peejay Posted January 13, 2014 Share Posted January 13, 2014 Greetings, all! Got a problem I could use your help with... 94 Pathfinder, on the first start of the day (cold morning), you can crank the truck, it will run for a few seconds, "hunt" for idle, then die...repeat, it does the same thing...usually on the 3rd and later trys, it won't even run... Now, if on the first try, you "feather" the accelerator pedal, it will stay running...after a few seconds of keeping the idle high enough so the engine warms, you can get off the pedal and the truck will idle fine... My thinking is, since I am having to give the engine more air, by opening the throttle plate (via the accelerator pedal), then the engine is not getting enough air when cold, right? (Don't cold engines require more fuel?) So I suspected that the Idle Air Control Valve (IACV)-Air Regulator must not be working properly. It is my understanding that the IACV is supposed to provide a bypass for incoming air...(not sure what it bypasses, i guess the "normal" path for incoming air into the intake?)...Anyhoo, I disconnected the hose from the intake tube of the IACV, put my MityVac pressure pump to it, and pumped it, to see if the IACV was not blocked...no reading on the gauge, and I could hear air coming out of the intake runner ports (this was all done with the intake off), so that makes me think the IACV is ok, well, at least it is open when cold (normal). Also, the engine never reaches a fast idle...i would think if the IACV was not working (stuck open), then the additional air would cause the idle to remain high...once warm, the truck idles at about 700, no fluctuation... Any ideas what the problem could be? My other thoughts are, maybe the engine is getting too much fuel during cold start...and when i allow more air in, i am balancing out the mixture? At what point does the ECM "take over" and control the air/fuel mixture? By that I mean, if I am giving it more air by tapping on the accelerator pedal, is the engine "revving up" because of this additional air ONLY, or is the ECM now being signaled to give more fuel, and that is what is raising the idle? I would think if the problem is too much fuel, then me giving it more air, is gonna give the engine even more fuel, and it would die out? Link to comment Share on other sites More sharing options...
adamzan Posted January 13, 2014 Share Posted January 13, 2014 I would check the ECU for codes (look in the how to section). Even if there is no engine light a code can still be there. You can check the IACV with a multi meter, it is in the service manual, which you can find in this section too. I believe the ecu takes over after the engine has reached a certain temp. It is fairly quick on warm days. Link to comment Share on other sites More sharing options...
ahardb0dy Posted January 13, 2014 Share Posted January 13, 2014 The butterfly and the inside of the throttle body could be dirty, not allowing enough air through when the butterfly is closed so it doesn't idle. When the butterfly is closed it is designed to let air through so the engine can run, over time dirt builds up on the edge of the butterfly restricting the amount of air that can pass, so when you start the engine cold and it doesn't want to idle by "giving it gas" you are opening the butterfly to let mover air through. Have you downloaded the free Factory Service Manual ? Lot's of diagnostic info in there, also have you checked to see if there are any codes in the ECU? When was the last time a tune up was done? Gas filter, air filter, PCV valve? I would check for codes first, if none check the TB and butterfly, than reply back, good luck. Link to comment Share on other sites More sharing options...
peejay Posted January 13, 2014 Author Share Posted January 13, 2014 (edited) Great! Ok, more info: new plugs were put in about 500 miles ago... just did a new fuel filter and new pcv valve about 100 miles ago... i did a "power balance test" recently on the running engine to try and diagnose a slight miss...well, i think that test messed up my injectors! because after the test, those two injectors (#2, #5) were giving me a code 51 (injector circuit)...coincidentally, those two cylinders were the only ones i was able to remove the plug wires on while running! bought two new injectors, replaced those... air filter "looks" clean... throttle body "looks" clean (i haven't looked at the sides of the butterfly to see if it's gummed up) oh, put a can of SeaFoam in the tank about a month ago, too...haven't tried it in the intake yet some google searches said it could be a weak fuel pump? could that be it? i do have FSM (and the Haynes!), they and this website have been of great help! I'll check again for codes... i'll also mention that i do think i can detect a strong fuel smell, not sure if it goes away as the thing warms up or not...could this be a too-rich engine? can an engine ever be too-rich when cold, short of flooding it? Thanks for your replies! Edited January 13, 2014 by peejay Link to comment Share on other sites More sharing options...
ahardb0dy Posted January 13, 2014 Share Posted January 13, 2014 The other things that come to mind are Oxygen sensor and MAF sensor. Were there any codes other than the "51" Link to comment Share on other sites More sharing options...
peejay Posted January 13, 2014 Author Share Posted January 13, 2014 ahardb0dy, been hearing alot about those two items, haven't checked them yet! i put a new Oxygen sensor in when i put new plugs in (had to replace the entire exhaust, and couldn't get the old Oxygen sensor out) "51" was the only code...before that, i was getting a "32" (EGR function) but i've fixed that...(it was doing the "dieing at idle" even with bad EGR, though) I will read (and perform) the FSM's test procedure on those sensors and report back, thanks! Link to comment Share on other sites More sharing options...
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