fine in dry weather (hot or cold) and in rain, but in the winter when it snows and rains the roads get slushy & this is where the problem occurs.
The truck starts/idles fine, drives great for about 10 minutes then as soon as I stop and let it idle, it starts bogging down and dies. Putting it in neutral and keeping the RPM up at a stop light will keep it running. This doesn't happen every time, it depends on how slushy the roads are.
Any help would be appreciated.
*Engine has new fuel filter, cap, rotor, wires, plugs, and the vacuum lines are fine. Engine set to factory specs.
Does your truck have a Standard transmission or Automatic.
This truck should have the ESC (Electronic Spark Control) installed.
There are some cases that the engine will have pre-ignition and ESC will retard the ignition timing. If the ESC sensor is malfunctioning it will retard the timing under a load and keep it there causing the engine to run rough and try to stall. This condition sounds like it could be the problem.
When the problem happens again check the timing to see how much the ESC Control retarded the timing. Also if you can scan the computer system to see if any codes are stored in its memory. A scanner can also monitor the ESC System to see if it is functioning properly.
A simple test would be to disconnect the knock sensor and see if the problem goes away. It may turn on the check engine light but that can be reset. If this doesn't work then try the service bulletin below.
This is a service bulletin on a problem similar to the problem you are having. Maybe it can help you.
Date: Mar., 1983
Subject: POOR LAUNCH (LOW ENGINE TORQUE AVAILABLE ON A GRADE UNDER LOAD) 1981-82 "C-K-G" 10-20 SERIES TRUCKS WITH LE9 (5.0L V8) AND MANUAL TRANSMISSIONSTO: ALL CHEVROLET DEALERS
Inability to launch vehicles equipped with engine RPO LE9 (305 CID, 4BBL with ESC) and a manual transmission when starting on a grade may be experienced.
The ESC system on the LE9 responds to engine detonation by retarding ignition timing (up to 20~ in 1981 and 1982). When under extreme load, the initial drive-away is accompanied by high levels of detonation. This in turn calls for maximum retard from the ESC system and causes significant loss of initial torque.
When launching the vehicle under heavy load, as soon as the clutch is engaged, engine speed drops to under 1000 RPM. When a knock is perceived at this low speed, the timing is retarded resulting in a loss of engine torque. This further decreases the engine/vehicle speed, forcing the driver to disengage the clutch.
A spark trap assembly (consisting of two traps in parallel), P/N 14068679, is being released for the distributor vacuum advance can. The trap assembly contains a bleed which will allow the vacuum advance to return to normal levels after approximately 5 seconds.
During the 5 second trap period, ESC retard will be offset by the trapped vacuum advance. This will enable a normal vehicle launch.
The use of this fix will increase the amount of knock allowed for a short period, and this knock may occur at all shift points. The fix should, therefore, be limited to only those cases where inability to launch due to ESC caused retard is a severe and consistent condition.
To install the spark trap, the following procedure should be followed:
1. Remove the vacuum hose from the vacuum advance can on the distributor.
2. Cut approximately five (5) inches from the end of the hose and discard.
3. Connect the hose end of the spark trap assembly to the vacuum can.
4. Connect the other end of the spark trap assembly into the vacuum hose.
5. Assure that the spark trap is installed in the correct direction. The green ends of the two (2) valves should be towards the vacuum can.
I don't know if this will fix your problem but is sure sounds like it could be it.
Driving in the snow and slush will increase engine torque and load and may cause the engine to Detonation or ping. You may not hear the pinging because the ESC System will retard the timing.
Let me know how you make out.