Bucking/Backfire problem. Even read Archives!! Help.

[Jon Pennington]

FauxZ said:

> Howdy,

That's my line, stranger. ;)

> via your web sites.  I'm also a member of SOGI (Supra Owners Group Int.)
> and se-r.net blows our main site away.  Bravo.

Boy; strong words.  SOGI used to have a similar Master:Monkey ratio as
SE-R.net, but with a MUCH larger membership roster.  Glad to hear you like
it here. :)

>  Plugs, wires, cap, rotor and new O2 sensor.  All this was a bust...   I
> checked the timing last night and found it past the 20 mark (did I
> mention bad mechanics?)... It's back down around 15 for the time being,

Being a Supra guy, I'm going to assume that you know better than to use
non-OEM parts.  You did this tuneup with all Nissan/NGK stuff, right?  Oh,
and kick your timing back up to at least 17*; 19* if you run 91+ fuel.  No
point in cheating yourself out of free, safe horsepower. ;)

> and this has seemed to help, but not eliminate the problem..  I might
> have a problem with the PAIR Valve leaking under some throttle
> conditions but I'll have to check again after reading that it opens up
> on Decel..

That sounds like a reasonable guess, but what do I know?  My chassis/motor
only has 45k on it.

> The "bucking" is much more pronounced than a simple miss... At 15mph and
> 2k rpm it will rock your head forward (like fuel cut on a supra)

Ouch!  The knock sensor is ignored at WOT, so it isn't that, and it
wouldn't hurt nearly so much if you were "just" knocking, I don't think.

> helps)...I plan to check the MAF when I get my Multi-Meter back, but I
> can't seem to think of anything else except cleaning the Injectors...

Sorry, I forgot.  How much of the rest of the fuel system have you
examined/cleaned?  If it only happens under certain throttle/RPM
conditions, I'd guess it's not a pinched fuel line, and I'd lean away from
replacing the fuel filter, but it's worth a shot for a good shade tree
mechanic.  Shoot, you might try checking the voltage going to the fuel
pump while everything's torn down.  Have you tried dumping some STP in it,
just for giggles and snorts?

Do check the MAF sensor ground ASAP.

--
-=|JP|=-        "Stays Fresh Longer!"

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