Fuel trim at 100%, clear KAM, code 0171 and 0174 | Ford Explorer - Ford Ranger Forums - Serious Explorations

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Fuel trim at 100%, clear KAM, code 0171 and 0174

jangel

New Member
Joined
October 21, 2005
Messages
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City, State
denver, co
Year, Model & Trim Level
1997 Explorer XLT - Wife
OK, my cel came on about 3 weeks ago.
I pulled the codes and got the 0171 and 0174 "too lean". I cleared the codes and ignored it since the car was running fine.
The light came on a day or so later. checked codes, cleared codes, ignored codes.

The light came on again, same codes, and my autoxray scanner tells me that all 4 short term/long term trim levels were -100%. And I finally had time to look into it.
I opened the hood and inspected vaccum tubes, elbows, etc. Everything looked good. Then I noticed the Oil Cap was gone. I had added a quart before the CEL came on and must've forgot to put the cap back on.
Great! I thought. I bought a new cap, changed my oil/filter, cleared codes and disconnected the battery for about 1 hour to clear the KAM so the fuel trim levels would return to zero (right?).

Anyway, the car is running fine, but when I scan it, the ST and LT fuel trim levels are all still -100%. Shouldn't these reset when I disconnect the battery for ~ hour?

Should I be worried?
I've only driven it 2 times since the oil change/KAM clear, so obviously the CEL has not come back on (yet?).

But what is up with the fuel trim levels?

TIA,
John
 
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lorenambrose

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February 6, 2008
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City, State
Norfolk, VA
Year, Model & Trim Level
1997 XL 4.0 OHV 4x2
I went through the same thing exactly. Problem only got worse. I ended up with a hard injector fault on #3 and #6. I replaced the upper and lower intake gaskets and all 6 injectors to fix the problem. Compounding my problem was the fact that I went thru 3 reman MAF sensors at the same time. A-1 Cardone sensors from Advance all read low by about 40%. Third one finally was correct. Short term fuel trim that far off is indeed indicating a serious problem that most likely will turn into a drivability issue. The fuel system can not compensate for the lean condition.

The problem is that the code is kind of misleading. The engine is running lean but the fuel system is running very rich.

Do not go replacing o2 sensors. That is just shooting the messenger, as I found out the hard way.

Do a vac check, fuel pressure check, and thorough inspection of fuel, ignition and air system components. If an injector goes bad, I would strongly recommend replacing all of them while you are there.
 
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BIGHVM

Explorer Addict
Joined
November 25, 2007
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City, State
UK, Richmond, Surrrey.
Year, Model & Trim Level
2000 Northface
Those code do point to inlet manifold gaskits needing replacement, they go hard and brittle being rubber. its not that hard to do and you could save a fortune doing it yourself- be sure to use a torque wrench as the manifold is plastic and tighten in the correct sequence- diagonal from outside in, thats 11 oclock and 5, 12 and 6, 1 and 7 etc, then spiral inwards using the same method.
a few turns at a time till you click out after a few rounds on all the bolts it will be fine- never tighten them all down to to torque at once.
Good luck.
 
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mfdbackdraft

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Joined
October 29, 2008
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City, State
Milwaukee WI
Year, Model & Trim Level
99 XLS 4.0 SOHC
Jangel-

Which autoxray scope do you have. I have 171/174 issues also but just a generic code reader. It sure would be nice to see what is going on in the engine.
TIA
 
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jp450

Well-Known Member
Joined
January 7, 2004
Messages
502
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1
City, State
Pepperell, MA
Year, Model & Trim Level
'05 XLT V8
Keep driving it until all systems have done the checks. I think you will find that the levels will drop. When you reset the CEL the PCM can go into open loop mode until all the systems have checked out OK.
 
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jangel

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Joined
October 21, 2005
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City, State
denver, co
Year, Model & Trim Level
1997 Explorer XLT - Wife
mfdbackdraft,
my scanner is at home, I'll get the model number for you.

FYI, i am still working on getting this issue resolved. I have been dragging my feet as there are no drivability issues. the car runs great. occasional hesitation from a stop, but not bad. i think I am actually getting better mileage now!

I did pick up an egr valve, soleniod and dpfe sensor. I'll try those in the next few days when I get time and report back. I really don't want to do the intake manifold gaskets if I don't have to. I've never done it and it would take me all day (or two) since I am very slow.

john
 
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Reach

Member
Joined
October 17, 2008
Messages
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Year, Model & Trim Level
1997 Explorer
I've got this issue on my new-to-me Ex. Only thing is, I've got the OHV engine. I understand that the intake manifold gaskets are an issue for the SOHC engine, and thus the 00M12 recall kit exists as a fix. Is this the same issue on the OHV engine (I wouldn't think so?)

Anyway, recurring 0174, 0171 codes on an OHV. Looking for some help. Sorry if this is a bit noobish, but I'm new to this car, and all my searches on the topic so far relate to the SOHC engine specifically.
 
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