Solved: Jerky/bucking acceleration, now: barely acceleration

Edit: I updated the symptoms here:

So I'm having a pretty bazaar issue. In only 4th & 5th gear going up a significant incline above 53mph. I get a jerky cyclic acceleration. Like the whole truck is dry heaving ( or appears that I'm doing so in the driver's seat). No burnt clutch or belt smell or any sign of so.

Info: Supercharged w/ stock 2.38 steel pulley no fuel mods 75k on SC'r. 1.8K lbs over stock vehicle weight. 3.4L w/ 5 spd manual tranny. 75k on motor, tranny & all the way to the exhaust tip. 25k on Lce procomp clutch & #38 flywheel. 118K on truck.

Stock AFR readings appear normal. As do TPS readings. No boost gauge to monitor boost. Battery has a bad cell, one’s on order/ Voltage appears good. No codes. Scangauge ii as the monitor.


A little back story. SC nose seal was leaking slightly. Maybe ¼ ounce at the most weeped out…
Replaced the seal, degreased the entire engine three times. And it's no longer leaking.
It started weeping sometime during a 1k mile road trip. Is it possible I saturated the belt? Or/ and glazed my SC and/or crankshaft pulley?

I'm going to start by replacing the SC'r belt, switch out the SC pulley and crankshaft pulley. Try replicating the issue. If no fix, then I'll move on to getting a boost gauge. Then onto swapping a low mileage used throttle body. The onto the alternator.

Anybody got any other wise ideas? Knock sensors? Etc?

@1997tacomav6

This sound like belt/pulley slip to you?

 

It could be something with the injectors and/or fuel lines...

 

Also, it sounds like your engine was rebuilt at about 43,000 miles...? Why, if you don't mind me asking?

 

That bucking you’re describing sounds like a fueling problem.

 

i am with ^^^. Check the filter then check the pressure.

 

Thanks Guys.

Um. Swapped the engine and transmission into the double cab @ 95k with the donor @ 54k. No rebuild. Donor was my original truck. Bought the donor back from insurance to not hassle with the 5spd swap. Iyi, double cabs never came in the 5spd configuration on the 1st gen.

Filter(oem-inline) has less than 10k miles on it. Pump is original @ 118k.
Here's the thing. AFR shows normal. AFR should lean out, no? I can romp the skinny pedal in 3rd all day long. And it doesn't show me any herky-jerk from what I've experienced. Ive also tested on a full tank vs a tank with two gallons in it. 1st, 2nd & third, no issues.
I do have an extra tank pump, but I'm not looking forward to that job..

Thanks for the replies.

 

That last part I knew...

Sounds like a classic "The way the manufacturer should have built it" build!

 

What's your actual afr, other then saying stock?

During normal driving
During issue

 

you are going to need to see fuel trims both short and long term. A few percent either way from zero is acceptable, anything more and there is a problem.

 

And in third gear I can see 12.1-1 without the issue appearing.

 

Good shit. Okay I'll program them into the SGii.

 

Lol

Your afr under boost (assuming sc is boosting, since there's no guage) seemed fine unless you're experiencing a boost spike which can cause the issue. Tho boost spike is more commonly found on turbo charge setup. But what i don't get is, without a fuel management or enrichment system, how are you able to get 12s in 3rd gear? You should be leaning out under pressure, not running rich.

 

I'm at 5500'. I'm lucky if I get 2# of boost from the SC'R under WOT. I'm never in WOT. SC is strictly for getting my fat ass up a hill & merging onto the highway. The issue arises at medium throttle input (40+/-%) & upper-middle RPM's (3-3.2k).

I just programmed LTFT 1/2 & STFT 1/2 into the SG. I'll report back the findings mid week.

 

And about seeing AFR in the 12's. Not sure. That's the reading from the stock sensor and the SG giving me the reading. The stock isn't a true wideband. And the SG can show me only between 17 to 12 iifc.
I've only seen lean conditions a few milliseconds after I engine break.

I'll look into if I need a specific xGauge code for my ISO OBD AFR instead of the stock code.

 

Yep, need a stand alone

 

watch the fuel trims at idle then rev it to 2k and hold and see if they adjust. What you are looking for is does the front o2 sensor fuel trims go rich, a positive number, then start to back off towards a zero reading. Rev and hold at 3k and repeat. No knowing how enrichment under boost is adjusted, I am assuming that positive pressure(boost) on the fuel pressure regulator enriches. If the fuel trims are double digit negative at idle and way positive at 2 to 3k I would suspect the Mass Airflow Sensor.
After rereading your initial post are you sure that the supercharger is working and not just a big intake restriction?

 

My truck (stock, no supercharger) was doing the same thing. A hill I drove up every day in 4th was suddenly causing my truck to buck and jerk if my speed and RPMs dropped a little. New spark plugs and wires and I was good to go, the difference was dramatic.

 

Thank you. Very easy to understand.

MAF is the newest part on my truck. And a "Denso" eBay buy. Tested LTFT, earlier. Doesn't look good @ +9%. Swapped to a spare MAP. Reset ECU. Will monitor.
Supercharger worked fine at SL before the MAP replacement two months ago.

 

Thanks for that.

 

I see your in AZ as you know SC's dont handle heat well , just throwing it out there