1992 Pontiac Transport 3800 why does the engine cough hard enough to knock off the vacuum hose that goes to that round thing the master cylinder is bolted to just happens sometimes when you start it?

Answer 1

There are many causes of coughing. Some are very serious, some are not. The checking and testing procedures are too complex to explain in just a few words, and to be able to say well it's this or no it is this other cause. Each test requuires the experience, and has its follow up test to further isolate and will confirm the problem. Too lean fuel mixture will cause this. Similar symptoms as valve and ignition timming. Camshaft problems, which shows up as loss of compression, which can be valve timing being out, ie. an intake valve being open while the exhaust or firing stroke is in effect. Broken camshafts are possible with this engine, as well. Valve lifters need time to pressure up, and if they are badly worn, or the oil is badly in need of a change, the lifters will be sluggish starting the manage the valves properly. If the oil is too thick, oil can't get ito the lifters quickly, and therefore won't pump up quickly. Ignition timing can do this, ( too much spark advance ). This also generally shows up as what is known as ping. With ping, there is actually an apparent knock when you step on the accelerator hard, and make the engine work hard. Worn timing chain. So loose that the camshaft is not in proper time with the crankshaft/piston strokes, and an intake valve out of time. The timing chian can actually jump a cog and still run, but it will cough, and usually not run really well. A compression test will tell the most quickly, and the condition of the valves, camshaft, and lifters, which might also mean burned valves, or possibly a worn or broken camshaft.