i have a 97 civic lx auto trans with a d16y7 and it seems to buck at any where between 45 and 70 mph problem is intermittent after reading on ht alot of people have had a similar issue most of them caused by an aftermarket tps but i have another symptom too. just before and during the bucking the tachometer goes nuts flopping around all over the place the tach also does this at idle or whenever it wants to. but the engine speed doesnt change. not sure if its a trans speed sensor or the dizzy possible torque converter maybe the tps but the tps is an oe honda one never been replaced any ideas its driving me crazy. also i have a cel on p0420 catalyst below efficency but thats the only code i have been able to pull nit sure if that would cause this issue but please help

 

Have the ICM in the distributor tested.

 

ok so i changed the whole dizzy problem did not change so i changed the throttle body. engine seems to run smoother but also seems to have a slight miss intermittently. and the tach fluctuates but the engine speed does not change. also when in reverse with my foot on the brake the miss or slight stall is at its worst thinking plug wires because plugs, cap, rotor, and dizzy are new. but maybe possible torque converter?

 

The fluctuating tach point to an electrical problem. I would check the wiring to the distributor. Don't throw parts at it you need to problem solve. My next guess would be the ecu so find one you can borrow and swap it out for yours.

 

what about the crank fluctuation sensor

 

Charging system or plugged cat.

 

well it does have a p0420 code and the cat came from the original motor wich was burning oil pretty bad. so i was already gonna put an ex style exhaust on it because it costs the same as an oe cat/manifold and the cats for an ex are cheaper and easier to replace when neeeded. and when the cel comes on it kind of flickers slightly like a candle its not a steady glow like it should be and i changed the bulb.

 

For one 2 cars when it miss fires its suppose to flash and if it happens on the second trip then the lift is illuminated. What I've learn and easiest way to know if ya a clogged cat hook up a vacuum gauge to the manifold and rev us slowly till u reach a high rom and it will drop back like its glitching. If its really clogged you will automatically know at idle when the vacuum signal is low like below 16. If u have a code reader your o2 signal will read high and short term will subtract and long term will be negative also.

 

problem is fixed there are three ground wires bolted to the thermostat housing that are for the ecu. my thermostat housing is only bolted to the block with one bolt because the upper bung for the bolt is broken and was like that when i bought the motor. the lower bolt was loose allowing the t-stat housing to move interrupting the ecu ground so i extended and relocated the grounds for the ecu to the fender well near the battery body ground. have had no issues since cel is still on for the cat p0420 but the cel is steadily on not flickering like candle light any more the tach reads steady and most of all the bucking is gone. another added bonus getting better fuel mileage too.

 

thank you for your thoughts and opinions everyone exhaust will be in within the next week to take care of that cat code