Clivano

Hi, i have a 1992 Honda Accord 4th Gen with -i assume- 2.0L F20A PGM-FI, cause the engine number only said NA - C00949. The problem is that, the RPM is fine when stationary, i revved it and it goes down to idle rpm like normal. The problem only occur when i started moving, the rpm is stuck, for example: from stationary i press the gas pedal to 2k RPM, once i lifted my gas pedal, the engine RPM wont go down, it's as if i have cruise control ON, and itll stuck even at 5k. Earlier we changed the Throttle Positioning Sensor, but before even changing that hardware, the problem already exist.

Is this a problem with the speed sensor?

Micro1989lxi

I have not come across this issue with my cars, but the things that I would look at are:

*Is the throttle and throttle cable closing all of the way on the fuel injection on the engine. The cable goes into the cruise control (controlled by vacuum). Make sure that it is not a cable or vacuum issue in the cruise control unit, even though you are not turning the cruise on. The cable it's self could be sluggish or dirty, even check the return spring where the cable connects to the fuel injection. *I think the vacuum hoses have one way check valves in the lines as well, perhaps if one is bad or has moisture in it. I think that these are the small 1/4" white connectors.

Clivano

Does the 1992 Accord actually has a cruise control? If it does then thats a massive news and Ill take a look at those cable.

Micro1989lxi

I have 5 between 1990 & 93 and at least 4 of them have cruise. The 5th parts car I have not bothered to look at.

Clivano

I saw what the Cruise control actuator looks like, and i can say that my model does not have a cruise control.

Micro1989lxi

I am not sure what else to look at , but I will continue to think about it. Do check to make sure that the throttle is closing all the way as it could be worn enough that the throttle spring is not compensating for the sticking throttle cable (peddle).

Clivano

My assumption so far is the Speed sensor and those vacuum rubber pipes that goes to the PGM-FI and everywhere. We dont know what kind of changes the previous owner did before we bought it.
Which hardware changes when the car moves?. Since the RPM stuck only happens 1 second after moving. And it stopped being stuck 1 second after stationary. There must be a hardware the determines and send signal to the engine that the car is either moving or stationary. Thank you for taking your time and analyze this problem!

I also found out a new problem, when i do a hard brake from 60kph to 0kph with my clutch fully pushed and even put it on neutral, the rpm goes down and my engine shuts down. So there must be a problem with the brake booster, or perhaps a wrongfully placed vacuum pipes from the booster to the engine giving an incorrect signal.

Micro1989lxi

Yes, perhaps it is a vacuum line placed on the wrong passage. If there is a white valve inline to the brake boost, make sure that it was not put in backwards. It keeps the booster from bleeding off air, but if backwards, it would cause it to loose air, dropping engine vacuum and causing the stalling.

I am not exactly sure what all is involved with the speedometer and tach. It looks like there is power steering lines connected to the speed sensor (or something like that). I have not looked into it, but I have wondered about why there are oil lines going to the speed sensor.

Clivano

I found out it was the TPS all along, Woops!. accidentally put it on the wrong place and stuck at 2+ volt. i dont know why i didnt calibrate it properly. The rpm stuck is now gone!