Hey guys-
My '81 280ZX NA with Auto tranny recently developed a flat spot at about 3k RPM. It pulls hard to 3000 and then again at about 3150. Engine is stock (F54, P79). For those of you with a manual trans, 3k RPM is about 65 MPH in 3rd gear in my ZX. I've checked my AFM swiper movement and also my TPS contacts and all seems well. Do you think this could be timing or fuel related?

Thanks in advance-

 

Does it A) do this all the time. B) only while accelerating (briskly) or C) only while cruising?

The reason I ask is to see if it's related to throttle position. The AFM could have an internal problem like a pit in the carbon track. I've got a post on fixing that one.It's pretty easy to do and I'm sure Rod's gonna jump on here and tell you to do it anyways so I'll just beat him to the punch Answer those questions and I or someone else can give you a more direct answer. Oh one more question: Since it's an auto this flat spot, does the tach keep accelerating and the car doesn't or is just like the car loses power and stutters real quick?

 

I only notice it when I'm on the freeway in 3rd gear. It starts at about 3k, and if I hold the throttle right at 3k or just slightly above then it feels like the car is decelerating until the rpm's drop to about 2950 then it will pick back up. It doesn't seem to do it in 1st or 2nd, but then again I am accelerating pretty quicly through those gears most of the time so it could still be there I just don't feel it as pronounced as when I'm on the freeway doing 65.

It started doing this in the last 10 days or so, after I replaced my alternator (bad IC regulator).

 

Sounds like it is most likely the Distributor... You might want to take a looksey under the cap and see if it's got the all-too-common 280ZX dizzy failure. If you see what looks like a ball bearing the size of a BB... That's bad. Also check to make sure the Vacuum advace is working. It could be something else of course, but this is a very common problem.

Rod.

 

Yeah I've had two distributors drop a bearing or two. Then the mech. advance gets stuck and the plate don't want to turn so then the vacuum advance cant pull the plate over anymore cause it's wedged in there. Then next thing you know the vacuum advance craps out cause it was too overworked and the diaphram ruptured. SUCKS but it definitely happens. Twice on the same car for me with two different distributors. Of course neither was new either though. Speaking of which, does anybody have a spare ball bearing they don't need. There aren't any Z's in the PnP around here and the reg. yards want me to buy the whole dizzy. I'll send you a nickel for it plus the shipping (probably just send you a dollar total for everything ).