RADO_4U2NV

iTrader: (70)

I am having an issue with a misfire. It is hopping all over every cylinder. Will misfire 5-10 times in a row then fire fine for 3-5 times then start misfiring again. I have changed everything on the motor (crank sen, cam sen, plugs, plug wires, removed the intake and replaced the intake gaskets even the tb gasket and so on) except the coils and injectors. I have tried the injector plugs and tightened them still no luck. I am at my wits end with this thing. Any help would be great. Here is a list of mods and info on the motor.

4.8 stock bottom end
228/230 Comp cam
Patriot Dual springs
Stock heads (862) with patriot dual springs
Hooker LT's off road Y pipe with Mangnaflow muffler. 3 inch all the way from collectors
28.8# injectors
Spectre cai
Autolite 103 Plugs .050 gap / AC Delco plug wires with heat sleeves
4L60E trans with shiftkit and a 3200 stall

Hemi2Slo

Has it been tuned yet?

RADO_4U2NV

iTrader: (70)

Yes it has been tuned. Sorry for that not in the description. I have returned to my tuner and we ran a log trying to see what it could be. Well nothing showed except the misfires. No sensors going bad or any codes, only the P0300 misfire code.

dmelvin

iTrader: (8)

I wonder if your tuner just didn't loosen the misfire tables up enough.

Hemi2Slo

Good question. Are the misfires physically noticeable or is it just throwing codes?

RADO_4U2NV

iTrader: (70)

They are noticeable really bad. After deleting the code and clearing the check engine light it will idle fine for a few minutes. I can stand outside the truck and tell when the engine light comes back on for the misfire. It changes the tone and idle that much.

I just got back from a ride. Went up to the parts house and got a $15 can of maf cleaner. Soaked the hell out of the maf and let it dry, it cleared for a while but the engine light will come on periodically then go off. I don't notice a change in the idle or engine tone now though.

I cleaned the maf not to long ago after putting a new one on a few months ago, but it was with an old can of cheap cleaner. The thing is though I have never had a code for the maf. I will get with my tuner and have him check to see if it a misfire or a maf code. Don't think it is a misfire though cause irc a misfire code will keep the light on after it comes on correct.

anheuserbusch08

iTrader: (11)

i have the same problem but itll come on rarely and my tune has low timing 12* @ idle. im thinking thats causing the problem

RADO_4U2NV

iTrader: (70)

After soaking the maf it only comes on when i hit low idle and the brakes together, like when slowing and turning into a driveway or something like that. I am not sure if it just a coincidence at low idle and it is actually from where i over soaked the maf. Tomorrow after work I am going to take it off and clean it again and let it out to give it plenty of time to dry good.

RADO_4U2NV

iTrader: (70)

Not sure what mine is set at. I dropped my truck off and told him to tune it to the way he would want his done. Figured he knows more than me about tuning so why try to tell him what to do.

Hemi2Slo

I used to have 9 degrees of timing at idle in mine. I never had a problem with a misfire. The only problem I ever had with misfire was when I first put the motor together. I was getting multiple random misfire codes, but it wasn't physically noticeable. But the reason for mine was that I had shaved heads and hadn't changed pushrod length yet. Once I got the pushrods right the misfires stopped.

My thought would be perhaps your tuner only tuned the MAF on the truck. If that is the case and the MAF is failing the truck will be reverting to speed density. If the VE table hasn't been tuned then that would explain the thing screwing up. That's a BIG cam for a 4.8 IMO, If your VE table is stock then it'll go all nuts if the MAF fails. That's just my thoughts though. Your tuner may very well have tuned the VE table and it may be something else. But its probably worth checking.