After a few local trips, it was time to break the Suburban in for real. A 900 mile trip to Florida from Pennsylvania. What could possibly go wrong? Fairly quickly we found out a previous owner had spliced together the high and low beams at the headlights, which resulted in the wiring overheating and constantly triggering the breaker in the light switch. Since half the drive was at night, it was a pain and we finally gave up and waited for the sun to come up before continuing.
Read about our fix of the problem here. This also eventually ended up melting some paths in the gauge cluster before we traced down the exact problem.
Overall the vehicle did very well. There was almost no squeaks and rattles, far less than expected for an older vehicle, and probably only the same amount it came from the factory with. The drivetrain ran perfectly. We recorded a gas mileage of 18 MPG average for the whole trip. The cruise control was intermittantly choosing not to work after a while. We will look at that when we have time. In the meanwhile it sort of works. When it wants to.
This vehicle had a remote start/keyless entry system installed by a previous owner, which adds nice convenience while being basically invisible and preserving the classic look since our Suburban came factory equipped with electric locks. The steering is adjusted properly and tracks well, and drives straight and smooth on the highway.
The next large task for our Suburban was to drive back up to Pennsylvania from Florida, and haul back a trailer load of tools, equipment, and household items. The trip north went fine, but as we reached our destination we realized the damage from the previous light circuit overload had worked its toll on the gauge cluster. The internal lights were not operating, making it difficult to drive at night.
We soldered a wire across the gap melted into the trace by the overload so we could get back home again with operating gauge cluster lights. We will fix this properly at a later date, and hopefully make some much needed updates to the gauges as well while still keeping a period and factory look. In the meantime, we hitched up the trailer and loaded up for the trip back south. We ended up with about 4,000 lbs gross trailer weight and a few hundred in the back of the truck.
It squats a lot when loaded, and we had balanced the tongue weight fairly well. The suspension does not seem to like towing and hauling. We will have to improve the suspension later. We headed out and made our way back south, uneventfully. The Suburban hauled wonderfully (if a little too light on the front), and the gas mileage dropped about 5 MPG, down to 13.
To make hauling and towing more stable, we added lift blocks for the rear springs after determining the spring sag when loaded was normal. The springs checked out ok, but raising the rear of the vehicle just slightly would make it level when hauling. A few loaded trailer runs verified this. Sadly we were in a hurry and did not document this.
Fixing the cruise control proved more difficult. The wiring for the switch where it passed through the steering column from the stalk was worn and was starting to fray into the copper, providing an intermittent effect. Read about our troubleshooting and repair of this system here.
This tow dolly followed us home, and after some repair work seems to match our Suburban quite nicely!
We used it to bring home a 1978 El Camino, which is in need of some TLC. The Suburban towed the El Camino quite nicely and smoothly.
Although we had preserved the orignal headliner in our restoration, it was starting to show too much age. It had begun to sag in spots, and had a few small issues. It was time for a change. We pulled it out and stripped off the fabric and backing, down to the bare backing board.
We purchased headliner material and adhesive, and after carefully preparation applied the headliner to the bare board.
After allowing the adhesive to dry overnight, we trimmed the edges and cut out the holes as necessary
Then we installed both pieces of the new headliner and, and all the associated trim and ceiling fixtures.
We finally had some time for some maintenance on our suburban. For a while now it has been illuminating the 'Check Engine' light after about twenty minutes of driving. We took some time to pull the codes, and found a code 32 and 45.
The code 32 is 'EGR valve error'. We first examined the EGR valve, and immediately determined a vacuum hose was missing. We replaced this hose according to the hose routing diagram on the vehicle and hopefully this will resolve the issue.
The code 45 is 'Rich exhaust'. We aren't sure about this one right off the bat, so the first trial is to see if resolving the code 32 affects this one at all since that was an obvious problem. We will have to drive it for a while and see what happens.
Due to the global coronavirus issue, we haven't been doing much driving lately. But the air conditioning has started leaking down, and increasing faster also. We decided to take a look and troubleshoot that with all the extra time we have these days. Also we did notice the engine code '45' has not gone away, so we will have to look into that in detail at some point.
A detailed examination of the air conditioning system revealed a possible leak at the compressor shaft seal. There is oil and some dye present underneath the compressor snout. These Harrison R4 compressors are known to leak eventually at either the shaft seal or the case o-rings. The cylindrical compressor slides into a steel outer shell, and is only sealed with perimeter o-rings on each end.
We took the system apart, disassembled and re-sealed the compressor, and pressurized it again. We used a newer style double-lip shaft seal and r-134a compatible seals and o-rings. For the time being it seems to be holding pressure.
Since we haven't been driving much, we also opted to change out the aftermarket throttle cable someone had installed a long time ago. It is too short and thus bends too sharply, resulting in minor cable binding and a notchty pedal response. We installed the correct factory cable.
We still are doing limited driving in general thanks to coronavirus quarantining, and this resulted in a discovery about the gas tank. In out efforts to conserve money we ran the tank a lot lower than we usually allow and at about 1/16 tank according to the gauge we got stumbling and misfires on acceleration Which went away after getting fuel.
Apparently the tank baffling is not enough to keep gas centered under the pump when the tank is that low.
In investigating this stumbling (before determining the actual cause of low fuel), we pulled and replaced the aged and mismatched spark plugs which have been in the engine for quite some time. But this needed done anyhow.
We are still getting the code '45', so the cause was not the spark plugs. We have not had time to fully investigate this yet.
It appears we still have a very mild stumble under light acceleration. This may also be related to our code '45' we are still getting after a while of driving. Both of these issues seem to only happen when the accelerator is pressed lightly and when the engine is under load (i.e. not coasting or hard acceleration, or light acceleration down hill, or constant highway speed). The symptoms seem to indicate a small fuel delivery problem under certain conditions.
These GM TBI (Throttle Body Injection) systems are very simple in operation for a fuel injection system. The engine uses several sensors to indicate basically how much fuel the computer should deliver through the two injectors on the throttle body above the intake manifold.
The sensors are throttle position, absolute manifold pressure, vehicle speed, engine coolant temperature, ESC knock sensor, and an exhaust oxygen sensor, not counting emissions controls and sensors which can also have an effect.
In this case it seems like our prospective fuel delivery problem is most likely caused by the engine seeing an incorrect reading from somewhere under the conditions where the problem appears. We tested both the TPS (Throttle Position Sensor) and MAP (Manifold Absolute Pressure) sensor. Both tested ok with a multimeter. Both of these sensors control the fuel delivery based on engine throttle position and engine vacuum, which tell the computer how much air should be entering the engine and the vacuum of the intake manifold which indicates engine load.
The TPS can be tested by measuring pin resistance at the sensor, and observing this resistance as the throttle is opened and closed. If the reading does not move, moves erratically, or is not within proper limits then it is bad and should be replaced.
The MAP sensor can be tested by measuring output voltage at the sensor while vacuum is applied and released to the sensor. If the reading does not change, is not within limits or moves erratically then the sensor is bad.
Here is the MAP sensor, which is mounted on the intake on the passenger side of the throttle body atop the intake manifold:
Here is the test for the MAP sensor using a multimeter and a vacuum gun to selectively apply a vacuum to the sensor. With the sensor disconneced we used alligator clips to connect the two outside power connections and connected the multimeter to the center pin and ground.
The computer supplies a 5vdc reference voltage to the sensor, and reads a return voltage out through the center pin. This voltage varies with vacuum and tells the computer approximately how much manifold vacuum is present.
With both of these sensors confirmed working, we moved to the vacuum lines that can also have an effect on these sensors. We found a small pinhole in the supply line for the MAP sensor.
We replaced this line and hopefully this will resolve our stumbling issues.