Buying a car you have never seen in person is always a gamble. A collector who posts as @LegitStreetCars took that gamble on a forest green GMC Typhoon, and it arrived shaking, smoking and misfiring.
He says he paid right at $21,000 for the GMC Typhoon, delivery included. He calls the color his dream spec and says it is one of 292 built in forest green metallic.
The seller told him it had barely moved in years. So before it hit the road, he had to find out why it ran so rough.
A GMC Typhoon That Barely Moved For Years
The previous owner and a friend trailered the truck to his shop in Illinois. According to the host, it had been sitting for about three or four years, and before that it saw maybe 400 miles in a decade. The odometer shows about 51,000 miles.
It fired up without a knock, which was a relief. Even so, the idle was shaky, the brakes were grabby and an ABS light was on. Under the hood, he could see the whole engine shaking. He guessed it was down about one cylinder.
He was nervous for a good reason. In the video he explains that his other turbo V6 trucks have all had major engine trouble, so smoke from the tailpipe worried him.
Chasing The Misfire One Step At A Time
First he pulls the intercooler to reach the fuel injectors. Then he unplugs them one at a time with the engine running. Each one changes the idle, so no cylinder is completely dead.
Next he checks what every cylinder shares. The old fuel smells stale, but fuel pressure reads just over 40, which he calls about right. The regulator isn’t leaking, and the plug wires are routed correctly.
That left the spark plugs, which sit behind the steering shaft and are hard to reach. One plug was already cracked before he touched it. “Yep, that will jump spark,” he says at 18:02, pointing to the broken porcelain.
Better still, a compression test came back strong on every cylinder he could finish. A borescope showed clean cylinders, too.
More Than A $3 Fix
New iridium plugs helped, but the truck still had a slight shake. So he kept going. A missing nut on the downpipe was letting a little exhaust leak near the oxygen sensor, so he replaced it.
Then he pulled the upper and lower intake. The old intake gaskets were coming apart, and the distributor inside was crusty with corrosion, so he replaced it. He also cleaned and resealed the injectors, fitted a new ignition coil and swapped the oxygen sensor.
Sandblasting revealed holes in the metal coolant tube for the intercooler. He couldn’t find a replacement, so a length of hose took its place.
One fix backfired. A new knock sensor set a check engine code, so he measured both sensors. The old one read about 3,900 ohms and the new one about 100,000, which pointed to the wrong part. Once he sorted the sensor, the light stayed off. He also found the ABS connector slightly unplugged.
What To Check Before Buying A Car That Has Been Sitting
His week with the GMC Typhoon is a useful checklist for anyone eyeing a low-mile car that sat:
- Expect old fuel, dried gaskets and tired seals, even when the miles are low.
- Chase a misfire with simple tests first: injectors, fuel pressure, plug wires and spark plugs.
- Pull every spark plug and look for cracked porcelain, especially the hard-to-reach ones.
- Run a compression test before you spend money on anything else.
- Check new sensors against the old ones, because the right-looking part isn’t always the right part.
Where The GMC Typhoon Stands
After all of that, he takes it out at night and again the next day with fresh fuel. “But, uh, yeah, it runs beautifully now,” he says once it idles down, and on the road he says it runs great and pulls hard on boost.
It still needs shocks, a gas gauge check and some cosmetic work, and he plans more underbody cleaning. For now, he says he intends to keep this one completely stock.
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