Engine Performance problem
1986 Jeep CJ7 6 cyl Manual
Hello from Austria!
I own a AMC Jeep CJ7 with 4, 2L 6-Cylinder Engine and Weber K551 32/36 Carburetor. The engine runs smooth and fine (high oil pressure) when it's cold or warm, but when I drive about a hour or more, the engine sometimes turns off when I use the brake at lower speed. At this time the oil pressure is very low (under 20). After this the engine doesn't have much power to accelerate and has dropouts when accelerating.
It seems like the carburetor doesn't find the idle. I do use a fuel pressure regulator (from Weber, at 3, 5 psi) and the original two output filter with fuel tank return. I have to adjust the fast idle speed many times cause it changes every day.
There is no white smoke coming out of the Exhaust and the engine looks clean and dry from the outside. No visible leakage. What can be the problem? I really don't have a clue. Oil pump? Engine Head gasket or the Weber Carburetor? Hope you can help me.
Does the engine knock at idle? At load (acceleration)?What kind of oil are using? Depending on where you live you might want to choose a uni-grade oil. Multi-viscosity oils such as 10W-30 might be too thin for your engine. (Your main and rod bearings might be a little worn). Also note that the idle oil pressure should hover around 12-18 psi.
The weber carb is very hard to tune. (Is this the single barrel or 2 barrel carb?) Make sure your timing is correct. Make sure the float setting is correct and the jets are clean. Then check for any vacuum leaks. Unfortunatly the entire emissions and engine managment system is controlled by vacuum so it will be very difficult to pinpoint a leak. Use a can of carburetor spray to check for leaks particularly at the carburetor base and intake manifold. If you have a vacuum guage tuning the engine will be much easier. Start by tuning the idle mixture screws all the way in and then back out 3 1/2 turns. Turn them out 1/2 turn each until you achieve the highest possible vacuum without touching the idle speed screw. Then adjust the idle speed screw to the idle speed on the emissions sticker. Other causes can include a plugged catalytic converter or a bad alternator. Also check your PCV valve for proper operation.