Power loss.

[ov10fac]

Hi,

My name is John Wright and I have owned my Explorer since 2000. I'm a retired AF pilot and have been doing my own maintenance for several years. Started with a 1952 Studebaker. I have even rebuilt Corvairs in the past just for the fun of it.

These newer cars are a little more of a challenge with all the sensors and controllers, so its a little more of a challenge for me.

I own a small computer consulting firm here in Omaha so the onboard systems are interesting from a professional veiw point.

The real reason I have joined is a problem that seems to defy logic.

My Explorer just developed an intermittent power loss. I had a Check Engine Light (CEL) which pointed me to MAF sensor, miss fire on number 3 and DPFE sensor problems. So, I replaced the MAF sensor, put in new plugs, replaced the ignition coil and DPFE sensor. I also replaced the DPFE sensor hoses.

All to no avail. The CEL is now out and the engine runs really well at low speed, but anything above about 40mph and it will loose power for a second or two then come back to normal. It may do that for an entire trip or not at all. Yesterday I drove about 20 miles on interstate with no problems. When I came home it started again. The real problem is that every once in a while it feels like the engine just quits for a second then starts back up.

I have no CEL and no codes. There are not even any pending codes.

Thanks for any help.

John

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 95-01 section. Check the fuel pressure, and the amount of spark going into each spark plug. You might have a bad coil pack or relay (fuel pump or PCM), fuel pressure regulator or fuel pump. When was the last time you replaced the fuel filter?

 

[nssj2]

What was the MAF code? I ask because the MAF in part controls your air fuel ratio. If the engine is too rich or too lean, and can't correct that, it will point a finger at the MAF or O2 sensors, when in reality it's a fuel delivery issue. The resolved check engine light would lead me to believe otherwise though. Like brooklyn said, fuel filter is the first to check. Then take a pressure reading off the fuel rail. Very easy, and 90% of parts stores rent a fuel pressure gauge.

Are you sure you're running the correct spark plugs at the correct gap spec?

 

[ov10fac]

Power Loss

Ok,

Last question first. I replaced the ignition coil and had my dealer replace the plugs with OEM, the dealer didn't like my Bosch, said Ford has a problem with them. Now, as to whether or not they were properly gapped? I will have to trust the technician did the job properly.

As for the fuel filter, I think about two years ago. In fact that was my next step to change that.

The fuel pump is next on the list. Thanks for the advice on renting a fuel pump pressure gage. Sounds like a plan.

I'll take a reading on the MAF code tomorrow and post it.

How would I check the amount of spark going to the plugs?

I bought an engine analyser yesterday, but I have no idea what the actual values should be. Is there some place I can go to find what the factory values for things like the MAF sensor should be?

Many thanks.

John

 

[lugnuts55]

Hello John, I read about your problem with your Explorer and I thought I was reading about mine. I have done just about everything that can be done without taking the engine apart. In fact, that is my next step. In a couple weeks, I will have the time to pull the heads off and see why #3 is misfiring. It started something new a couple days ago that makes me think it's an intake valve because it pops through the intake on acceleration.
The engine is a 4.0 OHV with aver 200k. I have changed the plugs, wires, coil, injector, fuel filter, cleaned the MAF sensor, replaced the upper and lower intake gaskets, and a few other things that I don't remember. After I get the heads off, I hope to see what the problem is. I will make a report here when and if I find the problem.
I wish you luck in your search for the problem.
Mike

 

[ov10fac]

Good Luck

Mike,

I wish you luck with your efforts. Let me know what you find, and I'll do the same.

John

 

[ov10fac]

Power Loss

Ok,

Yesterday the O/D Off light came on. No error codes that I could find, but maybe my analyser isn't high enough quality.

I tooks some readings while the engine was loosing power. Here they are. I don't see anything that would give me any ideas? Anyone else see something that could be the cause?


DTC_CNT 0 DTC_CNT 0 DTC_CNT 0 DTC_CNT 0 DTC_CNT 0

FUELSYS1 CL FUELSYS1 CL FUELSYS1 CL FUELSYS1 CL FUELSYS1 OL-Drive

FUELSYS2 N/A FUELSYS2 N/A FUELSYS2 N/A FUELSYS2 N/A FUELSYS2 N/A
LOAD_PCT(%) 71.8 LOAD_PCT(%) 79.6 LOAD_PCT(%) 80.0 LOAD_PCT(%) 77.3 LOAD_PCT(%) 80.4
ETC(°F) 190 ETC(°F) 185 ETC(°F) 185 ETC(°F) 185 ETC(°F) 190
SHRTFT1(%) -3.1 SHRTFT1(%) -3.1 SHRTFT1(%) -6.3 SHRTFT1(%) -1.6 SHRTFT1(%) 14.1
LONGFT1(%) 1.6 LONGFT1(%) 1.6 LONGFT1(%) 1.6 LONGFT1(%) 1.6 LONGFT1(%) 1.6
SHRTFT2(%) 0.8 SHRTFT2(%) -1.6 SHRTFT2(%) -2.3 SHRTFT2(%) 0.8 SHRTFT2(%) 14.1
LONGFT2(%) 1.6 LONGFT2(%) 0.8 LONGFT2(%) 0.8 LONGFT2(%) 0.8 LONGFT2(%) 0.8
RPM(/min) 2304 RPM(/min) 2464 RPM(/min) 2712 RPM(/min) 2528 RPM(/min) 2616
VSS(mph) 13 VSS(mph) 24 VSS(mph) 32 VSS(mph) 37 VSS(mph) 40
SPARKADV(°) 19 SPARKADV(°) 13 SPARKADV(°) 13 SPARKADV(°) 13 SPARKADV(°) 14
IAT(°F) 64 IAT(°F) 64 IAT(°F) 64 IAT(°F) 63 IAT(°F) 63
MAF(lb/min) 6.406 MAF(lb/min) 8.183 MAF(lb/min) 8.476 MAF(lb/min) 8.214 MAF(lb/min) 8.151
TP(%) 38.8 TP(%) 44.7 TP(%) 45.1 TP(%) 44.7 TP(%) 43.9
O2S B1S12--B2S1--- O2S B1S12--B2S1--- O2S B1S12--B2S1--- O2S B1S12--B2S1--- O2S B1S12--B2S1---
O2B1S1(V) 0.310 O2B1S1(V) 0.755 O2B1S1(V) 0.555 O2B1S1(V) 0.485 O2B1S1(V) 0.850
SHRTFTB1S1(%) 2.3 SHRTFTB1S1(%) -4.7 SHRTFTB1S1(%) -4.7 SHRTFTB1S1(%) -2.3 SHRTFTB1S1(%) 12.5
O2B1S2(V) 0.510 O2B1S2(V) 0.540 O2B1S2(V) 0.360 O2B1S2(V) 0.125 O2B1S2(V) 0.915
O2B2S1(V) 0.155 O2B2S1(V) 0.660 O2B2S1(V) 0.565 O2B2S1(V) 0.415 O2B2S1(V) 0.855
SHRTFTB2S1(%) 0.0 SHRTFTB2S1(%) -5.5 SHRTFTB2S1(%) -5.5 SHRTFTB2S1(%) -3.1 SHRTFTB2S1(%) 11.7
OBD OBD2 OBD OBD2 OBD OBD2 OBD OBD2 OBD OBD2
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[nssj2]

Before anyone tears any motor apart, a compression check will answer the question you're looking for, and a lot easier. Wow, can't say I've seen a code print out look like that. Everything looks to be right from what I can tell. The O/D code is stored in a different location than OBD2 can read. Usually you need a PCM(I believe that's where the code now is) reader, but I bet there are some high end OBD2 readers that have that capability.

 

[ov10fac]

Power Loss

I apologize for the format. My code reader is an inexpensive one from Harbor Freight, but it dose have a computer interface. I can record up to 60 frames of data either manually of based on a DTC event and then dump them to the computer for analysis. I just copied and pasted to the forum. I have them in a spread sheet but couldn't find a way to put a spread sheet here is a link to a screen shot of the spread sheet. I used manual as no DTC events were being detected.

Thanks

John

 

[JCat]

Even though the filter is relatively new. . . I'd take it out and see if there is anything blocking fuel flow.

 

[Joe Dirt]

Arcing spark plug wire?

BTW- Thank you for your service!

 

[2000StreetRod]

closed to open loop

Your PCM is transitioning from closed to open loop between 37 and 40 mph at medium (but fairly constant) throttle. When your PCM goes to open loop it commands the torque converter to unlock. Your short term fuel trims also change from slightly negative (running rich) to significantly positive (running lean). I believe open loop stored tables usually result in a rich rather than lean condition. It's difficult to determine if the A/F ratio change is causing the transition to open loop or if it is a result of the transition. The ignition timing stays stable but is less advanced than I would expect for the engine speed and moderate load.

I agree with BrooklynBay that a fuel pressure test is in order. I suggest adding a bottle of fuel injector cleaner to your fuel tank. The fuel filter should be changed every 30,000 miles. I also agree with nssj2 that a compression test would provide useful information. When you have the plug out check it for abnormal indications. Pulling the head to investigate should be a last resort after all other less costly (time and money) diagnostic methods have been performed.

 

[Joe Dirt]

Your PCM is transitioning from closed to open loop between 37 and 40 mph at medium (but fairly constant) throttle. When your PCM goes to open loop it commands the torque converter to unlock. Your short term fuel trims also change from slightly negative (running rich) to significantly positive (running lean). I believe open loop stored tables usually result in a rich rather than lean condition. It's difficult to determine if the A/F ratio change is causing the transition to open loop or if it is a result of the transition. The ignition timing stays stable but is less advanced than I would expect for the engine speed and moderate load.

I agree with BrooklynBay that a fuel pressure test is in order. I suggest adding a bottle of fuel injector cleaner to your fuel tank. The fuel filter should be changed every 30,000 miles. I also agree with nssj2 that a compression test would provide useful information. When you have the plug out check it for abnormal indications. Pulling the head to investigate should be a last resort after all other less costly (time and money) diagnostic methods have been performed.

:notworthy

 

[ov10fac]

Power Loss

Thank you all. I will be doing a fuel system check later this week.

In the mean time, I obtained another clue today. The O/D Fail light started blinking while at the same time the transmission was popping in and out of what seemed to be neutral. I checked and it seems this is common to the Explorer. I will be taking it to the Transmission specialist as well later this week.

John