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post #1 of (permalink) Old 03-01-2017, 09:39 AM Thread Starter
Thomas A
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Join Date: Jul 2002
Location: Overland Park, KS
Age: 34
Posts: 858
Stumbles upon initial Acceleration?

Been dealing with this issue for a while and am running out of ideas.

1997 Thunderbird 4.6L
AED SuperCharger 103k miles

When I first attempt to accelerate with the engine cold, it stumbles all over itself. It will do this for about the first 2 minutes, then the issue goes away completely. This is just normal acceleration as I pull away from the driveway and make the turn onto the first couple of streets to get out of the neighborhood on the way to work.

By the time I get to the first stop light, it accelerates perfectly fine, no issues. Operating temperature isn't fully warmed up, maybe up to 100 degrees at this point. I can watch on my scan tool to see if I can pinpoint that if it matters. Doesn't have even the slightest hint of this issue until I go to leave from work after the car has sat all day. Exact same thing, first few accelerations stumble really bad, then it clears up.

I don't believe it is a misfire issue; no backfire and no codes, and idles perfectly even when first started. Any thoughts on what to check. Mechanical issue or an issue with the tune perhaps? I have two different tunes from two different people, and it acts exactly the same with either one, so I am leaning towards a mechanical issues of some sort. I have searched out and tracked down any possible vacuum leaks.

During the past 4 months I've replaced the following:
Plugs & Wires
Fuel Filter
02 Sensors
IAC Valve
Intake Manifold Gaskets
Cleaned MAF
Harmonic Balancer

Its very consistent. Does this every time on cold start, regardless of outdoor temperature.

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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