Hesitation problems.

[Tankmech4]

Good afternoon all,

 

I have an 05 silverado, v6, 5 speed manual. A week or so ago I noticed a slight hesitation at highway speed. Didn't blow it off,but monitored it.

 

Best way I can describe the hesitation is you get that feeling as you just start to run out of gas. No noticeable rpm rise or drop on the gage, nothing felt through the gas pedal, just that momentary feeling of power loss through the whole vehicle.

 

Few days later it was getting worse. Thought of bad fuel, put bottle of Heet in tank and filled it up, helped a little, on a recommendation from a fellow machanic I was going to change the fuel filter and add a bottle of Seafoam to my tank. Come to find out my truck doesn't have a changeable filter, but I did add the Seafoam. No significant change.

Next step was check fuel pressure. Reading was slightly low; about 2psi below what the manual stated was normal. In researching this, and most I asked said it shouldn't affect things. However knowing that it had never been changed since I've owned the truck, I decided to go ahead and change the pump. Reprimed the system, started it, took for a road test only to find out problem is still there. My next option was the fuel pressure sensor, however this is located in the new fuel pump. Tried to find and follow vacuum lines, but having a tough time finding a reliable picture or diagram for my truck. What few i did find were in good shape.

 

Oh yeah, and I can't hook up a scan tool due to the fact it won't read my truck. Not sure where the disconnect is between the control modules and the OBDII port, but it is there and isn't reading anything.

 

 

I'm at wits end, any and all advice will be greatly appreciated.

[Swimmer8366]

Check your fuses to see if you have one blown. That may be reason your scanner won't connect.

 

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[Swimmer8366]

Another thing to check plugs wires, injectors, and oxygen sensors will cause truck to run poor. Stall. Run rich, lean, and stumble.

 

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[Tankmech4]

I apologise, I had meant to put this in the first part, however life happened and i forgot, but plugs, wires, rotor and button were changed spring of this year.

[Tankmech4]

Which fuse might cover this? I double checked my Haynes manual AND checked the under hood fuse box but didn't see anything that screamed "hey stupid"

Check your fuses to see if you have one blown. That may be reason your scanner won't connect.

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[Motor City Rick]

Please stop changing parts until the problem is diagnosed. Guesstimating will make you go broke and the problem will still not be fixed.

 

Does this hesitation come on, ...and end quickly or does it seem more like a gradual buildup of hesitation that gets worse then disappears when you release the gas pedal???

 

Does this problem occur in much lower gears at the same rpm's???

 

Disconnect the EGR connector, keep the connector away from any heat that will melt the connector. The check engine light will go on. Did the problem change or disappear???

 

Lightly "rap" on the MAF sensor housing (not the connector) when warm with rubber / plastic mallet, the wooden end of a hammer or similar soft heavy object. At idle, did the motor burp, buck, spit, jerk, hesitate just for a second??? If so, change the MAF ASAP with a "good quality" replacement.

 

Once you get a scan tool to work on your OBD2 connector (and hope it can do "snapshots" of data), ... I need you to focus on TPS performance first. When your problem occurs, ...press the log data button. If the TPS is the issue at certain throttle positions, the TPS voltage will change to zero, 5.o volts or jump all over the place. A TPS sensor in all vehicles is the "accelerator pump" for the ECM. Loose that signal for a milliseconds it will create hesitation, stumbles and a host of other problems.