I have a 91 Honda civic hatchback 1.5. I bought the car a few weeks ago, it has really bad idle problems. has new rebuilt head, timing belt, all new gaskets, cylinders in great shape, new spark plug wires and plugs. problem with the car,,, when its cold I start it up and it runs perfect then after about 10-20 seconds it all the sudden drops idle and runs like crap and smokes a lot and bad fumes. you cant give it any gas it just spits and sputters even though the car spits and stutters at idle. cut it off and start it back up, runs perfect then it drops idle again. same thing over and over. PLEASE HELP and no check engine light

 

Cold start injection hanging up possibly or bad injector.

 

well theres a sensor on the back of the throttle body with 2 vacuum hoses, I un plug that sensor and it still runs the same. could that be the problem?

 

Most likely it is the problem.