QuestionQUESTION: Hello! I have an 88 Nissan pathfinder, 3.0 V6, telling me one of the injectors (TBI) are bad - computer code 51. But, I took them off and had them tested, and they were both good. What could be causing the computer to say I have a bad injector when it appears to be not the case? Or, how can I get the computer to bypass the failsafe mode, which it doesn't allow me to go past 2750 RPM? Thanks, Scott
ANSWER: Scott,
A noid light and hook it to each injector circuit and see if the light flashes. You see, I think the injectors are fine and the problem is with the harness or connectors. The code 51 says the injector circuit and not just the injector so you will want to see that the circuit is firing the injectors properly. Email me back if you need more information.
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QUESTION: Thanks for the answer! I had the injectors tested and cleaned at a place called Dr. Injector in Tacoma. I put them back in, and one of the injectors did not work. I switched the wires, switched the position of the injector, changed the computer, and spliced new wires from the computer to the injector, and one of the injectors still did not spray. So I took that one out, put in an injector I bought from an auto parts store ($400!!), and lo and behold, both injectors worked, the failsafe went away, and the computer code said 55. However, now the vehicle idles VERY erratically - fluctuating between 1000-2000 RPMs continually. There are no vacuum leaks, fuel pressure is good, ignition timing is good, noid light checks out, choke functions, engine only has 115K miles. I even switched out computers with no change. What would cause the idle to go so bad immediately after replacing the injectors? (it idled very well before, even though it was on failsafe mode) I'm baffled... ALSO, I took the "bad" injector back to Dr. Injector, and he showed me it working fine on his diagnostic machine. It seems he must be giving this injector a different voltage or amperage on his machine than the Pathfinder, for how else can I not get it to work when attached to the vehicle? Anyway, I ordered another $400 injector ( I can always return them). Do you think two brand new injectors might stop this erratic idle?
AnswerScott,
The erratic idle would lead me to think the computer was in fail safe mode and that was where the steady idle was coming from. Pathfinders are known to have problems with the idle air control valve and the throttle position switch. I bet you could remove and clean the idle air control valve (stepper motor) and reinstall it and it should idle properly. The way the thing works is the throttle position sensor has a reading that lets the computer know it is time to go into the idle program. The throttle plate is closed and then the engine gets it's air via this idle air control valve. If it sticks or does strange things the car will hunt for an idle. With a Haynes manual and a digital volt/ohm meter you can check each sensor until you find the one that is defective. Now, if the idle air control valve passage is plugged or is hanging up you will get the hunting idle.
