Good day everyone,

I have run into an interesting problem on my 05 fx4. Hopefully I can get some ideas from the rest of you resident experts.

Let me give you some details on the truck.

135K

Cold air intake

underdrive pulleys

electric fan installed

Troyer canned tune installed

I recently had issues with my truck shuddering when trying to accelerate. After doing my homework, I replaced the plugs ( the old ones were 60K old) and the IMRC solenoid. I found that the control arm for the drivers side had falling off.

After doing the corrections on the above conditions the truck has run stupid crazy fast. Better than it has ever run. Instant throttle response and acceleration all through the power band.

fricking amazing!!!!

After doing some more homework on keeping the truck alive, I replaced the VCT solenoids.

Here is my problem.

Since changing the vct solenoids I have lost all my newfound power.

What is bizarre is if I reload the tune I get random spurts of power immediately after, then I lose it. When I say random spurts, I mean I can goose it at one stop light a get a little acceleration, (nothing like I had before) then another time it will take 5-6 seconds to get the rpm up past 2500

From idle to 2500 this thing stands still, then it starts to pull hard once I get past 2500.

Another symptom that shows up is I have smooth shifting after a reflash, then when I start having these random drops in power the truck bucks when I accelerate hard from a slower speed.

I have unplugged the vct solenoids, I have tried another tune with similar random results. What has me totally dishearted Is I had amazing performance for about 2 weeks, then with a change in vct solenoids (I also did LED headlights) I have even worse performance. I can't explain why.

Part of me believes my cam phasers are smoked and I'm having issues maintaining cam timing.

but when the issue with shifting, I have no idea why the two are connected.

Any suggestions on what I should look at?

I have an older xcal 2 tuning and software to pull the pid's. But most of that is cryptic to me.

Thanks,

Jim

 

Check the fuel injectors to see if there might be a leak.

 

@jgdarna


A seemingly nutty idea you might consider & investigate is something effecting a "Knock Sensor". I actually base this crazy idea on recalling personal experience with my truck similar to that which you describe, and based on recently acquired knowledge about some embedded logic in the ECU.


BACKGROUND: I've been digging, experimenting (or hacking) unpublished OBDII PIDs for some time with the Torque Pro App. I had built some gauges for monitoring Knock Sensor output on both heads. I noticed Bank 1 sensor's ambient voltage level was a good bit higher than Bank 2 KOER, by a good 50% to 70%. But not with Key On Engine Off, so I knew it at least worked. Unaware of any ill effect and assuming a simple calibration problem (plus the fact they are located under the IM), it was a NO REPLACE issue that mere curiosity caused me to monitor on Torque Pro occasionally.


BUT - that damn noisy, winning, A/C Compressor finally got to me and I replaced it. I very soon begin to notice that I felt the truck was much more responsive, would pull better, and seemed to have improved performance all the way up the power curve. Then, unrelated and coincidently, I pulled up my knock sensor screen on Torque. They were equal and BOTH running much lower than they had been. I made the logical connection, KS1 had been picking up noise through the block from the noisy A/C compressor.


BUT could THAT even be related? On dilligent research of knock sensors, I find there is yet another parameter the ECU applies to its operation called "Knock Retard". When it determines the signal profile from a knock sensor it determines to be 'pre-ignition' or 'detonation', it applies a Knock Retard (factor) to the ignition advance setting - for a period of time in an effort to protect itself. That 'period of time' is unknown to me at this time - but I think there is also a 'decay' rate applied to it, over perhaps a minute or more. But continuous or frequently reoccurring detections could keep a LID on the ignition advance the ECU applies during normal operation. THAT WILL NOTICABLY AFFECT POWER.


You mention it seems to improve for a period of time after you reflash your tune. Could this be related?


I am convinced (or have at least convinced myself) that THAT explains the improvement in performance I experienced simply by changing a noisy bearing on the front of my engine. Now I also wonder if that could explain so many power loss complaints from guys that have noisy Phasers or noisy lash adjusters/followers? Or other instances of anemic performance.


If you care to chase this theory, Knock Sensor PIDs on the 5.4L 3v are:


KS1 __ 16E6 __ Knock Sensor Input Bank 1 VOLTS
KS2 __ 16E7 __ Knock Sensor Input Bank 2 Volts


The formula I am using is ((A*256)+B)/128 . I can't guarantee that formula gives accurate voltage reading, but it gives a reference point sorta between 0 and 6 that is definitely proportional to noise detection.


I have NOT been able to find a PID that represents a "Knock Retard" value or a "Decay" constant????


I would be MOST interested in any addition information you shook out about these sensors and their operation. I'll be following this thread.


Sorry for the long post, and GOOD LUCK in your search for intermittent lost power.

 

Checked FPDM?

 

Certainly no intent to be combative. Just a curious and analytical old cuss. But is there a way the fuel pump driver module could give @jgdarna the symptoms described without a dtc code. He may have some code but he didn't mention it.


Wouldn't the result have to be a significant drop in fuel rail pressure, and thus a lean condition? It seems that would quickly drive fuel trims on both banks very positive by the time he would feel a loss in power. ?? (Fuel Trims greater than 25% for greater than 5 seconds will set a 0171 and/or 0174).


Just curious if there is something I'm missing or an area I can learn more about.