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Rebuilding a GM 4.3 Liter V6 Part 1


The beginning of the 4.3 V6 engine extraction

As I talked about in my previous post, The The New Project: 1991 C1500, I need to rebuild the engine in the truck I recently bought. It's a 4.3 liter V6 with TBI. I've been interested in learning to rebuild an engine since I bought my 1990 K2500, but I did a little research first to make sure I wanted to take on the task.

Should I rebuild?

There are few options when it comes to reviving a vehicle with a worn out or destroyed engine. I considered each of them before I made my decision.

Option 1: Get a Salvage Yard Engine

A lot of people say to just buy an engine from a salvaged vehicle. This would have been pretty nice. You buy the engine from a salvage yard and just swap it in. Very little down time and it gets you on the road faster. However, two of three of my local salvage yards said the truck was "too old" and they didn't have any engines available. The third place said they could get me one shipped in from another yard, but it would be high mileage engine and would cost at least $800. I wasn't ready to pay that for another engine that might be just as worn out as my current one.

So unless your vehicle is a bit newer, this option doesn't really work.

Option 2: Get a Crate Engine

A lot of places sell crate engines, either long blocks (engine block and heads) or short blocks (just the engine block and rotating assembly), that will fit in almost any vehicle. I searched a while for a 4.3 liter V6 and found I would essentially have to pay $1,800 and a core charge of $300 for a long block. That's a lot of money compared to rebuilding my current engine. There were also fewer options than I expected. I think this is because the V6 in these trucks is both not as common and not as desirable as the 5.7 liter V8. Also, many people swap in a newer engine like a GM LS. However, I am not interested in the wiring work that comes with that. LS engines are also very popular and expensive right now.

Option 3: Have a Local Mechanic Rebuild the Engine

I was tempted to have a local mechanic rebuild the engine for me. I'm too excited about driving this truck and I started getting impatient. I called a mechanic nearby and they told be "we don't tear anything down past the heads". This wouldn't work because my problem is likely connecting rod bearings ("below" the heads) and I want the engine completely rebuilt or new. I also got this truck as a hobby and to learn more about mechanic work, so farming out all the work defeats the purpose.

Option 4: Rebuild the Engine Myself

After doing the research, I decided I want to rebuild this engine myself. It's going to be a lot of work, but it's my cheapest option and allows me to learn even more about engine maintenance and repair. I'm estimating it will be around $1,000 after I buy the rebuild kit and get the block honed or bored at a machine shop. But after I'm done, I will know everything there is to know about this truck and its engine. I'll be using my Haynes Repair Manual to guide me, as usual. Wish me luck!

Here's a gallery of pictures I took throughout the process:

Rebuilding a 4.3 V6

The New Project: 1991 C1500


1991 Chevrolet C1500, the day I bought it

  • Year: 1991
  • Engine: 4.3 liter TBI
  • 262 cubic inches
  • Horsepower: 160
  • Torque: 235 lb-ft
  • Trim: ? (Mystery trim)
  • 2-wheel drive
  • Tires:
  • Miles when purchased: ~140k (maybe? speedometer is off by a lot)
  • Current miles: ~140k

It has been just over a year since I bought the 1990 Chevrolet K2500, so obviously I needed more to work on, right? Not really, but I couldn't pass this one up. I've been on the hunt for a very cheap short-wheel-base to fix up. I had a 1990 short-wheel-base Chevy C1500 in high school and it was one of those vehicles you say you should have never sold. This new one is a 1991 with a V6 and 5-speed manual transmission just like my old one. I paid $1,200 for it.

It had a rod knock and extremely low oil pressure at running temps when I got it, so I started tearing down the engine for a rebuild: Rebuilding a GM 4.3 Liter V6 Part 1.

GM OBDI Trouble Codes


OBDI trouble codes for 1988 - 1990 GM vehicles.

  • 13 - Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds.
  • 14 - Coolant temperature sensor signal indicates a temperature of over 275° F for 2 seconds.
  • 15 - Coolant temperature sensor signal indicates a temperature colder than -27° F for 30 seconds after the engine has been running for at least 30 seconds.
  • 21 - TPS voltage was above 2.5 volts for 8 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more.
  • 22 - TPS voltage was under 0.2 volts for 2 seconds when the engine was running.
  • 23 - Inlet air temperature sensor signal showed an air temperature below -22° F after the engine has been running for 5 minutes.
  • 24 - Vehicle Speed Sensor (VSS) Circuit .
  • 25 - Inlet air temperature sensor signal showed an air temperature over 302° F after the engine has been running for 5 minutes.
  • 32 - EGR open command did not change MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal.
  • 33 - MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%.
  • 34 - MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or the engine speed was over 1200 RPM with a throttle position angle above 21%.
  • 35 - Idle Air Control (IAC) System .
  • 42 - The EST signal did not change when the ECM applied bypass voltage to the ignition module.
  • 43 - The ECM did not detect a knock signal during near wide open throttle operation with coolant temperature above 194° F or the knock signal was present for 5 seconds or more during normal engine operation. Electronic Spark Control (ESC) Circuit .
  • 44 - Oxygen sensor voltage was under 0.2 volts for 50 seconds of closed loop operation. (Lean Exhaust Indicated)
  • 45 - Oxygen sensor voltage was over 0.7 volts for 30 seconds of closed loop operation with a throttle angle between 2% and 20%.(Rich Exhaust Indicated)
  • 51 - PROM error. (MEM-CAL)
  • 52 - CALPAK error.Fuel CALPAK Missing .
  • 53 - System Over Voltage .
  • 54 - Fuel pump voltage was not present at fuel pump sense line for 2 seconds after the ECM has sent the fuel pump on command.(Low Voltage)
  • 55 - ECM error. Replace ECM.Faulty ECM

Installing Headliner Insulation in a Truck


It's getting hot here in July and my 1990 Chevy truck's AC hasn't been converted to R134a refrigerant yet. And it's out of refrigerant. So I'm noticing all the ways in which the interior gets heated up. The other day I was sitting in the sun waiting for someone and I realized heat was radiating off the inside of the truck's roof. The front part was cool to the touch because it is double-layered metal, but the back part was another story. It was nearly too hot to touch and it felt like it was pumping out heat into the interior.

The interior headliner area before I added the insulation

That's what it looked like before I added the insulation. I used a roll of insulation I found at Home Depot. It was $10 for a 2 ft x 10 ft roll. I cut it down to 18 inches x 45 inches to fit the area I wanted to insulate. I then used 3M spray-on headliner adhesive to make it stick to the metal.

Insulating material and adhesive that I used

The interior headliner area after I added the insulation

I wish I would have measured the temperature before and after. It's a drastic improvement. I left the truck sitting in a parking lot in similar conditions for about the same amount of time as the day I noticed the heat. The interior insulation was barely warm to the touch when I came back out.

The stock headliner would have accomplished this insulation, but it's made of pressed cardboard-like material and had fallen apart over the years. I plan on adding an aftermarket headliner from LMC at some point, but this insulation will just add to the affectiveness of the headliner when I get it.

New Seats in the 1990 Chevy Truck


New seats from a salvage vehicle for the 1990 Chevy Truck

I finally got some "new" seats. These came out of a salvaged 1994 Chevy truck, but they were originally from a 1990 model. Either year would have fit. It took me about 6 months of watching and waiting to find some decent condition, blue seats for the truck.

Before installing the seats, I thoroughly cleaned them with Shout Auto Dirt and Stain Remover (you can get it on Amazon here). They came out very clean and smelling fresh.

Here are the old seats for comparison:

Old seats out of the 1990 Chevy Truck

I would say it was a worthwhile upgrade :).