Does your V6 do this... (Page 1/3)
donuteater306 JAN 25, 03:33 AM
Is it normal for a Fiero V6 to feel like it's got a misfire when in neutral and just lightly holding the gas right at tip-in?

After years of mostly trouble free, daily driving...2014 brought on weird issues with my 87 V6. Mis-fires, EGR codes, oil leaks, crappy TPS sensors, etc. After making all of these repairs, I'm now dealing with what sounds/feel like another mis-fire occuring just at tip-in on the throttle. My grounds are all clean and tight, i've replaced all of the typical tune-up stuff (plugs, cap/rotor, wires, fuel filtel). Is this something that they all do, and I just didn't notice before? I dont notice it at higher RPM's and it seems to run great otherwise. Thanks for your help.

Gall757 JAN 25, 09:16 AM
Does my V6 do that?.....No. but I wonder what 'tip-in' is exactly?
donuteater306 JAN 25, 11:32 AM
Tip-in is when you just, lightly touch the throttle. Slightly tip your foot into the gas pedal. For my car, it's bringing the RPM's up from idle "1,000" to 1,500-2,000. When I do this, I get what feels like a misfire that seems to disapear as the RPM's climb. A real PITA when chugging along in freeway traffic.
Gall757 JAN 25, 01:11 PM
Can you see the tachometer dip or wiggle when this happens?
donuteater306 JAN 25, 01:15 PM
Yes, the tach is reacting to the RPM changes.
Gall757 JAN 25, 01:25 PM
The thing about the 60*V6 is that it is so well balanced, that it will run on 3 cylinders. You can pull IGN 1 fuse or IGN 2 fuse and start the car. It would be interesting to see if the problem is still there with either fuse pulled.
85 SE VIN 9 JAN 25, 01:30 PM
Could your gas tank filler be rusting through? This would mess up the vacuum. Does the gas overflow or leak when you fill to the top?
Spoon JAN 25, 01:42 PM
As far as I can remember "Tip-In" was a term used with Carburetors. I don't believe it applies to fuel injected engines.

You may want to check your ignition timing with the engine in closed loop mode. Look for cracks in all those vac lines under the intake manifold.

I've experienced the same problem you have but that was with carbs. A plugged air bleed or problems in the enrichment circuit can cause these off-idle or transition problems.

No doubt some of the guru's will chime in later.

Spoon

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"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut

donuteater306 JAN 25, 02:09 PM
Thankfully I do not have rust issues. But the tank was down a few months back for a fuel pump. I'll double check the connections at the filler/evap lines.

It was acting up similarly to this prior to the fuel pump, and tune up. But far worse. before the tune up, if I tried to rev the engine in neutral it would just bog down at around 2-3,000 rpm. That said, it's hard to say whether or not this is a new issue, or if it was slightly masked by new ign. components.



cmechmann JAN 25, 03:47 PM
Tip in was the term of the action of moving the throttle off idle position when ported vacuum would come into play. On carb cars there was an issue when coming off the throttle circuit and increasing air flow into the venturi. If there was any restriction in the venturi circuit or weak accelerator pump, there would be a hesitation until more air flow would overcome the restriction.
Sometimes that was caused by intake and exhaust design flaws. Sometimes tip in response was sacrificed to be better at full throttle, cruise, idle, responce.
"Tip in" also used to be caused when there was a bad primary wire in the distributor and when first applying ported vacuum to vacuum advance would cause a stumble. Though it wasn't the carb "tip in" problem the term was still used for a stumble/hesitation at that part of the throttle. Latter when fuel injection came into play tip in was still used as a term but really wasn't there. On K jetronics it was used to to describe the stumble due to the small amount of time it took the air flow meter to react to the changing air speed causing a "tip in" stumble. We later called that Luft/lift lag. That was later fixed with Mass air flow sensors.
Most tip in response problems now are from small glitches somewhere else. Just examples. sticky pressure regulators with dirt or vacuum problem, low fuel pressure normally due to plugged filter,(causes slight fuel starvation until injector pulse width overcomes it), small glitch in TPS or MAP/MAF sensors causing false reading at time of "tip in", and sometimes ignition, Bad tach filter, Ignition module causing wrong coil saturation, weak primary current causing weird coil activity. Secondary ignition problems normally show up under load. But have had secondary do weird stuff because of things like wrong heat range/reach and fuel/oil fouling. And the hardest to find find are breaks in wiring causing intermittent problem but won't be consistent. The stuff like, engine moves back 1/4 inch it stumbles but more(under load) or less(idle) runs great. That used to drive me nuts on older J body V6 cars. Most of the time ended being where multiple power wires or grounds are met together in the harness.