Ok, hang in there for this one. It's a bit wordy. My 95 LT1 was purchased in August and ran very very well. About two months ago I had a problem with it not starting and took it to the dealership. Turns out the coil was bad. After the coil was replaced, she ran fine. I purchased a K&N filter and cut a spare cover and that seems to be when trouble started. It may all be coincidental but the idle became very rough after the installation and it began to run rich as evidenced by excessive carbon in the exhaust tips. I thought maybe i needed to disconnect the battery and allow the engine to "learn" how to breath in more air. It seemed better but that may have all been in my head. Now I have the same shaking at idle (not bad but noticeable), I can occasionally smell coolant though the level NEVER changes and it will fire right up cold, but cranks a while when hot. The rough idle seems to show up at or near opening of the thermostat. I fear a head or intake gasket problem. Who knows. It still runs like a scalded jackrabbit and except for these minor and occasional issues, gets 16.3 in the city and 26 on a trip. Am I in trouble or should I ignore it? Oh yeah, I do notice the cat smell of rotten eggs although it is very weak. :confused:

 

My guess is your MAF sensor maybe giving a bad reading. Your probably right about it running rich, this will carbon-up your spark plugs and give you a rough idle. You may have pulled the wires to the MAF when doing your filter. Check the electrical connector. Also for good measure check if the air temp sensor is facing the air flow( I think with the elec connector tab toward the throttle body). If that doesn't fix it, then pull your spark plugs when it starts to idle bad and check for any signs of fouling. Regarding the coolant, don't worry about the odor unless the reservior level drops(other than evaporation).

 

I'd lean towards the MAF myself in this case... what happens is the K&N air filters are heavily oiled when new.. when you put them in and step on it the 1st time, the oil can get on the MAF wires and damage them. This happened to me on my 86...

Another thing that might be complicating the idle issue it under the right fuel rail cover, there is a small plastic T valve that is suubject to a lot of heat, these have a tendency to break apart and cause a vac leak.

 

Check the connection of your IAT sensor as already stated. You haven't removed your throttle body lately have you??

 

I'm glad I don't have a MAF. I've heard this before, but I know a LOT of people who run K&N filters and have never had such a problem, including my brother's 99. Maybe K&N has started to cut back on their oil lately.

 

I think you should remove the MAF just to make sure nothing got stuck on the inlet screen and is givin the car an incorrect air flow reading. But I would also pull the vaccumn hose on the fuel pressure regulator and look for gas, even start the engine and see if any gas sprays out the port, some of what you are describing does sound like a leaky regulator, starts ok cold hare restart when hot. I just don't think it's the MAF I have not seen many new style MAF sensors go bad and if you damanged the connector it would have set a code. A bad O2 sensor can cause a rich condition and poor idle but unless the plugs are fouled up cold idle should be fine and get bad as it warms up. If all else fails remove a few plugs and see what you have.

David Fulcher