Mechanics

STALLING/LOPING IN GEAR

1992 Ford F-150 • 236,000 miles

I've had the motor stall out on me a few times when I put it in reverse. It's not a constant thing and it's happened both hot and cold. The RPM's drop slightly when it's put into gear. As in it's noticeable without a tachometer. I've changed the IAC valve, cleaned the throttle body (w/o disassembling it), cleaned the electrical connectors on the throttle body, and changed the transmission filter (heard they have a habit of dropping and causing this). Once out on the highway, the truck drives great for the most part. Though it does lack power when going up steep inclines, but hey, it has 237k miles on it. Looking for other suggestions to nail this problem down. I'm in the process of getting the money together for a motor, but being it runs fine on the road, I'm guessing there's another issue when at idle and putting it in gear.

Almost forgot, both in-tank fuel pumps have been replaced, as well as the fuel filter.
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MStrawder
May 20, 2013.



Check for a vacuum leak spray choke cleaner around and make sure bothsides of throttle plate were cleaned. Check intake vacuum if 15" or below at idle suspect clogged converter. Check fuel pressure it could be either high or low causing the problem.

Hmac300
May 20, 2013.
Just as an update. The plates are as clean as I can get them and I just checked the vacuum. I bought a combo tester that was supposed to do fuel and vacuum, but it doesn't test fuel pressure, just fuel pump pressure. Also, took it out driving today and it wants to stall all the time when I'm at a stop and it's in gear. I just changed the transmission filter yesterday and I'm 99.99% sure I put it in as snug as it will go.

Tiny
MStrawder
May 21, 2013.
Fuelpump pressure is fuel pressure, what was vacuum reading at idle off of intake was it low? The rpms should drop slightly when in gear as it is engaging the clutches in trans. What is idle speed fuel pressure shold 35-45 with key on engine off unless it's a 4.9L

Hmac300
May 21, 2013.
It is a 4.9. The vacuum was around 20-22. Didn't drop steadily during acceleration, but did drop suddenly when 'bumping' the throttle. I was told that's good. The gauge I bought said vacuum and fuel pump pressure, but only goes to 10 PSI for the fuel side. I assume to test check valves. I dropped the transmission pan again and the filter I installed yesterday was loose. Tapped her into place again (seemed to 'catch' this time), started it up, going through the gears, and no stall, but still a bit of a drop. Going to take that gauge back and get one that can definitely test both. Will let you know the fuel pressure then.

Tiny
MStrawder
May 21, 2013.
4.9 is 50-60 psi with key on engineoff. The one you got is for carbureted cars for f.I you'll need another gauge altogether.

Hmac300
May 21, 2013.