Still having idle and gas mileage issues

[sj9ers]

So for the past month and a half my car has been having idle and gas mileage issues. When I first start sometimes the car idle will shoot up to 1700rpms then hang for a little bit then fall down to 1000 for a bit, but then go back up to 1200-1500 then fall back down to 800rpm. This all happens within about 20 to 30 seconds. Also after I get to operating temp the idle gets a little rougher and I have a little surge in my idle. Also when driving out of first gear the car stumbles unless I granny shift it, and it happens in other gears at low rpms ,but not as bad and in higher RPMs the car drives fine. Also my gas mileage has gotten a lot worse. I use to get about 180 for the whole tank mostly city driving, but now it down to about 160. I have pretty much cleaned or replaced everything that I could think of that would be related to this problem, but no luck. The only thing I can think of is that my IAC is bad and cleaning it didn't help at all because it was already broken. Anybody else have another suggestions on what to check or look at?

Here's a list of what I've done.

New Motorcraft copper plugs gapped at.052
New Ford Racing 9mm Wires
New MSD cap and Rotor
New distributor
Timing at 11 degrees
New TPS set at .98 volts
EGR functioning properly
New Vacuum lines
New Battery
Alternator a little over a year old
Cleaned MAF, IAC,
O2 sensors a little over a year old
Fuel filter is less than a year old
Fuel pressure is good
Reset idle and computer a couple of times already
TFI module good

 

[CC'S95GT]

Any other mods? H/C/I? exhaust? CAI?
how old are the cats?
have you searched for vacuum leaks?
Have you ck'd for codes? you can have a stored code without having a CEL.

 

[sj9ers]

Any other mods? H/C/I? exhaust? CAI?
how old are the cats?
have you searched for vacuum leaks?
Have you ck'd for codes? you can have a stored code without having a CEL.

No mods except for BBK CAI, and off road prochamber
I don't have cats I have an off road prochamber
I pulled codes a few times already and I got 157 and 158 once for MAF voltage too high and too low and I cleared it and it never came back. Then the other day I got a 334 for EGR sensor reading too high so I replaced the sensor with one I had in the garage.
I've already replaced all my vacuum lines so I don't think i have a leak, but I will double check and have it smoke tested.
All these problems started after I did a tune up about a month ago, and I've made sure everything is correct and double and triple checked everything.

 

[CC'S95GT]

If it started after the tune-up,
Have a buddy double ck the firing order, make sure the plug wires are seated, swap out the plugs again,(the box may have been dropped).
What kind of dizzy did you get? I have had a remanned on go bad within a week.

 

[sj9ers]

If it started after the tune-up,
Have a buddy double ck the firing order, make sure the plug wires are seated, swap out the plugs again,(the box may have been dropped).
What kind of dizzy did you get? I have had a remanned on go bad within a week.

I already had the car brought to a Mustang shop to get it checked out, and it turns out I had timed it wrong and had it set it at 6 degrees because I didn't unplug the spout when I timed it. They also checked the firing order, plugs and everything, and they checked out and only things they could find wrong was the timing was off and the TPS needed to be adjusted. So they set the timing to 11 degrees and adjusted the TPS and reset the computer. After I picked up the car it ran great, but then that same day after I drove it a bit it started having issues again. When I drove it at night with my lights on the voltage and idle would drop randomly, and the stumbling issues came back. So I did what the guy suggested and gapped the plugs at .046 and that made the problem even worse. So I gapped the plugs at .052 and it made it run better, but I'm still having the issues I mentioned in the first post.

The same kind of thing also happened with the first set of wires and plugs when I first did my tune up. I had a set of MSD Street Fire wires on with the motorcraft platinum plugs, and the car ran like crap. So after reading online and because the MSD wires were touching the headers I replaced the wires with the Ford Racing ones and put in the copper motorcraft plugs and reset the computer. It ran a lot better after and had more power, but then gradually the issues I'm experiencing now popped up. Surging, bad gas mileage etc. (This was with the old distributor by the way)

The dizzy I got is a re manufactured one, and since putting it in no change has happened so I don't think the old distributor was bad. The car also seems to be running rich because I can smell the gas fumes sometimes and one time when I turned on the vent in the car I got a gas smell. I checked under the hood to check for leaking fuel and by the injectors but found nothing.

So right now as far as I can tell for some reason after anytime the plugs, wires are messed with or adjusted it will run better for a little bit, but then just have the same issues as it had before.

 

[toyman]

I'm thinking that since you can smell gas vapors on occasion that perhaps the vacuum line to the charcoal canister has come off or has split. Have you checked for vacuum leaks? The only sure way is to have a shop do a smoke test. This is the only way to confirm that there are no leaks in hidden areas. I see you said that there were new vacuum lines but I'll bet you didn't replace all of them especially the ones hidden in the fenders and in the heater/ac control panel.

 

[BLOWN 95GT]

Chech your fuel pressure regulator, usually when the regulator goes bad you can smell gas pretty bad because gas gets into the manifold vacum line! Do you have a fuel pressure guage? If so turn the ignition switch on and let the fuel pump prime turn the ignition off and look at the pressure guage. If the pressure drops really fast then you have a leak somewhere or the diaphram in the regulator is bad and needs to be replaced.

 

[sj9ers]

I'm thinking that since you can smell gas vapors on occasion that perhaps the vacuum line to the charcoal canister has come off or has split. Have you checked for vacuum leaks? The only sure way is to have a shop do a smoke test. This is the only way to confirm that there are no leaks in hidden areas. I see you said that there were new vacuum lines but I'll bet you didn't replace all of them especially the ones hidden in the fenders and in the heater/ac control panel.

Well I replaced the lines to the canister already and checked underneath the fender liner, but I'll checked to see if I missed anything and see if I can get the car smoke tested next week. I noticed a new thing today though that when the car is in idle and I press and hold the brake pedal down then release it the RPMS will go up a little bit then come back down. Is that normal?

 

[toyman]

I'm thinking that since you can smell gas vapors on occasion that perhaps the vacuum line to the charcoal canister has come off or has split. Have you checked for vacuum leaks? The only sure way is to have a shop do a smoke test. This is the only way to confirm that there are no leaks in hidden areas. I see you said that there were new vacuum lines but I'll bet you didn't replace all of them especially the ones hidden in the fenders and in the heater/ac control panel.

Well I replaced the lines to the canister already and checked underneath the fender liner, but I'll checked to see if I missed anything and see if I can get the car smoke tested next week. I noticed a new thing today though that when the car is in idle and I press and hold the brake pedal down then release it the RPMS will go up a little bit then come back down. Is that normal?

Since my car is still asleep I don't know but I suspect that any slight change in rpm's is due to the change in vacuum associated with depressing the brake pedal and it's release. The brake system is vacuum assisted through the brake booster.