90Mustangfan

Ok I finally got the everything working with the egr stuff and all the vaccum line are new, there are no vaccum leaks, I even retighten the intake manifold bolt(to double check), Replaced O2' sensors about 2 weeks ago. fuel pressure is good, timing is at 10*.checked the PCV hose. whats could cause it to be lean...I have no idea....I checked everything....the wires that go to the O2 sensors are good....basicly the only thing left would be the comp...maby I have a bad comp....I cleaned Maf,set tps,replaced wire, cap, rotor, I dont have a clue on what it could be....also, would my car still pass if i unplugged the O2' sensor, would that set off the Check engine light? what are thing to look for if its running lean, things that I havent alredy checked LOL

lunchbox99

maybe bad injector and I do believe an unplugged O2 will set of CEL.

Tims 88GT

how do you know its lean? are you pulling codes? if so what is the code?

90Mustangfan

codes 41 and 91...I reset the comp many times....I doubt its a injector, if it was an innjector than the car would run bad...my car run great. well it could be an injector, how do you tell, because one of my injector makes nosie kinda like a hiss sound, almost sounding like it momentarily losses fuel for a sec the regain the fuel...but thats just 1 injector. mabye ill try running injector cleaner fluid through it.

Tims 88GT

i see in you sig that you have no smog pump, how are the holes in your heads pluged?

90Mustangfan

the pipe that goes to the heads is still there. From the metal pipe foward to the smog pump is gone... at the very tip of that metal pipe that goes to the heads, there a valve that doesnt let any air to come foward towards the pump....

Tims 88GT

are all the vaccume lines ok?

90Mustangfan

yup replaced them all, and check the vaccum diagram for correctness. I dont know ehy it still running lean. Could it be the computer, whats the chance that the somp would only make the lean light go off and the car run perfectly fine...Im lost I have no clue, I have been chasing these codes for about 2months.....I need help

Derf00

Not up to date with OBDI codes, what do those mean? You replaced the vacuum lines but is the vacuum PSI correct at various throttle positions? If you can tell me what the codes mean I can help you figure out if it's on the top end (more than likely) it's leaning out or the bottom end (not typical).

You also mentioned timing at 10° is that TDC? If your chain is sloppy it could cause the Timing curve to be off which could cause it to lean out on the top end.

90Mustangfan

41. and 91. are the hego sensor say its lean...I just freakin replaced the O2' sensor....also its not the timing, I know that for sure. yes the vaccum is good, at idle its about 10 HG of vaccum and when rev'd it goes up to 15- 20 HG of vaccum...the vaccum is good. I dont even know if the car is actually running lean, it runs very strong and sounds very good....also will an exhaust leak cause it to run lean, I have a exhaust leak out of the cats where the smog to connect to the cats...well there is no smog tube so theres 2 hole in the exhaust.