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1986 Bronco 302, 1965 Ford Fairlane 289
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6 Posts
Discussion Starter · #1 ·
On this never ending mission to get this baby running right I now have a code 25.

Did some searching on here, found some posts saying if you have 2.4-2.6 volts at the connector you're golden.
The Haynes Manuel says it needs to be at least 5 volts with key on engine off. :eek:

I've got wiring gremlins for days. Kid I bought it from hacked everything up, and what isn't hacked is falling apart from age.

Had a bunch of ground issues, replaced all the battery cables, cleaned up as many grounds as I could find. Starts up perfectly even when heat soaked now.

Now my issue is I can let it idle in the driveway and get warmed up. Idles fairly decent. Drive it down the road about a mile, runs smooth. At some point it hits this invisible wall of loss of power and starts fluctuations in the idle right as you start to lay into the pedal slowly, I can let off the gas and it smooths out a little, I can stomp on it and it smooths out a little.

Now I've already tested and adjusted my throttle position sensor, no dead spots when testing.

The claim is that the knock sensor retards the timing when it sends a voltage signal to ECC, so assuming the knock sensor is bad and sending a signal to the computer causing this random loss of power, I disconnected the sensor and drove it around. Same result.

-----Unrelated to Code 25------
It's this weird bucking like it's going to shut off.
I've got a 65 Fairlane 289, when I first got it the gas tank had a hole in the top of it and the tank and never pressurized and the pump on the block struggled to feed gas to the carb.

This feels very similar to that, but the Bronco has a new tank, new in-tank pump, new high pressure pump and fuel filter. Pressure readings at the rail are good. Wondering if I need to hook up a vacuum gauge and fuel pressure gauge and run it down the road to see what changes when this strange event happens.
 

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29,116 Posts
Yo MATTYWATERS,
Iggie DTC 25, Knock not sensed during dynamic test.
The Dynamic Response code is a single pulse that occurs 6-20 seconds after the engine identification code. When/if the Dynamic Response code occurs, perform a brief Wide-Open Throttle (WOT). The dynamic response check is used on some applications to verify operation of the TP,S MAF or MAP & KS sensors.

YES! Hook up a vacuum gauge with extended hose and fuel pressure gauge with extended hose "...and run it down the road to see what changes when this strange event happens"!
I used to snake hoses up to wiper arm so I can view the,; chock hood open but secured with rope.


See my Vacuum leak test in post #11 incl jowens126 HVAC Control Panel info & Mikey350 tests @ Help with dtc codes and idle

163112

GL!
 

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Registered
1986 Bronco 302, 1965 Ford Fairlane 289
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6 Posts
Discussion Starter · #3 ·
Thanks again Miesk5!

Here are the results from riding around with the gauges hooked up.
Fuel pressure stayed within spec, but did fluctuate with engine vacuum due to the fuel pressure regulator.

Here is a video of what the vacuum gauge showed. I cranked it up, got it to temp, rode down the road, then this started.
I can let off the gas, it'll coast fine with no fluctuation in vacuum or idle.. Found out once this starts I can replicate it with keeping one foot on the brake and slowly accelerate.

 

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Yo Matt,
I have no sound on my ancient tablet so I'm trying to determine if it's a valve issue or engine misfire. I use this the vacuum test readings at 1996 Bronco/F-Series

if that needle drop happens while accelerating, checks foe an exhaust restriction.
 
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