'02 5.3ltr problems under load misfiring

[samotahoe]

double check that pcv again. ive seen too many times that would be a culprit in rough idle and load situations. also if you have access to a back pressure tester I would see how much back pressure you have. might be the cats. my main worry is in the picture there is a lot of debris. we have a lot of tahoes and ford trucks that come in and there would be rats nest under the manifold. and rats would chew up the wires. I would definitely double check wiring to make sure theres no breaks in a sensor wire that could be causing all these issues for you.

 

[Crazywelder72]

The truck has been running very good since my last post. No doubt that the oil buildup in the intake was due to the pcv valve from last year. I did replace it and on the vent from the opposite valve cover to throttle body I blew compressed air in there just to make sure it was clear.
The probality is high that I have loaded up the cats but hopefully they will clear up some. I don't have access to any of the back pressure tools you mentioned. The only time it misfires now is under 100% throttle and hold it to the floor. After about 10 seconds it's misfiring and the SES light will start to flash.

Lastly the critter check, that wasn't a nest, just seeds that fall from trees that got stuck in the oily residue. No signs of droppings or other nesting. I did check the continuity of the knock sensors and they were good.

 

[rockenthebowtie]

Hey CraCra.. Hows it going ?... Wow been following your post and gotta say I've never seen anything like this before and lets just say I have a little over 25 years in automotive industry... However it does look like you just about have most of the bugs work out... if I may make a suggestion you say you ran som chemicals through a intake manifold vacuum source was it the PCV vacuum port ? If not you might want to pick up a couple of bottles fuel injector additive you know the kind you add to the gas tank.. I was looking at the pics you posted and you see all that carbon build up on the intake galleys that also builds up on your intake valves preventing the valves to property seat allowing for a slight compression leak... So if you disconnect the PCV hose right off the top of the upper intake manifold you can get a 5/8 fuel line hose about 2 feet long and hold the throttle up about 2000-2500 rpm then dip the othe end of the 5/8 hose into the fuel injector additive bottle so that way it will help not only clean off more of the possible oil build up you were talking about but it will also clean off any possible carbon build up on the intake valves.. I really don't remember what you said you ran through the Intake vacuum source but I'm hoping kerosene wasn't one of them .. it has very low octane and is higher density than gasoline that will cause heavy engine deposits and degradation of engine oil and it can even cause permanent damage... chances are the pinging you were getting was of the lean condition due to the low fuel system pressure and or the excessive carbon build up that increases temperatures in the combustion chambers... for the most part if it was the knock sensors you would get a DTC p0332 if it was a knock sensor... but if your still set on replacing them dont forget to apply a bead of RTV around the rear knock sensor black cap only not all the way around leave an opening on the back side so that water doesnt puddle up to prevent water intrusion.. and last but not least ythe distributorless ignition system uses the crankshaft position sensor and the camshaft position sensor to let the on board computer know what cylinder is in the compression stroke then grounds the circuit of the ignition coil and fuel injector of that cylinder.. the camshaft sensor is more for the fine tuning for max performance while providing best fuel economy. .. its a book I know but hopefully you can use some of this info for future reference. . Good luck hope some of this helps

 

[ginogag]

flashing cel and pinging

hey guys , newbie , I got same problem, when I floor my 5.3 2003 tahoe , ( under load) engine starts pinging and cel starts flashing. After one minute , it goes out. I used to have constant cel and my mechanic told me I needed 02 sensors and cats , and he would have changed pcv valve. I put lucas fuel injector cleaner and light goes off. But anyway , about 127000 miles , only use premium. I brought to another mechanic once about solid cel and needed a second opinion , and he showed me broken vavle cover bolts, rear one on EACH side, and said that solid cel could be those broken bolts. I didn't feel like spending 1000 on the truck. I changed fuel filter about 4 or 5 years ago, changed plug and wires about5 or 6 years ago. when I floor it going uphill ,cel flashes for a minute and truck pings badly. Happened 2 weeks ago , and put 2 different scanners on and NO codes were on computer. Don't want to spend a ton of money , but was wondering if anyone couod help with advice
ps ....I was reading threads on knock sensor , don't know where it is.

Should I try plugs and wires or just do cats ????? thanks again
gino

 

[Crazywelder72]

Hey CraCra.. Hows it going ?... Wow been following your post and gotta say I've never seen anything like this before and lets just say I have a little over 25 years in automotive industry... However it does look like you just about have most of the bugs work out... if I may make a suggestion you say you ran som chemicals through a intake manifold vacuum source was it the PCV vacuum port ? If not you might want to pick up a couple of bottles fuel injector additive you know the kind you add to the gas tank.. I was looking at the pics you posted and you see all that carbon build up on the intake galleys that also builds up on your intake valves preventing the valves to property seat allowing for a slight compression leak... So if you disconnect the PCV hose right off the top of the upper intake manifold you can get a 5/8 fuel line hose about 2 feet long and hold the throttle up about 2000-2500 rpm then dip the othe end of the 5/8 hose into the fuel injector additive bottle so that way it will help not only clean off more of the possible oil build up you were talking about but it will also clean off any possible carbon build up on the intake valves.. I really don't remember what you said you ran through the Intake vacuum source but I'm hoping kerosene wasn't one of them .. it has very low octane and is higher density than gasoline that will cause heavy engine deposits and degradation of engine oil and it can even cause permanent damage... chances are the pinging you were getting was of the lean condition due to the low fuel system pressure and or the excessive carbon build up that increases temperatures in the combustion chambers... for the most part if it was the knock sensors you would get a DTC p0332 if it was a knock sensor... but if your still set on replacing them dont forget to apply a bead of RTV around the rear knock sensor black cap only not all the way around leave an opening on the back side so that water doesnt puddle up to prevent water intrusion.. and last but not least ythe distributorless ignition system uses the crankshaft position sensor and the camshaft position sensor to let the on board computer know what cylinder is in the compression stroke then grounds the circuit of the ignition coil and fuel injector of that cylinder.. the camshaft sensor is more for the fine tuning for max performance while providing best fuel economy. .. its a book I know but hopefully you can use some of this info for future reference. . Good luck hope some of this helps

Thanks for the reply... what i used was seafoam and ran it thru the vacumm port on the manifold near the rear, ( you have to snap the tab off then plug it when done). i did find the TSB about the rtv for the knocksensors. i did the swap and it wanst them. I can hear the enging pinging and the ses light will flash when it happens but then it goes away and no codes stored. for the past month it has been driving fine, the codes would get stored at low rpm such as getting off the highway at a red light, Cats running below efficiency. I just keep clearing them and going on my way.

today however it started to run like total **** again, bogging and hardly doing 35 up a hill. i will try the 5/8 line in the pcv valve port and the injector cleaner. seriously considering hollowing out the cats at this point but i dont want to. also heard about programming out the B1S2/B2S2 o2 sensors but not sure where or how to go about it. and any info on a simulator???

 

[rockenthebowtie]

Oh my thats starting to sound like plugged cats.. do you have a inferred temp gun.. if you do get the vehicle up to operating temp and or if you can get to where its boggling down measure the temperature before and after the cats and if the temp reading is higher in the front than it is at the rear theres a definit restriction.. a back pressure tester is more accurate but harder to come by but a inferred temp gun will work too

 

[rockenthebowtie]

Oh never heard of programing out the pist cat 02 sensors.. they have absolutely no affect on performance there just there to monitor cat converters efficiency

 

[rockenthebowtie]

*post cat

 

[Crazywelder72]

I do have a temp gun. I will give it a shot. Should they be exact before and after? Or is there a difference within spec? I found some "universal cats" from summit for about $90 each. Don't know if u can get them cheaper anywhere? I did read that upstream and down stream cats work together but that may have been vehicle specific.

Up stream cats show a rich/lean variable like fanning a fire and register with voltage accordingly. The downstream sensor should have a higher voltage showing no o2 present then controlling the fuel system to correct the values or something like that. If the downstream sensors don't affect the PCM, I may try buzzing open the bottoms and welding them closed before I go thru the expense and trouble of dropping the exhaust , fixturing up the dimensions, removing the old cat and welding in the new one.

 

[ginogag]

I do have a temp gun. I will give it a shot. Should they be exact before and after? Or is there a difference within spec? I found some "universal cats" from summit for about $90 each. Don't know if u can get them cheaper anywhere? I did read that upstream and down stream cats work together but that may have been vehicle specific.

Up stream cats show a rich/lean variable like fanning a fire and register with voltage accordingly. The downstream sensor should have a higher voltage showing no o2 present then controlling the fuel system to correct the values or something like that. If the downstream sensors don't affect the PCM, I may try buzzing open the bottoms and welding them closed before I go thru the expense and trouble of dropping the exhaust , fixturing up the dimensions, removing the old cat and welding in the new one.

well , as I told bowtie, just went thru this whole prob, last week had my cats replaced, 02 sensors replaced, and 3 intake manifold retapped and threaded. Ive been having cel, cat probs for 2 years now ,my mechanic FINALLY replaced them , worked like a charm, runs great, I was getting p300, and p301, and I think an 0101 code, all went away, .....1900 dollars later, now I hope I get a little better gas mileage, multiple mechanics I spoke to said if I put in aftermarket cats, I'd have probs after a few years , so I went with oem( prob gonna keep truck) it has 127k on it ..........he actually unbolted cats and truck ran fine.....that's how he knew it was cats ......ANYWAY GOOD LUCK

 

[ginogag]

i do have a temp gun. I will give it a shot. Should they be exact before and after? Or is there a difference within spec? I found some "universal cats" from summit for about $90 each. Don't know if u can get them cheaper anywhere? I did read that upstream and down stream cats work together but that may have been vehicle specific.

Up stream cats show a rich/lean variable like fanning a fire and register with voltage accordingly. The downstream sensor should have a higher voltage showing no o2 present then controlling the fuel system to correct the values or something like that. If the downstream sensors don't affect the pcm, i may try buzzing open the bottoms and welding them closed before i go thru the expense and trouble of dropping the exhaust , fixturing up the dimensions, removing the old cat and welding in the new one.

sorry , not intake.................exhaust manifold

 

[rockenthebowtie]

Should be around 300 degrees hotter coming out

 

[ginogag]

ALWAYS get intake and exhaust comfused

 

[Crazywelder72]

I unbolted the exahust from the manifolds and the truck ran fine. Guess its the cats. i ordered a direct fit off ebay for $245. only time will tell if it will payoff. it should arrive by tomorrow sometime. i will post a update later.
Thanks for the help. i wish i could say its been fun, but backbreaking work is never fun but it is rewarding. one hell of a learning lesson.

 

[Crazywelder72]

New cats fixed the problem!
Bank 2

Bank 1

 

[rockenthebowtie]

SWEET !!!

 

[samotahoe]

nice...

 

[Crazywelder72]

Update: the cats obviously fixed the problem but here I am a few months later and the SES light came back on. Bank 1 Sensor 2 again.

So something is causing this motor to slowly pull oil as before and contaminating the cats. Last time I thought it was that pcv valve as it was stuck. How and why is this doing this again. I will replace the $4 pcv valve today and inspect the old one.

WTF???

 

[tahowner1]

Update: the cats obviously fixed the problem but here I am a few months later and the SES light came back on. Bank 1 Sensor 2 again.

So something is causing this motor to slowly pull oil as before and contaminating the cats. Last time I thought it was that pcv valve as it was stuck. How and why is this doing this again. I will replace the $4 pcv valve today and inspect the old one.

WTF???

Any luck after replacing the PCV valve?

 

[Crazywelder72]

The motor just seems to consume oil and seems to be leaking a bit more these days. Still no marks on the driveway but the underside is wet. Anyhow it's not throwing codes anymore. I don't think the pcv valve did it, but it didn't hurt.