Warm Engine Misfire

[Justinlw]

I just replaced 2 injectors that showed low contribution. This cleared up my constant misfire and rough running problems.........

Now, I get an erradic idle and an intermittent misfire at idle. Running down the road, I don't feel anything. If I crank the engine up warm, it bucks about 3 seconds and then goes to the erradic idle.

On a cold restart it purrs like a kitten and shows no symptoms. After a 30 minute drive down the highway the condition returns.

I'm lost here, I don't even know where to start. I'm going to check the FICM harness, but that usually causes a constant problem, right?

Any ideas?

[SCUFFY828]

Originally Posted by Justinlw

I just replaced 2 injectors that showed low contribution. This cleared up my constant misfire and rough running problems.........

Now, I get an erradic idle and an intermittent misfire at idle. Running down the road, I don't feel anything. If I crank the engine up warm, it bucks about 3 seconds and then goes to the erradic idle.

On a cold restart it purrs like a kitten and shows no symptoms. After a 30 minute drive down the highway the condition returns.

I'm lost here, I don't even know where to start. I'm going to check the FICM harness, but that usually causes a constant problem, right?

Any ideas?

any codes at all, ficm harness was more 03 and early 04 , need to run a power balance test if it is a skip and that will tell you which cylinder , one thing i learned about a 6.0 quick , is a misfire code in memory doesnt mean thats the cylinder that it throws the code for is always the faulty injector

[Justinlw]

We picked up the bad ones on a CCT/Balance test. Using Ford's IDS. It cranked up and ran perfect this morning in the cool air, I'm sure the story will be different this afternoon after sitting in traffic. I'm thinking this has to be a sensor failing at temperature. It's usually worse when I'm towing and take a stop at a gas station or something. When I come back out, it sounds like an intermittent dead miss.

[SCUFFY828]

if it only does this concern after hot , monitor icp voltage , im wondering if icp sensor may be acting up, icp voltage should be between .18 and .24 volts , with key on engine off , if its in spec then try the power balance again when its acting up

[Justinlw]

I will be towing my boat this weekend and a friend will have his AE with him I'm guessing. I can get it hot pulling the boat and see if it acts up while I have that available.

As all things go, I can never get it to run bad when I get to the dealer.

I keep describing this as a miss, but maybe that is incorrect. The engine goes dead quiet when it happens, no injector noise or anything for a good 1/4 second or so.

[WEWILLE]

Whats your fuel pressure? How many miles does it have? What do you mean when you say it goes dead quiet? The way i understand your description is it only happens when idling. When under load, or decel its fine, correct? Just during a hot idle?

[Justinlw]

Correct. The fuel pressure is at about 62 psi at idle. The truck has almost 140k on it.

[Motown Fire]

Compression test ??? Could one of your bad injectors washed a cylinder down ???

[Justinlw]

I was thinking that, along with air in the HPOP was causing it, but it's not consistent enough. It's got to be electronic. It has mostly gone away now, I guess we'll see if it comes back after towing the boat Friday. Josh mentioned that with the larger injector nozzles, sometimes the FICM will cut cylinders to keep the RPMs down with no load. Said to try turning on the A/C next time it happens to see if the load stops it.

[quick26]

this is the problem that i have been chasing. i was told that the balance test looked good on mine. i think next time i head to west va i might stop in and see scruffy again. mine will even surge every now and then after i have been running it for a while or pulling a trailer.