I recently did a 2.8 for a 2.8 swap in a friends 87 gt. The good engine was pulled out of my 87 for a 4.9, and was running great when pulled out of my car. When engine was installed in car with bad motor, it started up fine but had a little bit of a popping noise when it is initially started, but subsides when the car idles out. It pops in park when you accelerate and let off the gas (rev the motor). Set timing properly, and idles great, but as soon as it is put in gear (car is an automatic), it surges a couple of times and dies, and pops even worse than when revving the motor. Fist thought the sound was coming from transmission area, (possibly torque converter), but had hand on muffler when friend revved motor, and felt like something inside was banging inside muffler. Initially thought muffler may have been clogged, but pulled exhaust away from y-pipe, and had same thing happen when put into gear. Does anybody have an idea as to what it may be causing this? Maybe a bad sensor? Timing out 180 degrees? I am at a bit of a loss.

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87 fiero gt 4.9
99 trans am ls1

Bad Torque converter selinoid symptom. Disconnect the selinoid to see if it still dies.

is that the flat plug that plugs into the tranny?

I plugs into the front side of the transmission. Points toward the drivers seat.

Also check your fuel pressure is good in the new body.

i went out and disconnected the torque converter solenoid, and it still make the popping/knocking sound when revving the motor, and it still cuts off motor when i put it in gear.

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87 fiero gt 4.9
99 trans am ls1

No the TCC would not seem to be your problem. ..

It might also be a bad MAP or tps sensors.
You might try unplugging the map and see if it idles any different.

Have you tired to flash the error codes to see if there is something there that might tell you what the problem is.

You might also get an aldl cable and copy or Winaldl or borrow a reader from a parts store.
You could then check if your map, cts, mat, map and tps are reading correctly...
Would also be worth your time to verify the fuel pressure is correct.

[This message has been edited by Dodgerunner (edited 01-06-2008).]