All, My 03 V6 3.0 Vulcan with Auto Trans and 229,897 miles will stumble and hesitate if I accelerate hard, or even attempt to floor it for a downshift. It will buck and stumble so I let off and it runs without any stumbles and continues to run OK. This will happen regardless if I am going uphill on a freeway on ramp or just driving on a flat road. I have noticed this on occasions as I don't floor it very often, only when needed. I also noticed that this happens regardless of the fuel tank quantity, It has done it with a full tank and with a half tank. Is this an early sign of a weak fuel pump?

I have recently (within the last 3K miles) replaced the spark plugs and coil pack, I have tested the spark plug wires and they test out OK, I don't have a check engine light on nor are there any fault codes.

Any help is much appreciated. Thanks!

 

Clean the maf.

 

Thanks Clappedout91! I knew I missed something, will try that and report back. :)

 

Alright so here is what I have done: As I was removing the air box cover to access the MAF I noticed that my air filter was dirty so I replaced it and proceeded to remove the MAF so I can clean it with CRC MAF cleaner on both sides. After assembly and subsequent drives I noticed a crisper response to the gas pedal but on the occasion of part throttle (half way pressing on the gas but not flooring it) I felt a slight acceleration, then a brief stumble followed by acceleration again. So still having some stumbles but not sure what next. RonD any suggestions? :) Thanks!

 

Here is another update, starting off from a stop with light throttle (normal acceleration) and I get a stumble as if I am running out of gas followed by normal running any thoughts??

 

Have you changed your fuel filter lately ?

 

2011 Superab, I replaced it (Oh, WOW!!) 4/27/2016 @ 208K miles. All along It seems like I just changed it but...... time flies. Thanks will order one and replace it again. Much appreciated :)

 

So here is another update, Thanks to 2011Supercab for the reminder I replaced the fuel filter. I am still getting the stumbling and or hesitation occasionally even during normal acceleration. The truck acts just as if it is running out of gas as it cuts out or stumbles is the best way I can describe it but even if I just keep my foot at the same pressure on the throttle it does it once or twice and than continues to run OK. Any suggestions from those that have been around these trucks for sometime as what it could be caused by? I had asked earlier if this was a sign of a slow or soft failing fuel pump but have not heard anything. Thanks for your time

 

Change the fuel pump, at them miles it has to have some wear internally only way to test is with fuel pressure gauge ... i replaced my pump at about 160k now almost 170k the other day i ran it too low on gas just 1.5 gall in tank before i filled it up...never do that again... getting back on the freeway 65mph it started bucking for a few seconds, i knew it was the fuel pump, bet it got overheated with running tank low.... no problems since then

 

Thanks for the response, what brand did you replace it with?

 

Use a Ford one, worth the extra money, there more because they're tested, the after market ones are not and most of them last only a year.

 

I got the DELPHI FG0872 $144-79 from rockauto.com... did not want to pay the ford price

 

Someone installed a Chinese Spectra brand in mine and it's still going.

 

Thank You all for your replies! Jeff R 1, funny on one hand you advocate the Ford one (and I agree the original Manufacturer parts do undergo rigorous testing to meet the stringent manufacturer specifications) and on the other hand you mention the Spectra :) I did replace my radiator with a Spectra but that was made in Canada, does that stand true to all Spectra products or.... as you said yours was Chinese

 

I only mentioned it because that's what some mechanic put on mine, I consider myself lucky so far that it's lasting, but I don't drive my truck much these days anyway.
And yes, it is made in China, the fuel line blew off when my Dad was driving it because there was no clamp on the rubber line. (mechanic didn't put one on)
When I pulled the bed, there was this big "made in China" sticker right on the top of the pump housing.

Spectra rads are made in Canada, I have one, but like any other company, they farm things out to save money.

If and or when the pump fails, I will put a Ford one in.

 

HT08, How's your repair project progressing? 4 months ago had a shop install a new timing cover gasket to deal with a coolant leak. Now i am dealing (maybe) with the same problem you are describing so really interested in what ends up being your fix. Best of luck.

 

mrgizmow, well things are on hold a bit as my truck was hit while parked and is currently in the shop, (nothing major) but new door skin, mirror and some new paint it will be just fine. It's the hassle of it all that gets me. I will update you when I get it back of what I end up finding as the issue is not consistent at all so I cannot always reproduce it.

 

Thanks so much. Mine is very reproducible with an extended push to the gas pedal. In the meantime will go through the basics. Good luck.

 

Engine stumbling and or cutting out under load, my solution. 2002 Ranger 3.0 with 87,000 miles recently presented me with some erratic running behavior. Normal around town running seemed fine but hard acceleration passing, freeway onramp inclines or long hills when autotrans kicks down the engine would stumble/cutout for a few seconds. My condition seemed pretty consistent under these conditions. After reading various posts i went about running injector cleaner mixed in two tank fulls of fuel. Installed new spark plugs, air cleaner, fuel filter and cleaned M.A.F.S. and throttle body with appropriate aerosol product. No codes were presented on the dash and code reader suggested no issues had been noted. As all my tools & shop had been destroyed by the Camp Fire in Northern Calif. a year ago it seemed to make sense to take the car into a shop for further diagnostics. The shop manager did a ride along with me and acknowledged the irraditic running under load. Seemed to be a 'transitional lean/rich condition' (my words) and he felt confident they would get me fixed up. Apparently they plugged in a laptop diagnostic laptop and went for a test drive (3x). No codes or any hint of a problem, fuel pressure was also checked. I was told they then tried something they referred to as a "sniffer" which seems to detect leaks around vacuum lines. Seems the Crankcase vent going from the passengers side valve cover into the intake tube that runs between air cleaner and throttle body was leaking as the result of a loose barb fitting where the tube connects to valve cover allowing air intake that would not be 'measured' by the mass airflow sensor. Truck now runs great. Will do a flow up within 2 weeks to confirm continued reliability. What the shop did as a stop-gap fix (no charge) is slide a section of 3/8" tube over each end of hard plastic vent pipe to seal. Motorcraft replacement from ***** Auto is $20.00 and will be ordered today. Hope this help others out and will in fact be the end of engine issues for awhile. Take care.

 

mrgizmow, that is Fantastic feedback and I am anxious to hear your 2 week review and update. I would also Love a part number and if possible a photo of the culprit. I just got my truck back from the body shop and will revisit this issue. I wonder if the shop discovered this by doing a smoke test or otherwise as I am in the planning of making my own smoke machine for these kind of situations. Thank You so much for the update. All the Best!

 

Rock Auto seems to present two MotorCraft Crankcase Vent options: Mine is KCV231 and a picture is included on website. Good luck.

 

I saw the part online and I know mine has a lot of weather cracking or cracking of deterioration from under hood heat cycling as mine had a bit more miles than your truck, my 2003 has 234K miles so I am sure it's in need of replacement. I don't have the truck with me at the moment but I will check tonight when I get home and confirm. Either way the part is not expensive so I can place an order for a replacement meanwhile. Thanks again for the response, much appreciated!!

 

Here is an update: I ordered, received and installed the new part (see old and new part in photos), unfortunately I tried it out on a freeway on ramp and I still experienced the brief cut out, stumble, hesitation whatever you want to call it. I did notice some sweating around the grommet where the PCV Valve sits in the driver's side valve cover, so I will order that one also and see if this will improve and eliminate my occasional stumble/hesitation.

 

Great pictures. I tested mine out twice. Once on the long hill going into the town of Paradise where we formerly lived. The last three drives up there (1500') it cut out badly. After the mechanics took a look at it and tired to seal the loose hose fittings with some fresh hose, i had occasion to test it out. The stutter/stumble could still be felt but was very much reduced, i did not push my luck with a hard acceleration test at that time. Three days ago, my breather tube arrived along with some new spark plug wires (mechanics suggested replacing my original wires). Have not had occasion to drive up the hill yet, but did do a number of pedal to the metal (carpet) tests. A rolling start up to 70 and no hesitation or hiccups. So, seems i have gained some ground and would like to imagine with the new tube, my problem is solved, but will only wait for a flawless drive to Paradise. The mechanic suggested during initial diagnostics, gaining altitude will exacerbate the impact of vacuum leaks. Your feedback is much appreciated. My hose looked much like yours. One of my retention tabs on the valve cover fitting had been broke so maybe it was still leaking a bit. Good luck and Happy Holidays.

 

Thanks mrgizmow, mine was on there pretty tight, in fact all I noticed on the valve cover end is that the O-ring was a bit flattened compared to the new one and of course you can see in the photo that the other end was badly deteriorated form age, mileage and heat cycling. Once I install the grommet for the PCV valve I will give another update.