1997 LX450 - Shudder under load at 50-60mph (1 Viewer)

[dyorkey]

Experiencing a shudder under load a 50-60 mph. It's like a momentary loss of power that pulses until I reduce speed or give it gas. Not sure if this is a tranny issue, driveline issue, or something else. It feels like it is in the front end almost like a tire is skipping or something like that.

Recently replaced the rear driveshaft for a bad slip yolk. The front drive shaft has new OEM u-joints about 20k miles ago and was recently lubed. I just did a rebuild on the front left steering knuckle as the seal had gone bad and grease and gear oil had mixed in knuckle and in the diff housing. RCV birfields and shafts. This is a supercharged engine. No noticeable tranny issues (except for typical reverse problem) with recent fluid change about 15-20k miles ago and new filter. 35" tires on OME kit with OME caster correction. Recent replacement of fuel pump with OEM denso pump.

Any ideas on what might be causing this problem? I am at a loss.

 

[doc_random]

I have a similar setup and similar shudder. '97 LX450, supercharged, 35" tires. I have called it a "stumble" around 2000 RPMs when going up a hill. To me it feels like a fuel delivery issue, but I don't know that for a fact. Overdrive off or give it more throttle and it works through it. Is this why people upgrade injectors (Supra) or add a 7th injector?

Similar symptoms on a '94, and other links in this thread. I don't see it resolved. Methanol injection is mentioned by many SC drivers, but I do not have it.

https://forum.ih8mud.com/threads/en...so added headers and a 3" exhaust (as did I!)

 

[doc_random]

OP says it fixed itself, maybe bad gas. Another said vacuum leak, tightened valve cover bolts at the rear.

Bad Hesitation (video included) where should I start?

Last night I tested the TPS per the FSM, and it passed. Then, I tried this test quick: https://forum.ih8mud.com/threads/fuel-pump-relay-and-resistor-the-60-second-test.95052/ The truck started up then almost stalled then fired back up, it did this a couple times before I turned it off. After...

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Torque converter lock up solenoid speculation, no conclusion that I can see.

A343 trans rpm wiggle under light acceleration

So I'm dealing with this rpm wiggle while dipping my toe into the throttle at cruising speeds. The scan tools shows my lockup solenoid coming on and off when the tach starts to wiggle. It only happens when trying to accelerate while at cruising speeds. I have changed the filter and fluid as well...

forum.ih8mud.com

 

[doc_random]

The problem traced back to an intermittent ground issue with the main engine harness, I built a temporary bypass harness for the fuel injectors until I can get a new main engine harness.
4 pages, good troubleshooting. I have repairs in the harness by the EGR pipe and this my be my issue, not sure. SC may run hotter exhaust, and the change in location of the MAF stretched the harness towards the passenger side.

Calling all you Diagnostic Gurus | SOLVED Stumbling on hard acceleration THANKS EVERYONE

SOLVED: The problem traced back to an intermittent ground issue with the main engine harness, I built a temporary bypass harness for the fuel injectors until I can get a new main engine harness. Read the entire thread for the diagnostic journey. Oscilloscope diagnostic techniques were used...

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[doc_random]

Spark plug wires:

What Did You Do with Your 80 This Weekend?

Friday counts as the weekend right.... a few days ago I noticed a slight hesitation and stumble on acceleration, right around 1800 rpm's. It seemed to get worse after a long interstate drive. The next night while making a quick grocery run the old girl suddenly lost power and started shaking and...

forum.ih8mud.com

Wire harness near the EGR, links to 6 other threads

Do yourself a favor and WRAP YOUR ENGINE HARNESS!!!

Years I’ve been here drinking deep from the well of knowledge and experience, and I don’t know how the heck I failed to learn about this common issue, but after an unfortunate PITA experience that I realize now could have been easily avoided, I’m on a crusade to encourage my fellow eightians to...

forum.ih8mud.com

 

[dyorkey]

OP says it fixed itself, maybe bad gas. Another said vacuum leak, tightened valve cover bolts at the rear.

Bad Hesitation (video included) where should I start?

Last night I tested the TPS per the FSM, and it passed. Then, I tried this test quick: https://forum.ih8mud.com/threads/fuel-pump-relay-and-resistor-the-60-second-test.95052/ The truck started up then almost stalled then fired back up, it did this a couple times before I turned it off. After...

forum.ih8mud.com

Torque converter lock up solenoid speculation, no conclusion that I can see.

A343 trans rpm wiggle under light acceleration

So I'm dealing with this rpm wiggle while dipping my toe into the throttle at cruising speeds. The scan tools shows my lockup solenoid coming on and off when the tach starts to wiggle. It only happens when trying to accelerate while at cruising speeds. I have changed the filter and fluid as well...

forum.ih8mud.com

Thanks doc-random. Turns out it was a vacuum leak from the valve cover, same as the previous post you highlighted. Two loose bolts on the valve cover (the far back ones on the passenger side). They were barely finger tight. A quick tightening and the hesitation and stuttering is gone! What a weird thing that the same thing happens at the same place, maybe the additional heat from the EGR port over there along with the expansion and contraction causes those two bolts to loosen up over time.

Thanks again!

 

[doc_random]

IH8MUD for the win! You are welcome, I'm glad it worked for you.