Stalling on Acceleration AND Deceleration

Keith Browning · December 10, 2009

1999 F450 7.3L 6-speed ZF. Intermittently comes and goes: Trans in NEUTRAL, tap the accelerator to make the RPM's rise about 1500 and the engine smoothly but immediately stalls. I later noticed that when this is happening, if I press down on the accelerator the engine also shuts down as the RPM's rise past approximately 2000 RPM. The engine starts right back up and it runs well otherwise.

Oddly, I discovered that if I turn the ignition off and then back to run before the engine completely stops spinning it WILL catch and idle.

No DTC's. All parameters appear to be in the normal expected range. Passes KOEO, KOER and Injector electrical self test. Fuel pressure is 40. It acted much like a sticking IPR so I looked in that area... it now has a new IPR, a known good ICP sensor and for giggles I installed my test IDM. No dice. The only thing that I *THINK* may provide a clue is that the LOAD PID goes to 0% and fuel delivery changes significantly, don't recall off hand... I should make some recordings to share.

At this point I am stumped... haven't contacted the HotLine yet and thought I would run this past you fellas.

Any thoughts?

Bruce Amacker · December 10, 2009

I'd start with basic electrical on this one. Batteries, connections, ACV, voltage drop powers and grounds, and then install a BOB to check waveforms and voltages. You could jump to the AP sensor and test/replace it with a known good, but my hunch is that it's base electrical.

Good Luck!

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Fordracer · December 10, 2009

I assume it has the new style cam sensor in it already but I had one do this a few years ago that had a new aftermarket cam sensor in it.

Keith Browning · December 10, 2009

Yes, as a matter of fact I also replaced the CMP knowing that we have had troubles with thew new ones as well.

exmod110 · December 11, 2009

check the vss.... the alt can mes it up when defective showing 160mph or some thing like that, and shuts it off seeing an overspeed. Had this on one several years ago... hard to figure out...

Keith Browning · December 11, 2009

I'd start with basic electrical on this one. Batteries, connections, ACV, voltage drop powers and grounds, and then install a BOB to check waveforms and voltages. You could jump to the AP sensor and test/replace it with a known good, but my hunch is that it's base electrical.

Good Luck!

Truck has one almost new battery and one very new battery. The VERY new battery had loose terminal clamps at both posts and BOTH batteries had dirty terminals on the inner part where contact is made. I cleaned all four and secured them. So far the shutting down has subsided... another recheck tomorrow will make me feel better that I solved it. The newness of the batteries suckered me into thinking there was no problem there. Then I went a lookin. Posted Image

Another example of "CLEAN POWER!"

LARRY BRUDZYNSKI · December 11, 2009

Ahh yes another bad battery connection. OUCH

dieseldoc · December 11, 2009

For whatever reason I had to work on a terra-gator(fertilizer spreader for ag applications) with john deere engine. Slow on our side, something to do beats going home unpaid. They brought it to our shop because we are the dealer for them. Check engine light comes on and engine goes into derate. John deere dealer had 5 service calls to repair this concern, couldnt fix it. There was lots of new sensors, modules and harnesses hanging on this thing. Remembering all the times we have talked about this, that is where I decided to start. I found the batteries are 10 years old and the battery connection about as crusty as can be. I took them apart to clean them and found one positive bolt broken. Installed new batteries (failed load test). I cleaned connections and installed a new bolt. Low and behold I can no longer duplicate the customer concern. The customer hearing what we did to fix it is extremely pissed off now. I am glad I dont work at the john deere dealer cuz this guy is gonna go huntin deere I think.

Bruce Amacker · December 11, 2009

I've seen it and been burned too many times by bad batteries and base electrical. I just changed three batteries in my family's cars yesterday for PM because they were 5+ years old. I've seen students chase gremlins and hang parts like crazy for bad base electrical. I think I sold a car a few decades ago for a bad battery because it would stall and not crank sometimes. After 5 minutes everything would be fine for a few weeks.

Man, I could tell you some weird stories about base electrical problems and complaints. The young guys in class think I'm bullshitting, but I shit you not......

Keith, I've got my fingers crossed your luck holds out.

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Keith Browning · December 11, 2009

Keith, I've got my fingers crossed your luck holds out.

Seems to be fine now. Posted Image

Alex Bruene · December 12, 2009

Not so long ago, I had a 2000 F550 7.3L that would not start at times. It came from an indi with a new PCM, IDM, HPOP, IPR, ICP, glow plug relay and lift pump for an intermittent no-start. I guess since there were no parts left to throw at it (other than batteries) they gave up. It took me the better part of 5 minutes to find the modules were not turning on because the voltage was dropping down to 8v when cranking... 2 batteries later, it was all good! It was summer, and by listening to the cranking speed you wouldn't have suspected batteries, but they were both pooched.

Bruce Amacker · December 12, 2009

by listening to the cranking speed you wouldn't have suspected batteries,

I've been burned by this, too, and always stress the importance of checking cranking speed with a scan tool. 7.3- 175 warm, (150 cold minimum), 6.0- 215 warm, (175 cold minimum), 6.4 250 warm, (200 cold minimum).

You can't tell if it's cranking fast enough by listening to it! 7.3's will start hard cold at 135rpm in our climate.

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Mikill · December 12, 2009

I have also had a 7.3 come in from an independent shop that just installed a pump and ipr for a no start. Two batteries later the truck was up and running fine.

cbriggs · December 14, 2009

I recently had a 6.0l with 15/40 in it, at -20`c could only reach 65rpm with a 1700 amp booster and a 90 amp battery charger on it. ( and good batteries in it)

jimmy57 · December 15, 2009

Gear reduction starters have done in some really good techs over the last few years. A few years back I was talking with a field engineer about the rash of start-stall problems on our vehicles. He had been working with lots of seasoned techs at different dealers and many different pats and pieces and procedures had been tried. I asked him what the voltage on problem units was when cranking. He said "I've asked several of the guys and they all say the engine is spinning over fine". I reminded him of the geared starters and the fact that adaptive fuel trims are held by sufficient batt V in the KAM. FE called a guy back with one sitting in his stall on that day and the batt V cranking dropped below 9 V. New battery did the trick.

Alex Bruene · January 25, 2010

check the vss.... the alt can mes it up when defective showing 160mph or some thing like that, and shuts it off seeing an overspeed. Had this on one several years ago... hard to figure out...

THANK YOU! I just had this exact issue last week. I'm glad I had the opportunity to have read of this prior to having it happen. I'm sure I would have figured it out, but I don't know how much hair I would have lost doing it!

Cheers! Posted Image