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72rolls

95 F150 stalls as soon as it starts to move

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1995 Ford F150 4.9L, fuel injected, automatic E4OD, 2WD. A am using an Actron CP9145 scanner. I have scanned, repaired and cleared all DTC's. All were engine related. It has not generated any transmission codes. The problem I have is the truck stalls as soon as it starts to move. The truck starts fine and runs fine in all gears as long as the brake is applied. As soon as the brake is released and the truck starts to move, it wants to stall. It acts like the transmission is exerting a load on the engine, causing it to stall. With the proper finesse, the accelerator can be used to keep the RPM's high enough to prevent stalling. Once the truck is rolling, it runs fine. It stalls when braking to a stop unless the transmission is shifted to neutral.

Any Ideas?

Edited by 72rolls
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72rolls...If this is EFI/ECU or engine related, it sounds like either the MAF sensor or the TPS.  The O2 sensor could be involved, but I would troubleshoot the MAF sensor and TPS before replacing the O2 sensor.  These devices may only show these troubles in live time view.  Test each of these devices in real time view while trying to simulate the stall/stumble condition.

Also consider an exhaust system restriction...Worth testing at least.  Cat or muffler internal clogging could create too much back-pressure.  A vacuum gauge on the intake manifold can be a revealing test.  See what happens to manifold vacuum as the stumble occurs.

Let us know what this turns up...

Moses

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Moses,

Thank you for taking the time to respond. I will try these suggestions.

If the transmission was generating any DTC's, would they be read by using my scanner the same  as I do for reading the engine DTC's or are they accessed some other way? I ask because it seems as if the torque converter is locking up at low RPM's causing the engine to stall. 

Thank you,

Larry

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Larry...I considered the converter but ruled that out when you shared that the engine idles properly in gear with the brake set.  If the converter was locking at standstill, you would have an immediate stall of the engine.  If you do have a converter lock-up issue, however, the vehicle speed described is just taking off.  If the converter locks just as you begin to roll, there may be an issue with the VSS or the speedometer sensor.

I'm unclear whether the CP9145 is for engine diagnostics only.  You have a transmission control module.  Explore the parameters of this tool.  You may need additional scanning of the transmission.  If this tool is for "powertrain" diagnostics, it should cover the engine, transmission and even the VSS controls.  If you get a speedometer or VSS code, that would be consistent with your hunch about the torque converter lock-up.

Before replacing parts, inspect the wiring and harness plugs.  A short or open could create symptoms...

Moses

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