WEIRD SURGING IDLE

Shocker10101

New Member
Jul 11, 2019
7
0
1
Virginia
Hey all,

Little background first. Just had long tubes and 2018 intake manifold with lockouts installed on my 2014 GT. New Dyno tune in but I'm having some weird idle issues every time my AC turns on or my cooling fans turn on. Check longtubes for leaks and all rest of exhaust system. Have checked all vacuum lines for leaks and looked for cracks in the manifold itself. Cleaned maf and throttle body to be sure. Cylinder 1 seems to cut power for a second after the AC or fans kick on but no misfire code. Tested wire voltage and all is fine but it will randomly cut power for a second once fans or ac kick on. Same with the injector in cylinder 1. Same thing seems to happen to the fuel in cylinder one when ac or fans kick on. Plug in cylinder one is practically new and looks absolutely fine and was working great before parts and tune were put on.

Is this a tune issue you think or some faulty electrical wiring somewhere?
 
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Hi Shocker. Your Mustang's problem sounds similar to a problem my 2006 GT had several years ago, so I thought I'd share in case it helps you. When my Mustang was a few years old, it started surging randomly. Always under 20mph and eventually when in park. It would do this when driving through parking lots, slow city driving, and when slowing for a light or stop sign. All this happened after the Mustang, over it's first few years, became gradually very slow to respond to the accelerator, then would peel out when the fuel hit the engine. It NEVER tripped a dashboard light and my trusted mechanic never found a problem during inspections, even when he was able to reproduce it. The problem was finally diagnosed after several years of this (and grew alarmingly worse - the Mustang would strongly surge forward while the brakes were applied hard), when the car stalled twice while driving down a (thankfully straight) steep hill. We immediately took it back to the mechanic, who told us to take it to a Ford dealer we trusted. It turns out the gas line from the tank to the engine was being compressed and worsening with time. That's why the acceleration response was slow, then it would surge when the fuel got to the engine. It was a $400 fix, but it has never done it since and that was maybe 4 or 5 years ago now. I hope this helps you!