Hello all, I recently purchased a used 1997 2500 with 8.0L V-10 4x4 5 spd (163,000 mi., new engine @ 85,000mi.). I have been having an issue with what I assume to be inadequate fuel delivery.

Normal city driving is fine at/under 65 mph (approx. 2k rpm 5th gear), until the engine is under load demand. Climbing a long dirt road hill to get to work in 2nd and 3rd gear (approx. 1800 to 2300 rpm) it will start to stutter, lope and lose power, as if running out of gas. If I travel on the highway at/over 70 mph (>2k rpm) it will do the same thing. If I drive it at higher rpm’s or just accelerate quickly several times it will begin to stutter and lose power.

I have changed:
Spark plugs, wires and coils
fuel pump
O2 sensors

I have also heavily modified the exhaust to a degree that the cats are not a factor.

Here is the catch: I have no check engine (CE) light. When I turn the ignition key to on, the light will flash on for the op check so I know it’s not burnt out. I have driven for two days with O2 sensors disconnected and no CE light illuminated. I get the two codes for both O2 sensors (P0132, P0152) on my “FIXD” obd2 reader, but no CE light.

One more bit of oddness: I drove for a couple days with the exhaust partially disconnected from the manifolds and the truck ran great at 80mph (approx. 2500rpm) with no stutter or power loss (what?!).

The only thing I can think of is that the previous owner or his mechanic messed with the wiring to bypass the CE light, and as a result will no longer register the O2 sensors. Either that or the wiring is melted/damaged somewhere (but why no CE light?). Maybe the exhaust pipes are clogged too? Does this sound logical?

 

The codes are "circuit high" codes which (supposedly) can happen when the mixture goes very rich. More often it is that 12V gets into the signal wire though. However the fact that it runs better with the exhaust disconnected makes me think the O2 sensors are reading wrong. From what I gather the FIXD gizmo has live data capabilities so look at the O2 sensor readings, the fuel trims and if the system is running in closed loop. The reader should also tell you if the check engine light (MIL) is commanded on, if the issue comes and goes the codes might be pending and not confirmed (yet).

 

Thank you DerTruck, for that idea. I will explore that option with the FIXD device.

Could it possibly be the MAP sensor causing this?

 

Our '98 360 never triggered a CEL for having downstream 02s dangling in the air (that actually was not my doing). I don't know if upstreams would trigger a CEL but I'd at least expect heater circuit codes if they're unplugged??

 

What brand O2 sensors were installed? If they weren't NTK, or Denso, they may be contributors to the problem. These trucks are rather picky about what sensors they will play with.

 

You can say it, Bosch. One of the worst.

I see conflicting descriptions for 152, A "short" doesn't exactly mean "high". Guess it depends on how much voltage is being returned. You should check this, If you are seeing a full 5 volts it's a short.
P0132 O2 Sensor 1/1 Circuit Voltage High
P0152 2/1 O2 Sensor Shorted to Voltage

 

I have the Heavy Duty Emission Cycle (HDC) so I only have two sensors, both upstream of the cats. No other codes are showing on my device. It is a little strange.

 

I couldn’t tell you what the brand was, they were probably factory. I installed Walker sensors, hopefully that is one step closer to solving the problem.

 

Yes, I have been searching for answers on this. I wouldn’t know where to begin to trace the problem. The fact that both are showing high voltage indicates to me a grounded/open wire, and I don’t know if it would be due to a previous mechanic meddling with that system in an attempt to get the engine light to go away (hence the strange lack of CEL when sensors are disconnected) or simply due to chafing.

 

Question becomes, how high is the 'high' voltage? If it is fixed at 5 volts, or 12 volts, matters.....