still missing badly...

[seether038]

I have a 1999 Explorer sport sohc v-6, severe misfiring/sputtering under a load.Looking for a little more input! 106k miles

Have changed the upper and lower intake gaskets. The truck now idles better than it ever has right around 700-750 at hot idle. When its put under a load it misses and sputters like crazy. The best way I can describe it is it feels like its struggling to get gas/spark. I have done the following with no luck

fuel filter
spark plugs and wires
upper and lower intake manifold gaskets(Not as bad a job as I thought would be
I have ran 3 bottles of injector cleaner through it with no luck

sometimes it almost feels like it snaps out of it for a second or two, then right back to the stumbling/sputtering. If I ease onto the accelerator very easy I can drive it. But its way low on power.

The stumbling/sputtering issue definitely seems worse since I changed those gaskets but I don't know how that could change much.

It does not run hot, or use any fluids at all. I was thinking maybe a blown head gasket or cracked head or maybe even exhaust manifold leaks?? I am a novice mechanic at best but I am learning. I just feel like this thing runs and idles to darn good to have something sinister wrong with it..maybe im wrong?
But I am off of the head gasket theory now as the truck uses no water and does not overheat at all. Any advice or input would be greatly appreciated.

I did manage to get my CAI installed and my head unit looks pretty nice so at least I have accomplished something LOL

 

[seether038]

also how to check the timing on these engines. Its worth looking at I would think or any other ideas?? Thanks so much!!

it also seems like when i do hit the gas a bit the rpms raise high but the truck is hardly moving like something is holding it back? almost like the tranny is slipping just a bit but I really hope not. Im getting ready to send this thing to a qualified mechanic for proper diagnosis....

 

[RomeovilleIL]

Check your fuel pressure. Should be 60+ psi at idle. There is a schrader test post near the battery tray.

 

[seether038]

I have its about 66 psi at idle. I have also changed the coil packs the original ones resistance was way off when I checked them, the new ones were right in spec. Still did not cure anything?

 

[lobo411]

Double check that the wires are set up properly. I always get mine screwed up when I change them and freak out when it idles/runs like crap on first start.

 

[2000StreetRod]

cone air filter

Did it start missing after you installed the cone air filter? Some are heavily oiled that contaminate the MAF sensor element. You might try cleaning the element with an aerosol MAF sensor cleaner. The element is fragile so don't touch it.

I agree with checking the spark plug wires:

It's a common mistake to miswire 5 & 6.

Do you have any diagnostic trouble codes?

What spark plugs did you install and what was the gap? What did the old ones look like?

 

[seether038]

it was missing before I installed the cone filter. Not as bad as it is now but had a pretty good miss to it.I have cleaned it with maf cleaner but nothing. But tonight I did unplug the maf and it seemed like the truck ran about 30-35% better but wanted to cut off when I stopped. It had a miss still but def ran better.

Also today I did pull those plugs (autolite platinum) and they just had what I would call a normal color, maybe a little gray. I cleaned and re checked the gap to .054 and made sure I got all the boots back on snug. I then checked all the plug wires coming off the ignition coils one by one and they all shot out good spark. Also checked the firing order and all was right. As for cel's I had 171 and 174 prior to intake manifold installation, they went away afterwards but today the light came back on. I have not gotten it scanned yet.

Its kinda making a sputtering/gurgling type sound when you try to accelerate. You can feel it surge like its starved for fuel.(i recently changed the fuel filter)

possible fuel injector issue? Ive ran 3 bottles of cleaner through it

clogged cat? Really feels like something is holding it back??

Timing chain slipped? Incorrect timing? I don't know how to check the timing?

ANother big clue that I dont understand is I can hear a sucking or hissing type noise thats hard to pinpoint. I am missing the dust cover on the engine so maybe its usually muffled? Not very familiar with this engine at all.

the truck does idle much better now after gasket installation, around 700-750 rpm at hot idle, but the miss has gotten much worse since then...I am baffled. its not using any fluids or running hot either, But it really loves gas right now

Any more help would be greatly appreciated!!

 

[2000StreetRod]

get the codes

It would be helpful to get the new codes read and post them. They may provide some insight. Does the engine rattle on start up or at mid-range?

 

[seether038]

yes I would definitely say a rattling feeling can be felt. Sometimes at idle it pulsates like a hard vibration back and forth back and forth but idles just fine. when accelerating can feel it also but it feels much more like misfires then.

I have no clue why it would run WORSE after doing those gaskets. I have triple checked and everything is plugged in. Idles better runs worse?

 

[2000StreetRod]

check the compression

If the new codes don't help you may want to check the compression on at least one cylinder in each bank to eliminate the possibility of timing chain slip.

 

[seether038]

ok so I founs a vacuum leak around the iac valve and replaced it with another from salvage yard and a new gasket. Then I re-installed the factory air box and those lean codes went away! Ive driven 600-700 miles since then so I have tacled the Lean problem it appears!
I am still getting some good miss firing when I get on it. almost feels like running on 5 cylinders. I honestly feel like its cutting out, starving for fuel at some point?

I have checked the fuel pressure with a gauge and it appears in spec right around 65 psi, my question is That I read fuel flow and pressure is different. Is it possible that I could have good pressure but possibly a clogged fuel strainer or the fpr? causing low flow? I know I have spark on all cylinders, fuel pressure and no engine light on. This thing honestly feels like its starving for fuel. thanks for any help guys- and I also got a compression gauge from harbor freightso I will be checking that this weekend!

 

[lincolntowncar]

Is there any way you can do a smoke test ? It surprised me how such a small vaccine leak can effect these motors.

 

[seether038]

I am not getting any check engine codes now? pretty sure I got all the vacuum leaks worked out I was wondering on the possibility of a clogged fuel strainer/pump maybe causing low flow to the injectors. still trying to get around to doing the compression test too.

Does anyone know if its possible to have proper fuel pressure, but still have a fuel flow problem on the rail or to the injectors? thanks for any help!

Another bit of interesting info is the check engine light will begin flashing at higher speeds maybe 75-80 but then i back off and it runs just fine and the light cuts off. no constant cel, and no codes whatsoever. Isn't a blinking cel a missfire? would that not store a code? I am lost. Previously I was having a couple of bad misses due to 2 plug wire arching off on the motor and during that time if I really got on it I would get a flashing light and the cat would be glowing red.excess fuel not being burnt in the combustion process was being burnt in the cat I suppose?

But with the missfires now, theres no codes and the cat no longer glows red at all.