lost all low end power?!?

[chevy393]

i have a 2000 chevy silverado 1500 4x4 with the 5.3L and for the last month its been acting weird like once and a while it will barley get out of its own way and other times it would take off like normal, well the last 2 weeks or so its done nothing but run bad its got nothing, i can still drive it with out a problem and dont hear anything but if i floor it it bogs down till like 2300-2500rpms then goes ok maybe not like it should but not a noticible diff after that (i think a kid on a trike could beat me 0-15mph its pretty sad : \ ), but if i give it about 1/4 or 1/2 throttle it will take off a lot better and actually go decently, i thought maybe lack of fuel dilevery but ive replaced the fuel pump about 4 months ago so i doubt it would be that but, if anyone has an idea were to start looking or knows what it could be weather it be ingition, fuel or something else compeltly diff plz let me know, the check engine light also comes on for like 3-4 days then turns it self off for like 3-4 days then back on ( checked it the 2nd time it did that and set of knock codes it said and then it turned off so idk), did that about 2-3 times and now it just stays on and then it started doing the no power thing, if anyone has anything i would greatly apritiate it,thanks. o and im thinking of seafoaming it in tommorow or next day to see if that helps or not, and if i shouldnt let me know lol, thanks

[j cAT]

this could be a number of things...first the fuel pressure must be 53-62psi...give the DTC codes found for area of failure.....

other problems COULD be a restricted exhaust....

whenever the vehicle has over 100,ooomi replace the O2 sensors [upstream] ....

the MAF/throttle body should be cleaned every 30,ooomi ...and using the MAF cleaner and throttle body cleaner will give good throttle response..

if the fuel pressure is low only use the delphi fuel pump....and if the vehicle is well over 100,ooo mi replace the fuel pump relay as well..

[chevy393]

ill check the fuel pressure at work and see but i put a new pump in it like 5-6 months ago, and for restricted exhaust i HIGHLY doubt that's it, i have true dual 3in stright pipe just cats so, but cat could be messed up idk, and i have 180k miles roughly, i was going to do a throttle body cleaning on it too some time might do that today. and O2 sensors i replaced one of them before but ill check the others, could it be a bad knock sensor cause this?

how do u feel on seafoam? i get mixed reviews on it so im not 100% sure i want to use it and cause more problems or help

thanks

[j cAT]

Originally Posted by chevy393

ill check the fuel pressure at work and see but i put a new pump in it like 5-6 months ago, and for restricted exhaust i HIGHLY doubt that's it, i have true dual 3in stright pipe just cats so, but cat could be messed up idk, and i have 180k miles roughly, i was going to do a throttle body cleaning on it too some time might do that today. and O2 sensors i replaced one of them before but ill check the others, could it be a bad knock sensor cause this?

how do u feel on seafoam? i get mixed reviews on it so im not 100% sure i want to use it and cause more problems or help

thanks

you have a worn/defective componet,,,sea foam or any other additive won't help..

fuel pumps failing after a few months/1 year are common...this is because the aftermarket is flooded with these defective parts....only use delphi...

so again did you use delphi ? O2 sensors 100,ooomi max life..upstream repalcement required.....if this is not done ,,at your mileage the cat converers may be damaged especially if you had a O2 sensor issue in the past and again the well over 100,ooomi replacement interval required by the manufacturers of the sensors...

even with 3in pipes any restriction in the flow is suspect,,,the fast way to check is remove the O2 upstream sensor on each side ,,then go for a short test drive ,,,if cat restricted you will see quickly..

testing for O2 failure when over 100,ooomi is like testing your spark plugs to see if they are still working at this mileage ...

[chevy393]

i just cleaned my throttle body completely, took it off and all about an hr ago and i felt top end performance but still the same no low end, im go take out my o2 sensors and see for clogged exhaust, and if not then ill just wait till tomm and ill hook a scanner up to it at work, i looked at my receipt from pep boys on the fuel pump and i cant tell what brand it was cause its kinda fadded but it still has its 1 year warrenty so it will be free if thats it

i apprtiate the help a lot

[chevy393]

o ment to say this to but forgot, is there an easy way to tell if o2 sensors are working or just by the scanner, i have one bran new one on driver side bank pre cat got like 3 months ago when wire frayed and broke, but any way lol thanks

[j cAT]

Originally Posted by chevy393

o ment to say this to but forgot, is there an easy way to tell if o2 sensors are working or just by the scanner, i have one bran new one on driver side bank pre cat got like 3 months ago when wire frayed and broke, but any way lol thanks

with 2 new upstream O2 sensors installed they should work together much better than ,,,,,, with old out of range sensor..

call up pep boys tell them you need a new fuel pump,,,,WHAT BRAND FUEL PUMP DO YOU USE FOR MY VEHICLE ????

If its AIRTEX its junk...

testing is the way to avoid needless part replacement ....but this is not always the case when you have parts that require replacement at specific intervals...failure to replace these componets at the correct time will save you money and unexpected vehicle failure...

If you buy a new vehicle every 3-4 years this would not apply...

[777stickman]

You really need to deal with the DTC's that are turning on the CES light. You indicated that it was a knock sensor code. In the future you should post the trouble code numbers.

The knock sensor/s will send a signal to the VCM to retard the ignition timing in the event of a sensor malfunction and/or actual knock or "pinging" (pre-ignition).

As to the previous replies, they are all good ideas. But deal with one issue at a time. The 1st one being the current active fault that is turning on the CES light.

Do a search for "knock sensor" or something similar . There are several posts in the main forum that address this issue.

[chevy393]

the engine code that poped up last time was P0327, said something like low input bank 1 sensor 1 or something like that, and some one said u can test to see if your knock sensor is good or not by tapping on the exhaust manifold while idling and seeing if the rpms change and i tryed that and nothing, is that a reliable way to test it or not really, ill hook up scanner and call pep boys tomm i guess, and also now that u say it it does feel like the timing is off cause i remember when my 87 chevy k5's timing was retarded it wouldnt get up and go it would stuter andwhat not till like 2-3k rpms then go fine, u cant fix the timing on the newer trucks its all ECU controlled right?

[j cAT]

Originally Posted by chevy393

the engine code that poped up last time was P0327, said something like low input bank 1 sensor 1 or something like that, and some one said u can test to see if your knock sensor is good or not by tapping on the exhaust manifold while idling and seeing if the rpms change and i tryed that and nothing, is that a reliable way to test it or not really, ill hook up scanner and call pep boys tomm i guess, and also now that u say it it does feel like the timing is off cause i remember when my 87 chevy k5's timing was retarded it wouldnt get up and go it would stuter andwhat not till like 2-3k rpms then go fine, u cant fix the timing on the newer trucks its all ECU controlled right?

if you wash your engine it is common for the knock sensor connections to get corroded...this code 327 is generated because of a circuit problem with the ks....reporting incorrect feedback to the pcm..

first check pcm connections wiring then you may have to expose the ks sensors for troubleshooting...

low fuel pressures can cause detonation as well,,,fuel does cool down the combustion chamber...

[chevy393]

i think ill check the sensors then cause when i go off road or anything and wash it i wash the engine, i heard it was under the intake and it had to come off? do i have to get a new intake gasket if i do and how hard is this, is it a simple take it off or is there a bunch of other shit in the way lol?

[j cAT]

Originally Posted by chevy393

i think ill check the sensors then cause when i go off road or anything and wash it i wash the engine, i heard it was under the intake and it had to come off? do i have to get a new intake gasket if i do and how hard is this, is it a simple take it off or is there a bunch of other shit in the way lol?

what is the fuel pressure///did you remove the upstream O2 sensors and test drive for improvement ????

or lets disassemble the engine????

[jyount]

Originally Posted by chevy393

i think ill check the sensors then cause when i go off road or anything and wash it i wash the engine, i heard it was under the intake and it had to come off? do i have to get a new intake gasket if i do and how hard is this, is it a simple take it off or is there a bunch of other shit in the way lol?

yes, the knock sensors are under the intake, no you do not have to replace the gaskets, but if its off I don't know why in the world you wouldn't, they ARE a common leak point anyway. the knock sensors are prone to problems, esp on the older engines. The fix is to replace it, then run a bead of silicone around the seals on the top. And when the intake goes on throw those stupid foam end plugs in the trash. There are two sensors, but in ALL situations I have seen a problem with this, they throw a code. By the way, the silicone damn was a GM technical bulletin when I worked at a dealer, this is the GM fix, not some shadetree crap.

BUT, as JCAT said, I can see no correlation between the knock sensors and your problems, if the computer is cutting the timing back, there is a reason, it will throw a code, so long story short, 99.9% of the time, this is not your problem. Like has been said, your Fuel pressure is below specs. Of the line and at full throttle, you are going longer pulsewidth, so you are pulling more fuel, less pedal, less fuel, bet thats were your problems are.

[chevy393]

well i didn't check fuel pressure today but i pulled the intake off and all that, i have to say this right now, if the sensors arnt bad it was DEFIANTLY worth taking it all off and cleaning it, the runners on the heads had so much carbon build up and just stuff and mud along the plenium? (the middle part were the sensors are?), the intake had a good thick layer of sludge and carbon in it and every thing ( btw toilet bowl cleaners fit perfectly lol, well mine did ) so imo it was worth it all just to clean the head valves intake and all, and for the sensors, i took off the little rubber thing on the front one and the little porcelin or what ever the white part is was in peices and crumbled, i unscrewed it and it looked like its been laying in a feild for the last 50 years, it was covered in rust and it just looked bad, i havnt taken the back one of yet as i dont have the right size socket and that ones in there better then the first but i plan on gettin 2 new sensors the right socket and gaskets, o and RTV i guess lol, but i really aprtiate the help and tips, 2 things i have to ask though is, is there a site or something online that will give u like procedures on how to take stuff apart and or put back toghter with pics or something? or just anything like that? i tryed lookin and havnt been able to find it, probably not searching for the right thing and for the last thing is there like another intake i could put on for better performance, like one off and LS1 or the 6.0L or something? ( i have the 5.3L, LM7) figure since i have it all apart why not throw something better on instead. o and if any of the other LS motors or whatever, any of there heads do better on my lm7 then whats on there now?

well this is the stage im at as of now, should get sensors in tomm

thanks guys