I'm bumping this to it's own thread, so if someone wants to get right to the "brass tacks", they don't have swim thru the original lengthy thread (just a lengthy single post).
For reference, here's the original
rth-experiencing-violent-truck-wide-shudder-accelleration thread.
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So to recap, I've been experiencing a progressive power loss in conjunction with events when acceleration is applied (even modestly) on a long incline (no additional load than standard cargo with plywood drawer system in rear). The onset of this condition presents the symptoms of the truck shuddering, ie... the whole truck starts to vibrate as if going over small rumble strips. There were 2 events when a heavy skinny pedal was applied to counter a driving hazard, where the sudden down shift and revs up over 3000 rpm met with a hesitation, CEL coming on, and then severe power loss & rumbling that required a limping home. This would occur chiefly on the highway, but once the degradation began, I could be in a neighborhood going up a short hill doing 25 mph (w/o OD) and the shuddering would begin.
Just about 2 weeks ago, I replaced both of the factory installed O2 sensors with OEM Denso's, repaired badly leaking cat gaskets, and reset the ECU. For the following 5 days, the truck's health was restored. No shuddering returned, until I had to pull back into traffic from an off-ramp and saw a car barreling down on me in the rear view. So I laid in on the gas @ ~45mph, it downshifted and as it the rpms crested over ~3200 it hesitated and then threw the P0303 CEL (Cyl #3 Misfire) with significant power loss. From that point on, it was a daily experience with the shuddering, even after clearing the CEL and reseting the ECU.
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Symptoms & Conditions
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Here's an example of the repeatable experience to or from the office on a ~11 mile trip:
Driving home from office...
1mi away @ light - idle is ~4600rpm
3 miles - as I'm halfway up first long incline, shuddering begins @ 50mph-2k rpm and need to turn off OD
5 miles. - next incline w/o OD, hit shuddering @ 40mph-2200 rpm.
7 miles - accellerating up slight hill from stop light, shuddering begins after shifts into 2nd gear reaching ~40 mph - 2k rpm.
9 miles - Can reach up to 50mph - 3k rpm w/o shudder on flat/level stretch of road.
11 miles - Reached home. Idle in park & neutral is -6200rpm; ~6000 rpm in drive w/ foot on brake.
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Diagnosis steps
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Based on the documented experiences of other Mudders, I checked out the possibility of the EGR pipe touching the wiring harness during torque-heavy conditions and thereby affecting ignition/injection signal.
To recreate the above condition, I conducted the following tests suggested by alia176's:
1) power break test: left foot firmly on the brake and right foot pushing down on the gas pedal to 2,000 + rpm. Tell us if you can recreate this issue.
2) Same test but try to drive up a sidewalk so that the engine has to work real hard. You'll be driving head on (perpendicular) to the sidewalk, assuming your sidewalk has a nice sharp edge and is fairly tall, 6" or higher.
3) Shift Tcase into "low" and then try the same test as above. Do the sidewalk test again.
Results:
1) Other than a slight hesitation (but not repeatable every time) when hitting 1800 rpm, nothing remotely like what I'd bee experiencing on the highway.
2) Conducted up against 8" curb. RPMs could never get above 2000 rpm, whether in D (OD), D(OD off), 2, or 1. - Unable to recreate shuddering condition.
3) Note to self... where one or two test attempts will do, avoid doing it 20 times. I overcompensated not knowing the threshold and doing this for the first time. WARNING - too many of these tests and be on the look out for the A/T TEMP light to show up! Ask me how I know.
- Needless to say, I never conducted the test in "low".
"If the issue returns during any of these three tests, then the engine torque (twisting) is messing with your ECU harness that goes right by the EGR pipe." -
This observation has been concurred by other members, so definitely be on the look out for this condition and should be one of the principal trouble shooting steps, IMHO.
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Assessment Findings and Remediation
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So I
pulled all 6 spark plugs and found #1-#5 all identical. They showed signs of running very hot, possibly in lean situation.
#6 was the surprise (since #3 Cylinder was attributed to the CEL misfire code), clearly showing oil deposits
(gunk) all over the element. How it was firing I can't fathom.
At this point, I'm reading in the archives as well as some newly offered opinions that the oil fouling could be from a few serious conditions, like the HG, or leaky valve seals, etc.
Not having access to a test manifold (like
this one from Summit Racing) to properly conduct a leak down test for the compression, I just swapped out the old plugs with new NGK Spark Plug
Part No. 7090, G-Power Single Platinum; BKR5EGP. All were gapped to FSM spec 0.031" and installed, with appropriate amounts of dielectric grease at the plug's ceramic base and wire boots. All plugs torqued down to 14.5 ft/lbs (per CDAN).
BTW, anyone ever noticed in the 1997 FSM that it calls for 20Nm or 14ft/lbs. These are not the same even close, at least on my torque wrench. I don't have the T-wrench in front of me right now, but IIRC, 20Nm is +15 ft/lbs.. maybe more towards 16 ft/lbs. I went with lower amount of the 2 to be safe, prior to seeing CDAN's quote. Just an interesting observation to mention.
The Distributor cap was pulled and the rotor plug found to have
heavy deposit build up and
scoring. After cleaning it up, you can see the
scoring much more clearly.
Not having a replacement Distributor Cap, I cleaned of the point contacts and they looked fine. Factoring the rotor plug's build-up as evidence of possible moisture in the cap, I'm guessing the cap's seal was compromised at one point. I was pretty liberal with the dielectric grease around it's edge, but still plan on picking up a new cap at first chance just to be safe.
I checked all the plug wires (aka FSM: high-tension cables) for resistance values. They are Nology HotWires that I swapped out for the original '97 OEM cables. I had these on hand for $20 new, so in they went and have been on for a good year now, I believe (checking on that). I still plan on getting a brand new set of Toyota OEM wires as soon as my budget can afford them.
Here are the resistance values for each wire. (smaller wire # = shorter length of wire)
Coil - 0.56 kΩ
#1 - 0.63 kΩ
#2 - 0.67 kΩ
#3 - 0.86 kΩ
#4 - 0.89 kΩ
#5 - 1.09 kΩ
#6 - 1.17 kΩ
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Net Results
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My LC is now running like it's back on its feet and producing strong responses to the throttle. From a dead stop, I took her up a hill that @ 1/2 mile in length @ a good 10° slope and she climbed solid and smooth all the way up to ~4200 rpm then shifted smoothly down to 3000 rpm and continued powering through the climb without significant hesitation... increasing speed the whole way up.
Now THAT's a remarkable difference from the recent experience of my "rollscnardly" condition (ie, rolls down one hill, can hardly get up the next). Every test I put her through, using short steep hills to long grade climbs, there's no doubt that I've gotten a significant amount of power restored in this ol' girl.
The real test was this morning's run to the office. At no point, with speeds ranging from 50 to 70 mph, did she even HINT at any of the shuddering from last week. Pretty amazing feeling, at least from my perspective in the DS.
So if I can find my OBDII reader, I'll try to capture some metrics on my laptop as she's running. I'll post them up when I can get 'em.
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Note of thanks
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As usual in my past experiences working with the membership of this forum, I'm always duly impressed by not only the breadth of experience to learn from, but also the vested interest folks put into helping others out. A number of you posted some solid info and experience that helped out considerably. In particular I just wanted to put a shout out to:
SeanAndHis80 for picking this one up from the start and running it through the course;
RacerLex, a local Mudder who offered up his new set of OEM wires for testing; and
alia176, for the surprise phone call/message from New Mexico. Those were some good tests you suggested and definitely helped guide the diagnosis path with what we were able to rule out. I appreciate the time on the phone and the experience relayed about your HG "fun" and more.
Hey, I consider their responses actually commonplace for Mudders, and that's why I see them as uncommon.
Cheers, until the next evolution.
RescueU
...sorry it is about 300mi North of you in New Hampshire.
Linear Mode
