1999 4.0 issues


wfo479

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Vehicle Year
1999
Make / Model
Ford Ranger
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Greetings fellow ranger gurus.

99 4.0 regular pushrod cast iron engine. 166.000 miles.
I have kept her alive for so long, never seen a salty Ohio winter, the frame and body are pristine.

What I have changed over the summer as regular maintenance.
Coil, wires, plugs, air filter, clean MAF, pcv valve, fuel filter, O2 sensors IACV. Found and fixed any air leaks (including one caused by the fan shroud to the intake piping)
Removed the (-) from battery and drained the capacitors via jumper to (+) for 10 minutes.
Over time: installed the updated manifold spacer gasket and new injector O rings.
No manifold leaks. ( contact cleaner test) Checked the EGR and associated vacuum switch, all ok.
Cleaned the MAF ( runs worse unplugged) Fuel PSi 60
No coolant use, no geyser when running from radiator. She does burn about a quart every thousand miles.

When looking for air leaks ( I plug the air intake hose and use soap and look for bubbles) I did have a leak at the throttle position sensor on the throttle body AND bubbles from the throttle blade shaft
under the return spring. I used hondabond on the TP sensor and the bubbles at the return spring went away

Things NOT done so far: compression check, my dang adaptor does not interface with the plug hole size....facepalm. But all the plugs look the same so I did't sweat the comp test.

The symptom:
getting the 171/174 codes for the longest time (found the air leak and repaired)
So the other day I get the typical symptom of the coil going out and a misfire of #3 cylinder.
I check the coil and it tests ok but I get a warranty one from Autozone. pulled #3 looked like new, Om'd the plug wire and swapped with an old one cleared code.
Drove for a few miles and the hesitation and bucking at low RPM was so bad I had to put in neutral at a light to keep her running.
Low RPM ran terrible, half throttle runs like a champ.
Then the rain came today and the truck just will not run, I cant get past 30 mph and the horrible egg smell (cat) is sickening.
The odd thing is....I am, only getting codes from the sensors I disconnect to test, nothing new code wise.

I have a rudimentary OBD tester, the O2 sensors seem to be in voltage range and react to carb cleaner.

I feel sad for the old girl, she is in such nice condition but I am at a dead end. I guess a trip to Ford to have it diagnosed is my next step as my testing equipment is not sophisticated.

Ideas please.

thank you
 


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RonD

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Could be fuel pump on its last leg

Limited volume means limited power, also lean codes on both banks as pressure drops in fuel rail
 

wfo479

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Location
Ohio
Vehicle Year
1999
Make / Model
Ford Ranger
Transmission
Automatic
hmmm one reply.....
stumped the gurus...

Ill take it to Ford and see what they say.
Will advise.

thanks
 


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