Re: [alfa] spark plugs

["John Gallagher" <gallagher41@xxxxxxxxxxx>]

Ethan:
Check all air hoses for false air.

----- Original Message ----- 
From: "Ethan Schartman" <ethans@domain.elided>
To: <alfa@domain.elided>
Sent: Thursday, June 17, 2004 10:08 AM
Subject: Re: [alfa] spark plugs


> i've heard people mention their V6s "running like crap" with platinum
> +4s. exactly how crap?
> 
> i've been running +4s for almost as long as i've owned my milano gold
> (4 years, 30k miles, or so) - long enough that i can't remember what
> it was like before i put them in. and, since i put them in i've had a
> peculiar acceleration problem (but they went in during my first
> re-valve, so there were too many other variables to eliminate). the
> problem is that below 1500rpm (in first, 2000 rpm in 2nd), if i lay in
> to the accelerator i develop a stumbling with very poor acceleration.
> if this happens, i just pull my foot off the throttle, and slowly roll
> back on. the motor "catches its breath", so to speak, and it goes
> fine. above about 1500 i don't have this problem.
> 
> the problem is not engine temperature dependent, but it is erratic -
> some days it is worse, some better. it seems to have a sweet spot when
> the external temp is about 40 degrees F where it is reduced or
> eliminated. above or below and it is back. its been a while since i
> reset the timing to stock, but advancing the ignition timing reduces
> the problem (Fred D suggested this when as a test of proper combustion
> back when i thought it might be an injector mis-spraying).
> 
> other data: all grounds are freshly cleaned, coolant temp sensor is
> good, afm is good (also swapped with other afm to double check),
> throttle switch is good, fuel pressure regulator is good (as of 3
> years ago when i replaced it), fuel filter is new, cold start valve
> doesn't leak, injectors were recently swapped with other used ones
> (the V6 they came off of ran fine), intake runners, and injector seals
> are good, intake air hose has no cracks, O2 sensor reads about .6-.7V
> at idle (seems to be within spec according to the "how to tune bosch
> fuel blah blah" book, plug wires, cap and rotor are new, compression
> is fine, valves reasonably within spec (no intake is more than .005"
> out of spec, exhaust are within .001"), cam timing is set properly,
> ignition timing is set to stock, cat is fine. no problems with hot or
> cold starts.
> 
> so, some things i am thinking about checking next: fuel pressure under
> load, double check proper functioning of intake air temp sensor,
> voltage at fuel pump (make sure its got 12V), advance the ignition
> timing again to double check original results (not a solution for the
> emissions test, though). other air hoses are way old, but i have seen
> no signs of their leaking (propane check) and false air doesn't seem
> to be consistent with the symptoms (they are on the list of eventual
> replacement, though).
> 
> so, should i add the plugs to my (short) list of possible causes? if i
> swap them, what kind should i put in? any other suggestions?
> 
> thanks,
> -ethan schartman
> -87 milano gold
> -princeton, NJ
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