97 Check Engine Ideas (1 Viewer)

[cali-cruiser]

I've had a check engine light come on several times now, only while pulling long grades in third gear over 3000 rpm, every time it has been a system too lean code.
As for vehicle and history, 97 taco, 2.7l 4x4,
-new fuel filter 10000mi ago
-injector wiring has been checked with noides
-All injectors effect the idle of motor when disconnected one at a time.
-no other problems what so ever, just when pulling hills every onces and a while it pops the code

does anyone have any ideas before I go and by new injectors to see if this fixes it.

thanks Josh

 

[LukeZero]

hows your air filter?

 

[cali-cruiser]

K&N cleaned about 5000mi ago

 

[FLYINGLOW]

Intake leak somewhere downstream from the MAF sensor? I think fuel flow problems would present themselves with a lack of power. Air leaks would lean it out if they are after the MAF sensor. The MAF sensor tells the ECM how much air is flowing in and the ECM then regulates fuel flow. If theres a leak downstream then there is more air than the ECM thinks there is. I think you will find that the lean code is triggered by the O2 sensor.

 

[SteveH]

I'd reinstall your last paper air filter (you saved it, right?) and see if the code sets again.

Steve

 

[FLYINGLOW]

Did you find anything? I would leave your fuel system and air filter alone for the time being. I have been thinking about this some more.

Here is fuel injection 101. Basically your MAF sensor measures the amount of air going in to the engine. Your ECM will regulate a certain amount of fuel to maintain correct mixture which is fine tuned with the O2 sensor in the exhaust. The O2 sensor measures oxygen in the exhaust to determine how much to adjust the fuel flow. So if a certain amount of air is going in, it is matched with a predetermined amount of fuel. If you have a leak downstream of the MAF (located between the filter and the intake manifold) sensor then the ECM does not know that there is extra air coming in and will not be able to adjust the mixture enough. The O2 sensor is telling the ECM that the mixture is too lean and exceeds parameters which brings up the code. I would look for any leaks on vacume ports, intake manifold, any emissions controls. It could even be related to the EGR. You may even look at the exhaust to see if there are any leaks to suck air in under certain situations. I think that chances are good you will find something simple and cheaper than a set of injectors.

 

[cali-cruiser]

I was sort of suspecting the same type of thing, I'll take a good look at it and see what I can find

 

[cali-cruiser]

the only flaw I see in this thinking is that it only does this when on long hills, not whenever I rev her up,
been two days now and no light, we'll see how long it lasts

 

[FLYINGLOW]

the only flaw I see in this thinking is that it only does this when on long hills, not whenever I rev her up,
been two days now and no light, we'll see how long it lasts

Well at 3000 rpm under load there is a large amount of air flow and a large amount of fuel flow. It may not produce the right conditions by just reving it up with no load. Fuel flow will be much less. The long hill thing may come into play if there is a predetermined length of time that the ECM will allow a lean condition, say 10 or 20 seconds. Otherwise it would flicker every time there was a quick power change before the ECM can compensate. Another thing that I didn't mention earlier is that the Throttle Position Sensor tells the ECM the position of the butter fly, which also determines fuel flow. I guess this could do it as well but I would look for air leaks first.