Strange power/throttle response :454 burb

[Mildphil]

I've been having some odd issue lately with my suburban (1999 k2500 7400 vortec) that I can't seem to find the root cause of. For example, if I am driving from a stop sign at a leisurely pace with constant peddle pressure, the rpm will remain the same but it will feel as if the truck will start to accelerate less before picking back up again or shifting, almost as if I had let off the gas. It feels like it loses power. Also, sometimes as I approach a red light and stop, the truck's rpm will drop real low and stutter for a brief moment before picking back up; This can be felt inside the cab. And today, I was driving on the highway and the truck had no power as I was trying to gain speed. At around 60-65 mph, I was trying to accelerate but it felt like nothing was happening, plus the truck seemed to shake/vibrate every 5 seconds or so. It was as if it kept shifting in and out of gear. I'm baffled by this and could really use some help, thanks.

 

[454cid]

I would check for current and past codes. Also fuel pressure.

 

[Mildphil]

I would check for current and past codes. Also fuel pressure.

I did scan for fault codes but it came up clean. I guess fuel pressure would be my next option then. Does it sound like a fuel pump? I was leaning towards that, TPS, or transmission. Also mor information since I just finished driving: if I slow to a stop from speed, that is when it stutters, but if I'm going slow (like a parking lot) it is fine.

 

[JackE]

I would definitely watch fuel pressures when it's acting up, but it sounds more like torque converter lock/unlock problems.

 

[Mildphil]

I would definitely watch fuel pressures when it's acting up, but it sounds more like torque converter lock/unlock problems.

Is there a way to test this? Recently I did throw the truck in reverse and nothing happened. So I threw it in neutral and then reverse again and it was fine.

 

[Mildphil]

Update: I just finished a 50 mile drive at an average speed of 65mph. The entire drive, the truck would shutter every few seconds, it seemed almost constant. It wasn't surging in power, but more of a harsh vibration than can felt in the gas pedal, floor, and seat.

 

[Mildphil]

Just took it for a night ride. It ran fone but as soon as I started giving it gas, all hell broke loose. Around 50mph the truck started stuttering and freaking out, then when I stopped at a light it was idling real low in rough until I threw it in neutral. The rest of the ride home, no matter the speed, was the car shuttering and surging. Below is my torqe info after I got home.

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[JackE]

Is there a way to test this? Recently I did throw the truck in reverse and nothing happened. So I threw it in neutral and then reverse again and it was fine.

I'm sure there is, but I'm not very knowledgeable on auto trannys. I know just enough to know when it's time to take it to a tranny shop and have them plug into it and tell me what's wrong. A good shop will run a quick test for free.

 

[Mildphil]

I'm sure there is, but I'm not very knowledgeable on auto trannys. I know just enough to know when it's time to take it to a tranny shop and have them plug into it and tell me what's wrong. A good shop will run a quick test for free.

Thanks, I just may do that this weekend. My research leads me towards tranny, cats, or fuel pump.

 

[Christian Steffen]

Thanks, I just may do that this weekend. My research leads me towards tranny, cats, or fuel pump.

Can you log fuel trims? It should throw a code if they're way off.. but it sounds like you're lean as all hell or maybe its misfiring? Check your cap and rotor?