JimmyB1232

The past few weeks I've noticed my throttle has been a bit sluggish, but when I'm on the hwy/freeway and have it on cruise control I have better acceleration using the cruise control. But if I disconnect the battery for 20-30 min my throttle response feels normal again for a day or two. And I've tried doing the "Throttle Reset" (turning the key on the pushing the down the throttle slowly and quickly pulling it back up and repeating a few times) but that hasn't seemed to do anything. Would this be the TB motor or sensor?

I haven't noticed any decrease in MPG, and haven't had any CEL come on.

This is everything that has been replaced in the past 5k miles.

Injectors (used wrong part # ), plugs (twice), COPs, FPDM, fuel pressure sensor, both cats w/O2 sensors, fuel filter, MAF, TB cleaned, K&N Filter cleaned & oiled. Plus timing solenoids, cam sensors, crank sensor, knock sensor, timing chain, tensioners, phaser lockouts with a dyno tune.

JByrd825

Hello, JimmyB

That's definitely a nice list of maintenance you've performed. Does me good to know that you've put the effort into maintaining your truck. (I used to work for a full-service shop and dealt with tons of neglect that would make a seasoned mechanic cringe).

Is the little wrench icon illuminated on your gauge cluster? Usually that points to a dirty throttle body that needs cleaning. And if the PCM isn't throwing any codes, I would think that your TPS isn't the culprit, but do not quote me on that. If I were to make an educated guess, I would say that the sending unit in your gas pedal could be faltering. It's basically a potentiometer that regulates a voltage output (signal) that tells the throttle to open, and at what percentage. If your cruise control gives you better throttle response, I'd say it wasn't the throttle body giving you an issue. The computer tells the throttle how to act when in cruise mode, since there's no mechanical linkage between the gas pedal and throttle body. The signal sent to the throttle from the cruise control command is separate from the pedal, unless you were to give the vehicle some gas and override the percentage that the PCM is calling for at the set speed. I've never personally heard of one of these units failing on our trucks, but nothing is impossible. It's even probable that the PCM needs to be reflashed. I know that GM actually specifies that for this kind of problem, and if that doesn't fix it, it's more than likely electromechanical. I hope that maybe this can guide you in the right direction.

JimmyB1232

Nope no wrench on the dash. I know everyone says a TB spacer is nothing but an expensive paper weight that whistles for ya, but I started noticing the sluggish throttle not too long after I took off the TB spacer. Would the PCM need to be re-flashed already? I've only put about 2,500-3k miles on it since it was dyno tuned. (TB spacer was removed after the tune if that could possibly effect anything?)

JByrd825

Ahh ok. I wasn't aware that you had installed a TB spacer on your truck. Personally, I've never used, nor messed with TB spacers. Not that I think they're useless or anything...I've just never personally wanted one. It is theoretically possible, that the tune you had performed may have negatively affected your PCM and if it parameters were set up for the exact way your engine was set up, that removing the spacer caused this action, but I doubt that. It's possible that your pedal isn't sending a proper signal to the computer. Think of it this way... The computers in our vehicles are pretty damn advanced, and are very happy when they stay the way the were programmed to be. Start messing around with them (even with proper programming) and it's possible that certain parameters are negated and cause issues. Much like a smart phone being "jailbroken". Again, I am not saying that this is for sure, but anything is possible. I would have someone who is experienced and intuitive take a look at your pedal and make sure it's putting out the correct voltage and signal. If that passes, Go to the TB and TPS. If all else fails, check with the shop that tuned your truck. Hopefully they can have an answer.

JimmyB1232

Any idea what or where I can find out what the voltage output should be?

JByrd825

Unfortunately, no. I don't have a subscription with AllData or ProDemand, and those would be the best bets on finding out a testing procedure. I know this is going to sound terrible, but perhaps there's something that can be found with a google search.

JByrd825

Hey Jimmy, I've got a bit of better information. I talked to my guy. A mechanic who's been around longer than I've been alive and asked for his input. He said that my theory with the pedal is plausible, however if the vehicle isn't throwing a code, then it most likely isn't that. The PCM checks the parameters of the pedal and TB every time the system is activated. Being such a critical system, it is always being checked. If there were any issue with it, then the computer would instantly throw a code. And the only proper way to check the in going and out going commands is with a scan tool.

Now, I asked him about the probability of needing to reflash the PCM. He agreed that this would make more sense than anything, agreeing with my explanation of your truck being tuned. Best advice I can give you: take it back to whoever tuned it for you and have them check every parameter they set. I think you'll find your problem there. If not, well then I apologize. I've thought of the most logical explanation with the information given to me.

JimmyB1232

Can't we just go back to Carbs and throttle cables? haha

JByrd825

Haha. Now where would the fun be if we went back to such simple components?