The dreaded P0300 CAUTION LONG POST
#31
10-22-2007, 09:44 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Kyle,
Last night after I posted a reply (ref; upper intake cleaning) where as I explained that I did a thorough cleaning during the MFI conversion, I got to thinking. Why would you ask about an intake tract cleaning, what was I missing here. Then after much tossing and turning, (didn't sleep last night) it hit me like a ton of bricks!! Carbon in the chambers, which combined with a lean fuel mixture (by design) could lead to detonation. It was then I understood where you were headed, the knock sensors were detecting detonation due to carbon deposits ( glow plug effect;for lack of a better way of explaining it) and the computer tried to adjust spark lead (retard timing) to compensate. The computer then saw unburned fuel as a result and concluded there was a missfire, at which time a code was set. It made sense (at 2:30 am anyway)
This morning before I left for work I checked the forum, just to see if there were any new replies and I found your post which confirmed the conclusion I reached earlier that morning. The more that I thought about it the more it made sence, except for one thing. Correct me if I'm wrong but doesn't the death rattle(detonation) increase as the load increases. This appears to me as a lean missfire. Or is what is happening is the mixture is at it's leanest( part throttle high vacuum signal ) as is programed in to the ecm to achieve the highest fuel economy with the least amount of emisions, and because of the detonation the computer backs off the timing and adds additional fuel to compensate ( to cool the intake charge below the threashold of detonation)? To me it makes sense, is this what you were trying to express?
I actually had not thought too seriously in this direction for the simple reason that when I checked the spark plus they didn't show any indication of detionation ( little fly specks on the insulators) or deposits (carbon) on the electrodes. But I have changed my thinking in this direction because it makes sense. I have to remember that unleaded fuel doesn't burn or color plugs like leaded or race fuel. I loaned out my spark plug viewer out and never got it back, so I have been trying to read plugs with the naked eye.
I guess the point that I'm trying to make is that I dismissed a diagnostic theory (tool) too quickly (STUPID) Is this the answer I've been looking for? It very well could be, it's something that I will most deffinately persue. Like I said in a previous post I have a feeling that this problem is going to come down to something so very simple that it would be easily overlooked. Detonation due to poor additive package in the gas we are forced to live with now?,....Go figure.
Even if this tends not to be the answer, I have to say that it is still a fantastic diagnostic idea, that I dismissed too quickly early on ( trying to make a mountain out of a mole hill) THANKS KYLE!!!!
I do remember reading the post you mentioned (ref; sea foam) don't remember where it was but a search shouldn't take long. I will deffinately put this advise to good use, and will post the results. It will most likely be towards the end of the week. One question though in regards to using sea foam as an intake (upper engine cleaner) should I remove my O2 sensors before hand. I just concerned that if this proceedure loosens up and removes excess carbon from the combustion cambers it has to go out through the exhaust system. Wouldn't the deposits end up coating the O2 sensors (causing an additional problem) or will it clean them as well? Same question in reference to the cat.
Any way again, Thanks fora Great idea
Gator
Last night after I posted a reply (ref; upper intake cleaning) where as I explained that I did a thorough cleaning during the MFI conversion, I got to thinking. Why would you ask about an intake tract cleaning, what was I missing here. Then after much tossing and turning, (didn't sleep last night) it hit me like a ton of bricks!! Carbon in the chambers, which combined with a lean fuel mixture (by design) could lead to detonation. It was then I understood where you were headed, the knock sensors were detecting detonation due to carbon deposits ( glow plug effect;for lack of a better way of explaining it) and the computer tried to adjust spark lead (retard timing) to compensate. The computer then saw unburned fuel as a result and concluded there was a missfire, at which time a code was set. It made sense (at 2:30 am anyway)
This morning before I left for work I checked the forum, just to see if there were any new replies and I found your post which confirmed the conclusion I reached earlier that morning. The more that I thought about it the more it made sence, except for one thing. Correct me if I'm wrong but doesn't the death rattle(detonation) increase as the load increases. This appears to me as a lean missfire. Or is what is happening is the mixture is at it's leanest( part throttle high vacuum signal ) as is programed in to the ecm to achieve the highest fuel economy with the least amount of emisions, and because of the detonation the computer backs off the timing and adds additional fuel to compensate ( to cool the intake charge below the threashold of detonation)? To me it makes sense, is this what you were trying to express?
I actually had not thought too seriously in this direction for the simple reason that when I checked the spark plus they didn't show any indication of detionation ( little fly specks on the insulators) or deposits (carbon) on the electrodes. But I have changed my thinking in this direction because it makes sense. I have to remember that unleaded fuel doesn't burn or color plugs like leaded or race fuel. I loaned out my spark plug viewer out and never got it back, so I have been trying to read plugs with the naked eye.
I guess the point that I'm trying to make is that I dismissed a diagnostic theory (tool) too quickly (STUPID) Is this the answer I've been looking for? It very well could be, it's something that I will most deffinately persue. Like I said in a previous post I have a feeling that this problem is going to come down to something so very simple that it would be easily overlooked. Detonation due to poor additive package in the gas we are forced to live with now?,....Go figure.
Even if this tends not to be the answer, I have to say that it is still a fantastic diagnostic idea, that I dismissed too quickly early on ( trying to make a mountain out of a mole hill) THANKS KYLE!!!!
I do remember reading the post you mentioned (ref; sea foam) don't remember where it was but a search shouldn't take long. I will deffinately put this advise to good use, and will post the results. It will most likely be towards the end of the week. One question though in regards to using sea foam as an intake (upper engine cleaner) should I remove my O2 sensors before hand. I just concerned that if this proceedure loosens up and removes excess carbon from the combustion cambers it has to go out through the exhaust system. Wouldn't the deposits end up coating the O2 sensors (causing an additional problem) or will it clean them as well? Same question in reference to the cat.
Any way again, Thanks fora Great idea
Gator
#32
10-23-2007, 09:16 AM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
I had thought the same thing when I originally was typing up that response, but the combustion process is quite complex and often fickle to say the least and an upper intake cleaning is cheap! Also, it is very difficult to diagnose detonation by reading the spark plugs on these newer, knock sensor equipped vehicles. The PCM cuts timing so quickly after detonation is detected that often you cannot even hear the detonation and must use a scan tool to watch the knock sensor active counts to diagnose such a problem.
The O2 and cat should be ok with the upper intake cleaning. I have never had a problem with either after doing this procedure on any of the vehicles that I have done this on. Although the possibility does exist, it could be that age old saying, "The straw that broke the camels back" type scenario. With a healthy cat & O2 sensors, you should be fine.
The O2 and cat should be ok with the upper intake cleaning. I have never had a problem with either after doing this procedure on any of the vehicles that I have done this on. Although the possibility does exist, it could be that age old saying, "The straw that broke the camels back" type scenario. With a healthy cat & O2 sensors, you should be fine.
#33
10-28-2007, 09:00 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
The rope is so short now, that I don't even have enough to hang myself.
Tried the upper intake cleaning, (Sea Foam) and talk about a difference! ( It really runs like S--- now!) Ok to be fair I kind of expected it to, sometimes things have to run their course. (get worse before they get better) I followed the steps That I found on the Blazer Forum, which were very close to the instrutions on the can. I'll spare the details, but when I got to the point of adding the Sea Foam until the engine died, it wouldn't (even with the key off) it just dieseled. It concerned me to say the least, as all I needed was to bend a rod or break a crankshaft.(It was that violent!) So I let it sit about 25-30 min. and hoped that no damage was done. I pulled the coil wire and tried to turn the engine over, andto my reliefit spun over fine. Reconnected the coil wire and tried to start it. It took quite a bit to get it fired and when it did, the smoke show began.( was like a misquito spraying truckfrom the old days) Anyway, I drove it like a getaweay car after robbing Fort Knox! The smoke only lasted about half a block, then was gone. Still I couldn't resist so I drove the hell out of it for about 25 miles. It felt like the plugs were fouled so I pulled them all out and none of them were, but Ireplaced them anyway. The miss was still presant, so given the fact that the situation didn't change from the previous, (before the Sea Foam treatment) I don't think that carbon was the culprate. But on the plus side now I have very little if any carbon build up in the chambers, and one more variable has been removed from the equation.
I really didn't want to spend the $ to add another pressure gauge to my tool inventory (cause I already have one,....... somewhere)
but I did.What follows is a summery of the findings.I hooked it up and gave it a shot. Key on, cycled until pump stopped (approx 1-2 seconds) 62psi. Turned the key and started the engine, 58 psi. Tied the gauge to the wiper arm and drove home (approx 10 miles on the highway, 65 mph) during the trip the pressure was steady at 56-58 psi (no fluctuations) Under light trottle, pressure was 54-56 psi. Any throttle application would bring an increase in observed pressure, up to as high as 62 psi. Off throttle it never dropped below 54 psi.
So now what?..... static test? Ok, here it is. Key on (no start) 60-62 psi, first 5 min, no drop. Key off after 5min. went from 60-58 psi. After10 mins. down to 56 psi. After 15mins. down to 50 psi. After 20 mins. down to 45 psi. soforth and so on. After 1 hr total loss was 34 psi. So after the first 5 mins.(holds pressure for the first 5 mins.)then drop starts and continues at a rate of about 2psi every 5 mins. I did check all connections and retested just to be sure (verify test) no change in results.
Now BEFORE we blame the FPR please remember that the spider was replaced (upgraded to MFI) less than 4wks ago. I know that just because a part is new dosen't mean that it is good, but the problem (the missfire) exsisted before the spider was upgraded. I pulled the Throttle body and the inside of the intake was dry as a bone, so I'm ruling out a leak from the FPR, metering block, injectors etc. The metering block came with O rings (for the supply and return lines) installed from the factory. If they were leaking wouldn't fuel be visable from the out side (pressurized) or is the rate of bleed off so small that the fuel would evaporate faster than it would collect or otherwise be seen? What amount of leak down if any is acceptable, over what period of time? Is there a check valve in the system (in the tank etc. ) that could be causing the bleed off. Or am I making a mountain out of a mole hill again?
I'm almost to the point of putting this truck out of my misery, I'm down to one bullet,.........which one gets it? Me or my Blazer
Gator
Tried the upper intake cleaning, (Sea Foam) and talk about a difference! ( It really runs like S--- now!) Ok to be fair I kind of expected it to, sometimes things have to run their course. (get worse before they get better) I followed the steps That I found on the Blazer Forum, which were very close to the instrutions on the can. I'll spare the details, but when I got to the point of adding the Sea Foam until the engine died, it wouldn't (even with the key off) it just dieseled. It concerned me to say the least, as all I needed was to bend a rod or break a crankshaft.(It was that violent!) So I let it sit about 25-30 min. and hoped that no damage was done. I pulled the coil wire and tried to turn the engine over, andto my reliefit spun over fine. Reconnected the coil wire and tried to start it. It took quite a bit to get it fired and when it did, the smoke show began.( was like a misquito spraying truckfrom the old days) Anyway, I drove it like a getaweay car after robbing Fort Knox! The smoke only lasted about half a block, then was gone. Still I couldn't resist so I drove the hell out of it for about 25 miles. It felt like the plugs were fouled so I pulled them all out and none of them were, but Ireplaced them anyway. The miss was still presant, so given the fact that the situation didn't change from the previous, (before the Sea Foam treatment) I don't think that carbon was the culprate. But on the plus side now I have very little if any carbon build up in the chambers, and one more variable has been removed from the equation.
I really didn't want to spend the $ to add another pressure gauge to my tool inventory (cause I already have one,....... somewhere)
but I did.What follows is a summery of the findings.I hooked it up and gave it a shot. Key on, cycled until pump stopped (approx 1-2 seconds) 62psi. Turned the key and started the engine, 58 psi. Tied the gauge to the wiper arm and drove home (approx 10 miles on the highway, 65 mph) during the trip the pressure was steady at 56-58 psi (no fluctuations) Under light trottle, pressure was 54-56 psi. Any throttle application would bring an increase in observed pressure, up to as high as 62 psi. Off throttle it never dropped below 54 psi. So now what?..... static test? Ok, here it is. Key on (no start) 60-62 psi, first 5 min, no drop. Key off after 5min. went from 60-58 psi. After10 mins. down to 56 psi. After 15mins. down to 50 psi. After 20 mins. down to 45 psi. soforth and so on. After 1 hr total loss was 34 psi. So after the first 5 mins.(holds pressure for the first 5 mins.)then drop starts and continues at a rate of about 2psi every 5 mins. I did check all connections and retested just to be sure (verify test) no change in results.
Now BEFORE we blame the FPR please remember that the spider was replaced (upgraded to MFI) less than 4wks ago. I know that just because a part is new dosen't mean that it is good, but the problem (the missfire) exsisted before the spider was upgraded. I pulled the Throttle body and the inside of the intake was dry as a bone, so I'm ruling out a leak from the FPR, metering block, injectors etc. The metering block came with O rings (for the supply and return lines) installed from the factory. If they were leaking wouldn't fuel be visable from the out side (pressurized) or is the rate of bleed off so small that the fuel would evaporate faster than it would collect or otherwise be seen? What amount of leak down if any is acceptable, over what period of time? Is there a check valve in the system (in the tank etc. ) that could be causing the bleed off. Or am I making a mountain out of a mole hill again?
I'm almost to the point of putting this truck out of my misery, I'm down to one bullet,.........which one gets it? Me or my Blazer
Gator
#34
10-28-2007, 09:24 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Have you tried different gas stations??
Have you ruled out the possibility of water/condensation in your tank by trying some dry-gas?
Man I'm really running out of ideas without telling you to come north to our soon to be winter wonderland so I can plug it into my scantool and have a look at those O2 sensor readings as well as record the pertinent operating parameters while it's acting up...
Have you ruled out the possibility of water/condensation in your tank by trying some dry-gas?
Man I'm really running out of ideas without telling you to come north to our soon to be winter wonderland so I can plug it into my scantool and have a look at those O2 sensor readings as well as record the pertinent operating parameters while it's acting up...
#35
10-28-2007, 11:17 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Kyle,
In answer to your questions,.......yes and yes. Both are things that I've tried before and had no success with. I'm sorry to keep posting questions about this problem, but I'm at a loss. I am coming to the conclusion that without a proper scan tool I'm SOL trying to diagnose this. I really hate to take her to anybody to figure out whats wrong. But I've run out of ideas, and I'm affraid that I've bored everyone here to the point where I'll soon be receiving boxes of bullets. (for me and my truck)
I cannot thank everyone here enough for trying to help me, I'm so very sorry that this has gone as long as it has. Everone here has been great and provided me with lots of ideas, and support. I did get a recommendation for an independant shop today, so I guess I'll take my a--whipping like a man, and let somebody else figure it out.
If and or when I can get this issue resolved I'll post a follow up, so at least maybe someone else can benefit without having to take a loan out on their soul.
Again Thanks to everyone for putting up with me.
Gator
In answer to your questions,.......yes and yes. Both are things that I've tried before and had no success with. I'm sorry to keep posting questions about this problem, but I'm at a loss. I am coming to the conclusion that without a proper scan tool I'm SOL trying to diagnose this. I really hate to take her to anybody to figure out whats wrong. But I've run out of ideas, and I'm affraid that I've bored everyone here to the point where I'll soon be receiving boxes of bullets. (for me and my truck)
I cannot thank everyone here enough for trying to help me, I'm so very sorry that this has gone as long as it has. Everone here has been great and provided me with lots of ideas, and support. I did get a recommendation for an independant shop today, so I guess I'll take my a--whipping like a man, and let somebody else figure it out.
If and or when I can get this issue resolved I'll post a follow up, so at least maybe someone else can benefit without having to take a loan out on their soul.Again Thanks to everyone for putting up with me.
Gator
#36
10-28-2007, 11:42 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Like I said way back when. P0300 is the worst code there is., and now you too have joined the lucky ranks of us poor souls to live through the ordeal.
I highly recommend a dealer service tech. Fork out hte $80 and let them do a complete diagnostic.
I'll give you $50 for the truck.
I highly recommend a dealer service tech. Fork out hte $80 and let them do a complete diagnostic.
I'll give you $50 for the truck.
#37
10-30-2007, 04:38 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
MY BUDDY HAD THIS PROBLEM ONCE BEFORE, AND IT TURNED OUT TO BE THE COIL. HE THOUGHT IT WAS FINE, BECAUSE IT WAS BRAND NEW. HE TOOK THAT ONE BACK AND STARTED RUNNING FINE AFTER THAT. IT MAY NOT HELP, BUT I HAVENT SEEN ANYTHING ABOUT YOU CHECKING YOUR AIR FILTER. GOOD LUCK.
#38
10-30-2007, 05:43 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Matt,
Thanks for the imput. As for the coil it's been replaced once (along with the module waaaaayyyy back in the begining) and I don't think that it's the culprit. It is something that I will definately take into consideration and retest. Usually a coil either works or it doesn't,......usually. I'm to the point where I either buy myself a really killer scan tool ( Kyle hooked me up with a really sweet web site link,........Thanks Kyle!!) or take it to a guy my parts supplier recommended and have him run a full system scan and see what he thinks. Then maybe I'll take it to the dealer and have them do the same. (just to compare the two) I still haven't made up my mind. If I buy the scaner, then I'll have it forever. But right now the blazer (the 01) is the ONLY thing I have that is computer controlled ( I kinda like it that way) So it's a matter of where do I spend the cash,.............tough call.
As for the air filter It's a K/N drop in (stock air box) and no it wasn't over oiled, and yes I've cleaned and tested the MAF sensor at least twice. I hope that a full system scan (whether by me or someone else )will finally show where the problem lies. God knows I've already worn out at least 3 fine tooth combs. But as I've said before I will take ANY suggestions,.........Don't want to miss the forest for the trees, so to speak.
Again thanks for the imput and I'll test the coil again just to be sure.
Gator
Thanks for the imput. As for the coil it's been replaced once (along with the module waaaaayyyy back in the begining) and I don't think that it's the culprit. It is something that I will definately take into consideration and retest. Usually a coil either works or it doesn't,......usually. I'm to the point where I either buy myself a really killer scan tool ( Kyle hooked me up with a really sweet web site link,........Thanks Kyle!!) or take it to a guy my parts supplier recommended and have him run a full system scan and see what he thinks. Then maybe I'll take it to the dealer and have them do the same. (just to compare the two) I still haven't made up my mind. If I buy the scaner, then I'll have it forever. But right now the blazer (the 01) is the ONLY thing I have that is computer controlled ( I kinda like it that way
) So it's a matter of where do I spend the cash,.............tough call.As for the air filter It's a K/N drop in (stock air box) and no it wasn't over oiled, and yes I've cleaned and tested the MAF sensor at least twice. I hope that a full system scan (whether by me or someone else )will finally show where the problem lies. God knows I've already worn out at least 3 fine tooth combs. But as I've said before I will take ANY suggestions,.........Don't want to miss the forest for the trees, so to speak.
Again thanks for the imput and I'll test the coil again just to be sure.
Gator
#40
11-03-2007, 06:15 PM
RE: The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER
Is the War over?[sm=patriot.gif]
If it is I'm not going to know how to act. I really hate to say anything for fear of jinxing myself, but here goes.
I took hanr3's advise an changed the cap, rotor and plugs,.......AGAIN, and saw little to no improvement. I was going to take the old girl in and have a diagnostic done, but it was so nuts at work this week that it wasn't possible.
I stopped by the parts store on the way home to pick up a new fuel filter( who knows what the sea foam dislodged in the fuel tank) and as I was walking out I saw it............Dielectric grease!
Ok, I know it sounds silly, but give me a minute and I'll try to explain. Back in the very begining I mentioned that the truck died on the way to work.( the very first post) The fix turned out to be a new coil, and a new..........module. This is the part where I admit to being REALLY STUPID[sm=headbang.gif]The new module did not come with any dielectric grease. In my haste to try to fix the problem I took a short cut,........I scraped the grease off the old module and reapplied it to the new one.[sm=icon_beat.gif]At the time I fully intended to pull it back apart and do it right. Of course when themodule replacement cured the no run situation I was so happy that I forgot to go back correct the short cut. Today I corrected that mistake,.........and the missfire is gone!
To be honest I'm afraid that I'm getting my hopes up, but after months of fighting this problem, to do something (anything) that seems to have cured the problem is a HUGE deal. Is it wishful thinking? I sure hope not! Time will tell, I'll know for sure in the morning.
In a way it makes no sense, in a way it does. Why would it (the missfire) only show up under part or lite throttle. Does the grease isolate the module from heat soaked up from the bracket? Or does it keep the module from grounding out on the bracket? I don't really understand why the factory located it (along with the coil) in one of the worst places you could find for radiant heat. (top of a valve cover above an exhuast manifold)
I know it sounds strange but so far it is what it is. If this indeed cures the problem I'll be happier than a tornado in a trailer park!!!!!!!!![sm=happybounce.gif]
I'll keep yall posted.
Gator
If it is I'm not going to know how to act. I really hate to say anything for fear of jinxing myself, but here goes.
I took hanr3's advise an changed the cap, rotor and plugs,.......AGAIN, and saw little to no improvement. I was going to take the old girl in and have a diagnostic done, but it was so nuts at work this week that it wasn't possible.
I stopped by the parts store on the way home to pick up a new fuel filter( who knows what the sea foam dislodged in the fuel tank) and as I was walking out I saw it............Dielectric grease!
Ok, I know it sounds silly, but give me a minute and I'll try to explain. Back in the very begining I mentioned that the truck died on the way to work.( the very first post) The fix turned out to be a new coil, and a new..........module. This is the part where I admit to being REALLY STUPID[sm=headbang.gif]The new module did not come with any dielectric grease. In my haste to try to fix the problem I took a short cut,........I scraped the grease off the old module and reapplied it to the new one.[sm=icon_beat.gif]At the time I fully intended to pull it back apart and do it right. Of course when themodule replacement cured the no run situation I was so happy that I forgot to go back correct the short cut. Today I corrected that mistake,.........and the missfire is gone!
To be honest I'm afraid that I'm getting my hopes up, but after months of fighting this problem, to do something (anything) that seems to have cured the problem is a HUGE deal. Is it wishful thinking? I sure hope not! Time will tell, I'll know for sure in the morning.
In a way it makes no sense, in a way it does. Why would it (the missfire) only show up under part or lite throttle. Does the grease isolate the module from heat soaked up from the bracket? Or does it keep the module from grounding out on the bracket? I don't really understand why the factory located it (along with the coil) in one of the worst places you could find for radiant heat. (top of a valve cover above an exhuast manifold)
I know it sounds strange but so far it is what it is. If this indeed cures the problem I'll be happier than a tornado in a trailer park!!!!!!!!![sm=happybounce.gif]
I'll keep yall posted.
Gator