Rough idle, lack of power when hot

ErickBaker · March 16, 2007

Hey guys, I have a 2001 F-340 DRW that runs fine first thing in the morning. After you drive it a while and get it hot it begins to have a lack of power/cutting out on acceleration as well as white smoke. The rough idle also starts after it gets warm. Then even if you let it sit for several hours and cool down it runs poorly until the next morning.

It passes cylinder contribution, injector buzz (both by sound and electrical), no continuous or KOEO codes, the uvc harness looks ok, mgp is about 11-12 psi, fuel pressure is a steady 60-65 psi, oil aeration is ok, I've tried a know good CMP, and changed the oil & filter, as well as the fuel filter. None of the sensors are biased. As a side note I can't get the scan tool to run the KOER self test.

Do you guys see anything dumb I'm overlooking? Everything looks normal and I've followed the lack of power symptom chart. I'm not sure as to what test to run next. Maybe pull the valve cover and watch oil spillage out of each injector? Do you guys think I should measure vacuum on the inlet side of the fuel pump even though I had good outlet pressure.

My gut leans toward a problem injector but I have been wrong before. You guys see anything elementary I'm overlooking? This truck is stressing me out. Thanks in advance for your help, I'm sure I'll get some pearls of wisdom from you guys.

jaysonfordtech · March 16, 2007

What scan tool are you using? Have you tried looking at the perdelta pids? Usually they will pin down suspect injectors. The not being able to run a koer test is bothersome.

ErickBaker · March 16, 2007

I'm using a MODIS and a Matco determinator. I have not seen perdelta in my PID list on either scan tool. I do have a PDS but there is no way in hell I'm paying $500 a year for updates when they cut my first subscription short. Anyway thats another story.

HGM · March 16, 2007

If you disable the fuel pump(pull the relay), when the problem is occuring it will help to identify an injector. The truck will run with 0psi(wont perform, but will run). If it smooths out when the fuel pressure is taken away, its at least one bad injector. Basicly, if your familiar with how the injector works internally, the fuel pressure will cause "blow by" in a worn injector. The fuel will go past the intensifier piston bore and cause a "hydro lock" of sorts in the injector. When you take the pressure away, it will fire more normally. There should be plenty of fuel to idle, just from the suction created by the injector.

Keith Browning · March 16, 2007

I have had IDM's cause similar problems with no codes so suspect them. I have an old "known good" IDM that I use as a test module which has saved me from a lot of head scratching in the past. I am concerned though that you can't run a KOER test. Other than that I have seen a lot of injector problems lately. If your fuel pressure is in spec and does not drop while under load then an inlet restriction test is not going to show anything.

ErickBaker · March 18, 2007

Thanks for the replies. I'll try the fuel pump relay trick on Monday. If that does prove to be an injector I don't know how I'd narrow it down to a specific few without an injector cut out box.

I've had IDM's cause this problem as well even though they have always set some kind of code. I didn't realize until late Thursday nite that I had a donor truck outside with an IDM that will probably work. I'll let you guys know something on Monday.

Thanks for your help.

Keith Browning · March 18, 2007

Yeah, the cut out box is great. I rarely need it but when I do I am glad I have one available.

jaysonfordtech · March 18, 2007

You can do it manually with the valve covers off. Just unplug one injector at a time and judge the change. I had to do this a few times before we got a box.

ErickBaker · March 18, 2007

The only problem with unplugging the injectors one at a time is that I don't really have a bad miss at idle. Its really just more of a rough idle. The big driveability concern is when the engine gets warmed up it has a lack of power/hesitation on accel.

I'll probably try the donor IDM first. I highly doubt that will fix it as that would be much too easy.

Bruce Amacker · March 19, 2007

When I suspect an injector barrel and plunger problem, I pull the fuel filter and put 1/2 bottle of Stanadyne Performance Formula in it and the other 1/2 in the tank. Most of the time when there's an injector problem it changes dramatically from the enhanced lubricity found in the additive. I think Ford's PM-17A is a similar product.

Perdels are the way to go identifying a weak injector at idle, but you have more than one problem by what I hear. #8 is usually higher than the rest. Double check voltages in your PIDS as well as temps and values, etc as maybe the PCM is substituting a known good value for one of them and that's preventing you from running the KOER. Fuel pressure was checked under load as well as in the shop, right? How does a fuel sample look/smell? This truck isn't an EMT squad or anything weird with a battery shutoff, is it? If it has one, it may clear the codes when shut off and throw you for a loop.

Just thinking out loud.

Good luck!

ErickBaker · March 19, 2007

The only problem with unplugging the injectors one at a time is that I don't really have a bad miss at idle. Its really just more of a rough idle.

I just realized that my last post made absolutely no sense. I don't have any idea what I meant to say there.

OHNO60 · March 19, 2007

i had one that did the same exact thing. was slight inlet pump restriction.took a bit of driving to get it to act up, as a matter of fact just about enough time to get it warm.

HGM · March 20, 2007

If you have the covers off already, what do the spill's look like? That can tell you allot....What goes in must come out..

ErickBaker · March 20, 2007

I put the donor IDM on today as well as about 10 gallons of diesel fuel. Right now it's running like a champ. I'm leaning towards a problem with the pick-up in the tanks sucking air or having a problem of that sort. The customer brought the truck in with about a quarter of a tank and the lower the fuel got the worse it ran. After I put the IDM in the low fuel light was on so I filled it to approximately the same level it was when it came in.

So far it runs fine hot and cold. I should of checked for air in fuel with I checked pressure, but sometimes you just overlook the simple stuff. I'll run it down until the light comes on and let you know what I find.

Thanks for all the replies.

Torqued_Up · March 28, 2007

So eric what was the outcome? I just finished a 99 350 that took 8 injectors. truck is used to land a boat and it apparently gets water in the fuel tank. After cutting off the straps because of rust we cleaned out the tank and looked at the pickup tube. the screen on the bottom was loose but it was there. The fuel heater was rotting away and there was a lot of rust in the bottom of the filter housing which we also replaced. You would think these trucks would run bad whilethey run water through the system. so much for regular water draining

ErickBaker · April 2, 2007

Sorry I thought I had posted the fix already. It was a faulty IDM. I replaced the IDM and it still ran a little rough and while on my road test but eventually cleared up. I wasn't sure whether it was the IDM or the fuel I put in it though. To be sure I put the old IDM on it again and drove it home and it ran like crap.

I don't know what exactly was wrong with the old IDM as it didn't set any codes or show any signs as to being faulty. Any one have any ideas or theories on this one?

Again thanks to everyone for their help.

Keith Browning · April 15, 2007

I don't know what exactly was wrong with the old IDM as it didn't set any codes or show any signs as to being faulty. Any one have any ideas or theories on this one?

Most of the IDM failures that I have seen were caused by water getting into the module through the vent hole in the back of the case. I am assuming that is some sort of a vent. It is most common with Econolines and I have also seen this on the older body style F-Series, older than 1999. Once the moisture gets into the module it causes corrosion.

If you encounter an IDM with water inside and there is debris behind the module trapping water and are installing a new module, run a bead of silicone sealant along the top edge of the back of the module where it meets the inner fender to keep water and debris from getting behind the module and into the vent hole. The debris I mention is typically pine needles, mulched up leaves and small wood chips that escape trucks that have leaf vacuums and wood shredders that shoot their discharge into a stake body or dump body. Some inevitably showers the front of the vehicle where it falls through the gaps around the hood. On the Econolines, water runs off of the cowl where the weatherstrip likes to fall off... onto the module.

Other than that, I guess they just burn up. Remember, the IDM not only controls the injectors and acts as a distributor, it also creates the high voltage it supplies to the injectors.

LARRY BRUDZYNSKI · April 16, 2007

Keith I believe that the rubber/silicone seal that seals the case is where the moisture gets in, on almost everyone that I have sold for moisture intrusion/corrosion the vent has been blown out of the IDM.