Random issue, bad mpgs, hesitation

ChevroletTough · March 11, 2020

Just an update:

Got the other Oxygen sensor replaced, I now no longer notice "visable" exhaust all the time. This is a better sign! The truck would always show exhaust even when it was warmer out (on warmer days recently in Wisconsin). Took it for a spin and I no longer see that after the engine warms up. I was noticing some milky residue on the oil cap here and there. After replacing the waterpump I no longer see that. (2 coolant flushes, 3 hoses, thermostat and thermostat temp sending unit).

I am making progress.

With the recent warming temps here, I am really getting excited to get that upper intake plenum ripped off. I have been soaking the EGR pipe nuts every couple days. Hoping that bugger comes free (1 3/8" double nut).

I have the intake gaskets, fuel pressure regulator, throttle body gasket, and new vacuum line in my cart ready to order.

I don't think I'm going to do the cap and rotor, truck isn't missfiring or having any issues, but perhaps this is the time to do it all: plugs,wires,rotor,cap. The wires are the good napa blue belden wires, I have always run those. I plan to pull the front 2 or 3 plugs and check them prior to doing this all.

I will ensure to put tape over the intake ports once I have the plenum off, so that I don't drop anything into the engine while I work on that dreaded FPR. God I hope the snap ring is pointing up in the right direction or I'll have to pull the whole fuel rail up with injectors. My luck, that's the way it will be. I will replace the MAP sensor while doing this job as having the plenum off makes it 1000 times easier to get to the hold down nut/metal plate.

This truck is a strong runner aside this random issue. The shop was pretty positive between the FPR and the fuel filter, the issue would be resolved.

When it gets nicer out, I'll tackle this job on a Saturday or Sunday. I imagine it won't take me all day. Disassembly might go faster. I'll take pics of the brackets on the back of the engine.

off topic: I plan to replace the AC compressor, accumulator, and orafice tube and get a full ac charge (after an evac). Boy my truck went from a $1500 to $5000 truck in no time! I'll have to plow a ton of driveways next winter. I won't have to worry about the bearings or brakes now though, so that's great. The front brake lines will need to be replaced at some point, along with all 4 shocks. I'll do the shocks myself. I also plan to replace the entire front end steering system (tie rods, stabilizer, idler, pitman).

Edited March 11, 2020 by ChevroletTough

ChevroletTough · March 11, 2020

Just a pic from this winter, putting her to work making money

Sent from my iPhone using Tapatalk

ChevroletTough · March 24, 2020

Shocks come today. Maybe the weather will cooperate this weekend and I can do the plenum work and shocks. I know this is a1 ton so it will ride rough, but I am anticipating the ride quality will improve quite a bit. I can't wait to show you guys the factory shocks... they are sooooo toast!

ChevroletTough · March 25, 2020

Sent from my iPhone using Tapatalk

ChevroletTough · March 28, 2020

Done! They were shot.

Sent from my iPhone using Tapatalk

ChevroletTough · March 28, 2020

Sent from my iPhone using Tapatalk

ChevroletTough · April 21, 2020

I still haven't gotten around to doing the upper plenum yet. I did find a factory GM bumper a guy has had sitting for 15 years... so with a little effort and my grinder, I put it on. No more dented bumper.

I had tested the 4WD after the recent ice storm and had a hell of a noise on the passenger side, even wheel hop! Took it out of 4WD, issue is gone. I was betting it was the CV axle.

Well, this past weekend I replaced the CV axle and no more noise!

Plan to change front diff fluid and transfer case fluid.

I am going to start to look at a weekend to get this plenum off. I have everything I need. Truck hasn't acted up at all. I did haul a bed full of wood 1 hour in 2 directions and it never hesitated.

I have all of the front end parts in my cart... $300 worth. That will be on deck soon, all parts are shot, lots of play in steering by grabbing a tie rod.

Edited April 21, 2020 by ChevroletTough

James Collier Jr. · April 21, 2020

Could also be a shot throttle position sensor. Is this truck one of the ones that was still TBI, or is it the PFI Vortec? I assume from OP's previous post is is a PFI model. Either way, throttle position sensors can wear out in the most common slide ranges (which depends on how it was mostly driven) and I have seen them go bad in a manner that did not set a code. Coolant temp sensors have been known to wig out and cause the injectors to drown the engine as well (most GM trucks I've seen have two, one for the gauge, and one for the computer to calculate fuel delivery and timing).

And the engine doesn't have to misfire to have a bad cap or rotor. I had a 4.3 Safari once that wouldn't start after a heavy rain. Turned out the cap was cracked and allowing condensation to form inside the distributor. Started and ran fine otherwise.

Edited April 21, 2020 by James Collier Jr.

ChevroletTough · April 22, 2020

Interesting. It’s got the actual side throttle body, not the goofy TBI of the 80s/90s.

I did replace one of the 2 throttle position sensors. At least I believe there are 2.

Sent from my iPhone using Tapatalk

ChevroletTough · April 29, 2020

Just want to add to this, the last tank i filled up I got 12.9mpg. That’s pretty good for a 1 ton.

I’ll be pulling my small trailer with 2 ATVs this weekend, I’ll be curious to see if it does the same thing as my big enclosed. (The running rough and eating fuel).

Sent from my iPhone using Tapatalk

ChevroletTough · May 7, 2020

Finally getting after it. Map and fuel pressure regulator replaced. Going to do cap, rotor, and plug wires I think.

Sent from my iPhone using Tapatalk

ChevroletTough · May 7, 2020

I did get the o ring out of the FPR housing/cup as well.

Sent from my iPhone using Tapatalk

ChevroletTough · May 7, 2020

There was also no fuel pressure to release on the rail. Is that normal? Truck has been sitting for a few days without a start.

Sent from my iPhone using Tapatalk