2.3L ('83-'97) '94 2.3 lack of power

[chode_rider]

So, been trying to figure this out fir a few months now an d figured I'd ask the ranger station. My 94 2.3 has a lack of power when you stomp on the gas, just won't get up and go. Seems to Rev normally at about half throttle but just kinda dies out when you go full throttle. However the idle is smooth and normal. Code says it's running lean. After I did a lot of tune up stuff I checked the fuel pressure, which is quite low - 40 psi with key on no start, 30 psi at idle, 40 w regulator vacuum hose pulled. I replaced the fuel pump but no change in the fuel pressure.

Here's what I've done so far:
Spark plugs
Air filter
Fuel filter
Deleted egr with aftermarket plate, put a screw in the pipe off the exhaust manifold
Fuel pump
Generally checked for vacuum leaks by spraying carb cleaner
Got rid of stretch in throttle cable w zipties
Checked compression which is good

My next thoughts are replace the fuel cap in case that's not allowing it to build enough pressure, and pull the intake manifold to clean it. (Intake manifold is kinda filthy with oil, because the truck was upside down for a minute back in September - original cause of this issue)

At this point I think the problem is the lownfuel pressure. According to my book it should be putting out 60 psi. I read somewhere on the internet that the computer assumes it's getting 60 psi and adjusts air accordingly so that would cause a leannl condition. Any ideas what else could cause pressure besides the pump?

thx

 

[alwaysFlOoReD]

I didn't think fuel pressures went to 60# until 96 or 97. Are you sure its not 40#?

 

[chode_rider]

I didn't think fuel pressures went to 60# until 96 or 97. Are you sure its not 40#?

You could be right, I was just going by the book I have -

 

[alwaysFlOoReD]

I've seen mistakes in books before. One time it cost me a motor.
Here is a thread that RonD posted in. I trust him more than a book...

Fuel pressure

What should the fuel pressure be when you check it and if you don't mind telling me how to check it that would be great. I'm not a complete dumbass when it comes to working on it but this is my first Ford v6

www.therangerstation.com

 

[scotts90ranger]

Yeah, that book is wrong, same pressure on everything until like '97 or '98

 

[alwaysFlOoReD]

Yeah, that book is wrong, same pressure on everything until like '97 or '98

I was just about to call you in. Thanks for confirming.

 

[chode_rider]

Thanks guys. Damn Haynes.....
So the fuel pressures good and that means I'm back to square 1.

 

[alwaysFlOoReD]

Have you used a vacuum gauge diagnostic on it yet? That can tell you a lot about the health of the motor. Including a clogged exhaust (cat).

 

[chode_rider]

I have not. I have a vacuum gauge though. What's the procedure? I forgot about the cat, it's definitely a possibility

 

[scotts90ranger]

Yeah, you'll get that...

A running lean code really just means that the computer isn't able to calculate the fuel correctly for one reason or another... since mid '90 and up use a MAF it relies HEAVILY on the MAF sensor to adjust to a table based on rpm and the volumetric efficiency it calculates from the MAF reading (I'll dumb it down from here...). So, unmetered airflow (IE vacuum leaks between the cylinder head and MAF sensor) make it think there's less airflow than there should be then it adjusts with the oxygen sensor once it's warmed up, once it adds a certain amount of fuel from that it causes a code for running lean... but a dirty MAF sensor will do this too... but so will restricted/bad fuel injectors which makes it hard to troubleshoot...

You say it's lack of power so a vacuum leak is less likely since they're going to be worse at idle where there's more negative pressure and less airflow in general. I think doing a compression test or something would be reasonable or trying to get a different set of injectors might not be bad...

 

[scotts90ranger]

pretty much put a vacuum gauge on a vacuum line and see how much vacuum it has at idle, should be 25" of h2O or thereabouts

On the cat that can really screw up the air fuel ratio and power... you could probably pull the pre cat oxygen sensor and see if that helps it have more power, will still have some codes but would be a quick easy test... not recommended long term though as you'll have fire somewhere...

 

[chode_rider]

Cool, this gives me a place to start tomorrow.
So I flipped it in September then it started running poorly a week or so later. There was oil n shit all over the MAF and air filter so I cleaned it, and replaced air filter. But maybe it did unfixable damage to the maf.
Will check the cat o2 sensor and for vacuum. I should just delete the cat my '90 is straight piped to the muffler and it's worth it just for the sound... lol

I did compression test it and it was in the 185 range for all 4 cylinders. In retrospect though I was a little lazy and didn't pull all the plugs at once, or block the throttle open. I don't really know enough to know if that would cause a false high reading, or what, maybe I should do it again.

 

[Brain75]

I would also worry about what all else the fuel drained into upside down - I was thinking the FPR and charcoal canister and and and would get logged with fuel.... my ex flipped a vehicle, decided to take the insurance total instead of messing with it (gas filled the headliner and interior and everywhere - only sat for 2 or 3 hours till we could get a way to flip back over)

 

[scotts90ranger]

I would venture to guess on the MAF, it's heavily used... after checking that I would then switch to the cat...

With that compression the engine should be healthy, when they're closer to 120 or less then you have issues... if you got that much without doing anything the health is fine.

 

[SenorNoob]

Usually leaving the throttle plate closed results in more like an 80psi...