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  #1  
Old 12-17-2010, 11:17 AM
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Default 1994 4.0 OHV Running Poorly

Okay. Short and sweet

4.0 OHV
145,000 miles

Engine idles at 550 or so rpms
When you goose it at idle, it hesitates (like the engine just stops for 1/4 a second)

General running and you get low power, poor fuel economy (8 mpg or so)

I know the cat is in rough shape and already have plans to swap it out.

Fuel pressure is 38 psi engine off, and 30 engine on (I think this was it, I can't remember and plan on doing it again tonight)

Anyways

Symptoms

Low Vacuum (14" Hg)
Low Power
Horrible acceleration in 3rd, 4th or 5th gear.
Poor Gas mileage
Slightly rough idle
1/4 second hesitation on the throttle
Oil around the threads on the #5 spark plug (with a fuzzy white head) and another plug (can't remember which one) was oil fouled.


Done So Far

Swapped Fuel Filter
Cleaned MAF
Replaced Spark Plugs
Replaced Spark Plug Wires
Cleaned Throttle Body
Checked operation of MAF
Checked operation of TPS
Retorqued Lower Intake Bolts (using the apparently incorrect outside - in method)
Retorqued Upper Intake Bolts
Checked for blown head gasket (Chemical test came back negative)
Tested Fuel Pressure (38 psi before start up and 30 psi at idle)
Checked compression (140 - 150 psi on the drivers side bank... couldn't get the damned compression tube into any of the cylinders on the passenger's side)
Sprayed Brakleen all over the motor and no change in engine.

Some other stuff I can't remember.



Truck has NO EGR system. I checked, thoroughly.


What I think could be the problem.
-Low fuel pressure could be either dying fuel pressure regulator or a leak between the fuel rail and intake manifold, maybe a bad gasket there.... I have no idea how to check to see which it is.
-Low Vacuum leak could be a leak between Manifold and Motor (but I retorqued those bolts and there was not a single sign of improvement) or it could be caused by excessive backpressure from the exhaust
-Oil fouled plug could be just a worn valve stem seal or could oil be leaking from the intake manifold?

I'm not afraid of spending the cash to buy replacement parts, I just don't want to replace what isn't broken or breaking.



Anyone have any ideas what I can do next? Really need this truck to be working before the even worse weather hits.
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  #2  
Old 12-17-2010, 11:18 AM
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Default Re: 1994 4.0 OHV Running Poorly

did you check the coil packs?
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  #3  
Old 12-17-2010, 11:31 AM
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Default Re: 1994 4.0 OHV Running Poorly

I checked them in the most redneck manner possible.

I did the old "spark jump to wire" method, which may or may not be more reliable than taking an Ohmmeter to it.

They all appeared good. If you have a different recommended method I am willing to try it.

Even if all the coils were bad though, it would not affect that vacuum leak or low fuel pressure, I do not think. And those I believe are probably the major causes of the shitty running of the truck.

Still though, like I said, willing to try anything to help.
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  #4  
Old 12-17-2010, 11:33 AM
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Default Re: 1994 4.0 OHV Running Poorly

HHMMM, thats a thinker now!
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  #5  
Old 12-17-2010, 11:39 AM
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Default Re: 1994 4.0 OHV Running Poorly

Yeah.... I've been thinking quite a bit on it.


And whatever repairs I have to do to fix this is on top of my Slave/Clutch swap this weekend....


It's probably a lower intake gasket leak, but all in all, that will cost me $100+ and about 6 hours of work and possibly not even solve the problem...


The oil fouled plug kinda worries me, of course it could just be a valve stem seal leak, which would require me pulling the valve covers, so I'm already looking at half the intake job right there.
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  #6  
Old 12-17-2010, 12:40 PM
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Default Re: 1994 4.0 OHV Running Poorly

the hesitation kinda sounds like plugged up injectors...

as for the oil on the spark plug, i think your right on the valve seal being bad. or you can check for oil blow by.
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1998 ranger extended cab, 2wd, 4.0 ohv, 5 speed, sony xploid 52 4 way watt radio, 2 pair of pioneer 240 watt speakers, Cobra 29 LX LCD CB radio pushing 100 watts, k&n air filter, 15 inch exploder wheels, dual exhaust with 4 inch stainless tips, 2 12 inch subs with a 1000 watt amp just for the hell of it!

new project: dirt track modified racing at the local saturday night track.
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  #7  
Old 12-17-2010, 01:20 PM
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Default Re: 1994 4.0 OHV Running Poorly

Quote:
Originally Posted by crowdpleazer View Post
the hesitation kinda sounds like plugged up injectors...

as for the oil on the spark plug, i think your right on the valve seal being bad. or you can check for oil blow by.

The oil in the one cylinder could also be oil leaking from a possibly faulty lower intake gasket. That's my concern.

I was thinking the hesitation might have been more of a vacuum leak issue.
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  #8  
Old 12-17-2010, 02:01 PM
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Default Re: 1994 4.0 OHV Running Poorly

how is the exhaust flow from the tailpipe? It could be possible the cat is so plugged up its creating to much back pressure, this would in effect cause exhaust gas to block the intake valve from bringing in air. Because there is no where for the exhaust to go...?
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Quote:
A Gladiator does not fear death. He embraces it. Caresses it. Fucks it. Each time he enters the arena, he slips his c0ck in the mouth of the beast, and prays to thrust home before the jaws snap shut. - Oenomaus
Ball Joints/Upper A-Arms How To
Replace Door pin/bushing
Repair broken dome light tabs
VIDEO OHC Install
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  #9  
Old 12-17-2010, 04:18 PM
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Default Re: 1994 4.0 OHV Running Poorly

Vacuum diaphram on transmission plugged?
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  #10  
Old 12-17-2010, 04:20 PM
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Default Re: 1994 4.0 OHV Running Poorly

Flow is quite poor...

We will see after tomorrow if it improves at all. Will be fitting a new cat and exhaust

----------

Its a manual tranny if that makes any difference Brinker.
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  #11  
Old 12-17-2010, 05:03 PM
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Default Re: 1994 4.0 OHV Running Poorly

I found that the hose that goes from the Evap Canister to the fuel tank was rust rotted at a connection at the back bottom of the engine bay.....

Does anyone know if this, or if the purge solenoid were not opening would cause any of the issues I am seeing?

The hose between the throttle body and Purge solenoid, and between the solenoid and cannister appear to be in good shape.


Oh and fuel pressure at idle is 39psi
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  #12  
Old 12-17-2010, 05:21 PM
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Default Re: 1994 4.0 OHV Running Poorly

I don't know if those would make that happen. I have ripped out all of that stuff on my ranger, but I also just kinda plugged one hose into another so nothing was left open.
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1999 | Ext. Cab | 4.0 | 4x4 | 4.10's
Quote:
A Gladiator does not fear death. He embraces it. Caresses it. Fucks it. Each time he enters the arena, he slips his c0ck in the mouth of the beast, and prays to thrust home before the jaws snap shut. - Oenomaus
Ball Joints/Upper A-Arms How To
Replace Door pin/bushing
Repair broken dome light tabs
VIDEO OHC Install
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  #13  
Old 12-17-2010, 07:38 PM
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Posts: 380
Default Re: 1994 4.0 OHV Running Poorly

do you have emision laws in your state? if not then why not just knock the guts out of the converter? save yourself some money
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1998 ranger extended cab, 2wd, 4.0 ohv, 5 speed, sony xploid 52 4 way watt radio, 2 pair of pioneer 240 watt speakers, Cobra 29 LX LCD CB radio pushing 100 watts, k&n air filter, 15 inch exploder wheels, dual exhaust with 4 inch stainless tips, 2 12 inch subs with a 1000 watt amp just for the hell of it!

new project: dirt track modified racing at the local saturday night track.
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  #14  
Old 12-17-2010, 08:48 PM
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Default Re: 1994 4.0 OHV Running Poorly

Yes we have emissions... and I do not want to knock the cat out for several reasons, least of which is in my experience with old vehicles that such an action invariably leads to much poorer performance.
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  #15  
Old 02-13-2011, 07:12 PM
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Default Re: 1994 4.0 OHV Running Poorly

i have a 94 ranger 2wd 5 speed manuel with a 4.0 and when i take off sometime it will go like it has all the power in the world sometime spin the tires but it also will like kick out the throttle and have a huge power loss and then kick right back in full power and back out repeditly other than that i have no engine light on or anything i have no idea were to start any idea please fill me in
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