in trouble-too lean

odeek9 · Apr 19, 2014

I'm kind of freaking. I'm 60 miles from home and have to get there. My gas mileage just dropped from 21 to 13mpg a few days ago. The truck is intermittenly cutting out. My little code reader is code 41=too lean. From reading I guess it's my MAF-just a guess. Is there anything that I can do just to get me home without burning valves, etc..
Please help me out here-Thanks, alan

adsm08 · Apr 19, 2014

I don't think the 86 2.3L had a MAF.

Anyway, it sounds like you have a bad oxygen sensor. Try unplugging the sensor and see if she shapes up.

Mikel89us · Apr 19, 2014

Too lean reading doesn't mean its running lean, if your fuel mileage dropped you're running way rich. My guess is you have some sort of an issue causing one cyl not to fire. When the cyl doesn't fire, the sensor sees a lean condition because the fuel isn't burning, which also means the oxygen isn't burning.. The sensor doesn't read fuel, only oxygen. Without a full burn oxygen is still present.

RonD · Apr 19, 2014

For the MPG to go down AND to get a Lean code doesn't make sense, maybe bad O2 sensor.
I would check around the fuel lines, including under the truck.
Only situation I can think of that would fit both of those conditions is a fuel line leak, gas is being pumped out of the fuel line(poor MPG) and not getting to the injectors(Lean condition)

A large vacuum leak could do that, but i think you would notice that in other systems.

odeek9 · Apr 19, 2014

There's no leaking fuel anywhere, or smell. I undid the sensor and the code 41 still shows. It runs great when hitting the throttle in the driveway, and on the way back from getting an air filter this morning I wound it out in second and it seemed fine. I did take the EGR valve off the other to clean it as there was a code for it also. But there's not too much to that.
I just want to get home without damaging the engine. But just in the past few days the mileage has dropped dramatically and the code is for too lean. I did a compression test a month or so ago and it was 190, 190, 188, 191.
Can I drive it?

RonD · Apr 19, 2014

If possible remove 1 spark plug and look at the tip, it should have blackish carbon buildup on it with MPG that low, so OK to drive home, not really Lean.

If you start to get "pinging" that is the true signal for Lean mix, if you get that then you could damage exhaust valves, but it would take constant "pinging/knocking" for that.

1986 Ranger would be a Speed Density fuel system, so would have a MAP(manifold absolute pressure) sensor instead of a MAF sensor.
MAP sensor measures engine vacuum, computer uses that info to set base air/fuel mixture.
MAP sensor is a small black device usually located on the Firewall behind wiring harness, it has a vacuum line attached and a 3 wire connector.
You can usually find it by following the vacuum line.
Find it, and check the vacuum line for leaks, one of the ends could be brittle and cracked, cut it off and that could fix the problem.

odeek9 · Apr 19, 2014

Thanks to all of you! I just don't have time to do anything else right now-have to get home. I took a plug out and it looked fine

P.S. Hope it's OK to leave the O2 sensor dangling-I broke the 30 year old clip. As far as the MAF is concerned I wondered why I couldn't find it where the manual says it is!!

Mikel89us · Apr 19, 2014

I explained best what's likely going on, you are running rich, but there is a cylinder not firing which is causing a high oxygen signal from the oxygen sensor. Your plugs should be a brownish color. White is lean, black is rich. I'm telling you though, you have a problem causing no fire on a cyl. Blown rings, burnt piston, bad head gasket, burnt valve, camshaft, or follower/lifter. Something is not right. It could even be a bad plug or plug wire.

odeek9 · Apr 19, 2014

I realize that you're much more knowledgeable than I am but the compression was perfect last month, no oil burning or loss, it's basically a new engine, and strangely enough it ran 65-70 mph all the way home today without any problem.
I'll do another compression test tomorrow but I just don't believe it's pistons, rings, etc.. The plug was black tipped. The mileage when I filled it up at home wasn't as it should be (21mpg) but it wasn't the 12, or so, from yesterday. It was 17.5mpg.
I'm taking it to a mechanic who can dx it and then I'll (hopefully) fix it

Mikel89us · Apr 19, 2014

even a sticking open injector can cause this, if you get too much fuel into a cylinder the spark plug cant ignite it at the right time and can cause incomplete burn.

adsm08 · Apr 19, 2014

Compression is not the only thing that can cause an incomplete burn. Weak spark from a dying coil or TFI can cause incomplete burn as well.

How is the gap on the plugs?

odeek9 · Apr 19, 2014

There are just too many possibilities for this old fool. I'll take it to a qualified guy who tell me what the issue is

odeek9 · Apr 19, 2014

adsm08 said:
Compression is not the only thing that can cause an incomplete burn. Weak spark from a dying coil or TFI can cause incomplete burn as well.

How is the gap on the plugs?

Fine-.045. It has been idling a bit roughly for awhile but I couldn't get to the clamp in order to loosen the distributor as timing kept playing in my mind. Also the other day while fiddling around the wire from the distributor to the coil wouldn't stay on so I crimped it a tad
Before these recent problems the only codes I got were for the temp. sensor but I think that's because I put in a manual sensor a long time ago, and 2 EGR codes-31 &34 if memory serves me correctly

odeek9 · Apr 20, 2014

One last question please and it probably belongs somewhere else. I did a compression test this morning (all plugs looked OK) and it was 195, 200, 200, 210. What I'd like to know-stupid question in all likelihood-is do garages have one machine that they can hook up my truck to? Checking emission components, ignition parts, sensors, injectors, etc. that will tell them where to replace a part? I don't want to do what I've done in the past when I wasn't such a pauper and , by trial and error, replace one part after another. Expensive and absurd. And what do I ask the mechanic for when I call? Thanks once again!!

Mikel89us · Apr 20, 2014

Yes they do, take it to a ford dealer, they can best diagnose it. It will probably cost you about $100 maybe a little more or less for just diagnosis.

in trouble-too lean

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