Why does my 6 run like a 4? | Ford Explorer Forums - Serious Explorations

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Why does my 6 run like a 4?

JOCO

Member
Joined
March 18, 1999
Messages
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City, State
Hampton, Virginia (Norfolk area)
Year, Model & Trim Level
93 Ed B, 2dr, auto, 4X4
A couple of months ago my 93 EB 2dr auto (186K) started to stumble when coming off idle. Fixed this same problem 2 years ago by cleaning MAF and throttle butterfly. Before I got around to cleaning both again, the engine began to shake at idle (tach steady at 750) and really shake at part throttle. Smooths out above 2000rpm, but there is a power loss. At 55 (1800) in 4th there is boom like lugging in a 65 VW. It does not stall and gets 16 mpg. Could not find any vac leaks, cleaned MAF and throttle several times, added gas anti-freeze and fuel inj cleaner, replaced plugs (looked good) and wires. Unplugged MAF and it ran worse. Pulled plug wires at EDIS with good spark. Ran codes using EEC and CEL several times, KOEO - 111, CM - 157; KOER - 111. I have not cleared codes ie. CM 157. Can anyone help?
 



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I would probably start by clearing CM. The CM 157 is probably from running it with the MAF unplugged. Then I'd check fuel pressure. I might do a cylinder balance test to rule out a misfire.
 






MRSHORTY thanks for the reply! This afternoon I did clear the CM157. I pulled the battery neg and pulled the MAF out of its housing to get a better cleaning angle. When I re-ran the codes I got KOEO 111, CM 513?, KOER 111.
On the second run the CM changed to 111. I also checked the right and left
O2 sensors for damaged wires (had the muffle replaced last month) but they looked good. I can't get the eec-IV to do a cylinder bal test after the KOER. There is no fuel in the FPR vac line, but I guess the fuel pressure check is next and I am going to replace the fuel filter because of the truck's age.
 






Not all '93's have SEFI, so the PCM may not be able to perform the cylinder balance test (though with 2 O2 sensors, I would expect it to be SEFI). You may have to do the cylinder balance test the old fashioned way: by manually disabling each cylinder (either pulling spark plug wires or unplugging injectors).

My code list indicates a 513 should be a KOEO, not CM code. A KOEO 513 indicates an internal failure in the PCM. Where it seems to come and go, it might be an intermittent fault. I'd double check this code before replacing the PCM, but if you determine that the 513 is real, that might be where you're headed.
 






I have been under this truck 100 times, but untill I looked today, I just assumed I only had 1 O2 sensor. I also figured that the code 513 was just a fluke. Before and after replacing the plugs I did pull each of the plug wires one at a time, but they all seemed to have the same effect (lower rpm when pulled - higher when replaced). Something I didn't mention before - after starting I,ve never gotten a CEL with this problem. Besides the x-mass tree on the manifold, FPR, air filter box, auto trans modulator, power brakes and cruise control is there another vacuum line I missed?
 






It turns out that the problem was an inoperative #2 fuel injector. It runs smooth as glass after replacement. Thanks MrShorty for the help.
 






Can I ask how you determined it was the #2 injector? You did the cylinder balance test in post #5, and indicated that all cylinders seemed equal. I'm curious what you did differently later to catch what the cylinder balance test missed.
 






Actually I didn't find the problem. After I replaced the MAF (the NAPA guy had the same problem and the MAF fixed it) and it made no difference, I had to take it to my mechanic because this is my business truck. I told him about the wet #2 plug I found. First he tested fuel pressure with good key on & run pressure and no leak down. Then he conducted a balance test by shorting each plug wire and watching a tach. Although all 6 plugs had great spark, shorting #2 made no rpm diference. inoperative #2 injector was the problem. I guess the codes won't pick up this problem.
 






Correct, EEC-IV (except maybe for '95's, but they've never been mentioned) doesn't have the ability to detect misfires, and the built in cylinder balance test isn't always good at catching a bad injector. And I guess when you tried the cylinder balance test by pulling plug wires (without a tach?) you were unable to adequately see the difference from cylinder to cylinder.

Thanks for sharing that. Diagnosis is often 90% of the battle, so understanding how something was diagnoses is often very useful information.
 






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