Hard starts slight miss at idle

[sonic_03gt]

I have 03 5spd gt....Recently it seems like i have a mild loss of power. My car seems to start hard now. It seems to have a slight miss every few seconds at idle tho. Under wot it seems ok just not as much power it seems. My idle is somewhat rough as well but not really jumping around more then 50-75 rpms. my mods are
slp lts
slp catted x
steeda uds
slp lm1 catback
Predator
bbk cai

Any help would b greatly appreciated thnx in advance guys.... Oh and i forgot to mention my fuel mileage is terrible... I am averaging around 13-15 drving easy w mixed driving.

 

[sonic_03gt]

Also i have just put new plugs in it,fuel filter,cleaned mass air,cleaned iac and egr. I have also checked for exhaust leaks their is none....And to make it really tough i have no ses light tho?? Got one earlier b4 tune for lean signal upstreams 1 and 2 i think. But hasnt came back since tune.

 

[phoenix99]

check for the compression in each cylinder

maybe a vaccum leak ?

 

[GT Tommy]

Hard Starts?

I agree with phoenix99, sounds like a possible vacuum leak to me. Is your idle at a higher rpm than it usually was? If yes, check all of your vacuum hoses, plastic tubing and 90 degree rubber elbows. You need to take each one off, one by one, and if rubber bend it to look for cracks. I recently replaced my son's 2003 GT Mustang 4.6 intake manifold due to coolant leaks. As I was removing the vacuum hoses, I came across 3 items that was either cracked or broken off completely. One of the 90 degree elbows was broken off completely, it was held together with just one thin layer of rubber at the top which made it difficult to see that it was actually broken in two. So, make sure you physically remove each hose, elbow or plastic tube, and look for cracks. By the way, what brand spark plugs did you use and what did you gap it at? Good luck, Tommy.

 

[sonic_03gt]

So this could b a compression issue?? It only has 49,000 on it? I have checked all vaccum lines completely unless their is some i cannot see? I used autolite double platinum at .053 nothing special. Did it b4 i changed them tho. I had it at the shop hear in town and they told me it b bc of the free flowing exhaust or the ud's.... This seems to b total to me. My car is not running nowhere near the way it should b... Im starting to think it is something bigger. Really throws me off that their is no check engine light.... I have the predator but it does not really tell me nothing. and also I kno this is off topic but how hard would it b to change the rear seal on the transmission where it connects to the ds?

 

[GT Tommy]

Check your fuel pressure!

If it's not your vacuum, meaning you don't have a vacuum leak, then I would check your fuel pressure. Get a fuel pressure gauge and mount it on your fuel rail. Your fuel pressure is suppose to be between 35 psi and 70 psi. If your fuel pressure is below 35 psi, this could be a sign that your fuel pump is starting to go. One important NOTE: I had to replace my son's 2003 GT Mustang 4.6 fuel pump, because he kept running out of gas. When ever you run your tank dry, you are taking away the life of your fuel pump. The fuel pump needs the fuel in the tank to keep it cool. The problem was his gas gauge would read 1/4 tank and his engine would die out. He did not realize that he was getting false gas gauge readings. At 1/4 tank, he was actually at an empty tank. This caused his fuel pump to short out. The picture below is his actual fuel pump after I removed it from the fuel pump module. This is the result of running your gas tank dry. If you have run your gas tank dry a few times, this could be your problem. Just something to think about. As mentioned above, the best way to check on this without removing your tank, is to install a fuel pressure gauge on your fuel rail. If you decide to do this, make sure you purchase the correct one which will work on your fuel rail like the one posted below. This fuel pressure gauge is for a GT Mustang. Good luck, Tommy.

View attachment 259786

View attachment 259787

 

[evolucion311]

GT Tommy,

What is that in the top picture (not the black and white diagram)???

 

[sonic_03gt]

Ok so kinda good news...Fuel pump is not bad i am running around a steady 42 psi which is good right? Then last night i finally got a cel....Brought it home plugged in the predator. It was p0133 i think....bank1 sensor1 response to slow. Then a code for the same bank to lean.... Now question is does this mean my o2 is bad. Even tho i am just now getting a cel? Or could it b something to do with my headers? also to note my pipe on my passenger side (bank1) smells much richer and is putting out more hot air at idle. Any help is appreciatd guys thnx alot

 

[sonic_03gt]

Ok so i got the new front passenger side o2 sensor and changed it bank 1 sensor 1.....Car is running worst now.... Took it for a test drive and did a second gear pull was so rich their was a cloud of smoke....when i stand behind it my eyes water....Check engine light went away b4 i changed it bnut code was still in the computer. Front sensor at idle is reading .5 .6 volts which isn spec i think but the one behind it is basically reading .0 to .01 at idle if i rack it off 3500 or so it will jump to about .46 .48 where it is supposed to be.... What is goin on here? I really need help guys...It seems as if only the passenger side is running rich (bank 1) and it sounds like it has a miss at idle but it sounds like it cant burn all the fuel....I am starting to wonder if i have big problems