1996 5.7 / Intermittent loses power-Bogs down. Died twice at StopLight. Starts right up and runs fine mostly

[OBS_Trash]

1996 - 5.7 - AutoMagic

Just recently noticed tiny bits of bog down, just a small chirp and then she's fine. (Days Ago) - Since then its getting more common, even to point where at a stop light and once in parking lot it died. I was able to restart and purs like a kitten, then out of no where (Bogbog). Like bad fuel

(Few Months ago) A previous endeavor which led me to replacing a wire that burned on my headers - i replaced the fuel filter as part of that troubleshooting

(About a year ago) I previously almost screwed up my Fuel Pump relay housing connections by attempting to hook up a kill switch. But its fine now, i jiggle it and it keeps connection

The previous owner said he replaced the fuel pump (But who knows)

It has Headers and Straight Pipe, Buddy said sometimes if the fuel line is running too close the gas can boil and vapor lock causing this issue. (My thinking is ive had this truck a year and its my daily pretty much, just now this??)

*****Things im going to do:
Order a fuel pressure test kit off amazon and tap the schrader to check pressure.
Change the O2 Scensors

Looking for any other ideas, the one my buddy (Very Knowledgeable) hit me for a loop, i wouldnt have thought that, So im hear to get anything i may be missing. Thanks in advance OBS Fam.

 

[Schurkey]

It's possible to boil fuel with exhaust heat. It's REALLY unlikely at ~60 psi. It was common with engine-driven fuel pumps where most of the fuel plumbing was under some amount of suction, and then the vapor got into the pump. Those pumps were fine with liquid, crappy with vapor. But with the pump in the gas tank, they'll never draw vapor unless you're out of gas.

Connect a scan tool, find out what the computer wants you to know.

How old are the usual "tune-up" items? Cap, rotor, plug wires, plugs, air filter, verify EGR, verify electronic spark advance, etc. Vortec distributors have a nasty habit of wiping-out the distributor gears, and the mainshaft gets wobbly in the plastic distributor housing.

If you have no catalysts, the downstream O2 sensors should be setting codes for catalyst inefficiency.

 

[HotWheelsBurban]

There's several possible suspects:
Fuel filter could be getting clogged and the crud is floating around, gets in a position to restrict fuel flow when it needs to increase (under acceleration).
Module or coil could be developing issues; electronic components don't like heat and humidity, especially old parts. And guess what we have plenty of in Houston area....
Just because the fuel pump has supposedly been replaced recently, doesn't mean it's still working properly. My Suburban runs so much better with the new fuel pump we got installed last fall, that I realized how long it'd been running acceptable (but not as well as it should have been).
Other members have had trouble with the factory distributor; knock on wood, I haven't yet.

 

[OBS_Trash]

Ok, so I bought OBD2 reader on Amazon - Cleared old codes and drove around till it did it.

Code: P1406 - EGR Valve

Best $35 buck I ever spent

 

[OBS_Trash]

Update:

The replacement EGR Valve ($130) did not fix the problem. I have since verified it’s not the MAF, I went to factory air filter set up. I checked fuel pressure supply and it’s fine.

I’m changing the 02 sensors because why not, (driver side done, had to get some torch and a special socket to pull the rounded off passenger side one- that is this morning)

It has headers and straight pipe so I only have upstream sensors.

The previous code was failed EGR valve, now I’m getting 3 codes.
1 and 2 are “no downstream O2 sensors” yeah I know, thankyou Mrs. Lipknickey

The 3rd is “Insufficient EGR Flow” different but same ballpark.

I’m going to replace the Fuel Filter AGAIN, thinking about returning the EGR as this one could be bad

Next I’ll be looking at Ignition Coil then Spider Fuel Injector system

I just wanted to buy a new steering wheel…….

 

[Schurkey]

Code: P1406 - EGR Valve

Download the free service manual for your vehicle from the links on this web site. Follow the official diagnostic procedure for P1406. It's not as simple as just replacing the EGR valve.

The replacement EGR Valve ($130) did not fix the problem.

Not hugely surprising.

I checked fuel pressure supply and it’s fine.

Define "fine".

For that matter, what are your short- and long-term fuel trims when the vehicle acts up?

I’m changing the 02 sensors because why not, (driver side done, had to get some torch and a special socket to pull the rounded off passenger side one- that is this morning)

Probably wise.

The previous code was failed EGR valve, now I’m getting 3 codes...

...The 3rd is “Insufficient EGR Flow” different but same ballpark.

I’m going to replace the Fuel Filter AGAIN, thinking about returning the EGR as this one could be bad

If you're getting a code for EGR, why are you replacing the fuel filter?

DIAGNOSE the EGR code, stop replacing parts with no diagnosis.

Next I’ll be looking at Ignition Coil then Spider Fuel Injector system

Any of that "could" be defective.

Diagnose the EGR first.

 

[VFJimbo]

Nice truck

 

[OBS_Trash]

Fuel supply pressure is in range almost 60psi, the one time it did it in driveway while I had it hooked up the pressure increased in response.

Ignition Coil Replaced
PCV Valve replaced
Can’t find a vacuum issue

When I replaced the EGR valve everything was pretty clean, but I sprayed some carb cleaner anyway, to my surprise the EGR code did clear.

The problem is still there. I’ve pinpointed through it dosent seem to be RPM related, more speed related. Once hit 50-60 mph it does it BAD. So I’m toying with idea of a speed sensor maybe, starting to research that. Haven’t made it into the spider injection yet and probably won’t.

Starting to give up and maybe just find a shop that can put a nice computer on it and pinpoint it hopefully. This one has me wore out. Tired of 113 degree driveway play in Texas. I think I’m going to Tap

If I do tap out, I will report back findings to help anyone one down the road.

 

[OBS_Trash]

Update: I found info that seemed to describe my exact issues. I replaced the $70 Crankshaft Position Sensor and the truck seems to be driving right. Still seems like it has a slight inconsistency but it could just be me. It came with a couple shims that may need to be used with high-high Mile trucks (fitment wear etc) I may add one at a time over a few weeks to see difference. But no more backfire/hard misses at 50-60mpg.

Fingers Crossed

 

[OBS_Trash]

Update: I found info that seemed to describe my exact issues. I replaced the $70 Crankshaft Position Sensor and the truck seems to be driving right. Still seems like it has a slight inconsistency but it could just be me. It came with a couple shims that may need to be used with high-high Mile trucks (fitment wear etc) I may add one at a time over a few weeks to see difference. But no more backfire/hard misses at 50-60mpg.

Fingers Crossed

Runs better, now at 65mph it sputter/back fires. I signed up to use the group scan tool.