94 Explorer feels like the engine cuts out

[fordprobegirl]

Ok, I'm going nuts over this problem. Had a head gasket leak so did a rebuild, replaced all the gaskets from the heads up, eliminated the air box and put a cone filter on, put all new silicone vacuum lines on, as well as added headers because my manifolds were leaking. Truck was running great afterwards, put around 800 miles on it including a road trip of 250 miles. Noticed a slight stumble every once in awhile but not so bad where I thought it would stall.
The other day I took it out and it was stumbling or bucking in all gears (5 speed) at all rpms. All my guages work except for the oil pressure 1, and nothing changed on them, not even an RPM drop. It doesn't feel like a misfire, more like it just cuts out for a second and comes right back. Not even enough to stall it.
Changed the fuel filter, no difference. Unplugged the MAF and it ran great. Replaced that tonight and reset the computer, not much change. Only does it under a load, and its really annoying. The weird thing is its kind of intermittent. Will run fine for awhile hot or cold, then all of a sudden starts to do it. Like I said it only does it under a load, and I see no drop in any of my guages. Please help, I'm supposed to take it for a trip this coming weekend to go to a concert and need it running good and reliably!
Ps I have a lot of mechanical and electrical ability so don't hesitate to offer suggestions even if you think they might be too advanced
Pps also I do have a code, its 335 which is the sensor by the EGR, the DPFE sensor. Don't believe this would cause it. It is the only code its throwing

 

[Anime]

The 335 code could be a bad DPFE sensor, or something else in the whole EGR system which was hooked up improperly with the intake/exhaust modding.

When you replaced the MAF, what did you replace it with? If it's another used sensor, clean either the old one and/or the new one and see if that makes any difference.

A KOEO 335 is set with the engine off, and the movement of the EGR valve isn't applicable. KOEO codes are almost always electrical in nature -- in this cases it points to a fault in the DPFE sensor circuit. Either there's a fault in the wiring between the PCM and the DPFE, or the DPFE itself has failed. As frequently as the DPFE's fail on these, I'd check the wiring and, if it checks out, replace the DPFE.

Because KOEO codes are set while the engine is off, they are almost always electrical in nature. In this case, it refers specifically to the DPFE sensor (aka EGR position sensor or similar) circuit. I would check the wiring between the DPFE sensor and the PCM. If the wiring is intact, then I'd replace the DPFE sensor, as they seem to have a relatively high rate of failure.

 

[fordprobegirl]

I'll double check the egr setup, bought a brand new tube for it because the old 1 was cracked when I took it off to rebuild the motor. I'll check the wiring too for the sensor. But my question is would this cause the problem I am having?
The MAF was brand new, tried unplugging it afterwards, truck died right out so I'm assuming I didn't get a bad 1. Didn't go with the junkyard part because I wanted to make sure I didn't get a bad 1 even though the new 1 was $40 more.

 

[Anime]

The 335 code and EGR/DPFE/emissions system issues seem to be a common thing with Fords, though some have the stumbling, others just have the CEL and it drives ok.

Generally it seems that replacing the sensors (DPFE, EGR) is the way to go, though you might try cleaning them first.


http://www.ford-trucks.com/forums/1087965-code-335-1994-exploder.html

http://www.therangerstation.com/forums/showthread.php?t=92666


https://www.google.com/search?q=for...&q=code+335+engine+site:www.explorerforum.com

 

[AlphaTX]

I would double check the timing.. With the rebuild, it's possible that the distributor (or camshaft position sensor housing if yours is DIS (Distributor less)) is "one tooth" off, or worse, 180 deg off...

My Father In Laws truck had a similar running issue and I've replaced every component possible in the intake and fuel/air system... The last thing I checked was timing (because it ran reasonably well). Come to find out, it was 30 degrees off.. 40+ BTDC vs the factory 10. I have no idea who, how or when the timing was messed with, that's why it was the last thing I thought about checking...

To re-time, I had to pull a "jumper" connection to prevent the ECU from trying to maintain timing while I re-adjusted. Once timing was set, I replaced the jumper and it runs like it was brand new now.

 

[Anime]

The timing is ECU controlled on these and isn't adjustable.

 

[fordprobegirl]

I didn't do anything with the timing, did head gaskets and up and becaise its a pushrod v6 there was no need to disassemble anything having to do with thr timing chain

 

[AlphaTX]

Not the timing chain I was referring to, but the component that looks like a distributor..

For example, in my 06 jeep, it doesn't have a distributor, but it does have an "Oil Pump Drive" that is exactly the same as an old school distributor except it doesn't have a spark plug rotor or contact points in the cap. Besides that, it's the same...

At the bottom, it has a "keyed" groove to attach to the oil pump, on the shaft is a gear to connect to the cam shaft gear, at the top is a small flywheel with indication teeth that work with the attached Cam Shaft Position sensor. So it does all the same functions as the old distributor, except control spark mechanically. Instead, the sensor reads the information off of the flywheel to determine what position the camshaft is in. That information, combined with the Crank Shaft Position sensor's data, allows the computer to determine when to light up the spark plugs. I had removed this housing on my Jeep, and when I reinstalled it, I was one tooth off. Even though the computer controls timing, I was still pinging/backfiring through the TB (too advanced) until I corrected the installation.

In order to have replaced the head gaskets, you likely removed the intake manifold, which I presume required removing this apparatus. So, I was just throwing out the notion that timing may be too advanced/retarded. I also recognize that it may be completely unrelated..

 

[jd4242]

Check your lower intake bolts.they like to come loose

 

[2stroke]

I have had the same exact problem for about a year now, and I have never got a clear cut answer. I have just been driving it. It always stumbled a little, but sometimes it will actually bog. I ran it for about 20 minutes one day when it was doing it, and I finally stopped because it wouldn't stop. It was smoking, and when I looked, my cat. was glowing red hot. I let it sit 10 minutes, started, and it hasn't been too bad since. I have a feeling it is the DPFE and it leaves the EGR open at the wrong times. I also get a 335 code, no other codes. Since I can just shut it off, and it seems to reset the problem, I just don't think its worth putting a new DPFE in a vehicle that should not be running. I always say, Fords will never run well, but they will always run.

Just wanted to add, I have the automatic. When It acts up, I can have it pinned and it either wont make enough power to go over 45 mph (and seems to have a miss), or it all of a sudden clears out and takes off like a bat from hell.

 

[MrShorty]

It was smoking, and when I looked, my cat. was glowing red hot.

2stroke: A cat that is glowing red hot is usually an indication that the engine is running rich. Other symptoms you list suggest that this could be intermittent, which would make it more difficult to track down. I would probably start by checking fuel pressure, especially when other symptoms are present. This might mean driving it around with a fuel pressure gauge hooked up so you can see if the fuel pressure jumps up when the engine stumbles.

 

[2stroke]

I've been through the whole thing, multiple times. I know for certain its running rich, the glowing catalytic converter was just a cool way to confirm it. That is why I think the EGR is being left open. The fact that the EGR is newer (about 10,000 miles on it), and the code, along with other things, makes me 95% certain it is the DPFE. That 5% is because it is intermittent, and the DPFE, being electrical, shouldn't be. However, I have heard the DPFE can cause intermittent problems, and develops the problem, because it gets water inside. I'm on the original metal one, which is supposedly worse than the new plastic ones. The way I see it, its not a bad enough problem for me to put a $50 part in that can't be returned if its not the problem. I still get decent gas mileage, over 10mpg. Its just getting to be its time, everything is wearing out. FYI fuel pressure was at 28 psi at idle, and should be between 30-45psi. Good enough for me!

 

[AlphaTX]

Wouldn't a glowing cat shorten its lifespan?

Not resolving the rich issue would cause the cat to die sooner and thus not replacing a $50 part would result in replacing a $250 part?

 

[2stroke]

I wouldn't replace the cat. I'd probably just put in a piece of 2" pipe where the cat used to be.

 

[awood]

If you have 10 minutes, below is a Youtube link that describes how to check the EGR system. The video is made by Scannerdanner, a well known auto technician/teacher. If you follow exactly what he does, you will have a valid test. I've done it several times on various cars around the neighborhood. Some of his tools are pretty advanced, but you can test all but the DPFE sensor with just a test light and a volt meter. His test vehicle is a Ford car, but the components are the same: EGR valve, computer-controlled vacuum switch, and DPFE sensor. Now... to test the DPFE, you likely won't have a bi-directional scan tool like he does, but you can verify operation of the EGR valve and vacuum switch with tools you DO likely have by following the steps in the video. If the switch and valve test good, and you still get the EGR code, you can safely guess the DPFE is bad (or end up with a bad PCM like I had, but at least I knew the EGR system was good after testing). Hope this helps.

http://www.youtube.com/watch?v=pH_kjRwD-Xw

 

[2stroke]

Yes, to the original poster- I have done all the tests described in the video, I even replaced all the hoses for the egr. Mine acts very similar to yours (closer than I've ever found from a post before). I am almost certain it is my DPFE, however, if you choose to fix it you have to be careful. With anything electronic; as soon as it is plugged in; it can't be returned. If I was to fix mine, I would buy one off Ebay for around $35, else you are risking around $70 from an auto parts store. One thing I have considered is an EGR delete. I know I'll get lots bad comments, but some cutting for a plate (the EGR already has the gasket you need), and a cheap bolt you can get rid of it. My guess is you might loose some top end, but who drives these things over 3500 rpms? Gas milage might suffer more. Best guess is if you just drive it around, I've heard they can get 18mpg, so it might go to 15-16.

 

[2stroke]

I think I have solved my problem. It stopped being intermediate, and ran very bad. I've heard you cant clean a DPFE, but being as mine didn't work anyway, I tried as a last ditch effort. Well I pulled it off, and the thing was badly corroded. I sprayed electrical cleaner spray in the tubes, and set it on the hood. Long story short, it fell and broke. I bought a new one, but beware, they don't know which one to sell you. There are 2 different styles I think, one simply won't plug in, and you have to bring it back. Make sure you bring the old one with you, and look at the pictures to make sure you have the right one. BTW, you cant simply unplug a DPFE, it does not help anything. It didn't hurt mine as it was already bad, but the engine seemed like it couldn't make up its mind, and ran really good for about 2 seconds, and then would switch to a very rough idle, then back. I've heard mixed reviews on what a bad DPFE does to a motor, but I have to disagree with most. Unless you block off the EGR entirely, the engine needs that to run. If the EGR is closed, when it should be open, the motor senses it needs more gas and floods the motor (what I think was happening). I think the DPFE only controls the EGR valve, but thats all it takes to start the chain reaction. I drove from Brainerd to Annandale (about 80 miles) and burnt nearly a whole tank of gas, chugging along on 4 or 5 cylinders the whole way. Now that its replaced, it seems to run well again. Only time will tell.

 

[awood]

Thanks for the reply with your fix.

Sounds like you're on top of it. However, it's the PCM that controls the Vacuum switch, which in turn controls the EGR valve. The DPFE provides a feedback signal telling the PCM what position the EGR valve is in. The PCM then decides whether or not to turn the EGR on or off (via the computer controlled vacuum switch)

 

[2stroke]

Thanks, I checked my PCM, but it seemed fine, and the 335 code reasured me. Apparently without the DPFE, the PCM still tries to work; its almost like a chicken with its head cut off. It will run fine, then it will bog terribly, then all of a sudden you get a huge burst of power as it is still adjusting the EGR. The EGR system is very complicated, and I definitely don't fully understand it. It seems to have a very small job, recirculate un-burnt gasses, yet has a million possible adverse effects on a vehicle if it acts up.

 

[nmfordguy]

Fordprobegrl, I was having the same issue it ran fine for about 20 minutes then it would miss buck only under a load. It would be fine at idle. Ended up being my fuel pressure regulator. Even though it wasnt leaking by. Try running it above 65 and see if it runs fine mine did. Hope this helps.