engine swap - runs, but not good-HELP!

[blk88lx]

just did an engine swap on my buddy's 88 LX. It was my old car and someone had put in a crappy speed density non-HO Tbird motor in it. We swapped in the motor out of my 93 into the 88. Its a stock HO, 70K, ran great. Did not change anything else except the computer.

Problem - car wont start unless I give it gas, like a carbed car.
Problem - runs rough, motor shakes, won't idle unless gas pedal is pressed.
Problem - gey smoke out the pipes, lots of it.

b4 the bird motor, it had an 88 speed density HO in it so I used that computer

The MAP sensor had a vac tub going to an outlet in the upper intake on the T-bird motor. My 93 never had a vac tube coming off the MAP. The outlet on the upper is blocked off and that's how I left it. I plugged the 88's MAP tube w/a screw.

Car will run at higher idle but smokes.
HELP!

[Nixon1]

Swap the computer. With how often those things are changed out, I'm almost positive it's programmed different. It's probably got different A/F maps and crap. Is it gray like dark gray or gray like lighter gray/white?

[sn95gt19]

you need to swap the computers too, mass air and speed density computers are different. they measure the air coming into the motor in TOTALLY different ways.

[blk88lx]

Unless the guy lied to me when I bout the car, the computer is for a speed density HO. It was in the car when I bought it. It had a non HO Tbird motor and it ran like crap so I put a Tbird computer in it. When we put the 93 in, we left the car speed density so I put the old computer back in. It's silver. How do I tell if it's a mass air computer or speed density computer?

[fiveohpatrol]

If you are wanting to use the speed density computer, you are going to need to run a vacuum line to the MAP sensor. This is Manifold Air Pressure, and is how speed density operates. Without the vacuum line, the computer has no idea of how much air is getting to the engine. The reason your 93 didnt have a vacuum line is because its not a MAP sensor, I believe it is called a BAP (barometric air pressure??). It relies on the MAF to read the mass of the incoming air, and therefore doesnt need the vacuum line. Speed density is a good thing until you start going with large cams that don't produce enough vacuum at idle and therefore send screwy signals to the ECU.

short version: run a vacuum line from the MAP sensor to the intake, and then see what happens

[blk88lx]

You're the 3rd person that has told me that. I'll hook it up. Funny how one sensor can jack up an engine that bad. Thanks!

[Nixon1]

Welcome to the world of computer controlled cars, my friend. My dad's Cavalier had one wire burn out..just one..and the car barely idled. I had to drive it home...it tried to idle at 400 rpms and would die, so at all stops or slow downs, I had to pop it in neutral and steady-pedal it at 1000 rpms. What a *****. Died on me in a busy intersection..sat there cranking for 20 seconds before I got it started. Boy was that embarassing.

[drewmp28]

The MAP sensor was it, o nce we plugged that up where it belonged it ran great, thanks for your input!!!