Old Indy hit 250k last week and decided to immediately begin acting up. On the way to work at highway speeds it started bucking at around 3100 RPM. It feels like the fuel delivery is being restricted and/or spark control is kicking in, similar to hitting a speed limiter. The CEL lit up and I read the code via Torque app/BT dongle and it indicated code P1158 - Oxygen Sensor Engine Rich *Codes* B D. Is that a pre-cat 02 sensor?

Below the magic 3100'ish RPM range everything goes back to normal. The temps here have been fluctuating wildly and it was in the low 20's the day this happened, so I thought temp may have been a factor and reset the code. Even though that code hasn't reappeared the issue persists. I read the codes again yesterday, no CEL, but thought I'd check anyway and there was a ghost code P0326 - Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor).

Anyone have ideas on what may be going on here?

I've read a lot of posts about issues with the VSS and it seems to cause the issue I'm experiencing, but my issue seems to be rev related, not speed related.

I thought I'd reach out for some advice before I start throwing parts at this thing.

 

My first guess is indeed the VSS based on your description of how your truck is behaving and my personal experience with a similar issue.

The easiest way to check it is to pull the connector off the VSS. You will lose your speedometer and odometer but not the tachometer. You will also throw a VSS code but that is obviously not the point.

 

Walt, I appreciate that info. That's an easy and cheap enough way to either pinpoint the issue or mark a potential issue off the list.

I'll disconnect the VSS this weekend and report back.

Thanks!

 

I disconnected the VSS and that didn't fix the problem. At this point, I'm thinking it's fuel pump related. Twice while trying to push past 3200 RPM today, the engine slowly died as if starved for fuel and completely shut down. I turned the key completely off and then back on and it started as usual, idled perfectly and ran fine again until 3200'ish RPM. Both times there was a weird gurgling from the fuel pump and once there was a mild thump from fuel tank area. Just filled it up with premium fuel, so it's definitely not for lack of having enough fuel in the tank.

It's been 4.5 years and 60k since the fuel pump was last replaced.

Also, no check engine lights or stored codes per the Torque app/BT.

Thoughts?

 

Still having issues with fuel/ignition cutoff around 3100 RPM. Within the past week, it has gotten worse. When cold, the truck will only rev to around 2700 RPM before cutting out. Once it's fully warmed up, it'll still rev to around 3200 RPM before cutting out. If I push it too hard for too long, it completely shuts down as if running out of fuel. Key off and restart and all is well again.

Here are the 6 faults I read yesterday via the Torque app.
P0300 Powertrain - Random/multiple cylinder misfire detected
P0307 Powertrain - Cylinder 7 misfire
P0326 - Powertrain - Knock sensor 1
P0340 - Powertrain - Camshaft position sensor
P1158 - Powertrain
P1316 - Powertrain

The below is what I've done so far and the issue still persists.

Disconnected VSS - No change, so reconnected
Replaced plug wires - STI 663
Plugs only have 10k on them, so I don't think that's the issue
Replaced vacuum line for fuel pressure regulator - it was cracked
Replaced fuel filter - 4.5 years old, so it was time
Replaced fuel pump - I actually just pulled the cover to inspect the wiring and fuel lines, but discovered the LR shop that replaced it 4.5 years ago installed a AEL pump in my non-AEL Disco. I actually have vacuum when I open the fuel cap now. Maybe too much. I'm thinking I may need a vented cap. Not sure if mine is or not. Is there a way to check a cap to see if it's vented/ non-vented? Also, I don't have an issue with fuel overflow any longer when I fill up. I always thought it was a cracked overflow tube. One less thing to replace!

Thoughts on what to replace next?
Crankshaft position sensor?
Camshaft position sensor?
Coil?

 

Also, forgot to add that I cleaned the MAF with CRC 5110 and replaced the air filter. I just received a new crankshaft position sensor and will install that this weekend. I checked the wires leading to the existing CKPS and the insulation looks good. No cracks or bare wire that I could find.

Any idea what fuel pump this is? This is a pic of what was in my truck. ​​​​​ I thought it was an AEL fuel pump, but it doesn't match pics of the AEL pumps I've seen. I was driving around for 4.5 years with that big return nozzle at the bottom completely open into the tank. Geeze.
I ordered the correct pump kit (non-AEL) from Lucky8. Easy replacement. I filled up today and the tank held 20 gallons with no spillage.

 

It's a vapor line fitting from the fuel filler neck, P38's used that style. Your cap should be vented for a 96. Your motor is dying because it's being starved of fuel, can't overcome the vacuum it's creating. Just replace your fuel cap with a vented one and take it out for a spin.

 

Thanks for the input, but I was having the issue prior to changing the old fuel pump which had no vacuum at all due to the huge hole in the top of my fuel tank! Just for ****s and giggles, I did purchase a new fuel cap yesterday (Stant 10819) at WalMart for $6. No change after I switched it out. Gonna see if that new crankshaft position sensor helps this weekend.

 

I'm pretty sure I just found the cause of my cutout issue. I removed the CKPS, carefully pulled the wiring to the engine bay so I could inspect and found the below. Not only was the wiring for the crankshaft position sensor connector bare, but the electrode piece at the end of the crankshaft position sensor is completely missing. I need to head to the store and pick up wire and shrink tubing. I sure hope I'm not missing a tooth on the reluctor.

 

Wow. Its a wonder it ran at all.