[kreil45]

94 gt with tf upper kit cai msd ignition. it start a little at a time. some times it would do it and sometime not. now it does it about all the time. it idles about 1700-2000 rpms some times it will drop to 1100. i was told it could be a vacuum like. where do i check for that. any perticular hose or could it be something else?

[95StangMX]

just check all the vaccum lines and maybe need to clean your TB. Also read this sticky in the 5.0 section about cleaning your TB and setting your idle. 5.0 Base Idle Reset
Hope this helps

[kreil45]

check engine light come on and off now. had the it check and this are the codes i got

173
177
556
314
311

[kreil45]

check engine light come on and off now. had the it check and this are the codes i got

173
177
556
314
311


and it said pcm rom failure

[95StangMX]

it should have said double post failure....sorry just kidding. I dont know those codes off the top of my head but you can probably find them on here or on google.

[95StangMX]

first is Oxygen sensor, second is rich left side, third says related to the fuel pump, couldnt find 314 except area code in MO, and the last said thermaceter air sys or something. I found them all on google if you want to look into them further. Feel free to rep me for my great usage of google....LOL....hope this helps good luck

[kreil45]

i found what they all are on alldata. but, 311 and 314 are the same thing just different sides. i was told that those codes are always gonna be there because the cam that i have. now i cleaned out the throttle body and thats when the check engine light started to come on. it comes on then goes off after about 2 minutes then comes on again after about the same time. the 173 and 177 are the O2 sensors left and right, rich bank 1 and 2. could i have burned them out when i clean out the throttle boby?

[Chris951]

Pretty sure i read somewhere that the 94-95 computers don't like aftermarket cams. An A9L would most likely help if this is true.

[95StangMX]

It will be fine with a aftermarket cam you just need to make sure to get a good tune after any mods with the sn95. They dont take well to anything really without a good tune

[chriswao]

dude its for shure a vaccume leake and you sould also check your engine mounts bc mine did the same and it was because the mount broke and let the engine tourqe and pull the line off.

[kreil45]

i am get it retuned to the 90mm maf i just put on this morning. so hopefully that will fix some of it. and i agree it is probably a vacuum leak. so my next goal is to just replace all the vacuum lines. and i also have a msd box.

[kreil45]

had it tuned and dynoed. he told that when he was tuning it he turned off the o2s and it ran fine. as soon as he turned them back on it keep stalling in reverse. he also cleared the codes when driving it home the check light came on. he said it probably the o2s. so i think thats what might be causing the high idle. cause there wasnt a problem with the idle when the o2s were turned off

[WildWill]

^^^then that sounds like a good place to start. when he turned the o2's off while tuning it, he was simulating the car running in Closed Loop, which essentially runs the engine of preset a/f ratios. When the o2's are on, the car is running in Open Loop, which takes readings from all the sensors and determines the a/f ratio on the fly. When the o2's go bad, it really screws everything up... read on...

"Open Loop vs. Closed Loop Fuel ControlAll of the previous discussions on how the ECU calculates fueling are based on an Open Loop (OL) control strategy. In OL mode, the ECU reads all its sensors, checks with its programming to determine the desired A/F ratio, calculates the required injector PW (as detailed previously), then sends that PW to the injectors, hoping for the best. It never really knows if it achieved the desired A/F ratio or not.

With Closed Loop (CL) control, the ECU has feedback to tell it whether it hit the desired A/F ratio target or not (well, sort of, as we'll find out). At part throttle, when the engine runs at the stoichiometric (chemically correct) 14.6 A/F ratio (required for minimum emissions, and maximum catalytic converter efficiency), the combustion products should ideally be only water vapor and carbon dioxide. If the A/F ratio was a little lean (too much air and/or not enough fuel), the excess (unburned) oxygen will show up in the exhaust gases. Using an O2 sensor, the ECU can now detect when the engine is running lean. Problem is, the factory O2 sensors have a narrow band for sensing oxygen. In other words, they can really only tell the ECU if there is some oxygen in the exhaust, but not precisely how much. So the ECU doesn't really know how lean the engine is running, only that it's running lean."