Ford 7.3L Power Stroke (1999-2003) :: RPMs Dropping When Coasting - Cruise Control Is On
Apr 19, 2017
RPM's are dropping way off when coasting downhill while towing (as if the motor shut down), CC is on and maintaining desired speed. When at the bottom of the hill, all of a sudden, with a big bang(in the motor) the rpm's have came back up and you drive on down the road as normal. This seems to happen only when towing. "99 F250 7.3 I haven't pulled any codes as of yet. Whats happening?
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I recently started noticing that when I am coming to a stop(usually a quick stop), the trucks rpms drop to low. hard to tell how low but looks like around 450-500 rpms. I can feel the truck struggle just for a second then the rpms bounce back to 650-700. i was sitting in my truck while in park and was revving up to about 1200 and then let off the pedal and it died. My positive battery terminals are getting pretty bad and am going to replace them soon(waiting on parts). Could this be the cause?
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This has happened 3 or 4 times now while driving down the road. Just cruising down the road the CC will just cut out. I'll hit the "set accel" button on the wheel and all is good again until it randomly decides to do it again.
The only thing I've changed recently is the rear end speed sensor to cure the ABS light. I wouldn't/didn't think this would have any effect on the cruise control, but IDK, maybe I'll put the original one back in and test it.
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Cruise just stopped working. The fuses all check out ok. What would be the next simplest thing that I could check before turning the problem over to a mechanic?
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So the PO tells me he was flying down the highway and went to cancel his cruise control and it wouldn't turn off. He claims he made it to the shoulder of the highway and killed the ignition. When he restarted the truck is was turned off and it hasn't been used since. I tried to use it yesterday but couldn't get it to work?
So I do the search and find out that the deactivation switch is most likely the issue. I just picked up a new one today and was curious if it is just a R & R thing or if it needs to be bleed off or something? Is there a need to test it or just change it out? Sound like something that would cause these issues?
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I have a 2001 f350 7.3 powerstroke electric shift 4x4 auto trans, truck cruise control just quit, no illumination at dash, when switched on, checked all fuses they are good, owners manual doesn't say much...
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Airbag light flashes on dash and then stays on. Cruise control and horn wont work. I cant find a blown fuse.
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OK, so a friend's F150 just went up in flames in his driveway and he told me that the problem was the hot link behind a plastic/ rubber barrier at the main brake cylinder. I had a recall notice on my old truck but since I left the US and took the truck I never paid much attention to it, thinking typical overkill. Now I already heard from another buddy who caught lit brake fluid dripping onto the front tire and got the fire out before it spread and looked up the info today. Looks like our trucks are affected. Best to unplug the harness that goes into the brake master cylinder will prevent this problem from occurring? I never use cruise where I am, the roads are too small and slow.
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All, i have an issue ( or at least i think its an issue) with my 99 f150 5.4. When i use my cruise control, i notice when i put on the brakes slightly to slow down, it feels like its not coasting because you can feel the engine still engaged and wont coast. I think this happens even without the cruise on. What this could be? I have the latest update on the cruise control harness. I believe that was for power always to it even in off, causing fires.
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So the truck has been stalling out and dropping power randomly, symptoms pointed to needing the 50 cent mod, changed the cps for cheap insurance and peace of mind just in case it wasn't the uvch, no dice. So last night I yanked valve covers for the first time here's what I did while I was under there, check my work.
1st I ohmed out injectors thru the 42pin harness according to tuglys sig link. My meter would only go down to a 0.4 when testing the test leads just to each other
DS injector ohms
#2 3.5
#4 3.4
#6 3.6
#8 3.6
PS injector ohms
#1 3.6
#3 3.6
#5 3.5
#7 3.6
DS glow plug ohms
#2 prong to ground 2" away 0.9 ; white connecting wire back to gp relay 0.3
#4 0.9 wire to relay 0.5
#6 infinity ohms up thru highest meter setting, checked multiple times and different ground spots,(replacing tonight) wire to relay 0.5
#8 0.5 wire to relay 0.5
PS glow plug ohms
#1 1.0 ; white wire back to relay 0.6
#3 infinity multiple tests as well (replacing tonight) wire to relay 0.5
#5 0.9 wire to relay 0.6
#7 1.0 wire to relay 0.7
Next up, ebp sensor was reading 1.9 higher than map/baro koeo, gently cleaning sensor earlier didn't work. Installed new motorcraft, will check it with Torque pro koeo once the batteries are reconnected
Next I checked the uvch connections which felt good, darn it, maybe a smidge of movement from the DS, but nothing halfway disconnected or anything. Hmm. I ground down the quarters to the top of his head and installed.
Next I torqued down the 4 bolts per cylinder of the rocker arms at 20 ft/lbs, all were perfect and snug
Next up, injector torque. I've read on here below 50, or 80 in/lbs depending on different threads and opinions that I would need to replace o-rings.
So I set the in/lb click torque wrench at 50 in/# and tested the wrench's click on the higher torqued rocker bolts, then checked all the injectors, all were good
Reset for 80in/lbs, tested, then hit all injectors, #6 almost budged but clicked immediately before the handle moved
Reset for 100 in/lb, tested on larger bolt, 2 injectors took a 1/8 turn;
Reset for official spec of 120 in/lb , tested wrench, all injectors took 1/3 to 1 full turn
Reset for 130 in/lb (above official spec, but highly recommended on here by those way more knowledgeable than me on our engines) tested on a larger bolt, slowly and carefully gave all injectors almost an extra 1/2 turn to click; whew, finally a relaxed sphincter.
At this point I knew I needed to buy 2 glow plugs today, replace, then I'll check all glow plug torque at 14 ft/lb in one go, so I got everything ready for a hot torque after I do glow plugs tonight ("unloaded" the torque wrenches) and finally installed the RiffRaff AIH delete plug. My cell phone's alarm went off to get the kids ready for school, so hit the snooze and got everything put up. Now for a nap, then buy 2 Motorcraft GP and check back on here before going back at it tonight.
I also checked the turbo for play in all directions, was nicely solid and spun smooth, no wheel damage. Up pipes and well basically everything exhaust under hood had zero signs of soot/leaks with inspection mirror.
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I do run a small battery maintainer during the winter months plugged into a three way with the block heater. Alright after sitting out side for approx 9-10 hrs in 22 degree weather I did these checks. Battery voltages at 12.55V and 12.6V on batteries.
Voltage coming into for was also 12.5V. When glow plugs activated I am getting 11V on the other side of the gpr. After cycling glow plugs battery voltages drop to 9.6V during cranking and as soon as she starts back to 12.5V.
Do these numbers sounds right? In my opinion isn't the drop to 9.6V during cranking a little low or is that the normal?
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Ran torque for the first time on my f250, I used it for diagnostics to see if i can find out whats causing the surging. At a red light sitting idle it shows my icp at 705psi seems high to me? I'm running a dp tuner, it was set at stock for this run. It starts surging between 35-50mph and when coasting at about 60mph, surges during light throttle or maintaining throttle at low speeds. If i go about 70mph and up it runs like a champ. Ive changed the tps(entire pedal assembly), uvcg connectors, icp and pigtail. No CEL comes on, torque shows ipr is good, working on hpop pid. I just bought the truck last month and haven't been able to enjoy it much since it started doing this. ...
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I just installed the Donaldson B085011 filter last night. I understand the swoosh noise when shifting is normal. But, I noticed a chirpping when coasting. I first suspected suspension parts maybe but after reading on here could it be surge? I've seen some videos of what surge sounds like and it does sound like that but most people say it only happens under load and I'm hearing it just coasting down my farm market road to a stop sign without hauling anything. I'm researching billet compressor wheels now. Am I on the right trail to resolve this?
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Yesterday coming home from Morgan Hill I noticed my injectors making a odd sound on all the down hills while coasting - IPR % would drop between 9.8-9% making it almost sound as if the motor was about to complete shut down, RPM range was 500 -800 rpm, ICP 450-550 but the motor almost had a sputter to it... no codes, lights and it didn't run weak or have a lack of power but I've never noticed it before ...
ICP is only a couple years old
IPR is about 1.5 old
Both replaced with OEM parts .. Is this normal - or do I need to start digging somewhere?
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My issue can be while driving with cruise on, or accelerating, the truck just losses power, then recovers. At idle, the rpm can, but not always, fluctuate.
There is no "misfire" when it happens, but it just falls on its face. I have NO diagnostic tools, and my injectors are not stock, so I am unable to unplug my DP.
My thoughts are to unplug the ICP and give that a shot? Meanwhile, I will put in a order for a elm327
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How to fix SES P0670?? I understand there's a whole procedure on checking fault.
P0670:GPCM Glow plug control module control line failure. Open/grounded circuit, open/shorted GPCM, failed PCM
But how did you resolve problem? replaced GPCM, found open circuit, short --if so where?-- or replaced with updated harness.
(4C3Z-12B568-AA connector upgrade kit as in picture)???
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Have to get rpm's over 2k before trans will engage, then in between shifts I either have to let off throttle or let engine rev over 2k to get trans to shift...
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I had a nice level straight stretch in front of me and engaged the cruise control. No go! I tried a few more times and it still did not engage, even with various button sequences. My thought was that this truck is a computer on wheels. So at the next opportunity I stopped and shutdown the engine, turned the ignition switch OFF and then restarted started the engine (and rebooted the computer). The cruise control works fine!
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I have a 6.7 diesel extcab longbed 4wd with the 3.31 rearend. I have been experiencing a surge primarily told by the boost gauge when using the cruise control unloaded and either or both going up a steady climb in elevation or headwind. It does not surge if I shift down to 5th. Does not occur pulling a load. Still occurs in manual mode and tow-haul mode. Does not occur if your controlling throttle with your foot. I find that it happens at speed of 65-70. It will boost to about 10 pounds then fall to about 3 and will continue this until maybe a hill or change in direction. It does not occur with a tail wind. I took it to the dealer today and ford had a new flash for the pcm and the tcm. Hoping that this would fix it but I don't believe it did.
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Just looking for comments on using the cruise control while towing? and what's the recommended weight for using the tow haul mode. The enclosed trailer I have is about 3300 lbs. taking it across the country empty. 2004 6 liter.
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I've tried everything I can think of to get my cruise control working again to no avail. I have a late 99 with a 6 speed. So far I have checked all the fuses with a multimeter, I've checked continuity from the harness under the dash through the clockspring to the switches, truck does not start without the clutch pushed in so the neutral safety switch works, has the upgraded switch and harness off the master cylinder. the previous owner said the cruise was intermittent about a year after they did the harness and switch recall on it. is there a way to test the harness and switch? I got a 1800 mile round trip coming up in about a week and I am gonna have a sore foot if I cant figure this out.
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