1994 Explorer Won't Accelerate!!

[x5050160]

History: Mother bought new in 1994, tons of city driving TONS!! Very very seldom revved above 3800 RPM. Very rare for throttle to be applied past 70%. Mom went to trade it in they refused it. (She smoked :smoke: in it like CRAZY!!!) Never cleaned it yuk. Now its as good as new except for....
Ok so 1994 4 door, Push Button 4wd, Automatic, Auto Hubs, 110,346 miles on it. Problem:
Engine idle is good and steady. 1% to 60% Throttle application is decent. 61% to 100% throttle and it falls on its face hard!!!!! Anything past 60% and the X looses speed. :thumbdwn: It'll kick down a gear and rpms will rise but engine stops breathing stops making power. It does this whether I "hammer down" or if I just ease past the 60% threshold. It almost acts like i am pulling a manual choke once I reach 60% throttle. It seems as though the engine is breathing through a straw.
Cleaned Throttle body, IAC, MAF, throttle linkage cleaned and oiled. NO slack in throttle cable. Engine does not miss. Catalytic converted replaced with rest of exhaust from manifold back.
This is the throttle plate a WOT.

It doesn't open all the way at WOT because of this spring being worn out. It's some stupid design that is like a 2 piece system that opens the plate up.

THIS IS WOT

THIS IS CLOSED (Idle)
But it does open well past 90%. So I do not think that this has much to do with it.
This is the vacuum "main"

I don't think that the red cap is stock. So I believe there is a hose missing? If anyone has a good pic to share that would be great. I can't figure out what is missing from the crappy vacuum diagram in the engine bay.
So any worthwhile input would be much appreciated.

 

[eric4welches]

Just a thought...Have you tried pulling codes? May give a point of direction.

$.02
Eric

 

[Roadrunner777]

Looks like you covered airflow. I had one like this, discovered a rag sucked up into the air filter. (Ex mother-in-law, bless her soul).

I'm thinking fuel flow. Change the fuel filter lately? Could be a fuel pump going out too.

It could also be ignition system, plugs and wires.

If it were me, I would change out the fuel filter, plugs, and wires if they have not been done in recent history. That's just preventative maintenance anyway.

Does it do this if you are parked and revving the engine? If so, you could hook up a fuel pressure gauge and rule in/out fuel delivery issues.

 

[Maniak]

I'd also lean towards fuel related issues based on what you described.

Go after the fuel filter first and it if still does it, I'd probably change the pump.

Last year our X started to have issues when using more throttle and rpms. It would just fall flat on its face.

Over time it go worse. It got to the point where you could only use 50% of the throttle. I changed out the fuel pump assembly and viola its happy again...

~Mark

 

[x5050160]

I did the plugs and wires at 80, 000 miles.
Codes brought back EGR low flow, running rich at part throttle, and fuel pump secondary circuit fault.
What is the seconday curcuit??? Pump was replaced at 95, 000 miles. Ill look at it tonight. Codes didnt say anything about fuel pressure regulator though

 

[Roadrunner777]

The computer cannot read fuel pressure, no sensor. I have seen that secondary circuit fault before... I'll have to look it up.

 

[Roadrunner777]

Did you notice... in the vacuum tree picture, there is a black tube at 1 o'clock towards the upper edge, it is worn through and is surely leaking.

 

[awood]

Had a 94 Ranger once (same engine) that I bought for a great price since the previous owner couldn't figure out a stumble/stall at about half throttle. I got it home (barely), and performed a KOER test (instructions are in the forum sticky's). It faulted a throttle position sensor. 30 dollars later it ran like a champ - no wasted parts purchases.

 

[x5050160]

I dont see the vacuum leak? Are you looking at the bend in the tree for the break booster hose?
Didn't get a code for the TPS. Im gonna try the fuel filter first. I don't want to drop the tank and put a fuel pump in that is the same pos brand/manufacturer as I did before. Had to do it twice the fisrt went out in 1 week. Anyone have a line on a upgraded fuel pump?

 

[Maniak]

I didn't get the codes like your getting when it was our fuel pump.. I'm rethinking fuel pump BUT without being able to watch fuel pressure while driving its hard to know.

For the vacuum leak, look at the hose physically "under" the brake booster hose. Its a hard plastic line and as you follow it you see what appears to be a section that is worn. Its possible its just stuff "on" the line but to me it also looks like a vacuum leak.

Now, for how to watch the fuel pressure.. I see 2 ways.. One is to take off the hood, hook up a normal fuel pressure tester gauge and zip tie it up so you can see it while driving..

The 2nd way is to make your own tester gauge. I'm going to do this since I have wanted to watch fuel pressure while driving a few times. I'll take an old (broken) fuel pressure test gauge, cut the hose, use 300 psi transmission hose and barb connectors and then use a 100 psi FPR gauge from summit. I'll make the hose long enough that I can snake it out from the engine bay and zip tie it to the wiper arm. This is just for testing things but I expecte it to come in handy... This is the gauge I was going to use. http://www.summitracing.com/parts/sum-800199

~Mark

 

[Roadrunner777]

I'm not saying this is the cause of your problems. In terms of vacuum leaks, it isn't much of a leak. But, it is disabling whatever is on the other end. I can think of two things that that might be. One is the heater bypass valve, the other is the fuel pressure regulator. I'm still recommending a new fuel filter.

 

[Blue91Ex]

if that hole is as big as it looks, its a big deal, with mine, you take off one hose (got a tub with a nail in it instead of that red plug you have) and it runs liek complete garbage. so i would say fi thats a hole, you should look into fixing it.

 

[MrHendren]

Just my 2 cent in this fight but it sounds like a fuel pump/filter problem. I had a 07 busa that did the exact same thing. Swap the pump out and fixed the problem. It would bog down once you hit so a point, and would not go.

 

[Roadrunner777]

busa?

 

[Maniak]

busa?

180mph+ Suzuki fuel injected motorcycle I'd guess (hayabusa)

 

[Roadrunner777]

Oh. You know, I once pegged out a Trans-Am. But that was no 180mph. And, I had an actual car around me. Need for speed, I need not.

 

[x5050160]

I'm not saying this is the cause of your problems. In terms of vacuum leaks, it isn't much of a leak. But, it is disabling whatever is on the other end. I can think of two things that that might be. One is the heater bypass valve, the other is the fuel pressure regulator. I'm still recommending a new fuel filter.

That hard line does NOT have a hole in it. Just looks that way in the pic. I checked it and every other hard line no leaks.
So looking closer at the vacuum main manifold there are 7 inlets. 2 of the inlets are capped.
I need a picture of someone else's 94 vacuum manifold!!!!
Cause this diagram makes not much sense:

I guess i will really dig into the vacuum when it cools off outside. But I would really like a pic of someone else's vacuum setup if they could provide one. Has to be a 94 also 91-93 are different. Thanks.

 

[x5050160]

Oh im gona make a youtube video of exactly what the truck is doing when it falls on its face

 

[Maniak]

I need a picture of someone else's 94 vacuum manifold!!!!
Cause this diagram makes not much sense:

Makes sense to me (I had to make all new vacuum lines over the years). Anyway, I doubt many people's vacuum ocotpus thing will look stock after 20 years...

So, here is what you should find on your 1994.

1 hose to the EGR/DPFE system (driver side of motor)
1 hose (big) to the brake booster (driver side)
1 hose to the Fuel Pressure Regulator (fpr is on passenger side of motor)
1 hose that later splits (hose runs to passenger side) - one line goes to the bimetal valve thing on the air box (top of it) AND to and also eventually ends up in the cab of the truck (its the source vacuum for the blend door and the heater control bypass valve)
1 hose to the cruise control ball looking thing (IIRC that's still on the driver side on the 1994)
IF you have an auto trans you will also have a line that runs down to the transmission (runs behind motor and then down)

For anyone else.. If you don't have EGR that line will be capped off on the T (think 1991 and 1992 vehicles).

~Mark

 

[Roadrunner777]

I tried to get a picture. It's too bright to show any detail. Everything looks right. I have a factory cap instead of your red one. I will try later when the sun is lower.

But... I want to say this again. I don't think vacuum is your issue. I think fuel delivery is the problem.