slow, little power, sputter, backfire on acceleration.

VinCecil · Dec 28, 2015

Been trying to figure this out for about a year. Its my daily driver so chances to work on it are slim.

It starts perfectly fine. Idle sounds a little high, but have no rpm gauge so idk.
Acceleration is slow, it hesitates, and upon any medium to heavy gas, it sputters like a wild horse. It violently shakes and occasionally has a small backfire or pop that sounds very faint, but i can definitely feel it jerk.

Problems have been consistant over this year before i made any repairs, but what i have done.

New plugs twice, tried platinum i think, then went back to copper i believe because i read copper ones are better? Idk its been a few months.
All wires look good, but i replaced one cus the inner boot came out and stuck to the plug.
Cleaned maf many times.
Air filter is getting changed next weekend cus i like $10 things that keep it healthy. Its really not bad yet.
Ran seafoam multiple times.
Cleaned iac (gasket is chipped but not to the insides)
Replaced pcv. There was a half inch if gunk around it.
Replaced fuel filter below drivers door.
Did a transmission flush.. wow thats another story.

Only codes im getting are 02 sensor or running lean on both banks.
And it seems if i run my gears further its not as bad, but without a rpm gauge im scared of damage. Also when it is 70 degrees on these florida december mornings, it runs better til it warms up. At least i think im awake enough to tell.

Ive searched on the forums many times and found threads of similar problems, but none that match mine. So any and all help or pointers in appreciated.

stmitch · Dec 29, 2015

Address the fault codes first. Posting the specific codes may help us to narrow it down even more to something like a faulty fuel injector on a specific cylinder, etc.

If it's running lean (and it sounds like it's running lean based on what you've said), it's not getting enough fuel according to the PCM, so check to make sure you're getting appropriate fuel pressure at the rail. If you have good fuel pressure at the rail, then move on to the injectors. If you don't have strong fuel pressure at the rail, then look at the fuel pump or filter.

The O2 needs to be replaced regardless. If your fault code is only for a single O2, you may be able to get by for awhile with just replacing the faulty unit, but I'd assume that they're all about the same age, so if one bank is failing, the other probably isn't far behind. It may fix all of your problems since the PCM uses input from the O2s to determine fuel/air ratios. At the very least, it will eliminate a possible issue and should improve your fuel economy/drivablility.

VinCecil · Dec 30, 2015

P0171, p0174.

Replaced the pcv a week ago, and it hasn't backfired or popped yet. After it gets warm it shakes when i press the gas, unless i just barely feather it. Like the same issue as bad coils in my wifes jetta

VinCecil · Dec 30, 2015

After doing google searches for days, supposedly those 2 codes together out of the blue, points mostly towards a vacuum leak.

Also wondering if my oil fill neck broken off would cause trouble? Its been like that since the day i bought the truck and never had issues til a few years later.

stmitch · Dec 31, 2015

The condition you're describing sounds like a misfire. Misfires occur when the air/fuel ignites at the incorrect time. This occurs when the fuel/air mixture is incorrect, or the spark arrives at the wrong time.

Since the codes you listed apply to both banks of the engine, we can probably rule out an issue on a single cylinder so it's not likely to be an injector, spark plug, plug wire, or valve issue. So, look at things that would affect fuel supply, air charge, and spark to the entire system.

1. Check fuel pressure at the rail to make sure it's within spec. If it is within spec, then you can probably eliminate an issue with the fuel system.
2. Check the coil pack.
3. Check the major sensors that affect the entire system (MAF, O2s, Cam Synchro and it's corresponding sensor, DPFE sensor if your truck has it)
4. It's possible that you have a vacuum leak like you suspect, but it would have to be multiple leaks, or a single leak someplace like the lower intake manifold to cause both banks to run lean. Typically vacuum leaks result in unsteady idle/ low speed driving issues though, not what you've described.

How many miles are on the truck? I'm really leaning more toward a sensor issue here. Cam Synchros and their sensors probably need to be replaced every 100-150k. If you have an EGR system with DPFE sensor, they fail often (60-100k miles) and are cheap/easy to replace. O2 sensors will gradually slow down as they age and become less accurate, so replacing them after 100k isn't a bad idea at all.

This is a helpful diagnostic:
http://www.aa1car.com/library/ford_lean_codes.htm

VinCecil · Dec 31, 2015

198k miles. How do i test the coil pack? And how about the cam synchro?

VinCecil · Dec 31, 2015

Also i don't know why the backfire stopped, I've been driving hard to make it hapoen again but it won't. Only thing ive done is the pcv since.

VinCecil · Dec 31, 2015

Thanks for the link btw, great help. So I'll get all this checked out.

stmitch · Dec 31, 2015

VinCecil said:
198k miles. How do i test the coil pack? And how about the cam synchro?

Here's a decent vid for checking a coil pack:
https://www.youtube.com/watch?v=XcmWa2Bt12U

I'd be a little surprised if the coil was your issue, but its a good idea to find out if it's healthy or not, even if it just eliminates it as a possible cause of your condition.

For the cam synchro, there's not much of a test. The 3.0 originally had a distributor/rotor. In the mid 90s, Ford replaced the distributor/rotor with a cam synchro/coil pack system. The synchro is basically a distributor with the top cut off and replaced with a sensor that alerts the coil pack when to send the spark.

Both the distributor setup, and the synchro design drive the oil pump, so if one fails completely, the engine will starve for oil and lock up. It's probably the leading cause of death for the 3.0. Over time, the bearings of the synchro can dry out, and the synchro may start to chirp. I'd say the average life of a cam synchro in a 3.0 is 100-150k miles. After more than 15 years, and nearly 200k miles, if you haven't replaced the original cam synchro, I'd highly recommend you do. And stick with the Motorcraft brand part. All of the cheap aftermarket versions are crap that fails in half the time.

VinCecil · Jan 1, 2016

I have no symptoms of the cam synchro going bad, I'd rather not even touch it. I have no oil issues or weird noises.

I don't think i mentioned but doesn't have any of these issues under 30 mph or in lower gears. Also if i stay in a gear longer it won't happen.

Rearanger · Jan 1, 2016

VinCecil said:
Acceleration is slow, it hesitates, and upon any medium to heavy gas, it sputters like a wild horse. It violently shakes and occasionally has a small backfire or pop that sounds very faint, but i can definitely feel it jerk.

In a past life I had two situations that had those same symptoms and which also took me a long time to trace.

1. A blocked fuel filter which worked OK until heavy acceleration/load. You've replaced the filter but a pressure check should be done as suggested.

2. A shorted/ing coil, which under load, especially heavy up hill, would cause the sputter, shake, backfire you describe as well as bucking as the coil fired then didn't fire.

VinCecil · Jan 6, 2016

Rearanger said:
In a past life I had two situations that had those same symptoms and which also took me a long time to trace.

1. A blocked fuel filter which worked OK until heavy acceleration/load. You've replaced the filter but a pressure check should be done as suggested.

2. A shorted/ing coil, which under load, especially heavy up hill, would cause the sputter, shake, backfire you describe as well as bucking as the coil fired then didn't fire.

Thanks for the input. When i get the extra funds ill have some pressure tests done on everything mentioned. For now I'll test that coil pack with a multimeter the best i can.

Rearanger · Jan 7, 2016

VinCecil said:
For now I'll test that coil pack with a multimeter the best i can.

You might find something, but I suspect without load on the coil pack you won't find anything. My coil ohm'd OK.

It may be just one of those "throw a part at it" situations.

If you could do the tests on a dyno, duplicating load, speed, etc., with a scope connected, that would be best, but that expense would probably be more than a coil pack.

VinCecil · Jan 11, 2016

Still haven't gotten around to checking it. Runs fine as long as im driving responsible &#55357;&#56838;. Pulling out into traffic really sucks.

Its been cold for the last few days, and i can literally floor it without reproducing my problems, until the truck is up to temp, then it acts up. What sort of things don't act up when cold but do when warm?

pjtoledo · Jan 11, 2016

electrical connections

slow, little power, sputter, backfire on acceleration.

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