Ford Truck Enthusiasts Forums

Ford Truck Enthusiasts Forums (https://www.ford-trucks.com/forums/index.php)
-   1997 - 2003 F150 (https://www.ford-trucks.com/forums/forum25/)
-   -   Miss at low RPM, light throttle. (https://www.ford-trucks.com/forums/1006602-miss-at-low-rpm-light-throttle.html)

WillaminaOR 11-02-2010 03:46 AM

Miss at low RPM, light throttle.
 
My 01 Super Crew 5.4l is missing at light throttle. Cruise control on flat hwy, no miss, slight incline, starts missing. Put my foot into it and either it stops missing or it covers it up where I don't notice it. No codes set at this point. It's got about 135k on it and for all I know it may have had the original plugs in it so I figured I'd change them. Changed the plugs, still misses. Shortly a code set, something about the EGR sensor (it's got another name but I forget what it is at 1:30am). I found I had broken a hose while changing plugs, fixed it, no more code, still misses. When i sent my GF up to get the non-existent codes checked the parts guy sold her some Lucas fuel system cleaner. I'm figuring a COP going out but the cleaner pretty much completely fixed the miss, till that tank of gas was gone. Few tanks later and it's back again as bad as ever. I bought some seafoam as I've had good luck with that in the past. It almost completely fixes the miss but I get a rare 'bump'. What do I need to look at next? Can it be the fuel filter? I'd think no because I'd figure it'd be even worse at greater throttle opening. Injector? How do I check them? I also posted another thread on a weird fuel economy observation I had. I mention it here as maybe they're related issues. Not sure how to post a link to the other thread so just take a quick look for it.

Thanks for reading this far and any help,
Bryan

Bluegrass 7 11-02-2010 08:47 PM

The missing under the driving conditions you discribe is likely one coil.
It is not a hard fault so will not set a code because the PCM cancels the fault's short term 'miss' count history.
The coil likely has intermittant turns shorting causing low output voltage to the plug.
The missfire is caused by a very lean mixture under cruise conditions when the EGR is called to open.
Under these conditions, the voltage required to fire rises sharply and fails..
Since no code is set to tell you what cylinder is at fault, you need to either sub one coil position at a time, have all the coils stress tested or use a good scanner to trap the fault when it ocurrs during a drive cycle or possibly look at each cylinder's history with a high end scanner (not a reader) looking for an indication.
There you have it. Not an easy way to solve the issue but you know what is involved and what can be done.
Good luck.

WillaminaOR 11-03-2010 02:20 AM

Sounds good and a failing coil would have been my next guess but how is fuel system cleaner fixing a bad coil?

Bluegrass 7 11-03-2010 06:42 PM

Cleaner is not "fixing" a coil.
It will however change the air/fuel ratio by vertue of it's effects within the gasoline mix.
Other things that happen is the PCM can re-adjust the fuel amount as a reaction of the OX sensors to the addition of the cleaner to the gas.
If the coil is at all temperature sensitive, then anything can happen in any sequence at anytime.
Just don't make the mistake of jumping on circumstantial evidence of what appears as a link to the trouble.
Many owners in simular trouble as you, change plugs that seemed to clear the issue only to have it come back again after several hundred miles, then really get confused over a faulty coil.
What happens in that case is the new plugs are easier to fire when new but quickly fall back to the old level of operation the original coil fault cannot fire again. Missing returns.
The original problem was just a coil as indicated by the specific conditions under which the miss shows up.
Complicated isn't it?
Good luck.

WillaminaOR 11-03-2010 08:19 PM

Where is the best place to get a COP so I can swap one around till the miss goes away? Is there a good quality brand to look for? Or one to avoid?

Thanks,
Bryan

jamrock 11-03-2010 11:06 PM

Napa, Autovalue(Canada), online at rpm, they have some performance ones, if you're running any other engine mods. Just about any decent autoparts shop will sell them or just go online, or buy from dealer, maybe easier that way.

thomastl 11-04-2010 07:16 AM

Easist way I have found (although this will sound wierd) is to drive the truck and force the misfire consistently enough for the code to set. Get it into a lug mode with the misfire and hold it there. Truck will buck and act like crazy and you think this can't be good. But it will continue the misfire long enough for the computer to set the code. P030x will be the code. x is the cylinder number. Numbers are 1 - passenger front. 4 - passenger rear. 5 - drivers front. 8 - drivers rear. One COP will cost you about $40.00 or so at the local parts store.

the_munc_e 12-06-2013 08:41 AM

Sorry to revive a dead thread but I'm having this exact same problem with 2007 5.4 triton. Started with knock sensor. Had it and plugs done. Could be noted one of the plugs was bad and it took us awhile to figure that out. Put a new set of Accel coil packs on after that bc one was bad. Immediately had a sulfur/gas type smell through the AC vents. It got worse, then truck started missing. Took Accels off and put stock back on. Evened out, except for previous miss, and the smell instantly went away. I brought the Accels back and ordered a set of COPs online for cheaper. Installed them and fixed the miss for about a week. Then it came back. It's at low idle, just like OP. It's still present, but more RPMs I guess it's just less noticeable. Like I said, it ran fine for a week, and I'm curious if something can be causing the COPs to go bad, or do I just have bad luck? I was thinking injectors, but with no code, that's a pretty expensive shot in the dark. Maybe I will take one of the originals and start swapping to see if it goes away. My luck, I will grab the bad one.

405Ford 05-28-2016 05:24 PM


Originally Posted by thomastl (Post 9517381)
Easist way I have found (although this will sound wierd) is to drive the truck and force the misfire consistently enough for the code to set. Get it into a lug mode with the misfire and hold it there. Truck will buck and act like crazy and you think this can't be good. But it will continue the misfire long enough for the computer to set the code. P030x will be the code. x is the cylinder number. Numbers are 1 - passenger front. 4 - passenger rear. 5 - drivers front. 8 - drivers rear. One COP will cost you about $40.00 or so at the local parts store.

I would not recommend this method.. A couple years ago I was having the problem that my truck would miss and shake badly whenever on the hwy with low rpms when trying to speed up a little or trying to keep my speed to get up a hill. Well since it would only do it somewhat rarely and had a lot going on as it was I decided to get to it later when I was able to. Whenever it would start to do it I would either drop my speed to let it shift down or I would put it to floor and force my rpms up to try to push through it. This happened maybe 5-6 over about 2 months before one morning I was getting onto the little hwy by my house when it began to miss and shake like never before, but I needed to get my speed up with cars coming up behind fast, so I put my foot in it, about 3-4 seconds into doing that there was a large bang and the very loud and continuos sound what I would describe as almost what a co2 gun sounds like when it's being fired without any bullets. The end result was I had blown a plug out of the truck, which isn't hard to do with aluminum heads. But that's just my opinion based on my experience with this type of problem. Which went from one fairly simple problem to multiple difficult problems..

Bluegrass 7 05-28-2016 06:17 PM

Stop all that nonsense and do it the correct way.
Use a Scanner to call up mode 6, test 53.
There you will find the misfire records for all the cylinders.
The cylinder with the high count, out of limits has a faulty coil.
Change the coil and it's all over with.
Good luck.

Radman171 09-20-2016 01:18 PM

Hi Bluegrass 7,

New user here, and I saw your post reference using a Scanner to find the misfire records for the cylinders. Exactly what type of scanner are you recommending, and where would I find one? I've got a handheld code scanner but it doesn't do any specific tests, etc.

Any info appreciated...thanks!

Bluegrass 7 09-20-2016 02:10 PM

You apparently have just a Reader.
They cannot display live data.
Advance Auto, Auto Zone, Sears all have various Scanners.
In using a Scanner, you need to understand a lot more to interpret the data displayed and have some understanding of the operating system on the vehicle your using it on..
When I reference mode 6, it is a specific part of the diagnostic that allows access to many self test results of the program.
.
The test 53 is Ford specific and collects misfire data on each cylinder separate from the normal misfire detection and code/CEL display.
This section has no ability to set code or CEL but is useful to detect ignition faults.
This is an example of knowing about the system and how to get more out of it.
The highest level of Scanner allows the user to actually input commands to the system and see the reaction that is supposed to result.
This level instrument is not normally for the casual owner due to the cost, skill and need to have one.
Good luck.


All times are GMT -5. The time now is 11:57 AM.


© 2019 MH Sub I, LLC dba Internet Brands