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6 Posts
Discussion Starter #1
bucking getting more noticeable/more common/worse
==starts immediately.
==cold idle cammy/surgy sometimes. warm idle almost always smooth but sometimes cammy.
==not bucking cold.
==warm weather bucking once needle hits bracketed area.
==cold weather bucking a while after hits bracketed area, def by mid range.
==bucking when overdrive kicks in, also when overdrive selected to off.
==bucking between 45 and 60. 1100-2000 rpm. seems to correlate with lock up on low end (even if OD selected off. lock up in 3rd?) goes away at 60mph and higher.
==doesnt do it in that speed range if foot off throttle or very little throtle/light load, also pushing pedal a little deeper/moderate accelerating thru that speed range will end bucking until you go back to light throttle.
==oil level fine, tps is 6m old and it doesnt do anything weird when goosed in park
== no codes, hutch mod done a few months ago.

Some info from last week—-

I instaled my new purple motorcraft CPS this afternoon. Drove about 20 miles. Still same symptoms.

Figured out how to get the parameters you mentioned using my Torque app and the OBD dongle.

I don't know very much about them or what they mean but here is what I saw driving to/from kids karate at 45mph with and without cruise control (still bucks with cruise on) with a few good acceleration runs and downshifts.....

EOT - rose continuously from cold start to ~185F 5-7 miles later.

Boost - usually pretty low, like single digits, but peaked at ~17psi

IPR - ~10% at idle peaked at 51, i think it hung out in teens and twenties most of time.

ICP/HPOP - 550psi cold idle, warmed up a bit, peaked 2800 held ~2400-2600 during my redline accel runs up to ~80mph. 450-475-500 variable hot idle when got home.

TPS - 0-25% for most of drive. 0 when cruise on. It shows full range via OBD when pedal pushed.

Injector PW - usually 2400-3200(us) idle, peaked at 4400. Seems to bounce around a lot without reason.

EBP - 15.3 idle, peaked at 45psi.

Some info from 2 days ago—-

Not sure how to check fuel pressure but pump Duty cycle is 100%

I checked the tin nut and it’s tight. The valve cover connector on driver side is really stiff but firmly clipped and shows no sign of melting or cracked or arcing I can see.

I have more numbers for you....

While driving cold and warming up.

Pw idle 2400 2200 2500 2400 2600 2400 2500 2300 2700 2400 2300 spikes at 4400 when lugging accel

Icp idlecold 500 580 520 530 494 514 585 570 510 494 hot 450-500

Ipr cold idle 10.44% 10.8 steady 10 hot

Map 14.65

Mass fuel 8.75 7.5 7.3 8.1 7.7 8.7 7.5 8.6 7.2

Fuel pump duty 100%

While driving warmed up at 45-50mph pretty steady...
Torque converter slip.
4.9 16 26 16 10 26 16 bounces a lot

670 780 800 700 bounces a lot

13.9 14.7 bounces a little

2800us 3000 2900 3200 but anytime I dipped into throttle for a slight hill or to speed up a little it would hit 3800-4000. Also hit 3800-4000 when lugging engine around 45.

Seems to do it after tc locks, when pw is higher. Also can get it to happen if I accelerate and it doesn’t miss but then let off throttle a little to keep speed.

Assuming sensors are good, Is it a tc issue, an injector issue, a fuel pressure regulator issue, or a fuel pump issue?

Any ideas or input?

idea's ?

Sent from my iPhone using Tapatalk

316 Posts
I recently was having a very similar issues with my truck. I'm in Texas working so I didn't have much time to work on it. but in the short time I did worked on it, I found out via my scan gauge that my icp would just drop out and the truck would die. I could throw it in neutral and fire it right back up and keep, but with in weeks in got worse. I thought I had a short somewhere in the ipr's wiring. I tore in to the wiring and found nothing wrong or chaffed to the idm or at the Valve cover 42 pin connector and so on. My truck is not stock by any means, so for me it could be a little more involved to hunt down. I have dual Ipr's for example.
Based off of the research I did I figured it was either a short in the system, water/moisture in the idm, bad Ipr, or even the throttle positioning sensor/throttle assembly. Also, I had no codes, so it was even more frustrating trying to diagnose.
Also I did notice that my truck would do this only when cruising and trying to maintain a steady speed regardless of speed. It almost seemed to be in the first 15% of the pedal, but also very intermittent as well. I could drive for 100 miles and nothing for even days at a time then it would just die. But it did progressively get worse, to the point the truck would barely drive. So to catch you up to speed, I did have both Ipr's changed, and this did the trick. I'm not saying that this is your issue, but for me it was.

7 Posts
I had a fuel pump lay down a little while back and the truck started violently shuddering, made me think it was a tc/trans issue, headed to my shop with it and the pump finally completely died then I realized I couldn't hear the pump, swapped it out and fired right off, I've seen pumps die slower also, I would check pressure and rule out a fuel delivery issue
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