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Old 01-18-2008, 01:50 AM   #1
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Default 93 Explorer runs like **** when warmed up.

Hey everybody!

I just found this site tonight and must say I'm very impressed. I've been on 'another site' for a while trying to get a situation resolved but can't seem to get my point across to them or find information that I need, specifically a testing procedure for the MAF sensor. Thank you very much for that BTW...

Here's my problem. A little long but I want to give you all of the details...

I recently bought a used explorer. It had a leak in the water pump and the fuel gauge didn't work. I fueled up at a nearby gas station and got some water to be safe. It drove fine all the way home and drove fine for nearly 200 miles (all short trips) until one day at an intersection, it started sputtering. Luckily I was right next to Hess so I filled up and headed back out to the same stop light. It was running fine at this point. As soon as the light went green and I hit the accelerator, everything went south… quick. It felt like the engine was just cutting off and then surging back on. If I hit the gas hard, the RPM's would drop. If I backed off, it would pick up, but I couldn’t accelerate normally and could only get to about 25MPH. I struggled to get home and let it sit all of the next day. The following morning it started just fine and drove great! Drove for another week and a half until it started sputtering again (less than 100 miles later) Once again I limped home.

I figured there might be something like dirt or rust in the tank blocking the fuel pickup when the level got low, and that was stirred up more upon fill up. I dropped the tank only to find the sending unit float rolling around the bottom. The sock filter on the end of the pickup tube was rather dirty and felt weird, kind of spongy.I tried to remove it but it wouldn't budge. I didn't remove it for fear of breaking something. I re-installed the tank and replaced the fuel filter (it was plugged badly!)

Now the vehicle runs good only until I get a few miles down the road and it warms up and the computer kicks in, then the same hesitation, surging and the extreme loss of power and acceleration returns. It will rev OK in Park or Neutral. There is a slight hesitation but it will get to 3-4K RPM and sounds pretty good.

So far I have inspected, cleaned, tested or replaced the following:

Replaced Fuel Filter on frame rail - It was rather plugged as stated before.
Tested Fuel Pump - Indicated 35PSI at idle and with increase in RPM. Pressure remained after shut off.
Tested Fuel Pressure Regulator - Held vacuum when applied with pump. Disconnected vacuum w/ engine running and pressure increased to 42PSI. Pressure returned to 35PSI when vacuum re-applied.
Tested Engine Vacuum Used old gauge but reading was in upper green region and steady.
Cleaned IAC Valve RPM changes when connector is removed
Tested TPS Read 0.95V at idle. Resistance change was smooth from 3.2K to 300 Ohms
Cleaned MAF Sensor Used Non-Residual electrical contact cleaner. Performed ‘Thump & Wiggle’ test.
Replaced Spark Plugs & Wires 2 plugs on Driver Side were black with soot. Remaining plugs had tan deposits on tips but also had sooty deposits around base of insulator. No. 5 had slight oily residue.
Replaced Water Pump 'nuff said there.

Actron CP9015 Code Reader Results

KOEO 159 MAF Signal Voltage Higher or Lower than expected
CM 111 System Pass
KOER 137 HEGO(O2)sensor not switching during Run Self Test - Rich Bank #2
KOER 173 HEGO Sensor indicates Rich Bank #2
KOER 538 Insufficient RPM change during Dynamic Response Test. (Didn't hit gas quick enough?)

The night I changed the plugs and wires, I took it for a test drive and it ran great, spinning tires from a stop, good acceleration and smooth running. I thought I had the problem licked... until I went to register it the next day and it couldn't get out of its own way!

I'm going to test the MAF and check the intake manifold bolts tomorrow morning, but is there anything else the experts here can think of?
Could the ECT be causing this? The EGR? Thanks in advance for any help you can give. I can't go fishing till I fix this!
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Old 01-18-2008, 09:23 AM   #2
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These engines are notorious for intake manifold gasket deterioration.

A clogged cat will also give the symptoms you describe.

The heads also crack easily if the engine has overheated. shady
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Old 12-21-2017, 02:00 AM   #3
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When it’s doing it once you’ve driven a little see if your cat is glowing red
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