Good Morning! I recently had the head replaced on my 1991 244, it has new plugs, wires, cap and rotor, fuel filter, and runs fine! except when I am first starting out from a light or a stop sign it takes a while to get up to speed, once there it is fine. someone mentioned cleaning the throttle body? any ideas? thanks don 91 244 98k, 79 245dl 179k

Hello,

Had the same issue and it turned out to be the Fuel Pressure Regulator. Easy to change out and you will know right off the bat if that was the problem.

Could also be a vacuum leak. Check the lines for cracks and splits. But a rough idle goes with that.

Regards,

PT

Check the health of the knock sensor. It is an inexpensive part that "listens" to the engine, senses knock and automatically retards the timing. They get full of crud etc. and give false information. Incorrectly retarded timing will give you a noticeable hesitation.

A "slightly" faulty AMM, i.e. during low air mass conditions, can output a too low "air mass" signal to the ECU causing a too narrow (lean) basic injector ON pulse width. Carefully check the AMM's wiring harness plug. Slight misalignment of the female contacts can cause ECU input problems.

Clean throttle body.

Is your temperature gauge correct? Is the engine heating up properly? Is the thermostat working properly?

The fuel pressure regulator is worth a careful inspection. The fuel pressure must rise instantly in response to the vacuum signal fall that accompanies a throttle opening. A hardened diaphragm might be causing the fuel pressure that has been lessened by the fuel pressure regulator to not increase as rapidly as it must and you won't get the appropriate fuel quantity in spite of lengthened injector duration. Try an acceleration test with the vacuum hose pulled off fuel pressure regulator. Easiest way to check the FPR is to pull the vacuum hose off of it while the engine is idling. If the idle picks up, your FPR is good.