Still Trying.. (One Last Shot pt2)

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

have you checked your feulcanister thing?? what if it's full, and it sucks in feul if there is no checkvalve?

Talking about the charcoal canister under the stock airbox location? There is a check valve on the vac line to the TB but it wouldn't hurt to check it I guess?

 

[skolman91]

Re: Still Trying.. (One Last Shot pt2)

Talking about the charcoal canister under the stock airbox location? There is a check valve on the vac line to the TB but it wouldn't hurt to check it I guess?

that would add fuel, you have two different sources saying your going lean. id have to agree with mike and checkout or change the inj harness real quick as your next step, some sort of mishap or interference in that would make sense in the lean condition. more fp would make that sudden stumble that much more noticeable with the sudden cutoff, just my :2cents:.
what all was installed when the fp gauge was put in?sender off the rail?
do you have an aftermarket tach?
after following your first thread you've done a great job so far as far as effort goes, keep it up one way or another its gonna get fixed.. i hope:lol:

 

[Quickstop [UK]]

Re: Still Trying.. (One Last Shot pt2)

I didn't change the injector harness when I did the engine harness but I wonder if the gremlins could be in there?

If you had frayed wires in the injector harness then you would lose current at specific voltages and have parasitic capacitance, weird resistance effects etc etc.

This could affect the RPM at which it occurs as the larger injectors will draw more current potentially depending on their impedance.

Presumably you have the High Z injectors in - it may be a lot of effort but have you thought about installing the ECM mods and trying a low impedance setup?

Maybe someone can loan you a modded ECM and some low Z injectors for comparison.

For the ease of swapping out an injector harness with someone with a known good truck it's worth looking at.

To get a signal off the oscilloscope, set one connector to ground and one connector to the ignition terminal/wire.

What you are looking for is change in the waveform at the relevant RPMs. You might need someone to setup your timebase to get the waveform on the screen but I am inclined to agree this is an electrical problem.

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

I think that may have been total coincidence. I've since changed ECMs twice and I have tried 2 different eproms with different tunes. I have also tried running the truck on the stock memcal with the same results.

Its funny because this problem showed its face again after removing my A/F gauge which was tapped in the O2 signal wire. And adding an FP sensor to the rail. That was my thoughts for changing the engine harness. Honestly aside from the short block everything has been changed at one time or another... The problem seems to come and go and I can't pin point it or make go away now. Its still there when it's "gone" it's just way more drivable and less prominent

It's just a little strange that the A/F gauge and previously chaning the ECM/PROM made a difference... the common item to both situations is the wiring harness... I'd inspect every wire from the ECM to the firewall...

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Hey Don thanks for the offer! It's always nice when guys step up to loan out parts and pieces, I appreciate it! :tup:

I actually got a PM about buying one for $40 so at this price it will be more convenient for the both of us and less of a hassle. I will swap it in real quick when I get it to see what happens. Mike's logic sounds good enough for it to be worth a shot. :tup:

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

It's just a little strange that the A/F gauge and previously chaning the ECM/PROM made a difference... the common item to both situations is the wiring harness... I'd inspect every wire from the ECM to the firewall...

Rob I agree but I just changed the entire harness from the ECM, through the firewall, to the engine and each sensor.that logic and theory is what made me break down and spend the money to replace it all and eliminate it. The only thing I didn't change was the injector harness (which I just bought). That kind of makes sense as a culprit and could go back to turboJ's injector theory...

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Stupid spam folder made me miss some of these posts! The injectors have 2 miles on them and they were brand new so there's no chance they are creating the same problem as the 50s that came out. I agree with inj harness theory as it makes sense in more ways than way than one.... If its a current issue through the wires then it would support why dropping the fuel pressure makes it get better. Less FP would require less current to fire the injectors which goes back to turboj's theory (old thread). He guessed injectors based on the current to fire injectors varying with fuel pressure but it could be the current traveling too the injectors rather than the injectors themselves

Worth a shot...

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

well I swapped out the injector harness with one that I bought from Vito and no change :tdown:

I hooked the laptop up and went for a 45 minute ride. The "bad spots" are 2200 and 2800. At those points while driving it feels like the driveshaft is going to come out of the truck it runs so rough. It also has an off idle stumble and feels like it has no power in the low RPM range. In between those RPM's it's fairly smooth considering it's not tuned for these new injectors. I sent the log file to Nolan to start tuning on it what we can. This is getting ridiculous. WTF else is there to change?????




I'm still dumbfounded that changing to bigger injectors moved my "rough spots" up 300 RPM's from the prior RPMs with the 50's.. that has to be a clue???

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Pat (SloGN) suggested tach signal interference. Is there any easy way to eliminate the tach reference signal with out cutting wires? I'm pretty sure I would want to eliminate the Signal to the cluster and not to the ECM. If there's an easy way it may be worth a shot :dunno:

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Could engine harmonics cause any of this? It almost feels like the truck has an engine vibration. Could be the miss causing the vibration or the vibration causing the miss? When the stock motor broke a rod everything came to a dead stop and seized. I'm not sure if the balancer was changed with the rebuild honestly... I saw what the sudden seize did to the converter and flywheel so I imagine the balancer would have some effects as well if it is indeed the same one. I would guess it was changed but I'm not sure? Just thinking out loud again...

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

You've got a relatively high stall converter... does it do it during a boost launch??

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

You've got a relatively high stall converter... does it do it during a boost launch??

It's been so long since I've done a boost launch I don't even remember! It's probably been 2 years since I've done one, not since I put the new trans and waller rebuilt 9/11 in it.


EDIT: Let me come back to this... IF I try to bring the RPMs up against the converter the truck will stumble and surge at 2200 and 2800 until I get it passed 3K.


However if I flat punch the truck from a roll or a stop it will blow passed the bad spots without skipping a beat. It only seems to react to those RPM's if I creep up on them slowly...

 

[MikeRenz]

Re: Still Trying.. (One Last Shot pt2)

so this problem didn't start until you installed a new tranny?

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

so this problem didn't start until you installed a new tranny?

No it started almost 4 years ago when I installed a fresh motor, 50#r's, AFPR, RPM A2A, battery relocate, and ultimate chip. I rebuilt trans about 2 years and not many miles ago

 

[skolman91]

Re: Still Trying.. (One Last Shot pt2)

but you said it went away for awhile then came back.. just to be clear, it started 4yrs ago when u put the engine in, then went away for reasons unknown, then came back when you installed the tranny/converter, or just came back outta the blue?

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

but you said it went away for awhile then came back.. just to be clear, it started 4yrs ago when u put the engine in, then went away for reasons unknown, then came back when you installed the tranny/converter, or just came back outta the blue?

it never really went away completely.. when it was "gone" i had more of a flat spot in the RPM and a slight vibration instead of a lean miss and bad vibration. It was drivable but I always noticed it. It actually "came back" when I removed an A/F gauge and installed an elec fp gauge. Could have been total coincidence since I changed everything I touched. Again, not to be confused it has always been there for the last 4 years it just seems to get better and worse without reason. The hotter the engine temps get, the worse the flat spot/miss gets. I've always had an issue with the same RPM's since blowing up the stock motor and changing everything. :dunno:

 

[eviltwin]

Re: Still Trying.. (One Last Shot pt2)

i know someone asked but i couldnt find an answer. did you try a new harness thing that goes from the distributor to the coil?

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

i know someone asked but i couldnt find an answer. did you try a new harness thing that goes from the distributor to the coil?

That is the only piece of the harness I did not change... I didn't have one and I can't really see it being the issue but who the hell knows?

 

[stl_ty]

Re: Still Trying.. (One Last Shot pt2)

i was maybe thinking the ignition control module (icm), cause i had similar issue with the stumbling. The only thing that throws me with that is that the distributor has been changed. i had the original icm in and then it started stumbling, then changed to another icm and it went away. That sounds like it could be a bad connection to the icm or bad harness. i also tried changing tunes and even back to the stock memcal and those didnt help.

 

[Quickstop [UK]]

Re: Still Trying.. (One Last Shot pt2)

You say this only happened after the new motor went in. You'vechanged everything and even had the engine out 4 times.

Could there be something wrong with the bottom end or the block? A loose main cap or something?

The 300rpm kncrease on the trouble spots suggests electrical or fuel for sure but I wonder if it's worth thinking about.

Given the hassle you've had it might be time to swap out the whole motor/rebuild it. You've done EVERYTHING else.

Have you measured the temperature on the exhaust ports when you get the stumbling? Is it cylinder specific or all of them?

I think we need a syty donor fund to buy this truck as a group school project. I for one am dying to know what the he'll is wrong with it. I can only imagine your frustration.

You'll find it....