Truck loosing power

[ASkipper]

I got a 2005 Silverado Crew Cab Z71 w/5.3. I have 295/70r17 Toyo Open Country MT tires on it. I was driving it Saturday on opening day of deer season- which means I had a lot of stop and go driving with a lot of mud, water, and dirt road driving. Truck started acting funny about mid day. I could press the gas pedal and it would not hardly go. When it got to about 2000rpms it seemed to take off. I noticed it did not have any take off power. It would not even spin the wheels over on a dirt road. I had to lock it in 4wd low one time and it still did not want to take off. It had the SES light burning and I checked it when I got home and it was for one of the knock sensors not responding. The SES light had been burning for awhile as I have not had time to fix it. I cleared the DTC's with HP Tuners and the power was back. I drove it Yesterday and it was fine till later on in the afternoon. Then it started doing the same thing. I know I could try taking out the Torque Management. I dont understand why it would be fine one minute and then no power the next. The SES light has not come back on and still the power is gone. What could I try the truck is bone stock down to the paper filter. Only changed the tires.

[MonteC]

fix the knock sensor.

[TurboWS6]

Originally Posted by MonteC

fix the knock sensor.

^This.

A bad knock sensor will make the computer pull timing like crazy, all it has to do is tell the ECU you have knock and your timing goes away (if its bad its telling the ECU your knocking) along with that, your power. Chances are its got water or oil under the grommet in the valley pan, not saying you had the truck in water though, it accumulates over time due to the high humidity of the south and heat cycles. When you change it make sure you seal the rubber grommet with some silicone and seal the other one while your there to and this shouldn't happen again.

[LXtasy]

Yup. Could look like this.

[ASkipper]

I was told while I had the intake off that I should replace both sensors and the wire harnesses. That is around $150 in parts. What do yall think.

[BigdaddyDupree]

If you are going to do it swap them both and the harness. I can sell both knock sensors and the harness for about 150 through the dealership i work at. Get a good silicone to seal around the top of knock sensors also.

[ASkipper]

Originally Posted by BigdaddyDupree

If you are going to do it swap them both and the harness. I can sell both knock sensors and the harness for about 150 through the dealership i work at. Get a good silicone to seal around the top of knock sensors also.

Is the harness you can get plug and go or do you have to splice it in. The one at Oreily's is one you have to splice.

[TurboWS6]

The GM one Dupree is offering is plug and play. Make sure you get the GM intake gaskets to, the aftermarket ones are hit or miss, I bought a set of aftermarkets and couldn't get them to stay in the intake long enough to bolt it down, thought I had it and one popped out didn't notice it, started the car and had a bad vacuum leak because the intake cut the gasket. Bought GM they stay in like a charm. You might get lucky and not have to change them too just depends on whether or not they a smashed once the intake comes off.

Another pit fall is the oil pressure sending unit, when you pull the intake makes sure it only comes up and forward, if you let the intake go back toward the fire wall the sending unit will break, and you will be out another 50 dollars to replace it.

[BigdaddyDupree]

The one i have is plug and play

[ASkipper]

Originally Posted by BigdaddyDupree

The one i have is plug and play

I wish I was closer to you I would jump all over it. Sadly enough Im in Conway. Do you happen to have the part #'s and maybe I could get them through my local dealer here for a decent price.

[BigdaddyDupree]

12601822X1
12589867X2

[ASkipper]

Originally Posted by BigdaddyDupree

12601822X1
12589867X2

Thank you sir.

[AverageJoe]

I had a knock sensor code on my 01 and found one of the sensors unplugged. Plugged it back in, new intake gaskets and it was gtg. I guess the factory must not have snapped it on all the way and it worked its way off in 9 years. Been a couple years and ~40k and still no codes. Good Luck!

**Edit: I wish I had replaced the oil pressure sensor while I had the intake off, I am getting some erroneous low or no oil pressure readings sometimes. That is some extra money I would recommend spending, not so much the harness (unless there is damage, of course).

[schardbody]

knock sensor code wont cause timing to be pulled, atleast on my truck it doesnt. i've verified with HPtuners that it runs exactly what my map says with the code on or off.

the felpro gaskets are fine, and i actually prefer them over OEM in truck applications (totally different gaskets than car).

DO NOT take the intake off without replacing both sensors and harness with OEM parts, or you'll be doing it again.

remove the foam from the bottom of the intake. use RTV (i prefer grey) to build a dam around the knock sensor connectors after install (you'll see what i mean when you get the intake off). the rear sensor will be rusted and have water/mud sitting in the valley. the foam prevents moisture from getting out so its got to go, the dam/sealant is to keep the moisture out.

take a GOOD look at your steam vent line/s i've seen quite a few rusted through or about to rust through.

leave the fuel rails on, no need to remove them. you will have to feed the evap purge solenoid nylon hose/line through the drivers side but its easily done.

i use a wet/dry vac to clean the heads intake mounting surface as soon as the intake comes off, you'll see why.

[2001hawk]

Originally Posted by schardbody

knock sensor code wont cause timing to be pulled, atleast on my truck it doesnt. i've verified with HPtuners that it runs exactly what my map says with the code on or off.

the felpro gaskets are fine, and i actually prefer them over OEM in truck applications (totally different gaskets than car).

DO NOT take the intake off without replacing both sensors and harness with OEM parts, or you'll be doing it again.

remove the foam from the bottom of the intake. use RTV (i prefer grey) to build a dam around the knock sensor connectors after install (you'll see what i mean when you get the intake off). the rear sensor will be rusted and have water/mud sitting in the valley. the foam prevents moisture from getting out so its got to go, the dam/sealant is to keep the moisture out.

take a GOOD look at your steam vent line/s i've seen quite a few rusted through or about to rust through.

leave the fuel rails on, no need to remove them. you will have to feed the evap purge solenoid nylon hose/line through the drivers side but its easily done.

i use a wet/dry vac to clean the heads intake mounting surface as soon as the intake comes off, you'll see why.

Why your vehicle would not pull timing when the knock sensors detect detonation is NOT normal. Every GM vehicle I have seen lays down like a dog when the knock sensors tell the PCM. Usually 12 degrees of timing is pulled and that is noticeable. Some of the guys rely on the knock sensors to pull timing for there nitrous. It is a little strange because if the knock sensors had been tuned out at some point it shouldn't be able to set off your MIL.

[2001hawk]

Loosey you got some 'splaining to do. LOL.

[BigdaddyDupree]

if you need to get a good deal i could always mail them to you

[schardbody]

Originally Posted by 2001hawk

Why your vehicle would not pull timing when the knock sensors detect detonation is NOT normal. Every GM vehicle I have seen lays down like a dog when the knock sensors tell the PCM. Usually 12 degrees of timing is pulled and that is noticeable. Some of the guys rely on the knock sensors to pull timing for there nitrous. It is a little strange because if the knock sensors had been tuned out at some point it shouldn't be able to set off your MIL.

working knock sensors detect abnormal knock and send that information to the PCM to make changes to ignition timing. under these circumstances a code is not set.

knock sensor codes are set when the PCM does not get input from the knock sensor/s either because the sensor is bad or the circuit is bad.

there is no code for "too much knock".....


when my truck had a knock sensor "A" code i was wondering how much timing was dropped because of the code so i logged ignition timing, then replaced the sensors and harness and logged again. no change in ignition timing so i compared the numbers to the map and it was the same.

the PCM has the ability to advance the timing based on input from the knock sensors, i believe the PCM might not do this with a KS code, but Jaime would probably have a better understanding of this part. i've never looked at adaptive ignition, i tune for zero knock retard and then let the PCM do its own thing.

[TurboWS6]

So out of curiosity, doesn't the SES light throw car/ truck in limp mode, and use that timing table. Hense reducing the timing?

[2001hawk]

I know there is no code for the knock sensors pulling timing. I have had to pull an intake off before because the little harness had been smashed and eventually chaffed through grounding out which threw a code.