302 3K rpm flat spot in power

[storlied]

Under moderately heavy throttle after I shift into 2nd as the rpms are rising it'll hit 3k rpm and the power just sits, I do raise in speed but once that couple seconds is over it just screams and pulls like it should.

Replaced MAF, Cleaned it after a year also.
IAC
Sea Foam [May do again]
Plugs and Wires
Coil Packs
Fuel Filter
Power system is at it's best with thicker grounds on the truck, no voltage drops.

Review on the specs:
3.73ls + 33x12.5 R15x8
Race Tune
Shift Kit
CAI

I don't remember when it started.
No codes, I never have had a check engine light.

Ideas:
Vacuum leak, I can't find one?
Bad MAF?
I highly doubt it's the fuel system but running some injector cleaner wouldn't hurt, I've heard the best is like... BG 44????
Is it possible this is due to gear ratio? Is normal? More stress due to my ratio/tire size?
Would a PCV cause this?

Can it be a tuning issue? I'm going to hunt down a cheap laptop and get in touch with James about datalogging.

I'm also going to try and post a video in this thread.

Any help is greatly appreciated.

 

[GETMYBELTSON]

If your tune is on a chip, try running without it. Also i'd be weary of using a shift kit on a truck valve body, let alone with a tune (since both will be raising line pressure).

 

[storlied]

If your tune is on a chip, try running without it. Also i'd be weary of using a shift kit on a truck valve body, let alone with a tune (since both will be raising line pressure).

It's not a chip. I had James [my tuner] adjust for the shift kit to try and level the pressure but I still have a hard 1-2 shift... Anyways, the engine is my main concern here.

Btw, the Transgo shift kit came from Explorerexpress for this truck.

I'll try and return the tune to stock and see if it persists. I know my hard 1-2 shift does. It's fine at first but when the computer learns everything again, hard shifting comes back again for 1-2 and I believe the power loss will too.

In the meantime, any other ideas before I report back? Anything else to look into?

 

[Turdle]

You are on the right track. I think data logging will be needed to find this-
It may be a slow 02 sensor doing this, but you really need some data to troubleshoot this one. Sorry I can't be of more help

 

[2000StreetRod]

Constant throttle?

Is the throttle changing at the shift from 1st to 2nd when the flat spot occurs? If so, then I suggest you check your TPS for linearity. Drop outs are easier to detect with an analog meter because it samples and displays continuously.

If the throttle is being held constant, then I suggest you record vehicle speed, engine rpm, throttle position, mass air flow and spark advance. The torque converter will change the effective gear ratio under moderate loads in 2nd gear between 2,000 and 3,000 rpm. If you see the vehicle speed increasing but the engine rpm remaining almost constant "flat" that could be due to the torque converter reducing its multiplication.

 

[storlied]

Brand new OEM TPS.

Yeah, this coming payday I'ma find some POS laptop off craigslist and do some datalogging.

The throttle will be constant, if it's in this flat spot and I press harder it just sounds like it's working harder.. might pull a lil bit harder but until it pulls outta the flat spot I'm not going anywhere quick.

 

[jah81592]

Daniel,

The tune in this truck has been written for well about 2 years 11 months (about a 1 year 4 month ago readjusted). I don't believe that the tune is the culprit. Yes datalogging will find the issue.-j

 

[storlied]

Well the hard shift for the longest time I thought was normal due to the shift kit and tune aggressiveness but I've learned it shouldn't be so hard at all by a couple tranny experts but they always blame the tune.

As for the flat spot, I always figured it was normal due to my gear ratio and tires until I found a couple threads on this forum about it being a problem on untuned trucks.. unfortunately the person who had the biggest problem with it gave up and traded his truck in for an F series truck before anyone got to any kind of conclusion.

I'm not really saying your tune is causing issues, but datalogging can definitely tell you more than I can online or over the phone... with a video also so you can experience slightly what I am when I'm driving.