I have a 1991 Trans Am with a 350 TPI engine with 95,000 miles. The car is currently in the tranny shop cause it was bogging and I thought it was a tranny problem but they say its a motor problem. Nothing wrong with the tranny.

Ok here is what its doing. When the car is cold or has sat for 2-3 hours when I get in it and drive as soon as it shifts in 2nd it bogs down, when it shifts into 3rd it bogs down even more but 4th is ok and once it warms up it is ok. If I manually shift it holding it to higher rpm's it shifts fine and doesnt bog.

What could be my problem?

Could it be the Cold Idle Air sinsor or could it be clogged injectors?

 

You're loading and revving the engine before it is warmed? That could be a part of the problem.

 

Im just going easy down the street like I have always done. It just started doing this here recently.

 

Apparently, I misunderstood your description.

About the only difference between cold and fully warmed operation is the mode of the ECM. With a cold engine, the ECM should be in Open Loop Mode, which is normally more rich and with slightly retarded timing as compared to Closed Loop Mode.

There is no "Cold Idle Air" sensor. There is an Intake Air Temperature or Mnnifold Air Temperature sensor, but they don't have a lot of bearing on fuel mixture, even on a Speed/Density setup and even in open loop mode. The coolant temperature sensor is a far more critical input.

Clogging injectors would likely exhibit the same symptoms when warm as well as cold, and would likely cause a condition similar to an ignition miss at idle.

It is possible that open loop mode is too lean, however, and that would be the case if the fuel pressure is incorrect (too low).

Are there any error codes stored in the ECM? Have you serviced the ignition system/filters lately? Do you have any idea what the fuel pressure is? Is there any more history or detail you can provide?

 

If it only happens during a cold engine, that makes me lean towards an emissions problem....or a sensor problem...
This sounds like a crap shoot to me, so I'm gonna start tossing ideas.

EGR valve stuck?

Or maybe a bad CTS... Sounds like something could be giving it a poor mixture in the low rpm range. Too rich maybe.

Possibly a broken pressure regulator diaphragm or bad vaccum line to it causing it to run full fuel pressure all the time? Even still though, that should affect your warm operation as well. Check the fuel pressure at idle and then rev it and see what happens. It should go up, although it might dip for a second before it does.

And check your vacuum too....a vacuum leak can do all sorts of weird things.

 

Thanks Guys Ill try some of both. Im just grabbing at straws cause its really aggravating and its not throwing any codes.

It does seem to be running rich, I get alot of rich smelling exhaust. But I thought maybe that was due to me running no cats and Headers. I have nothing to check the fuel pressure so Im screwed on that.

About the history of the car i dont know much about it. I bought it the way it sits and the guy I bought it from had done alot to it so im not sure what is disconnected and plugged and what isnt.