One last shot... Breaking up!

[turboj91]

Re: One last shot... Breaking up!

My opinion is already on file (through a pm) and if it turns out to be the winner, I'll take a bow but don't want any reward $$.

Just as a reminder (as there is a ton of info to read) is that the problem was there a long time ago and was then tuned out (don't know exactly what was done but I have an idea) and now it's back. A big factor is that it is very rpm specific and not under a heavy load rpm. On the boost up to redline is fine but at 3 very specific and consistant rpm's it goes lean. Certain things can be eliminated with just this little info as some things either work or they don't and/or are not logically capable of having an issue at only 3 specific rpm's. The rpm range where the problem exists is very short ie at 1500 rpm but not at 1400 and not at 1600. Keep thinking guys. But remember, he has already thrown just about everything at this problem but to no avail. Logic plays a factor as well as a deep tuning/mechanical working knowledge. Waiting patiently to see what the final outcome is.

 

[sly dvl]

Re: One last shot... Breaking up!

You know I lie awake at night thinking about this. :lol:

You know what might help in the diag.? Can you take it to a local shop and have them put a gas analyzer on it to "sniff" the tail pipe? If you could measure the CO & HC readings when the misfire occurs, this might help to determine whether it's really going lean, or whether it's going pig rich and blowing out the spark, creating a false lean.

Just a thought...

 

[TYTILIDIE]

Re: One last shot... Breaking up!

if your #6 is always wet then there is your answer. You said earlier you swapped injectors right? Or did I read wrong?

 

[BoostedSUV]

Re: One last shot... Breaking up!

Autometer elec FP gauge and took out Air/Fuel gauge. (Could be total coincidence??) Didn't drive the truck 4 days after I installed the gauge, but it ran perfect when I parked it the day I did the install. I've done a lot so there's going to be a lot of info to try and save some suggestions so bear with me.


from your post, if it started right after you did this you have found where the problem originated, check that wireing and did you have to move any other wires when removing the a/f guage?

This seemed to bring the problem back. I had this issue before but it kind of just went "away." I feel like I have gone over every wire I've touched multiple times by eye and with a multimeter... I may be missing something?

 

[BoostedSUV]

Re: One last shot... Breaking up!

if your #6 is always wet then there is your answer. You said earlier you swapped injectors right? Or did I read wrong?

I didn't swap injectors yet, that's next. #6 just seemed to be a little more on the rich side than the rest but it wasn't fuel soaked

 

[BoostedSUV]

Re: One last shot... Breaking up!

Hard to diagnose a problem like this over the cpu...where u at in NJ...honestly all these posts have me intruiged...Id like to come take a look at this truck if you are willing.

I would love for another set of eyes to come look over this truck if you are willing! I'm in central jersey, somerset county. You are south of me down near Atco Raceway. I'm 1 hour and 20s mins from Atco if that helps any?

 

[BoostedSUV]

Re: One last shot... Breaking up!

You know I lie awake at night thinking about this. :lol:

You know what might help in the diag.? Can you take it to a local shop and have them put a gas analyzer on it to "sniff" the tail pipe? If you could measure the CO & HC readings when the misfire occurs, this might help to determine whether it's really going lean, or whether it's going pig rich and blowing out the spark, creating a false lean.

Just a thought...

Kevin. the WB shows the same thing that the O2 shows and the WB is an independant unit. Wouldn't that show me what a tailpipe probe would?

 

[Houseofperformance]

Re: One last shot... Breaking up!

i´ve read the whole thread, and the only thing you haven´t checked/swaped yet are the injectors.
together with the load specific behavior, wet plug and the fact that you changed the sending unit/gauge in the fuel rail your best bet is, that a little metal debris found it´s way from the fuel rail pressure port to injector nr.6 when breaking loose the old gauge or thightening the new sending unit, forcing inj. nr.6 open - how long does your fuelpressure stay in the rail after you stoped the engine?

 

[turboj91]

Re: One last shot... Breaking up!

I'm going to reply when maybe I shouldn't but how would debris holding the #6 injector open cause a rpm specific lean condition (and a very lean condition at that). How would that debris come and go and always cause the lean condition at the listed trouble rpms... consistantly! Other than the trouble rpms, the afr's are fine and when on the boost, everything seems to be fine right up to the shift point. The #6 plug was slightly wet compared to the others (if I understand correctly, the plugs were checked once and this was noticed). This could be simply due to an injector cycle just before an ignition firing for that particular cylinder when the vehicle was turned off and the plug got wet with fuel and never fired. It happens. As many times as he has been into this issue, if an injector was stuck open and bleeds the pressure down, he prob. would have noticed fuel wash in the oil by now. Maybe even a hard start or a stumble at start, neither of which have been mentioned.

 

[bezerk]

Re: One last shot... Breaking up!

you took the shredder valve out of the feulrail to install yout fp gauge, maybe you cracked something off and it's now blocking 50% of your feul after the shreddar valve.

 

[warmpancakes]

Re: One last shot... Breaking up!

do you have a temp gun, no need to pull or swap the injectiors, run the truck for about 20 minutes and check temp of manifolds stop throwing parts at the truck

 

[BoostedSUV]

Re: One last shot... Breaking up!

you took the shredder valve out of the feulrail to install yout fp gauge, maybe you cracked something off and it's now blocking 50% of your feul after the shreddar valve.

I took the shredder valve out of the truck 5 years ago when I installed the mechanical gauge. All I did was remove the gauge off the fuel rail adapter and install the elec sender in it's place. I'm going to pull the fuel rail off next week and blow it out. When I had the tank out it did blow through the lines with air to clean out any debris...

 

[BoostedSUV]

Re: One last shot... Breaking up!

do you have a temp gun, no need to pull or swap the injectiors, run the truck for about 20 minutes and check temp of manifolds stop throwing parts at the truck

I do have a temp gun... Wouldn't I need to hold the truck at 2500rpm where it breaks up the worse then check the temp at each specific exhaust port on the manifold and look for a hot or cold cylinder compared to the rest?

 

[warmpancakes]

Re: One last shot... Breaking up!

that would work, does it pop out the exhaust? or the intake?

 

[BoostedSUV]

Re: One last shot... Breaking up!

that would work, does it pop out the exhaust? or the intake?

I can definitely hear it popping out the exhaust

 

[BoostedSUV]

Re: One last shot... Breaking up!

And the truck does hold fuel pressure. I've never looked to see how long but it holds. It won't hold it over night but it will for at least an hour or so. Not sure what's normal?

 

[WyoSyclone]

Re: One last shot... Breaking up!

Did you ever try removing the vac line from the AFPR to see if it changed it at all?

 

[warmpancakes]

Re: One last shot... Breaking up!

popping out the exhaust could be several things , does it do it at like a "sustained cruise"
or no throttle deceleration
or when accelerating

 

[BoostedSUV]

Re: One last shot... Breaking up!

popping out the exhaust could be several things , does it do it at like a "sustained cruise"
or no throttle deceleration
or when accelerating

When I'm sitting in my driveway, truck in park, and slowly bring the RPMs up the truck will stumble slightly at 1500, then again at 1900. When I get it up to 2500 it will stumble and pop out the exhaust like its on a 2 step. I can keep slowly depressing the pedal and RPMs will not increase right away. At some point in the throttle the truck will get past the troubled spot and jump 500 rpms and be pig rich.

When I'm driving and under normal acceration the truck will hit the trouble spots and surge and stumble. If I hold it right at 2500 the truck bucks and will not accerate smoothly unless its prior to or after the bad "bad spot".

If I try to powerbrake the truck it surges and the rpms jump up and down until I'm past 2500 then it builds boost as normal

I don't notice it really during deceleration and if I rev the truck quickly it goes right past the bad spots fine

 

[turbodig]

Re: One last shot... Breaking up!

If I try to powerbrake the truck it surges and the rpms jump up and down until I'm past 2500 then it builds boost as normal

I don't notice it really during deceleration and if I rev the truck quickly it goes right past the bad spots fine

What's the wideband do when this happens?