progressive stumble?

Neelsonwheels

Neelsonwheels

Donating Member
Alright guys I have had a slight miss that has progressed into a all out stumble. It went from very slight and infrequent to all the time while driving light throttle. I completely misses(bucks)
under partial throttle. If i increase the pedal it goes away and pulls great. I am at a loss. I have done the usual Plugs,cap,rotor,wires,new digital 6 with noise filter (capacitor), coil, grounded everything from battery to firewall with 0 gauge and from there to coil,alternator case,frame,ignition,front support (for fans), and Block (upper intake included) all with 8 gauge wire. With the exception of the Alt. case that is #2 awg. Still bucks bad. I am now thinking fuel delivery. Could a clogged fuel filter cause this issue? I will be changing it out when it arrives in the mail from Hood. I do have dual Walbro's in the tank. The first pump does all the work until the second one comes in at 25% TPS. My other thought could be first pump is quiting. My fuel gauge reads 40 plus PSI at idle and it does climb on boost. Any thoughts would be greatly appreciated! Thanks.
 
qbnkiller

qbnkiller

Conflaguration Specialist
Re: progressive stumble?

Check fuel system. You might have a failing pump or clogged filter
 
Don W.

Don W.

Stab it and steer it
Re: progressive stumble?

0 ga ground wire? Wow, that's huge. Not your issue, just commenting. Can you log? Do a log with the motor off and key on of the TPS voltage. It should be linear and smooth. If FP is holding at FT I doubt it's the filter but worth the change just so it's eliminated. With key on after the pump runs for the 2 seconds does the FP hold? If not you need to track that down. I'm thinking leaky injector that's getting worse. Do a little driving with it stumbling then pull the plugs and look for the culprit. I doubt it's ignition only because it runs well under FT where ign problems usually show up. How does it idle? Is throttle response good off idle?
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: progressive stumble?

Fuel filter will be first then pump I guess. I will let you know how it goes.
Yep 0 gauge. Grounding will not be my issue. As for the injectors I just had them cleaned and tested and cleaned so I don't think it that. Thanks for the help guys.
 
Don W.

Don W.

Stab it and steer it
Re: progressive stumble?

Neelsonwheels said:
Fuel filter will be first then pump I guess. I will let you know how it goes.
Yep 0 gauge. Grounding will not be my issue. As for the injectors I just had them cleaned and tested and cleaned so I don't think it that. Thanks for the help guys.
Click to expand...

No prob. just throwing thoughts out there.
 
0966Sy

0966Sy

Code what?
I would double check your wires (ohm them) and pull and inspect your plugs. Who tuned your current tune? If it's part throttle stumble that goes away, how much more TPS does it require to go away?
 
Mingus

Mingus

Member
Re: progressive stumble?

Is it intermittent or does it happen every time you accelerate? As a previous poster mentioned it could be the TPS. I had a Camaro that had a bad spot in the TPS and it would stumble every time until you got past it. It could also be any of the other suggestions on here or a few dozen other things. Diagnosing is so much fun. :)
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: progressive stumble?

It started out as a slight miss. Now it is a straight up buck.
That is why I am leaning towards the fuel filter. I will swap it out
As soon as I get home from camping. Thanks everyone for the replies.
I will post the outcome.
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: progressive stumble?

Changed out the fuel filter while I did an oil change. I will take it out for a spin today after work. Fingers crossed.
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: progressive stumble?

Okay! little update. Went out to the garage to try to start the truck and take her out for a spin. Cranks fine no fire! WTF. Let it sit thinking I must have flooded it. Try again. Nothing.
So I decide to check the plugs. All of them were wet with fuel and a little black. I changed them out. Try to start the truck.... Nothing just cranks. MAN. I decided to remove the coil and throw on a known good one. Truck starts right up!! Nice time for a drive. Start going around the block and the truck starts to miss or stumble a little. Back to the house. Swap out the TPS with a known good one. Hop in. Start truck and drive down the road. I runs really nice.
So what I think happened is: Failing Coil causes plugs to foul and miss. Bad spot in the TPS.
I had two issues. All is well. Thanks to all that replied!!!
 
Don W.

Don W.

Stab it and steer it
Re: progressive stumble?

A mechanics nightmare. Two intermittents at the same time. Glad it's fixed.
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: progressive stumble?

You guys are going to think I am an idiot but the stumble is back!!!!����
I drove the truck to a car show on Saturday and it was pretty bad.
I could drive around it kind of it really pisses me off. So I got home and
Parked it and as usual for the past couple of days go over and over in
My head what could be causing this and a plan of attack to fix it or figure
It out. Fast forward to this evening. I decided to replace the plug wires with
A set that I took off at the last tune up. Then headed out for a spin to get
Gas. It still stumbled at light throttle and again I could drive around it. Yes
It once again pissed me off. Pulled into the gas station and filled her to the top
With 93 octane and headed home. ALL THE WAY HOME RAN LIKE A TOP
NO STUMBLE OR HESITATION!!!�� Could I have a fuel tank issue ?
Like a pump that makes proper pressure just not volume? Could there be
Split in the line to the pump that is submerged and doesn't cause a problem
Until I get to a half tank of so of fuel. I am pulling my hair out here.
Any thoughts ??
Thanks
 
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