TOPIC: 1994 Explorer 4.0L mod. My first!

1994 Explorer 4.0L mod. My first! 01 Sep 2012 16:56 #1

  • RD
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Hi all,

I just grooved the TB on my Explorer. It is not the cleanest cut, you can see some slight scalloping. Otherwise it is somewhat tight in holding the bit in the after-cut test.


PCV VALVE
I found the PCV valve (Left rear valve cover) and taped off the end of the hose for a temporary blocking of the vacuum port, on the intake manifold. I left the PCV valve open to the ambient air. I'm not sure where I should port the PCV valve to. I don't want to block it and I think there should be a connection to induce venting air flow through the block. Where?

IDLE AIR
Not sure about this. It appears the port for Idle air starts before the throttle plate and bypasses the throttle plate bore entering the intake manifold after the throttle body. The gasket, between throttle body and intake manifold, does not allow for air passage into the throttle body (top port in pic). What do I do with this if anything?



EGR VALVE
The picture above shows a heavy buildup on the intake manifold side of the throttle plate. Is this normal? How does the EGR affect the vacuum levels and the effects of the groove?

The next picture makes me think the port next to the throttle bore goes to the EGR or near the EGR in the intake manifold.



BEFORE MOD
This is a learning experience, for I'm not an auto mechanic, but I've rebuilt two engines, swapped out trany's, and all the mechanics on my personal vehicles. Needless to say, I like pre-70's engines; so much simpler but I own none. So here we go.

Going into this I have some pre-existing issues. Rough cold startup. Engine hesitates on throttle increase from a stop and sometimes at speed. After warmup, the engine idles fine. I've replaced the plugs, fuel filter, and run a fuel injector cleaner through the system. No change. I will check the fuel pressure at the rail next and then onto the injectors.

AFTER MOD
I've only driven the SUV a couple short trips around town for maybe a total of 20 miles. At first startup, engine idled real rough but settled down in 3-4 minutes. Driving around the block a few times, the from-stop-hesitation seemed to be minimal but I didn't notice any real difference in 0-60 responses. My second drive was about 15 miles and the responsiveness seems to be better at highway speeds. Some of the hesitation has come back.

I've not done any before and after exhaust analysis. My results are for me, so I get to be on the intuitive level. I'll be looking at the gas mileage and drive ability for my analysis.

I'm looking forward to the betterment of my vehicles and invite any and all suggestions toward this end.

Thanks all,
RD
Portland, OR

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Re: 1994 Explorer 4.0L mod. My first! 01 Sep 2012 18:02 #2

  • TacomaKarl
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Hi RD,

Nice job on the groove, almost looks like you've been doing it for awhile :)

Don't know if you did this, so I will mention it anyway...

Your Idle Air pathway (as noted in the picture below), if you haven't done this then you want to get a piece of flashing to make a replacement gasket.





Where the idle air opening is, you want to make the hole size 1/8". This will increase the manifold vacuum and still allow the IAC to function.

Keep in mind as Ron has mentioned more than once, the groove is not a cure all for what ails an engine. But it usually helps. :)

Things that keep popping up in the way of "worn out" are the O2 sensors, the symptoms you are describing may involve them. If you have a scanner, you can monitor the voltages to make sure the sensors are functioning.

I wouldn't worry about the egr, that typically is activated in a pulse fashion to re-introduce the stored gases at minimal vacuum loss.

The buildup for a 1994 vehicle... normal.

The PCV valve hose you want to reconnect on the intake side of the TB, if there is a passive air hose going back to the air cleaner you can "T" into that as long as it is after the air filter.

On the plugs, be aware of the possible issues with the factory brand, after some extended use they may have a tendency to physically fail. Check the other posts.

Again, nice job and welcome aboard

Karl Fortner
Tacoma, Washington

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Re: 1994 Explorer 4.0L mod. My first! 02 Sep 2012 04:23 #3

  • Tracy Gallaway
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Hi RD, decent lookin' groove for your first. I second everything Karl said.

How many miles this Ford? I would suspect the TPS Throttle Position Sensor on side of throttle body if original to vehicle. Check everything connected to intake manifold for vacuum leaks. Vac. leaks hurt the Groove effect badly, gotta hunt 'em down and eliminate them.

Glad you're here, RD, keep us posted, ask questions as you have, read as much on this site as possible. Heaps of good info for you all over this Site, I've explained about the PCV mod repeatedly. Look 6 posts down from this one at 1990 Honda Accord 4 Cylinder thread, I explain how the PCV System works there. I'm just a guy w/ a big Mouth:silly: maybe my rant there might help ya!:)

Welcome to Gadgetmanland!!:cheer:

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Re: 1994 Explorer 4.0L mod. My first! 02 Sep 2012 22:09 #4

  • RD
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Thanks for the info Karl and Tracy.

It has 130K miles.

I made a new gasket with 1/8" hole in the IA port. I tightened up one loose vacuum hose, and I checked the throttle position sensor which gives a consistent ohm reading change on the swing of the throttle plate.

On the O2 sensors, one of my preconditions was getting a check engine when driving at highway conditions. Checking the codes, I would get Lean left and Lean right every time. I think I will replace the O2 sensors next.

Thanks for the pointer to your PCV valve description. That should be in a tech topic all it's own, easier to find. Mine is very similar to the Accord. Is there a slight vacuum seen at the air tube connection of the breather tube? Would teeing here have a slight draw from both points on the valve cover, covers in my case?

Results today;
Very rough on startup....oops I forgot to put the plug wire back on after checking brand of spark plugs....autolite.
Restart and she is a little rough but smooths out soon. First three block she ran real erratic than settled down to a reasonable operation. Still some hesitation from stand still or accelerating. I will take her out for a longer road test tomorrow and get new O2 sensors Tuesday. And I still need to check the pressure on the fuel rail.

Thanks guys.
RD

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Re: 1994 Explorer 4.0L mod. My first! 03 Sep 2012 06:44 #5

  • Tracy Gallaway
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Hey again RD. I believe there often IS a pressure drop at the breather connection to the incoming air stream. I have seen some slight oil aspiration at this nipple after the PCV hose mod, esp on engines where the nipple is close to the TB on the air duct.

Remember when this mod is done the PCV system changes from flow-through circulation due to manifold vacuum, into ventilation of the crankcase into incoming filtered airstream. At idle/low engine rpm/load less blowby is created. Higher RPM/loads cause more blowby. Airflow into engine follows right with RPM/load.

This is all my opinion, I'm not an engineer or engine designer, but I think I'm right about all this.

I've learned that in Carburetors, there is reference to 3 types of vacuum: Manifold, Ported and Venturi. Refers to where a vacuum hose port/connection/nipple is located and under what conditions a pressure drop (vacuum) will occur at such point.
Manifold: connected into intake manifold direct, below throttle plate, vacuum always present if engine is running.

Ported: mostly only on Carbs. A nipple positioned on Carb throttle body base such that at idle the port is above throttle plate,(no vacuum). As throttle opens the port is exposed to manifold vac. This allows a vacuum signal to be timed, off and on, usually for distributor vacuum advance on such older engines.

Venturi: the nipple connects into carb bore, but higher above throttle plate often in main body casting of carb. As throttle opens up airflow increases in the bore and at a certain point the Venturi effect occurs at this port, namely: as flow increases so does airspeed. Increasing air SPEED causes air pressure this port is exposed to to drop somewhat. This vacuum signal is/was used often for control of emission control devices like EGR.

Sorry for all that, RD! Reason for it is to explain my ideas of how/why a modest pressure drop can occur at the breather nipple in the air duct--it gets Venturi Vacuum applied to it with increased engine RPM/load. Plus with higher RPM/load we get more blowby, increasing crankcase pressure/gas volume. Crankcase pressure is vented into incoming airstream and exposed to a moderately lower pressure. So we are still Positively Ventilating the Crankcase (in my opinion) B) And yes by teeing the 2 hoses together into the breather nipple on air duct both will be ventilating as I describe, though many PCV Valves have a tapered needle valve that can open/close under different conditions.

you asked good questions, RD!! Hope your eyes don't hurt too much...

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Re: 1994 Explorer 4.0L mod. My first! 03 Sep 2012 15:20 #6

  • Ron
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RD wrote: Thanks for the info Karl and Tracy.

On the O2 sensors, one of my preconditions was getting a check engine when driving at highway conditions. Checking the codes, I would get Lean left and Lean right every time. I think I will replace the O2 sensors next.

RD


RD,

When you get lean codes on both O2's (prior to The Groove) that is almost certainly due to a pretty severe vacuum leak. At least one...

Keep Groovin'!
Of course, any engine with more than 50K probably has sluggish O2 sensors and they should be replaced as a matter of routine service. That will help with the ECU Relearn procedure, but the possibility of issue cannot be ignored.

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Re: 1994 Explorer 4.0L mod. My first! 17 Sep 2012 21:10 #7

  • JDiemicke
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Hi guys I have a 1991 Ford Explorer, it`s the same body style as the 94 model, same engine, same everything. That being said about a year ago I got Ron to do the groove on it. I put the throttle body on it, took care of the PCV valve, fixed all the vacuum leaks, and made the new gasket for the IAC valve. I tryed it and really for about a mounth and got no real results, but then I found out my engine needed rebuilt so Im trying it again and I am geting a little bit more power off the line but im not seeing any increase in my fuel millage.

Another thing is on the IAC valve gasket, I made it out of a peace of aluminum, with one hole being 1/8 inch. and the other hole being 1/4 inch. big, and when I start up the truck it runs like its guning to turn off, and even when it warms up it`s not as bad but it still idles rough, but if I take the gasket off it runs fine. I was thinking about drilling the 1/8 inch. hole out to a 1/4 inch. hole, and see how it does.

Thank you for any help on this.

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Re: 1994 Explorer 4.0L mod. My first! 18 Sep 2012 14:26 #8

  • Ron
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On older engines, it is important to see that your valves are sealing well. What happens is Lac, the foundational element in lacquer and a compound in all HC motor oils, forms a plaque on the springs and valves, causing them to slow dramatically.

If the valves are moving more slowly, the combustion chamber only maintains its integrity for a portion of the time in motion. The result is loss of power as a direct result. More importantly, it reduces vacuum.

As a test, place a piece of heavy paper over the end of the exhaust. If the paper is sucked into the tailpipe, then your valves are DEFINITELY out of specs. This shows that the intake energy is pulling exhaust gases into the combustion chamber rather than air from the throttle assembly.

Vacuum Leak.

What you do about it is handled by doing a good engine flush. For more severe systems, I recommend about 8 ounces of diesel or kerosene in the crankcase at an idle for 30 minutes and check the exhaust again. If the popping is reduced, let it run a while longer.

If after an hour of idle, there is no change, then you may have a bad valve.

Once the system is cleaned and the exhaust going the correct direction (out instead of in) then turn the engine off and perform an oil change. Only this time, use one quart of transmission fluid in place of one quart of oil and run like normal. This will not only complete the cleansing process but also condition the seals which are in all likelihood dried out and in danger of cracking if not cracked already.

Check the tailpipe and come back.

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Re: 1994 Explorer 4.0L mod. My first! 18 Sep 2012 20:54 #9

  • JDiemicke
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Well, Ron I did what you said with the exhaust and it blew out the paper the whole time, dident suck it in at all. And I can tell it has plenty of vacuum because I found a collapsed vacuum line under the hood from it sucking so hard.

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Re: 1994 Explorer 4.0L mod. My first! 19 Sep 2012 03:26 #10

  • Ron
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Hey Jamieson.

the way you describe the vac line collapsing indicates to me a very real area of concern. Your vac lines.

You see, when the lines get soft enough to collapse under normal engine vacuum, it indicates oil penetration which is VERY bad for hoses. In all probability, you have others that are in similar condition.

You need to check all vac lines. You should also do a pump-down on the booster. Somewhere, you have a leak. Most probably, more than one, and something serious somewhere.

Look long, look hard and leave no stone unturned to ensure the integrity of your intake system

This cannot be understated as to its importance at this point.

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Re: 1994 Explorer 4.0L mod. My first! 19 Sep 2012 03:44 #11

  • Tracy Gallaway
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Here's three cents worth...Ford has used both rubber and Plastic vacuum hoses for decades. The plastic ones get brittle--and can get cracks or just break in the darnedest places! So closely examine every one of those hoses/vacuum lines their whole legnth. If a plastic one would be hard to entirely replace, you can always do a splice repair w/ rubber hose...

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Re: 1994 Explorer 4.0L mod. My first! 19 Sep 2012 12:33 #12

  • RD
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I am having similar results to JD. I am still getting hesitation on accelerating from idle and accelerating at highway speeds, especially climbing a hill.

I checked the fuel pressure at the fuel rail. The specs call for 30 – 40 psi at idle and 40 – 50 psi with the vacuum line removed. I am getting 29 psi at idle and 39 psi with the vacuum line removed. Further, the bleed down after shuting down does not hold pressure for five minutes, it drops down to about 20 psi in the five minutes. The manual says the fuel pump may be bad if pressure is not held for five minutes. Should I replace the in-tank fuel pump? I also have an issue with the fuel tank level sensor, it generally does not work, except every once in awhile it does work. Any correlation here?

A number of my vacuum line are the small diameter, hard plastic type. I found the connector boots on the fuel pressure regulator line were loose. Also, they had a fluid in the boot that makes the boot slippery. I cleaned out the fluid on both boots and reinstalled adding zip ties to each boot to tighten them. I still get the same results on the pressure readings.

After the last posts, I'm going to look at the vacuum lines more closely.

I will also do the check on the exhaust pipe recommended by Ron.

Thanks for all the advice. Looks like doing the groove has prompted me to resolve all the other issues I seem to be plagued with.

RD

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