running rich bad mpg runs rough after warm up

[camaro9407]

i dont know why but i am getting 12.8 mpg i have a 94 3.4l camaro with stock everything except a flowmaster 80 series and a gutted cat. when it gets warm around 220 it runs ****ty and is very very sluggish. if at idle irev it up to 4500 black smoke comes out. can n e one help me?

[HeadyFirebird'00]

Re: running rich bad mpg runs rough after warm up

black smoke = bad. u probably have some major engine problems. could be tons on things. get your head under there and look around for problems

[black95maro]

Re: running rich bad mpg runs rough after warm up

black smoke isnt as bad as u make it out to be.....it could just be a sensor starting to go out sending a wrong signal and running rich like O2's or something but then again it cojuld be something a little more in depth have it scanned for any codes and history codes they may be of a big help...it took me forever to find my problem but finally got it after almost every sensor replaced

[camaro9407]

Re: running rich bad mpg runs rough after warm up

i replaced the o2s and the codes were egr solonoid 1,2,3 and short circuit 02s, so i replaced the o2s and i dont have an egr valve. what sensor was your problem and did you have the same problem i am haveing. the motor also only has 10,000 miles on it. black smoke is running rich i think he is thinking about blue smoke.

[black95maro]

Re: running rich bad mpg runs rough after warm up

i replaced the o2s and the codes were egr solonoid 1,2,3 and short circuit 02s, so i replaced the o2s and i dont have an egr valve. what sensor was your problem and did you have the same problem i am haveing. the motor also only has 10,000 miles on it. black smoke is running rich i think he is thinking about blue smoke.

i had right bank and egr sylanoid misfuntion and crank 3x or 7x cant rem what it was replaced them all and its alot better
i also did the 24x crank

[superman18]

Re: running rich bad mpg runs rough after warm up

when my mustang did that it was the fuel pressure regulator. it was only like 35 bucks to replace. I would start there.

[reillyracing]

Re: running rich bad mpg runs rough after warm up

i replaced the o2s and the codes were egr solonoid 1,2,3 and short circuit 02s, so i replaced the o2s and i dont have an egr valve. what sensor was your problem and did you have the same problem i am haveing. the motor also only has 10,000 miles on it. black smoke is running rich i think he is thinking about blue smoke.

How do you not have an EGR?? Did you bypass it or something?

[camaro9407]

Re: running rich bad mpg runs rough after warm up

yes i designed a blockoff plate out of the egr itself. and my fuel pressure regulator is $385. what is a 24x sensor what are those.?

[Two Black Marks...]

Re: running rich bad mpg runs rough after warm up

When cars are running rich its often just the temp sensor that is broken and it is sending false data to the ECM, saying that the engine is cold when it actually is warm.. so its putting in more fuel than it needs. You can ohm it whit a multimeter to check it by looking at the values while heating it up.

Or too high fuel pressure because of bad fuel press regulator.

I do not now where the the temp sensor is on this engine, but find it and un-connect it, then the engine PCM will go (should go) into "emergency" mode and just use an default reading for the temp usually around 70 degrees celsius (we dont use farenheit here.. around 210 degrees farenheit or something but not sure..) Then it should run ca. normal when the engine is hot, but may be hard to start if its cold..

Could be other things but something like this is common..

Hope helps. :burn: