My dump truck has been giving me some troubles lately, I will be driving and all is fine. Next time I depress accelerator it falls on its face, if I try and step on gas it actually slows down, when I gently let up on the peddle it comes back to life. seems like it wont go over 2400 rpms and about 25 mph. I replaced fuel pump in tank, fuel filter and some vacuum lines. all was fine for a week then it started again. I again replaced fuel pump under warranty, and ran great for a week hauling equipment and tons of materials, Bamm! on the way home it starts again, can barely get back home, shut it off, next day runs fine for a couple miles, No load, then starts acting up again! I'm looking at rewiring the pump? possible voltage drop or spike? I just don't know, we tested pump pressure and it was fine, oddly it had very poor volume, no kinks or problems we can visually see with fuel lines etcc.. any thoughts or ideas? think I may have to must resistance in wiring? Thanks for any leads, Bruce
Gas tank is very clean! seems like I have a "sweet spot" on the gas pedal, about a quarter pedal and all is fine, a tad more and it slows down? oddly in neutral it revs just fine, first gear no problem, 2,3,4, andOD is when the throttle problems arise.
It may seem unrelated but check your coils at each spark plug. When mine (99 E 150 Triton V8) started to fail I had symptoms similar to yours.
thanks Lee, most of the coil packs have been replaced, but will be going over all electrical stuff, wish it would have happened during Jan/Feb while work was slow! will a coil fire intermittently as it is going bad? I thought they would just quit.
You need to use a scan tool to check for trouble codes and check data. The worst thing you can do is start throwing parts at it. With the poor quality of replacement parts, you may be creating more issues. than you started out with.
No codes found, two different times. it was a Motorcraft pump both times. It is Now at my friends auto shop and even he is having trouble with it. We brought in a Ford tech. 30 years experience, to no avail yet. Keep the Ideas coming Cuz I'm getting ready to shoot it!
On our V-10, the coil boots dry rotted and cracked. You get a bunch randomly misfiring, its like being up against a rev limiter. In my case, they weren't misfiring enough to trip the light though
thanks Jason and Bob, New catalytic convertor, new plug wires, plugs and coil boots. when it happens, I have pulled over and shut it off, then restart and runs fine for a few miles, then problem is back! Any thoughts on why it would have good fuel pressure but no volume? as far as I know ( and my shop) the fuel system seems to be in good order, that's why we keep leaning towards electrical supply to Fuel pump is erratic, checking on that today!
Rare to see a fuel pump that has correct pressure and low volume. Have you taped a pressure gauge to the windshield to see what happens when it loses power? Does the pressure drop? BTW, 99 450 probably does not have a misfire monitor, so misfires may not set the light or store a code. If a coil(s) is going bad, it usually will buck a bit, not just lose power. I would be suspicious of a voltage drop to the pcm. partly broken wire will only carry current for a short time.
thanks Steve and Ben, appreciate the Ideas and will use them all to figure this out, will check out MAF if we haven't already, and the fuel gauge on the window is a great thought as well. thanks for the Help gang! when running, truck does not sputter,or feel like electrical interference, when depressing the Gas pedal it takes off just fine in first gear, then shift into 2nd and if you push the pedal more than a quarter of the way it falls flat, let up just a tad and it comes to life as normal, weird? when acting up, I cant even pull a empty trailer!
ECU? I had a 2000 years ago, I vaguely remember some issues with a control module located behind the drivers side wheel well, I think?????
I know our mustang goes into limp mode when it senses overheating. We had a head gasket issue that heated the water where the sensor resides. It would subside when it cooled down. Maybe you have a bad temperature sensor or connection making the computer evoke limp mode? Cheryl
Does your “Ford tech with 30 years experience” happen to have IDS? That would certainly make short work of determining whether you are having a misfire issue or fuel issue. One of the most useful features of IDS is the live power balance test. You can do a lot of diagnosing without even opening the hood, sitting in the driver’s seat with IDS and a laptop. Mode 6 data is also very well-layed out on IDS.
At this point you need a new mechanic. 3 fuel pumps with out proper diagnosis is a waste of time and money. Fuel pressure gauge when driving is 101 stuff. Start there.
