Solved: Jerky/bucking acceleration, now: barely acceleration

I'm in the mountains. We barely see triple digits even in July. It's November.

 

Your boost sounds low check the bypass valve to make sure it is actually activating and shutting as it should under boost.

 

Any easy way to test it?

I checked that the diaphragm holds.

Do I just bypass it?

 

When you give it hard accel (you can do this by pulling on the throttle cable underhood) you should be able to see the lever fully move without moving back the other way. If it does you have a leak in the diaphragm. If it doesn't move at all either the valve is fully bad or you may have to check vacuum source to it.

 

Okay I'll give that a try at break.

 

Welp, bypass valve seems to operate normally. Opens when starting the engine and closes upon opening the throttle.

I actually don't know what my boost levels are. No boost gauge.

But I believe the stock pulley delivers 6psi.
And iifc every 1000' lessens the pressure .6 or .7 psi? So if that's correct it's like 2.1-2.7 psi that is all I have to work with.

 

I'd like to bump this up.

So this issue of jerky acceleration with heavy load has developed into the truck not even being able to do 50 mph up a 40° grade, even at 4k RPM's. All gears is a very noticable lack in power. No pending or posted engine codes.

Regarding fuel trims. I don't see a dramatic ST or LT reading that suggests an extreme issue. LTFT is around +8. Sometimes +7 & sometimes +9. STFT is mostly 0% and under heavy load I see -3 to -4 and for a split second -5 then -six.

The cats don't strike me as clogged. I can touch them with my bare hands for about 300-400ms after a 30 minute hwy drive.And don't feel noticable concerning heat at the tail pipe.

Regarding the Supercharger. The bypass valve and nose coupler are intact. I don't understand having an issue severe as this, this can be SC related. AF readings on my Scanguage read about 14.4- 14.5 in closed loop.So im not seeing an intake blockage. But i'm far from being that knowledgeable on FI.

Parts diagnosed were the MAF, complete TB swap, plugs, coils, AF sensor and all mentioned above. AF sensor tested a 10th of an ohm over the high limiting limit resistance in the Fsm, but my meter hasn't been calibrated in 14 years. So in reasonable error.

To be honest. It feels like I'm not getting fuel. RPM's in the 3.0-4k sound like 2k RPM's. Since the fuel filter was replaced 14 months ago (16k mi) I'm hoping this is the pump. I understand pumps either work or they don't. But the issue feels mechanical in nature.

I plan to replace the spark plugs and fuel pump with a good used unit the wkend. But that's all I got.
My truck is my home and my only means to get to work at the moment. So any ideas or recommendations on what the problem can be are appreciated.


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Sounds like plugs and wires to me.

 

Not S/C'd, but I had a similar sounding loss of power issue on my truck. My truck would lose power and begin to buck. If I held it or tried to get through it the CEL light would flicker on but go off. Easing off on the throttle would smooth things out. I could not replicate it unless the truck was actually moving. It took a while for the CEL to finally stick on and the code was for a misfire on cyl #4. Pulled the plugs and I think it was the #4 had a broken wire. It had broken right where it attached to the plug. Swapped out the plugs and wires and everything has been fine since.

When you go through with your plan this weekend, do one at a time so that you can see for sure what fixes it.

 

Thanks guys. I have some good used plugs in storage next to by fuel pump. Sure, mine testing good. But electrical components can fail in funny ways. Really appreciate you guys replying.

 

Oh I forgot to add. My PCV oil catch can has been collecting more blow- by vapors then normal. Historically after 7k miles the CC would be 1/2 to 5/8 full. Now I'm seeing 1/6 collection after 200 mi.
Somebody correlate that?

 

Bump. Anyone have any other ideas? Currently waiting on a tow now.

 

Good job guys.
It was plugs and or plug wires. The secondary of the coils and of each of the coil side of the plug wires were heavily corroded. Bank 1 spark plugs were toasted after about 35k miles. They're IK20's and supposed to be 100k mi plugs.
Try to update this post with pictures of the plugs and wires. Didn't have much of a choice and had to purchase wires from the Dealership at a 'shove it in raw' price of $97.14.

 

Oof, and I thought my dealer went in dry. Glad that it was an easy fix though. When my wire broke it stayed on the plug and wouldn't let the socket seat. Wound up needing needlenose vise grips to pull the wire off.

 

Yeah also glad it was simple. Interesting that the symptom of appearing to be not getting enough fuel was actually plenty of fuel not being properly combusted and that wasn't enough to throw any codes.