Misfiring bad problem

Yosoydominic · May 1, 2016

So my car will run perfect with the first start of the day. As I'm driving to work for example if I hit a bump my car starts to misfire. As I'm driving it'll keep bouncing rpms and I will hear back pressure from exhaust.
If it's a case where I drive and the car doesn't misfire and I walk into the gas station and come out 5 minutes later I start the car and it starts jumping rpms from 1k - 2.5k
I have no idea what problems could be and even my friends are stumped and we've replaced some things but can't seem to figure out what to check anymore.
Anyone know what this may sound like or could be?
I have a 1994 GT.
Any suggestions appreciated and I can answer any further questions asked

Frank.JD.Perez · May 1, 2016

Do you have any coolant leaking? Does your oil look milky? Have you replaced any gaskets lately!

the5.ohh · May 1, 2016

If you hit a bump it misfires? Not being a smartass, but make sure everything is connected and bolted on where it ought to be. Car stock or modified?

95GT86SS · May 2, 2016

the5.ohh said:
If you hit a bump it misfires? Not being a smartass, but make sure everything is connected and bolted on where it ought to be. Car stock or modified?

This

95 GT BBK CAI TB MSD 6AL O/R H SLP LM1
Coming soon GT40 Heads Intake and e303 cam with Long tubes

Yosoydominic · May 2, 2016

Oil is great just changed it last month. No coolant leaking anywhere I already fixed that when I threw in my new cooling system.

Everything is connected I've already ran all my lines and nothing is brittle or broken or cracked so yeah. Only thing that's been touched is my timing and I advanced it 4 degrees other than that a new coil pack and thats it

the5.ohh · May 2, 2016

You advanced the timing, are you running a higher octane fuel? If you're still using 87, that's gonna most likely be your issue. You can't advance your timing and use the same grade fuel. Try 93 octane.