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1/22/2020 12:12:56 PM
Posted: 1/15/2015 1:45:47 AM EST
[Last Edit: 1/15/2015 2:23:32 AM EST by Trollslayer]
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.
Link Posted: 1/15/2015 1:55:15 AM EST
What is the oil Pressure?
Link Posted: 1/15/2015 2:22:55 AM EST
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.
Link Posted: 1/15/2015 2:26:16 AM EST
[Last Edit: 1/15/2015 2:28:59 AM EST by xsrfs]
Mass air flow sensor or o2 sensor

Runs well cruising under low load. Around town and stepping on it load (fuel) increases, falls out of equilibrium with air
Link Posted: 1/15/2015 10:31:39 AM EST
It's odb1, you can read codes with only a paper clip.
Read the codes and then look up the code online.
Link Posted: 1/16/2015 9:07:54 AM EST
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.
Link Posted: 1/16/2015 9:49:33 AM EST
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...
Link Posted: 1/16/2015 11:40:56 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By DarkCharisma:
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...
View Quote


Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC.

Previous 93 Explorer Owner
Link Posted: 1/16/2015 6:13:19 PM EST
What is "loping idle"?
Link Posted: 1/16/2015 6:44:03 PM EST
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.
Link Posted: 1/16/2015 7:36:42 PM EST
[Last Edit: 1/16/2015 7:37:09 PM EST by Trollslayer]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By keroppl:
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.
View Quote


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.
Link Posted: 1/16/2015 7:58:11 PM EST
[Last Edit: 1/16/2015 7:59:33 PM EST by Trollslayer]
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?


Link Posted: 1/16/2015 8:08:05 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
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?


View Quote



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.





Link Posted: 1/17/2015 12:28:40 AM EST
[Last Edit: 1/17/2015 12:31:11 AM EST by Trollslayer]
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.
Link Posted: 1/17/2015 6:37:51 AM EST
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..
Link Posted: 1/17/2015 1:08:01 PM EST
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.

Link Posted: 1/17/2015 11:00:28 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
What is "loping idle"?
View Quote


When first turned on, your engine will Rev up and down... Not smooth
Link Posted: 1/17/2015 11:43:03 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Breedy:


When first turned on, your engine will Rev up and down... Not smooth
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Breedy:
Originally Posted By Trollslayer:
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.
Link Posted: 1/18/2015 9:30:24 AM EST
[Last Edit: 1/18/2015 9:33:18 AM EST by Bullseye100]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
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.
View Quote



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.



Link Posted: 1/18/2015 11:50:07 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Breedy:


Vacuum issues usually result in loping idle and does not throw a code to turn the check engine light, IIRC.

Previous 93 Explorer Owner
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Breedy:
Originally Posted By DarkCharisma:
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
Link Posted: 1/18/2015 10:36:19 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
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.
View Quote


By definition EGR tubes are dirty.................
Link Posted: 1/19/2015 1:06:24 AM EST
LOL!

Yes, but at some point the build up becomes an obstruction. I've seen pictures of tiny particles trapped in the narrowed (venturi) section of the tube that caused a pressure differential problem for the emissions control system.
Link Posted: 1/19/2015 1:08:27 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By DarkCharisma:


Listen to this guy
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By DarkCharisma:
Originally Posted By Breedy:
Originally Posted By DarkCharisma:
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).
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