Jamiemadroxxx

Just replaced brake booster and master cylinder. New calipers, rotors, and pads in the front and drums and shoes on the back. Fixed the major problems I was having with the brakes, but I am still having a few problems I am stuck on....

Related to the brakes: I am getting a hard pedal after putting the car under any kind of load. If it's a smooth ride and I don't push the car at all, I don't usually get a hard pedal, but if it's accelerated quickly or is working hard to get up a steep hill, I will undoubtebly have a hard pedal.

Unrelated to brakes: When accelerating, I always have a pulse rhythm to it. The RPMs will dip slightly and then pick back up. It happens about every other second and only between about 25-50 MPH. I am not mechanically inclined under the hood and I have heard about 20 different causes to this. Any help would be appreciated. Also, it seems that the problem is maginfied once I have a hard pedal to go along with it.

I am also losing coolant and boiling the water in my reservior ONLY when I have a hard pedal. It seems incredibly strange to me that my brake pedal having anything to do with the car running hot enough to boil the water. But I have tested it and tested it and it will only do it when my pedal has become hard. Granted, I only get the pedal when I put the car under any kind of load, but I don't drive aggressive or anything.

Those are my biggest problems with otherwise a nice little project car...It does tick and rattle and sound like rocks in a tin can, but I can get over that. Any help would be greatly appreciated!!! THANKS IN ADVANCE!

td1238

TPS will cause hesitation. Check for wear. Voltage or resistance (depending on which you test) should change smoothly, and shouldn't jump around (forward, backward, and/or run flat). TPS IS removable. Screws have no slots. Remove throttle body and saw slots in the screw heads and then remove. Adjust new TPS so that it reads about .45 to .5 volts with the throttle closed (throttle adjustment screw turned all the way out), and about 4.5 volts with the throttle all the way open. Measure between the center signal wire and TPS ground wire. Do not measure to chassis ground. Electrical loads will throw off reading due to voltage drops through the non-isolated chassis ground. Adjust with key on, but engine not running.

MAP sensor can cause hesitation. The earlier map sensors read about 1 volt at idle and about 2.75-3 volts with key on, engine off (atmospheric pressure). The newer ones measure about 4.5 volts with the engine off. Again, measure to the sensor's ground wire, and not chassis ground. I believe that the ground wire is the green wire.

Typically the O2 sensor doesn't cause hesitation, but it can cause non-ideal fuel ratios and a lack of power. IT is not the likely cause of your trouble here.

A faulty ignition system can cause hesitation under hard loads. It is more difficult for a spark to be produced if there is a large combustion mixture compressed in the cylinder than when there isn't. The spark is going to take the path of least resistance. If the plugs are worn, this also increases spark resistance. Dirty plugs will carry the spark across the carbon. Oil on the tops of the plugs will carry the spark here, due to the carbon. Dirty and/or faulty wires will arc. A worn distributor cap will increase spark circuit resistance. A faulty coil in which shorts or carbon trails have developed between the windings with the coil will have a reduced output, as the spark will prefer the shorts within the coil to the higher resistance of the spark gap at the plug. The coil may still produce a spark, but it will be of reduced power. The ignition coil secondary, at room temperature, should measure at least the minimum allowable resistance specified for the particular coil. If not, then the coil likely has internal shorting. I am not extremely familiar with all of the ignition coil types that Honda has manufactured. Many coils that test open-circuit are faulty. The resistance should fall between the minimum and maximum allowable. Certain BMW coils have a special capacitor discharge system within, however, and will measure open-circuit when they are in fact fine. If the coil is not supposed to test open-circuit, however, then it is faulty. An open circuit will increase the resistance of the spark circuit, and the spark will look for the easiest path, which may be from turn to turn within the coil instead of out of the coil and through the entire spark circuit.

If your engine falters, vacuum to the brake vacuum booster will be lost. Many, but not all, vacuum boosters have a one-way valve to prevent instantaneous loss of power brakes in the event of an engine failure. Still, if you are going from pull to coast, vacuum should not be lost if the engine is running properly.

Coolant boiling after a hard pull can be caused by many things. If the cooling system is not working properly in the first place, the coolant will boil. The fans should be turning on at the right time. The thermostat should be opening at the right time. The pressure relief cap on the radiator should maintain proper pressure. If not, the coolant will boil over easily.

Excessively advanced or retarded ignition timing can cause overheating. Improper fuel mixture can cause the same, though in my experience a clogged fuel filter actually caused the engine to run cooler. A long time ago, when my '90 Civic DX started blowing radiator hoses, I had the rather bad idea of removing the pressure seal from the radiator cap. This worked fine with the original fuel filter in place, but when I replaced the fuel filter, suddenly the engine started overheating and boiling out all of the anti-freeze. Replacement of the pressure seal solved the problem. I then took the smart approach of replacing all of the coolant hoses. Now, with a properly functioning cooling system, the temperature gauge holds steady.


A blocked exhaust, usually caused by a clogged catalytic converter, can cause overheating and coolant boiling. This can also cause hesitation and engine stalling when going from pull to coast. If doing a hard pull, pressure will build up in the exhaust. The excessive pressure within the engine and lack of removal of the hot exhaust fumes will overheat the engine. When shifting from a pull to a coast, the excessive exhaust pressure may stall the engine or cause it to partially stumble, which would cause the brake assist to lose vacuum, if a one-way valve is not used. Vacuum drops on a hard pull, anyway, with the throttle being held open, which is why the one-way valve is helpful for maintaining brake power assist.

Coolant can boil over in any case if the right amount of anti-freeze is not used. Typically the ratio is 50/50 anti-freeze/water, though the recommended ratio for your model year may be different. Too much water and it will boil.

td1238

A blown head gasket could cause coolant boil-over when the engine is under heavy load, due to exhaust gases pushing the coolant out of the system. It's best to assume other causes first, but definitely check compression. A cylinder or two adjacent cylinders with lower compression could indicate a gasket leak.