Posted: 1/15/2015 2:45:47 AM EDT
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You guys have previously helped me with this issue, so I thought you might help again.
I have previously done some emissions systems work on my truck but am getting the "Check Engine" light again. This time, it happens very consistently. The engine runs really well while on the freeway because the throttle is constant. However, if I open the throttle then let off on the throttle the Check Engine light comes on almost immediately. When I return to a steady throttle position and hold it there, the light goes out after about a minute. Any idea what is causing this? I am under the impression it is the EGR system. I have not had a chance to pull any codes from the engine. This is a 1993 Ford Explorer. |
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I do not have a numerical reading of oil pressure. The oil pressure gage indicates what it has always indicated, a relatively high value. It does not fluctuate.
There is no indication in the oil of a bad seal (that I know of, no blackening of the oil) and no blackening of the rear bumper near the exhaust pipe. |
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Get yourself some MAF spray cleaner and the security bits they use to hold it in and clean it. Not only spray, but use a Q-Tip very carefully and wipe it gently with it soaked with the MAF cleaner. After wiping clean, spray it again. It's avery fragile wire sensor. If you are the clumsy, gorilla type, get someone else to do it. If you can play the Milton-Bradley Operation game with success, go for it.
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Does it stumble under sudden acceleration? How does it idle, and does it idle lower or higher than you remember? Considering the age I would think EGR or vacuum issue first and foremost, but I'm not particularly familiar with Explorers specifically... Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC. Previous 93 Explorer Owner 
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On those older engines, generally the EGR will cause a stumble under acceleration. The quick fix is to just disconnect the vacuum line and plug it. This is not a viable approach for me, as I have to take it in for a smog check this summer. The inspection would catch that and I'd automatically fail. I need to go check the codes. I think I'll go do that right now. |
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Okay, so I'm supposed to let the engine warm to normal operating temperature before running the KOEO test and I did not do that. I believe this is needed for the Key On Engine Running test but not just to retrieve codes. If I am mistaken about this and it caused bad code readings, please let me know.
I ran the code reader on a cold engine (it's about 65 deg outside right now). I got these codes - 186 - Fault in injector pulse width circuit/high 335,336 - EGR sensor circuit voltage higher than expected during self-test So, what do you guys think from these results? |
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Okay, so I'm supposed to let the engine warm to normal operating temperature before running the KOEO test and I did not do that. I believe this is needed for the Key On Engine Running test but not just to retrieve codes. If I am mistaken about this and it caused bad code readings, please let me know. I ran the code reader on a cold engine (it's about 65 deg outside right now). I got these codes - 186 - Fault in injector pulse width circuit/high 335,336 - EGR sensor circuit voltage higher than expected during self-test So, what do you guys think from these results? The older Fords have a history of the EGR position sensor (on top of EGR valve) going bad. A new one usually fixes it but I know techs that change that and the EGR valve. Changing the EGR valve is USUALLY not necessary however if it is stuck open it will not idle well and may need to be replaced FYI - I have 30 years turning wrenches in a general repair shop. We work on almost everything here. |
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Tomorrow, after running some errands to warm the engine, I will recheck the codes and do the KOER tests.
I don't recall this car having an EGR position sensor. It has a MAF sensor, new DFPE, a new IAC valve, new EGR valve, new EVR, etc. I have had a sneaking suspicion that the EGR tube may be dirty, restricting the EGR flow. I thought I'd use my shotgun brushes to clean it out. |
| would probably clear the codes or disconnect the battery for a few minutes to clear them then drive it till the check engine light comes on then recheck codes would only do the koeo test first to see if any codes or stored. dpfe sensor often do go bad but if its new could be a old code stored in memory so would really see what code or codes come back after clearing them and go from there.. |
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The codes were cleared after changing the DFPE and other emission systems components. When I said they are "new", I meant they were changed about a year ago prior to the last smog check. You cannot pass inspection if there are any stored codes. So after replacing the various components, I cleared all the codes and passed the emissions test.
Now, it's throwing codes, again, and test time is coming in a few months. |
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When first turned on, your engine will Rev up and down... Not smooth Quoted:
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What is "loping idle"? When first turned on, your engine will Rev up and down... Not smooth Ah, I will assess that tomorrow. I didn't get to work on the car at all today. |
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Tomorrow, after running some errands to warm the engine, I will recheck the codes and do the KOER tests. I don't recall this car having an EGR position sensor. It has a MAF sensor, new DFPE, a new IAC valve, new EGR valve, new EVR, etc. I have had a sneaking suspicion that the EGR tube may be dirty, restricting the EGR flow. I thought I'd use my shotgun brushes to clean it out. I should have looked up the EGR system before giving BAD advice. You are correct, no EGR position sensor - you have the DPFE instead. Simple test if you have a good scanner available. First, with the scanner connected and looking at the live EGR data, KOEO the DPFE voltage should be about 1.0-1.1 volts or very close. If over that you have a bad DPFE (most cases they are over 3.5 volts when bad) Second, hook a vacuum gauge in line between the EGR valve and the vacuum hose going to it. Warm up the engine and select KOER. During KOER you have to push the brake pedal, cycle OD and 4WD buttons if present and turn the steering wheel. Do all of that quickly and go look at the vacuum gauge for the remainder of the KOER test. At some point the vacuum gauge will move to about 5-10 inches of vacuum. (needle will rise slowly and come down quickly) If that happens, your EGR system is functioning properly and you most likely have a clog somewhere and the DPFE will not detect the EGR system is working. I hope I did not confuse you. |
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Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC. Previous 93 Explorer Owner Quoted:
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Does it stumble under sudden acceleration? How does it idle, and does it idle lower or higher than you remember? Considering the age I would think EGR or vacuum issue first and foremost, but I'm not particularly familiar with Explorers specifically... Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC. Previous 93 Explorer Owner Listen to this guy 
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Tomorrow, after running some errands to warm the engine, I will recheck the codes and do the KOER tests. I don't recall this car having an EGR position sensor. It has a MAF sensor, new DFPE, a new IAC valve, new EGR valve, new EVR, etc. I have had a sneaking suspicion that the EGR tube may be dirty, restricting the EGR flow. I thought I'd use my shotgun brushes to clean it out. By definition EGR tubes are dirty................. |
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Listen to this guy Quoted:
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Does it stumble under sudden acceleration? How does it idle, and does it idle lower or higher than you remember? Considering the age I would think EGR or vacuum issue first and foremost, but I'm not particularly familiar with Explorers specifically... Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC. Previous 93 Explorer Owner Listen to this guy I did notice a small change in idle speed with a cold engine. There's what sounds like an electric clutch clicking, then a speed increase (~100 rpm change). |