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Rough Idle.... Getting codes

pteepee69

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I have posted in several threads trying to get answers. Still not getting help. I will try once again. Have a '94 Explorer. Idles rough. So far I have replaced lower intake gasket, upper intake gasket, fuel injector o-rings, thermostat, radiator cap, battery cables, replaced 2 vac lines going to EGR that had holes in them, cleaned the MAF and Maf housing twice, cleaned the throttle body, ran Seafoam through the PCV line, put Seafoam in the gas tank, performed a pressure test(engine cold and engine hot) held pressure for 10 minutes until I released it. Ran codes and I am getting KOEO 114: CM 157, 189, 192: KOER 116.

Forgot to mention I also found 2 holes in my breather tube that I have patched temporarily until getting my idle issues solved. Had my coil tested and it checked OK.

I have been trying to get help, but I thought maybe I have been posting in the wrong place so I am trying again. Any help would be appreciated.
 
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FIND

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114: IAT sensor out of range

157: Mass Air Flow signal is/was low or grounded

189: Fuel system was lean at part throttle - Left or Front HO2S

192: Fuel system was lean at idle - Left or Front HO2S

116: Engine Coolant (ECT) sensor out of range
 
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MrShorty

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KOEO 114/KOER 116: Almost always, these codes indicate that you didn't adequately warm up the engine before the test. Repeat the tests after getting the engine up to operating temperature. If you are still getting either of these codes, test the offending sensor. They are simple thermistors (resistance varies with temperature), so they are pretty easy to test with an ohmmeter/voltmeter.

The other codes point to a fuel control issue (sometimes the hardest to diagnose). If I may ask, what does
performed a pressure test(engine cold and engine hot) held pressure for 10 minutes until I released it.
mean? Are you referring to fuel pressure? What conditions are you testing the fuel pressure (KOEO, KOER, under load)?

You've got codes for the left side, but not the right side. I wouldn't call this diagnostic by itself, but it is interesting. Do you see anything with the left O2 sensor/wiring?
 
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pteepee69

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I pressure tested the cooling system for possible head gasket problems. No, I haven't checked the oxygen sensors yet. Before testing I let it warm for about 5-10 minutes.
 
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FIND

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I pressure tested the cooling system for possible head gasket problems. No, I haven't checked the oxygen sensors yet. Before testing I let it warm for about 5-10 minutes.

If you did let it warm before the test, the problem with the ECT could just be from faulty readings from the IAT. Test your IAT, somewhere on here someone posted resistance for it at whatever temperatures.

The other tests suggest a fuel issue, which may be related to a bad O2, bad MAF, or a different issue.

The way the MAF works is by heating a pair of wires. Air passing over those wires cools the wires, thereby increasing resistance. The computer figures air flow based upon how quickly those wires cool given whatever ambient air temperature. Therefore, if your IAT is malfunctioning or not working, you may return MAF codes.

O2 sensors work while heated. Lean mixtures create more heat, rich mixtures can cool the exhaust charge. This can cause unexpected readings for the ECU, oxygenated fuel can magnify this problem.


I recommend you pull plugs and have a look at them. You will need to test your IAT and O2 sensor on the left bank. If you have a spare MAF, or one you can put in temporarily/borrow for testing, then do that as well. I cant remember off the top of my head what resistance you are looking for across your MAF, but I am curious what you cleaned it with, and if it was completely dry when you restarted your engine.

Also, what is the ambient air temperature that you have been doing your diagnostics/observations in?
 
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pteepee69

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I cleaned the MAF with MAF cleaner. At idle it tested drifting between .88 and .90. It read 12.7 on the B positive terminal. Don't have an extra to try. It dried for about 15 mins. When I pulled the codes this morning it was between 20 and 30 degrees.

I have also cleaned the IAC with the MAF cleaner. Does a '94 have an IAT? If so where is it located? In my Haynes it shows it being in the air cleaner duct, but on my '94 the only thing coming from the air cleaner duct is the hose going to the oil filler neck.
 
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FIND

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I cleaned the MAF with MAF cleaner. At idle it tested drifting between .88 and .90. It read 12.7 on the B positive terminal. Don't have an extra to try. It dried for about 15 mins. When I pulled the codes this morning it was between 20 and 30 degrees.

I have also cleaned the IAC with the MAF cleaner. Does a '94 have an IAT? If so where is it located? In my Haynes it shows it being in the air cleaner duct, but on my '94 the only thing coming from the air cleaner duct is the hose going to the oil filler neck.

I cant honestly remember where it is located on a 94. On earlier models I know it screws into the UIM though. Check there, ahead of the IAC.

Those maf readings sound close anyways.
 
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pteepee69

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I have also changed the fuel filter which was a real blast.
 
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huntman58

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Just an FYI normally a MAF or FPR problem would be affecting both sides of the motor now that’s normally. If you have a weak link it may be just enough to fire that weak link off.
Testing with out side air temps of 20 to 30 makes it hard some times to do test as most manuals are stating there facts on an out side temp of 70.

MAS cleaner is not always the best cleaner for an IAC. The MAF your cleaning more or less dirt and not carbon and oil residue were the IAC it is more carbon and oil gunk your cleaning that is why most use a carb / throttle body cleaner for it.

I would also do a fuel pressure test of the FPR to cover that part so you know your not over pressured or under and or leaking extra fuel threw any part of it as you cover your bases here.

The IAT sensor I believe is on the driver’s side of the upper intake manifold closer to the firewall then the IAC but in roughly the same area. It’s not on the air intake tube but it is on the side of the upper manifold it's self.
 
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pteepee69

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I just ran outside and checked and it is located beside the IAC to the back of the upper intake.

Would brake or throttle body cleaner do the trick?
 
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huntman58

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I have used both but first go to would and should be the throttle body cleaner.
 
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pteepee69

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I was checking out parts online and what we are calling IAT I think they are calling the air charge sensor or are they 2 different parts?
 
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pteepee69

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I think I saw a post where this sensor can be cleaned also.
 
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pteepee69

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On a '94 it is known at the parts house as an air charge sensor. Replaced it today and cleaned the IAC. Still missing, so I had already pulled the plugs on the drivers side about a week ago. Well today I pulled them on the passenger side and what a surprise. The front and middle plugs were gone. I mean no electrode no insulator. Replaced and it is as smooth as a babies bottom. But what I want to know is this signs of a bigger problem or is this a shady mechanics trick. I am almost 40 years old and have always done my own mechanics work and I have never seen anything like this. If I can figure how to post pics I will show the plugs to you. Gonna drive it to work tonight and keep an eye on the plugs for a couple of days. Hurray for 6 cylinders instead of 4.
 
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FIND

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On a '94 it is known at the parts house as an air charge sensor. Replaced it today and cleaned the IAC. Still missing, so I had already pulled the plugs on the drivers side about a week ago. Well today I pulled them on the passenger side and what a surprise. The front and middle plugs were gone. I mean no electrode no insulator. Replaced and it is as smooth as a babies bottom. But what I want to know is this signs of a bigger problem or is this a shady mechanics trick. I am almost 40 years old and have always done my own mechanics work and I have never seen anything like this. If I can figure how to post pics I will show the plugs to you. Gonna drive it to work tonight and keep an eye on the plugs for a couple of days. Hurray for 6 cylinders instead of 4.

Sounds like your plugs just wore out, it happens. Has this taken care of your codes? This should get rid of your O2 sensor codes at the very least. Probably MAF too.
 
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huntman58

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I would be willing to say just worn out also. unless you know how many miles they have on them because you were there or did the work there is most likely no way to know how long they were in it. I was chasing a random miss for over a year before it got to were I could nail it down but all a long #5 plug showed signs of miss deeds from foiling out to not burning at all. Well my new (two year old) Accel coil went dead on #5 tower! Got the old one back in it but it has a weak spark and why I change it to start with. So now I still have a small miss and a smell of fuel in the tail pipe but tell I get a new coil I am not going to chase it. Story is ya just never know why only a few plugs or one tower would wear out / go bad and the rest look normal but it happens and so we go nuts and then replace them.
 
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pteepee69

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drove it to work last night.....totally different truck. Checked codes this morning all I got was KOER 536, was asleep when I should have been pushing the brake. Also did the cylinder balance and it flashed 9 whatever that means. Keeping my fingers crossed, thanks for the replies, appreciated not being alone on it.
 
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