I'm having an issue with my 2001 4.6 that I have been chasing for awhile and can't figure out. I get intermittent power losses while accelerating that last no more than a half second. Oddly, this seems to happen most when I make a left turn. The most common scenario would be slowing while approaching an intersection, making the left turn, then starting to accelerate at the end of the turn. It feels like the engine completely shuts down....total loss of power, as opposed to one individual cylinder dropping out. I can drive on the highway for 10 hours and no problem. On a few occasions it has done this while accelerating at slow speed in a straight line but it is much more prominent when making a left turn.

A mechanic friend hooked up his Snap On monitor and we went for a drive. We found 3 different coils which were having a misfire every now and then.

To date I have replaced all coils, the fuel pump(that had been acting up earlier), and the crank position sensor. None of these items changed what it is doing.

I'm not sure what to try next. And I am beside myself trying to figure out why a left turn seems to be such a factor. It will do this with a completely full tank(if anyone was thinking fuel was sloshing away from the pickup when turning). The computer shows no trouble codes. Anyone have any ideas on this?

 

Dang it, you stole my first thought.
How about any tight wires getting pulled, or a cracked vacuum fitting that only leaks when the weight shifts to the right?

 

I can't find any pinched or pulled wires or vacuum lines. I'm scratching my head on this.

Yesterday it did this twice while driving in a straight line. The first time I was slowing for a car in front of me that was making a right turn..........just when I started to accelerate it dropped out. The second time I was going about 45 to 50 and it did the same thing though the jerk was more pronounced. That's the first time this ever happened at speed.

The other thing I noticed is that every once in awhile it will have an extended crank time but won't start. I let off the key and then crank again and it will fire. This symptom has been around for years and I always thought it was the fuel pump. Well, there's a new fuel pump in there now and it's doing the same thing.

Could a cam shaft sensor cause all this?

 

The answer is no. I replaced this sensor and the same issues persist. I guess I'll just have to wait until whatever it is to fail completely to figure it out.

 

The same thing happened yesterday but this time I happened to be looking at the tach when it happened. The engine was up to about 2K rpm and when the power dropped off for the split second the tach dropped to about 1800 rpm. For whatever that is worth.

 

I think the only way to really find out what is going on is to hook up a data logger, and log a power loss event and see what is going on with the engine during a power loss. It's not a sure thing, but at least it could help to determine if the fuel pressure is correct and ignition still firing and what not.


Another thing:
Not familiar with the 01 fuel pump setup, but does it also have a fuel pump driver module like the '05 has mounted on the drivers side on rear frame? If it has one, it may be failing.

 

It's been awhile and nothing has changed. Still the same symptoms. I just took the truck from Florida, through various places in Georgia, and up to the mountains in North Carolina. Not one single problem with all that highway driving. I only had once "event" when making a left on a switchback on a mountain road.

Around town, when making left turns is when this is still happening. I can't find any problems with vacuum lines and I checked that one wire which runs over the A/C line and it is fine.

At this point I am just driving it hoping it will die so I can finally diagnose what is going on. But the truck won't play my game. I will also try to catch up with my mechanic buddy to see if we can hook up his Snap On scanner and catch this in action. I'll be sure to come back and post my findings if I ever solve this.

 

Does the level of fuel in the tank affect if the issue occurs or not?

 

No. It will do this with a completely full tank or running on fumes. Fuel level is not a factor.

 

I dunno then, unless it's a wire getting tugged only when making that left turn?

 

Have you inspected the steering? Maybe something is catching on some component when you do a left turn? A crazy thought is that the steering rack and the power steering pump is exerting more resistance on the engine when making a left turn, but I don't know if that's even possible to such an extent that the engine is loosing power.... I'd imagine that the belt would slip and scream if so...

 

How heavy is the keychain? Turning left would swing a heavy keychain out and tug on the ignition switch. You can test that by pulling out on the key while driving.

 

An update. This condition exists to this day. Still no codes. The key has nothing more than the key fob on it.

The newer thing is now when this happens, I sometimes here a muffled pop. Like it is backfiring into the exhaust. To me it sounds like this is happening on the driver's side of the engine.

 

Could the dpfe sensor cause these symptoms?

 

Start the car up and wiggle every wire you can find and see if you can duplicate it when not driving. It may be a short somewhere.