TtopsMan85

Hey guys I was wondering if someone can help[ me with this issue so I do not have to go buy a bunch of parts I don't need. So here is my problem. I have an 1988 305 TPI Trans Am and lately I have been getting a very weak idle in both park and drive as well as my heat deciding only to work when it feels like it. Here is the work I have done to it:

New Spark Plugs and wires
New oil filter w/ oil change
New air filter
Had all injectors machine cleaned
Engine decarb

It will always jump between maybe 4-600 rpm at a stop light and act like it might die because it is running so weak but it never does die. The no heat issue has just started 2 days ago but when the heat does work it comes out nowhere near as hot as it used to. My car does not overheat at all it actually stays at a very reasonable temperature. The really weird thing is that my check engine light ONLY comes on after I drive the highway for around 10 minutes or so doing 60+ mph. Then the light does come on and it seems like I lose some acceleration power. Then as soon as I turn the car off and back on, the light goes off. The light stays off until I drive the highway again.

In other words I am extremely confused. Can someone give me an idea on WTF this could be?? All input appreciated

novafirebirdguy

Well the first thing you need to do is find out why the check engine light is on. You can do it with a hair pin, I believe there is an article in tech section on it. The SES light only coming on once the car is warm indicates and o2 sensor.
You said that you replaced the plugs and wires, did you replace the distributor cap and rotor as well? If not do that.
Also replace the fuel filter. God knows when it was replaced, if ever.
If the car has more than 100k on it (which I'm sure it does) you need to replace the timing chain and time it.

As far as heat is concerned. Your heat problem may just be because the car is not running right and the above may fix it. If it doesn't try a new thermostat, bout $3. If it's stuck open or opening too early the engine will take forever to warm up and may not if it's cold enough. A water pump is another possibility, if it's worn it simply can't pump enough hot coolant to the heater core.
One way to check the water pump is with the car idling (and warmed up) squeeze the upper radiator hose. You should feel a pressure surge as your releasing if the pump is working properly.
Good luck
Alex

TtopsMan85

Sweet thanks man ya that is exactly what I was thinking to do was replace my thermostat and fuel filter. I did replace the rotor and distributor though as well. I think I am just going to go ahead and replace all of those little sensors and things like that. IDK if the last owner really took 2 good of care of it, she used it as a work car. Surprisingly though the motor runs like a damn top starts right up and runs really strong except for the small idle issue. I pray it's my thermostat and not the heater core I know those are a pain 2 change I forgot to mention one other thing that it does! The lights all work fine and all but at night I notice that the lights seem 2 dim until I press on the gas and than all of the sudden they get a whole lot brighter. Is this normal? I just got a brand new battery and the car doesn't seem at all starving for power. Sorry for asking so many questions this is my first 3rd gen and I love the car and I want to take really good care of it! It's my new BABY. F the fourth gen's ya their nice but these 3rd gen's look sick in good shape