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Cwheeler
04-01-2007, 09:59 PM
1991 Explorer 4.0L standard trany


heres my problem my truck will start and idle fine, even revs with out issues, but go and try to drive it, it just just hesitates and stumbles on acceleration. but will return to idle fine. I pulled the codes and it gave me 41, O2 sensor lean condtion, all cylinders are firing, fuel pressure is around 30 psi but here is wher I found an issue it bleeds off as soon as you shut off the truck, I replaced the fuel filter and pressure regulator to limited effect the pressure still bleeds off rather quickly, It was suggested that perhaps I have a leaking injector? is there any easy way to cheak them? or should I be looking in a different location for my troubles first?

Thanks, this is getting rather annoying

In The Zone
04-02-2007, 07:37 AM
if a injector was leaking in to the cylinder consatntly you would be running rich in that cylinder pull the plug check for fouling..

there is a bleed down test u can do more than likley u replaced the regulator for no reason...pressure should hold around 12-20 psi when not running...
the hesitation and stumbling sounds more like a emissions related issue...

sparkes3
04-04-2007, 09:27 PM
does it have an ignition module .sounds sorta like what mine was doin . also check timing

duff
04-04-2007, 09:38 PM
check for leaks between the engine and mass air flow meater, like a torn air intake tube broken pcv breather hose, ect,

blacker_69
04-05-2007, 11:59 PM
if youve got lean codes, and pressure drops off after the engine stops running youve got internal pump failure. if your reading 30 psi running its more like 40 with the regulator vacuum line unhooked but your internal bypass valve in the pump is most likly shot, put a pump in it. if you want to get technical and have a shop scope you can ramp up yer pump and check it. but otherwise... pump.

nykoma
04-06-2007, 08:57 AM
check the EGR side of things, if this fubared it will make the engine run good at loww rpms but run like a pos you call for fuel slowly[cheers]