94 Explorer Stumble on acceleration and loss of power

[phantaztix]

I have a 94 Explorer, XLT, 4x4, Manual Transmission, CA Emissions. Over the last several months there has been a developing "stumble" during acceleration, mostly under 2200 rpm. It started as a single misfire feeling, then progressed into what it is today. A huge loss of power and a very bad stumble under anything more than granny-like acceleration. Most commonly when I start from a light if I give it a bit more gas than a normal super-slow takeoff it will not only stumble hard but the engine starts missing, like all 6 cylinders are misfiring several degrees off. You hear the engine grumbling hard but you don't go anywhere fast, until you let off, let it smooth out and try again slow and get the rpms over 2300 or so.

I have changed the plugs with Bosch Platinum +2 (the old plugs were fine and barely worn), New Plug Wires, Fuel filter and Air Filter.

I have read the forums suggesting it could be the Mass Air Flow Sensor, Idle Air Control Valve, or the Ignition Coil. What would be a good way of going through and checking before replacing expensive parts? Are there any other items I could easily check for, as I don't have a lot of tools or money.

As a side note, it passed CA smog with flying colors WHILE having this problem.

 

[quicklook2]

read codes and throw out the bosch plugs and get motorcraft regular platinums.

check ign. wires.

welcome.

 

[mawrazen]

If you changed your plugs and wires, check for a vacuum leak. (hose disconnected)

 

[phantaztix]

I guess it's also prudent to mention a few more things...

The truck has 175,000 miles, when the engine and engine bay are cold, it won't stumble on accelerating, but I still have a loss of power, the stumble only develops once it warms up a bit.

Could anyone tell me how to read the codes? I've never done it and don't have a diagnostics computer. The CEL is not on.

Thanks guys.


((Just what I wanted, working on my truck on my birthday.))

:bdrunk:


P.S. Where can I get Sea Foam in San Diego (particularly near Escondido)? It may just be me, but I'm having a ***** of a time finding it.

P.P.S..... I found Sea Foam. Did all the stuff, didn't help.

 

[///Manuel]

What did you find out?

 

[phantaztix]

Ummm

Nothing. I found out that I can modify my driving style to compensate for it, but I can't fix the problem. I'm thinking it's acting like a vacuum leak, but I can't find the leak. Although my brake booster empties out overnight.

 

[///Manuel]

Clean the MAF, disconnect battery. Or maybe it's the O2 sensor?

 

[GeLu_ThEiSt]

You need to check your air filter, if that's good, check the box for cracks or wholes. If that's good unplug the MAF. Drive it around and see what happens. I've had to completely disconnect my MAF.

The next thing I would check is the throttle positioning sensor.

 

[boggs1227]

Nothing. I found out that I can modify my driving style to compensate for it, but I can't fix the problem. I'm thinking it's acting like a vacuum leak, but I can't find the leak. Although my brake booster empties out overnight.

if you got a loss of power and your booster is empties over night ...it could be (just guessing here ) that the rubber grommet on the booster unit is worn and leaking (where the vac line hooks into the drum) .

could be related to your problem.

btw....happy b day

 

[fordnut71]

id lay my money on the Bosch Platinum Plugs. i bet 1 or 2 of them are broke

 

[phantaztix]

The problem existed before the plugs were changed, and the plugs I pulled out were Motorcraft and showed very little wear. Air filter clean, no leaks or cracks in intake. Haven't tried MAF yet. Rubber on booster good. Man, talk about a gremlin.

 

[griffigr]

This happened to me recently. It turned out to be a combination of two things: cheap gas clogging the fuel filter and leaking upper intake vacuum lines. Check all vacuum lines running to the upper intake. Keep in mind that such a stumble can be indicative of a failing lower intake gasket, as well. Keep an eye out for coolant loss.

 

[Alan_V]

The truck has 175,000 miles, when the engine and engine bay are cold, it won't stumble on accelerating, but I still have a loss of power, the stumble only develops once it warms up a bit.

Your comment here suggest it's going lean. The enrichment for cold running is compensating somewhat, but at normal operating temps, after the ECM leans it to hot running conditions, it get mad.

Couple of things.

Going back in time, did you do anything mechanically to it prior to noticing the condition? If so, carefully go back over what you did.

Did it come on suddenly or did it slowly degenerate to its current state? If the former, it's a component type failure, and I include a loose or torn hose, plugged fuel or air filter, vacuum leak, etc. If the later, then it's likely to be something having to do with wear and tear, possibly wiring as well.

The comments about a vacuum leak are valid. Pinch off every vacuum hose at the intake manifold and see if you can induce a change.

Put a vacuum gauge on it. If it's below, say 15 - 16" (I'm guessing here based on mileage), or if it's unsteady, It could be EGR stuck open, plugged CAT, vacuum leak. Concentrate on induction issues.

Throwing parts at it could be expensive, so before replacing anything more, see if you can at least narrow it down.

 

[phantaztix]

Thanks for the tips guys. I'm going to do a more extensive search on the vacuum system today. If no dice there then I'm going to go looking at the rest.

 

[454burb87]

Cps Maybe???

Well it could also be (going out on a limb here) the CPS...when an engine is cold *below 180* it runs off of KNOWN values. After it warms up it goes off of Given Values.

 

[phantaztix]

Well it could also be (going out on a limb here) the CPS...when an engine is cold *below 180* it runs off of KNOWN values. After it warms up it goes off of Given Values.

ok, You're gonna have to tell me what a CPS is.

 

[MDewell]

First thing I thought was the Catalytic Converter is in need of replacing...does it smell like rotten eggs when it's warm?

 

[Mic_]

ok, You're gonna have to tell me what a CPS is.

crank posn sensor

 

[phantaztix]

Thanks for CPS.


No it isn't cat. It's fairly new.

 

[phantaztix]

OK, checked all vacuum lines. Couldn't see a problem there. Checked MAP, it's clean and putting out all the proper voltages. Double checked connectors to fuel evaporator, and pcv. Nothing seemed to be wrong. And of course for good measure I changed the air filter.