I have the above vechicle with a straight six engine and with 100,000+ miles and have a problem that has been ongoing for sometime and am totally confused as to what to do. The pickup starts great in the morning and idles fine. No roughness during accelleration or anything while idling. I take my daughter to the bus stop and seems to be running fine. When I drop her off and drive for a short while the engine gives a bucking kind of sensation. This happens at the low end of the “Normal” range of the temperature guage and apparent when driving around 40 - 45 mph. I think that it may slightly be running a bit rough at freeway speeds but I cannot for sure tell (Idaho roads are not the smoothest. ha). When the engine gets warmer it doesn’t seem to be happening.
What could be causing this? I gave it a tune up before (OEM plugs, wires, rotor, cap) and it still happend. I made sure everything was even Motorcraft to see if that had anything to do with it! My nephew replaced the hoses at the top of the engine (I think they are return hoses) because they were bad but still having problems.
Any help is greatly appreciated!!
Throttle body needs cleaning? The mass airflow (MAF) sensor (cleaning first)? I’m guessing, as I’m expecting a more concrete answer in any second.
Is this still the old 300 Cu.in Straight Six?? 4.9L…Try tightening all the bolts and studs that hold the intake and exhaust manifolds on…
You might try adding (with the gas tank below 1/4 full) a can of Techron or BG-44K to clean the injectors…
Check out the coolant temperature sensor. It plays a major role in changing how things operate between cold & hot engine. If it is off - either telling the computer the truck is warmer or colder than it really is during that warm up time it can make a mess of the air/fuel mix.
Is the transmission an automatic? Anytime someone has bucking and something like the 35-45mph range in the same sentence I’m wondering about torque converter clutch lockup problems.
This is a manual transmission pickup and has the straight six. I will try the throttle body cleaning and see if that helps anything. I have not tried the injector cleaning items that Caddyman suggested, but I have tried a few injector cleaners and it did not help. I even put it in both tanks.
Is there a way to test the MAF or coolant temperature sensors?