Truck loosing power

[LXtasy]

Just shoot it with all that timing pulled

[RoadconeTuning]

MASH DA MOTOR

[schardbody]

Originally Posted by 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?

From what I seen the base timing table was still used with or without the code or error present. People think dtc's put the car in open loop but that's not the case with most codes the vehicle still runs closed loop, so the pcm is still receiving data from input sensors and making live changes. A lot of older pcm's didn't have this ability and would go open loop in the event of an error code.

If he has hptuners it would be very easy to see if I'm right just log ignition timing and compare it to your map like I did.

[ASkipper]

I was tolod at dealer that it may be the fuel pump. I drove truck all day Monday and it lost power around 4:00 and the SES light is not burning. I am wondering if it may be the fuel pump. I hear it cost a lot to get it fixed.

[LXtasy]

remove bed. replace pump yourself. put bed back on.

[bwelch]

just put a walbro in the stock bucket....$100 is better then $300 ish

[Dride76]

Fought the same issue for months. Put in 2 fuel pumps. The whole time it was crank position sensor. Didn't throw the code when you weren't driving.

[ASkipper]

I think I have found the culprit. I put my fuel pressure gauge on the truck- 60psi even when driving and still no take off power. The SES light was not lit so I checked the DTC's and low and behold P0336 code but no light. I cleared it and drove it down the road to a dirt lane near my house. It would take off good. I drove it around more and noticed the power gone again. No light- Checked the DTC's and the P0336 code was back. cleared it and power was back. When I day power is gone I mean think of it as TM times 3 it is dead until about 2200-2500 rpm. If I have time tomorrow I am going to log it with HP and see what happens with and without the code.

[schardbody]

crank sensor on an LS motor is unlikely but a possibility none the less.


it is common for the fuel pumps to break down over time, usually cause higher amp draw and burn up the stock connector first though (usually diagnosed as a fuel pump). normally wont cause a low rpm issue though, more than likely you'll see the problem going up a steep grade or other high load situations. based on what you said its probably not a bad fuel pump.

[schardbody]

posted at the same time as me... wonder if you got some water in the connector from the hunt club.

[ASkipper]

Originally Posted by schardbody

posted at the same time as me... wonder if you got some water in the connector from the hunt club.

Light has been on for 6 months for the Knock sensor. It is a good posibility about mud and water as I was going through a lot of mud.

[gearmesh, inc.]

When you are losing power, take a look at your fuel trim parameters to see if fuel is being added. You mentioned fuel pressure stays at a constant 60 psi like it is supposed to, so that should rule out the pump.

Fuel trim values typically run +/- 10% when things are running right. Since you have enough fuel pressure, a abnormally low reading MAF can under-report how much air is actually coming into the engine. As a result, fuel delivery won't be enough to mix with the actual air mass going in the engine. This causes the HO2s to read lean, so the PCM will add more fuel in order to get the HO2s to switch rich for a moment. The more fuel the PCM adds, the greater the positive fuel trim correction percentage. MAF sensors don't always set a code unless they crap out all the way.

Another way to check to see if a MAF is reading what it should is to watch how many grams/sec of air are reported from the MAF sensor when you run WOT to the top of the tach. The max number of grams/sec should be approximately 80% of the horsepower the engine is normally capable of. For example, if the engine is advertised at 300hp, you should see around 240 grams/sec of air coming into the engine at WOT redline.

[ASkipper]

Originally Posted by gearmesh, inc.

When you are losing power, take a look at your fuel trim parameters to see if fuel is being added. You mentioned fuel pressure stays at a constant 60 psi like it is supposed to, so that should rule out the pump.

Fuel trim values typically run +/- 10% when things are running right. Since you have enough fuel pressure, a abnormally low reading MAF can under-report how much air is actually coming into the engine. As a result, fuel delivery won't be enough to mix with the actual air mass going in the engine. This causes the HO2s to read lean, so the PCM will add more fuel in order to get the HO2s to switch rich for a moment. The more fuel the PCM adds, the greater the positive fuel trim correction percentage. MAF sensors don't always set a code unless they crap out all the way.

Another way to check to see if a MAF is reading what it should is to watch how many grams/sec of air are reported from the MAF sensor when you run WOT to the top of the tach. The max number of grams/sec should be approximately 80% of the horsepower the engine is normally capable of. For example, if the engine is advertised at 300hp, you should see around 240 grams/sec of air coming into the engine at WOT redline.

I drove it all day today and it lost power once and then the SES light came on. I cleared the P0332 code and the power was back. Last week I was burning a lot of gas. This week it did not burn near as much. I know I am going to change the knock sensors tomorrow. Then go from there.

[98z-28camaro]

HAVE YOU REPLACED THE KNOCK SENSORS YET??? ITS NOT A BAD JOB.....

[ASkipper]

Got it fixed today.

Intake off


A little dirty


Rear sensor


Front Sensor


Front sensor plug


Rear Sensor Plug Notice the stud is rusted completely into. That's supposed to be in sensor.


Rear sensor out




Took me about 2 hrs to do it. It would not have taken that long if I could have found my fuel line tool. For some reason it has disappeared. I had to make a tool out of some hard round plastic to get the fuel line off. If it hadn't been for that I could have had it done in a little over an hour. No wonder that it was throwing the P0332 code for the rear sensor the stud for the harness was rusted into and not getting a good signal. Now to see if that's the only problem I have. Fingers crossed.

[TurboWS6]

Pretty nasty in there. Seems this rusty knock sensor is becoming a common problem.

[schardbody]

its been a problem since LS motors went in trucks in late 99, i assume its because the engines sit at an angle in the trucks as compared to the cars, could have something to do with the intake aswell.

as long as you take the foam off and use RTV on the sensor plugs you shouldnt have a problem with them again.

i havent seen one with the top rusted off like that, i could see that sending a false knock signal to the PCM and pulling a ton of timing, but i'm still skeptical.

[2001hawk]

LOL at tags.

[schardbody]

Anonymous tags = no balls.

If you want to dispute something I said lets see who has the knowledge and experience. Post up!

[2001hawk]

I am not responsible for the tags, but find them funny nonetheless. I could call you a dumbass, or a stupid fuck, or a moron, or a lot of other things, but what would be the point.