5.0 stumble issue

[Xeek]

Have a 97 5.0 past month or so it started as I would turn right at a little more than a 90 degree turn into my driveway. One of those sloped gutters that pops you up some. By the time both front tires get up it tries to stall. If I go slower it will stall, if I just keep my speed and lightly accel it won't do anything. Literally no other turns or bumps cause it, just my driveway lol.

About two weeks ago sometimes it'll stumble a little for a couple seconds after starting it, I think all cold starts. Around the same time when it's warmed up and I run into the store when I come back if I don't wait like a minute or two before putting it in reverse it'll stumble or stall depending on if I give it enough pedal or not. If I wait long enough it's perfectly fine. It's also fine if I put it in drive.
I tested that once and it would idle 700-800, dip to 400-500, then back up, etc. I switched to drive and boom it's fine, back to reverse, and it's back. After a few times it worked itself out and was back to normal cause it had been running a couple minutes.

I had a spare iac new laying around so I swapped that in, no difference.
I also cleaned the maf, no difference.

No codes being thrown at all. I have an edge insight digital gauge/scan tool thing. I can see values of stuff as I'm driving of whatever the computer can read. Maf, fuel, o2, temps, etc. I could provide any values that might be helpful.

 

[EB4X]

Hard to believe but it could be your torque converter.... or possible vacuum leak.
I have basically the same problem.....new IAC's ...new gaskets.... not as frequent but still happens....when tranny goes (new torque converter) hopefully that resolves it with me.

 

[410Fortune]

97 5.0 how many miles?
RWD or AWD?

When it stalls does it re start immediately?

Suspect CRANK SENSOR, after reading your post that is the first thing that popped into my head

 

[Xeek]

Hard to believe but it could be your torque converter.... or possible vacuum leak.
I have basically the same problem.....new IAC's ...new gaskets.... not as frequent but still happens....when tranny goes (new torque converter) hopefully that resolves it with me.

I sure hope not, for you or I! Vacuum would be much easier. I know they go bad around the pcv. It's just a pain it get my hand in there and check it.

97 5.0 how many miles?
RWD or AWD?

When it stalls does it re start immediately?

Suspect CRANK SENSOR, after reading your post that is the first thing that popped into my head

AWD. Yea it has no issues restarting and starts pretty well overall.
This is the second 5.0 that's been in it since it's been swapped from a sohc. First one blew apart oil filters lol. I think it should have around 210k on it. It was a nice strong donut machine in the donor truck lol.
I don't hear the typical chirping from the sensor so I haven't suspected it to be an issue.

 

[410Fortune]

CRANK SENSOR not cam synchronizer, they are different
Crankshaft position sensor is located one the crankshaft balancer on the front of the engine

also turning and climbing a curb, THuROUGHLY check your power cables, IE battery terminals and cables. The 5.0 has a ground on the front of the engine top of oil pan front timing cover next to crank balancer, sometimes a ground right to the frame below the battery and a ground that leads to the radiator support.......if whomever swapped the sohc for 5oh and then to 5oh again missed a ground you will lose power at times.... or if battery terminals are questionable

 

[Xeek]

CRANK SENSOR not cam synchronizer, they are different

My bad you definitely even put crank sensor in all caps lol.
I'll look into that. Is it something I can throw a multimeter on to check it out?

 

[410Fortune]

you can OHM the sensor yes and check its wires for continuity

 

[Xeek]

I replaced the crank sensor for the hell of it. Getting the belt back on was the worst part lol. I found a thread by mbruffey saying to take tensioner out and that definitely made that easier.
Problem persisted after replacement. So I took the ground wire going to block/frame and cleaned it all up with sandpaper. Then also ran 14g speaker wire(two of them glued together soo 7g effectively??) From battery to frame and frame to block. I feel they're satisfactory unless there's something special about speaker wire.

Neither thing helped. So far I'm guessing vacuum, the converter thing, or iat sensor where I read in another thread. This is frustrating. Grr.

 

[Xeek]

So here's exactly what it's doing for one part of this. I drove it around and warmed it up. Turned it off for a couple mins, then the following two mins after starting it did it's thing in reverse. In the end you can see it cleared up and didn't drop in reverse anymore.
If you look at the edge device I have you can see the rpm listed to monitor.

I also unplugged the iat sensor and it reads -40. Plugged in and not fully warm it reads about 100, but I have seen it run 130-160 when really warmed up and driving. I don't suspect the iat anymore.

 

[Xeek]

So in short, my issue is completely fixed, but I'm not sure exactly why.

It had been getting worse, rarely stalling, but more issues with a terrible idle at times.
I decided to check fuel pressure and got 0psi. Okay so I press the Schrader valve on the fuel rail with a screwdriver and nothing. I get a core remover and it starts spewing out fuel that's under pressure as I unscrew it. I reconnected the fuel pressure gauge with no core in the valve and boom I get a fuel pressure reading. 40psi off, 32psi running, and 42psi with fpr vacuum line pulled off. All seems normal.
So I goto the junkyard and grab another core and put it in. Now I can press the core and fuel with spray out like it should.
And now the truck has been running at 100% for a few weeks now.

I don't understand but I'll take it lol

 

[410Fortune]

Very interesting! Hopefully the issue stays gone
What did the old core
Look like? Any debris plugging it up? Wondering if there was some blockage in your fuel rail? Perhaps a piece of debris from when the engine was out of the truck?
With stuff like this unless you can put your eyes on an actual issue these things usually come back! So please keep this updated

 

[Xeek]

There was just a tiny bit of gunk in the core. I would think it would be fine that way, but I'm no professional lol. I don't think it leaked either cause I never smelled any fuel.
I had been talking with boomin about it and he thinks the same, that it could've been a blockage in the fuel rail and maybe I dislodged it. Or the fpr was stuck and removing the vacuum line to check it it was working unstuck it.
If there was gunk in the rail and it's gone now I'm assuming taking the core out shot it out of there.

Whatever the case may be I'll of course see if anything happens and see if the same fix fixes it again.

I might pop the old core in a tire(so I don't have to worry about spraying fuel lol) and see if it still doesn't release pressure.

 

[410Fortune]

I believe you had some
Blockage in the fuel rail
You may want to run some concentrated fuel treatment for a while in case any of that sludge is still behind the injectors
Good idea to replace fuel filter soon also

 

[Xeek]

Ive ran two bottles of berrymans prior to this fix. My issue had gotten worse so maybe they moved the clog lol.

You say concentrated, so two bottles in one tank? Or 19gallons of it? Jk