87 accord lxi with 2.0 litre pgm fi. the engine idles high and pulses when i turn on the headlights and run the heater at the same time or head lights and brake lights. i thouhgt it was a charging problem but checked the alternater un der load and it is working fine.the intake manifold gasket has been replaced recently along with the injecters and inj. o rings.

oh and the belts will squeal when this problem is occuring

 

Same problem when I bought my 86. Its a common aging problem with old hondas. Here's what happened and what I had to do to clear it up. The pulsing didn't occur until I had to get the emmissions inspection done. The mechanic really didn't treat the car right because it was old. He loosened up the nut on my EGR and FIV valves then closed my throttle ajustment screw all the way to make the car "pass."

The FIV valve is located at the rear of the engine near the throttlebody. To fix it I took apart the FIV valve and checked the thermo sensor located on the rounded end of the assembly. Just take a lighter to heat it up and the little rod in the middle should move out as it heats up, it will not move in as it cools, thats what the spring in the valve is for. In this case the thermo sensor needed to be replaced. I cleaned out the gunk in the valve and replaced the vaccum line going into the valve. Obvious there was a leak in the line or gunk shouldn't be in there in the first place. Then the plastic nut that holds the whole thing together was put back on but this time as tight as it will go.

The EGR was easy, I just tightened it back up. Besides loosening the EGR in an attempt to make a car passable is really lowering feul efficiency.

Next I pulled the throttlebody at the air intake and cleaned off the carbon buildup with carb cleaner. When finished cleaning check the brass gasper plate by closing it and spray a puddle of cleaner onto it. If it leaks through the edges of the plate either the body itself needs replacing or the gasper plate needs replacing. More than likely the plate would be worn down as its made from softer softer than the body itself. After reassembly I waited about an hour for the car to cool down and adjusted the throttlebody's air/feul mix as the car warmed up to get rid of any loping left in the idle.

Other things that were checked were all the vaccum lines and the rpm sensor at the cruise control.

Change your air filter and that should do it. If not then you are looking at computer problem but that's a rarer case than the above mentioned.