2003 w/4.8 no power, bogging, misfire on even cylinders

[kenman1717]

My '03 has been getting worse, towards the end of last year every couple weeks it would throw a MAF performance code under a hard acceleration from a stop, cleaned MAF numerous times and replaced air filter numerous times, got fed up and replaced MAF in February of this year under the advice of a GM driveability tech. Truck was good until about June then it threw lean codes for bank 1 and 2, under hard accel from a stop, cleared codes first time, bought a fuel filter but didn't get a chance to change it. light came back, about 2 weeks later scanned same codes, didn't bother clearing, light went out a few days later. Changed the fuel filter and put in injector cleaner, but the next day the light came back on after an uphill accel from a stop, didn't bother checking it or anything, then on Friday of the 2nd week of July, I could hardly go up a hill, truck was bogging and had no power, so I went and scanned it was for CAT efficiency bank 2, I couldn't do anything about it, as my truck was going to the body shop for an insurance door for about a week, so I cleared the code. When I got the truck back, not really thinking about the check engine light coming back I went for a drive on the highway to see if the body shop fixed the wind noise, so i'm accelerating up a hill, it bogs down and the check engine light starts flashing, when I get to the top and start to cruise, the light goes out, turn around, same thing happens again. Unable to do anything about this right now I try to baby the truck this week. Light stayed off until today, was flashing, going out, staying on solid, didn't matter up hill or not. I scanned it again, all it says now is p0300 cylinder misfire, checked misfire history all even cylinders on bank 2 had thousands of misfires. At idle it wasn't misfiring, only when I reved it up did they start. I read online about similar problems that people are having with these trucks, and it seemed that a common thing was the CAT and deteriorating spark plugs do to the ethanol in the gas. I just took a bosch spark plug course, and they talked a lot about ethanol ruining the plugs so they introduced iridium plugs that stand up the high content of ethanol. So I guess i'm wondering if, updating the spark plugs and doing something with the CATS might remedy this situation. Any help is appreciated.
2003, 4.8l, 247000kms, plugs/wires done 20000kms ago, in feb 2012, fuel filter at same time, I try to do it every 20k, did it in june for the lean code.
sorry for the long post, a lot of info, maybe not all needed.

[MT-2500]

Originally Posted by kenman1717

My '03 has been getting worse, towards the end of last year every couple weeks it would throw a MAF performance code under a hard acceleration from a stop, cleaned MAF numerous times and replaced air filter numerous times, got fed up and replaced MAF in February of this year under the advice of a GM driveability tech. Truck was good until about June then it threw lean codes for bank 1 and 2, under hard accel from a stop, cleared codes first time, bought a fuel filter but didn't get a chance to change it. light came back, about 2 weeks later scanned same codes, didn't bother clearing, light went out a few days later. Changed the fuel filter and put in injector cleaner, but the next day the light came back on after an uphill accel from a stop, didn't bother checking it or anything, then on Friday of the 2nd week of July, I could hardly go up a hill, truck was bogging and had no power, so I went and scanned it was for CAT efficiency bank 2, I couldn't do anything about it, as my truck was going to the body shop for an insurance door for about a week, so I cleared the code. When I got the truck back, not really thinking about the check engine light coming back I went for a drive on the highway to see if the body shop fixed the wind noise, so i'm accelerating up a hill, it bogs down and the check engine light starts flashing, when I get to the top and start to cruise, the light goes out, turn around, same thing happens again. Unable to do anything about this right now I try to baby the truck this week. Light stayed off until today, was flashing, going out, staying on solid, didn't matter up hill or not. I scanned it again, all it says now is p0300 cylinder misfire, checked misfire history all even cylinders on bank 2 had thousands of misfires. At idle it wasn't misfiring, only when I reved it up did they start. I read online about similar problems that people are having with these trucks, and it seemed that a common thing was the CAT and deteriorating spark plugs do to the ethanol in the gas. I just took a bosch spark plug course, and they talked a lot about ethanol ruining the plugs so they introduced iridium plugs that stand up the high content of ethanol. So I guess i'm wondering if, updating the spark plugs and doing something with the CATS might remedy this situation. Any help is appreciated.
2003, 4.8l, 247000kms, plugs/wires done 20000kms ago, in feb 2012, fuel filter at same time, I try to do it every 20k, did it in june for the lean code.
sorry for the long post, a lot of info, maybe not all needed.

Pitch the bosh plugs in trash can and get the proper Motor craft plugs for it.
Comfirm good fuel pressure on road running.

[j cAT]

I am surprised mt2500 recommended Motorcraft plugs.

these engines require ac delco iridium . these last about 100,ooomi. . the engine is very sensitive to plug type. also do not try to gap plugs doing so will damage the small tip. If the gap looks wrong the plug is defective.

I in the past used the bosch plugs. they do not last and with the ac delco iridium I found the engine starts much faster.

check the fuel pressure and do the fuel pressure test procedure.

measure plug wire resistance if any too high get the same plug wires with the same OEM resistance. you may have to buy ac delco plug wires for this to be correct.

O2 sensors are good for 100,ooomiles. the thing that Damages them would be engine coolant or excessive oil burning. the MAF will get damaged if you use the wrong cleaner. only use MAF cleaner . CRC is a good brand. do not touch the small sensor wires. also make sure the air ducting is secure.

[Tech II]

I agree on using A-C/Delco plugs(yeah, I don't understand the Motorcraft suggestion either), but I don't think that is the cause of your misfire, since it is misfiring on all cylinders on the same side.....sounds like that cat is partially plugged, and the engine can't "breathe" on that side......

Whenever that CE light flashes, that means you have a misfire that is so bad, it can harm the cat(incomplete combustion sending unburned fuel to that hot cat, will melt the catalyst)......

Concerned about the lean codes for both banks though.....could be fuel pressure(low), or a vac leak affecting both sides.....or even the MAF(especially if aftermarket).....double check the integrity of the snorkle between the MAF and the intake....

[MT-2500]

Sorry about that I had Ford on my brain.

Ac Delco for GM.
Motor craft for Ford.

[kenman1717]

I thought he was suggesting I get MotorCraft plugs that would work in my truck. I know we used to get ac-delco eqivilants for the fords when needed.
When I did the tune up last year, I was working at a GM dealer so I used all GM plugs and wires at that time as well as a ac-delco fuel filter. But the ones I put in last year were ac-delco double platinum. When I changed the MAF, I got a GM one. I know all about not touching the wires and the proper cleaner, don't worry. I used a Napa fuel filter a couple weeks ago when I did it. I wasn't saying I was going to use a Bosch plug, I was saying I took a Bosch course that explained about the ethanol and the iridium plug, and was wondering if I should upgrade to iridium. I will check fuel pressure. No oil or coolant burning.
"sounds like that cat is partially plugged, and the engine can't "breathe" on that side......" that's funny I had a couple people say that exact thing to me word for word.
On sunday I can get my truck on the hoist, I think I will pull the ypipe off and see if it runs any better with out the cats, I know it will be noisey but if the engine can "breathe" then at least I will have piece of mind.
I will check fuel pressure as well just to see. I'm hoping what ever is wrong its nothing major on the engine side, i'm building another one, this one knocks loud when its cold, the other one only has 16,000kms but has been sitting on a shelf for 10 years, just don't want to spend a lot of money on the old engine, depends on whats wrong.

[kenman1717]

It was the cats. Took the y-pipe down and put a scope camera down the pipe, the pass side one was partially broke up and looked like the small stuff was plugging the part that wasn't broke. The one on the drivers side was still intact but it looked like 1/4 of the holes were plugged. Since this is a long weekend and nothing is open until Tuesday I cut the cats out and clamped a couple pieces of pipe in there place. It was running better, no misfires, checked fuel pressure, about 59-61 in there was where it was at. Went for a drive, no check engine light flashing, I thought it would come on it closed loop because I removed the cats, oh well. On Tuesday i'm going to see about getting a new set of cats. I plan on picking up a set of iridium plugs as well.

[kenman1717]

I put the iridium plugs in and my new cats came in today, so I put the new ypipe in after work. Lots of power, no check engine light, but I do miss the way it sounded without them, I'm going to look into a muffler now that rumbles better.