2004 Mazda RX8. Tachometer idles back and forth from 1250 rpm to 1000 rpm and then drops down to aboud 750 rpm and dies. had to restart twice and rev it up to keep it past 1k rpm. once it warms up it doesn't idle rough. the only thing I have on the car is a gutted cat and a cold air intake. This didn't start happening until I seafoamed my car. Could it be because of the left over seafoam or maybe some got left on the spark plugs?

 

Test your oil for coolant, pressure test the cooling system. One morning hold the gas pedal to the floor to cut fuel, then crank a few times, then pull the plugs. Is there coolant on them?

There may be other issues, but cold idle trouble after starting could easily be a coolant seal failure that leaks coolant into the housing while the engine sits, which fouls up stuff until it gets swept out.

 

Thanks for the info, I will definitely try those. ill pull the plugs and see of there's coolant on them. Do you think it could be caused from the seafoam? Maybe it wasn't the correct brand?

 

Seafoaming does tend to foul the plugs, however it won't produce these symptoms. It would be rough all the time, hot or cold.