check engine light on

[sonomadude4x4]

so im comeing home the other day in the crew towing my trailer down the highway its a 6x10 enclosed trailer truck is in over drive and my truck starts to slow down so i start giving it more gas so it drops out of OD and tach is reading 3000 rpm still slowing down then the check engine light came on so i pulled over cut the truck off and started it back up and the light was off so i continued home with out any more problems about a week later it does the same thing while towing . . . when i got home i unhooked the trailer and took it down the road and put it one the floor whent through 1st and 2nd gear fine but once it shifted into 3rd im running 70mph and it came on again but running 70 in OD is fine , , ive tried this a few times and it only happens at speeds over 70 but happens at 60 or below while towing . . went to advanced while the the light was still on and they said it was a misfire in cylinder #3 but im a bit confused because the truck runs fine and idles fine and for normal every day driving runs great. . what do u guys think?

[RebelKid1822]

this is the exact same problem i have been having. i tried plugs and wires and etc, to no help. today i found my y pipe was cracked. i found another user on here who had the same problem, hence y i looked. the crack was very hard to see, it was between the bank2 o2 sensor and the y pipe junction, right along the factory weld. it was mostly on the side up agianst the engine. this may be your problem, jack it up and take a look.

[sonomadude4x4]

so many things it could be i dont even know where to start looking

[HenryJ]

Start with the basics and work you way through all those first.
Air-Fuel-Ignition

[RebelKid1822]

today i welded my y pipe, wasnt it. light started flashing, truck was sluggish on the highway. light never stopped flashing, went to autozone, they said my mass air flow sensor was bad. just threw a new one in and the truck runs great, better than it has in a while. i hope this will solve the problem i have beeen having. this may be it if the basics dont pan out for you.

[HenryJ]

Sluggish? Is it warming up quickly? Does the intake sound loud? Got that "BWAHH" sound under hard acceleration? Is it worse when it is warm? Crappy fuel mileage? Is the exhaust very quiet? Have you ever smelled rotting eggs?

Plugged Precat

Pull both forward O2 sensors out and see if it runs better with them out. This can be enough to relieve the excessive back pressure.

[RebelKid1822]

slugish, in the sense that it did not have super get up in go. intake seems normal. bwahh sound yes, if i stop on it-3-4k rpms, temperature never seems to matter, exhaust is very quiet. and i have never smelled rotting eggs. second o2 sensor has been replaced. fuel millage use to be around 22, now i am lucky to get 17. i have replace the fuel pump before, it was an airtech-not wat i wanted to put in, but had to with the time frame i was limited to. i will drive the truck for a few days, if it starts doing those symptoms agian, i will try removing the o2 sensors.

[sonomadude4x4]

replaced air filter and changed oil today while under it i checked out the exhaust didnt see any problems there air filter was nasty but truck is still running the same . . once i get to 70mph thats about it . . runs great till it gets to 70 just no more after that o2 sensors havent been in to long replaced those a little wile ago mpg"s are about the same around 17 which is normal for me with the gearing and tires i have

[sonomadude4x4]

so mass air flow sensor maybe? also exhaust seems to be the same its kinda hard to tell cause mines all ways loud lol

[RebelKid1822]

maybe, i just replaced mine a few hours ago, henry j said that a MAS going bad was unikely, i will drive my truck for a few days and let you kno what happens

The MAFS failures are pretty rare in my experience. They can get dirty and fouled, but cleaning them with aerosol MAFS cleaner, or careful swabbing with a Q-tip and rubbing alcohol usually restores proper readings.

Clear your codes and reset the operating parameters by removing both battery cables for three minutes after you make any change or perform service work. This will set a new cold start sequence and refresh the cold run information.

-this is what henry put on another one of my posts, wasnt sure how to link it to you

[RebelKid1822]

hj- i just read the page on the precat, i do not belive this is my problem, my truck runs well except for the loss of power on a high demand. if im not accelerating on the highway uphill at 60-70mpg, or towing, the light never flashed. i have never had misfiring was noticable, or an overheating issue. these were the systoms i foudn that people in that post had when they removed there precat. however i do realize that the precat may still be or become an issue. i will keep it in mind over the next few days as a watch at how my truck preforms. thanks for all the links you find for me, they help alot and i enjoy reading them

[RebelKid1822]

ok after a day of driving here are my results. the truck runs way better. however. when driving home on the highway, the ses flashed twice-three flashes both times, while do speeds between 70-75. i got gas today, not sure if it is realated, only ore drivng will tell. there was no performance difference in the truck. b4when the light flshed it would keep flashing untill i stopped or sumtimes not until i shut the truck off. today it just blinked. i dont have a scanner at home so idk what theses was for. only more driving will tell. ill keep ya posted

[HenryJ]

Retrieve the codes.

[RebelKid1822]

where is a good place to get my own scanner? which kinds are the best?

[HenryJ]

WallyWorld , Autozone, O'reileys carry an inexpensive scan tool made by Equus/Innova. I have no experience with their bottom of the line models. The 3100 series are not too expensive and do a good job.
Weigh the cost vs benefit. Scangauge II is a very good value for these trucks.

[RebelKid1822]

i want one that tells me the code, and a description. its a tool i need to get, just nvr hav

[sonomadude4x4]

fuel pump went out in the crew the other day i put a new one in today its running 10 time better than it had in the last 6 months i was towing my trailer again when it went out . . the truck got really sluggish like it has in the past and on came the check engine light then the truck quit after about a min of the light being on and wouldnt start back up it was the pump that made it quit running but do u think it is possible that the fuel pump out of the last few months has caused the light to come on and throwing the code of a misfire in cil #3 due to lack of fuel pressure?

[RebelKid1822]

i had replaced my fuel pump and still had the cyl 3 misfire code happen alot.

[RebelKid1822]

my cyl no 3 misfire turned out to be a cracked y pipe.