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Thread: 78 280Z, bad AFM? Anyone have one?

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    Default 78 280Z, bad AFM? Anyone have one?

    Replaced the intake gasket of my 78 280Z only to find the car no longer would run well. When I take the hose off the AFM, it runs strong. I figure my AFM is bad which is probably why my intake gasket blew out (so the engine could breathe). Thoughts? Anyone have a 5 pin, 3 bolt tested AFM for sale?
    Thanks!
    Jeff Woodard

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    That is some different kind of logic there. Which hose did you remove? What do you mean by "no longer run well"? Did it run well before you replaced the intake gasket?

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    which hose? the one from the air cleaner or the one between the AFM and the throttle body. I am thinking if You're engine runs good with the hose removed it may not be you're AFM, and I doubt that a bad one would cause the gasket to blow. does the flap inside move smoothly? I would do more testing before searching for a very expensive part.

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    The car is at a fairly competent shop specializing in Nissans. The intake gasket had been leaking but recently got much worse. They replaced the gasket but found the car didn't run well after the work. The mechanic is able to unplug the hose between the AFM and the throttle body and the car runs great. The AFM that was on it was a rebuild unit from Z Car Source. I picked a replacement up from Advanced Auto but it was a 4 bolt unit whereas the original is a 3 bolt. Didn't matter, didn't make a difference so I returned it to AA. That's where I'm at.

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    It's probably running rich. Without the AFM, the ECU only adds idle enrichment fuel. When the AFM is attached the extra fuel from the flap movement probably makes it extra rich. Your shop should check the coolant temperature sensor for function and make sure that they didn't accidentally connect the sensor plug to the thermotime switch by accident or leave it disconnected. Two plugs on the thermostat housing that look the same but have different functions.

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    Registered User grantf's Avatar
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    I second what Zed Head said (that rhymes!) about the two sensors, It is an easy mistake to make and one that could very likely occur after putting the intake manifold back on and reconnecting everything, I know, I just whent through this about 3 months ago. Again test before just buying a new AFM, it may just need to be adjusted or cleaned. Also does this shop that specializes in Nissans also specialize in "old Nissans"? Try this: take the hose that leads from the air cleaner to the AFM off and hold the flap shut if this results in the same condition as removing the AFM to thottle body hose being disconected (meening it "runs just fine") than that would indicate a very rich running engine and somthing else is amiss. It just sounds like the AFM is not the problem.
    Last edited by grantf; 12-28-2011 at 07:32 PM.

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