We are at it again with Steve and his chick magnet, minus the chicks, on avoiding TPI gulch.
'Somewhere in automotive never-never land, there's a place called TPI Gulch. Walk to the edge, look down, and you'll see heaps of brand-new throttle-position sensors, mass airflow meters, manifold-absolute-pressure sensors, manifold-air-temperature sensors, coolant-temperature sensors, oxygen sensors, idle-air control motors, knock sensors, and electronic control modules. Among skeletons and empty wallets, a gentle stream flows around the discarded heaps of high-tech gadgets. The stream carries the blood, sweat, and tears of frustrated '85-'92 C4 and Gen III F-body owners.
We're not bashing on TPI cars, in fact, we love 'em for delivering massive amounts (330 lb-ft) of low- and midrange power while delivering fuel economy in excess of 18 mpg around town. But you can visit TPI Gulch if something goes wrong and you attempt to repair your Corvette, Camaro, or Firebird without the proper resources. That's what I did when the "Service Engine Soon" (SES) light in my bargain-purchase $6,000 '85 C4 lit up like a roman candle after I pulled its L98 350 to repair a spun rod bearing (read all about it in "Why Ask Y," Sept. '06). Fortunately, my trip into TPI Gulch was a brief one.
The trouble started after my Swiss Army Knife on wheels (open the hood, doors, and hatch for the full effect) was reassembled after the unexpected nuisance-and $657.89 expense-of the damaged crankshaft. In keeping with the low-buck theme, I removed, repaired, and reinstalled the engine myself, but instead of a clean startup and a tire-smoking drive-off, the darned SES light appeared for the first time in my ownership of the car. Something was screwed up again.
But what? Being a good car crafter, when I fixed the crank, I was very careful to completely document the engine removal process with no less than 250 digital pictures so I could put the unfamiliar C4 back together just the way it left Bowling Green, Kentucky, 22 years ago. I practically wore out a pair of shoes running between the car and my home computer screen to review the pictures during the painstaking reassembly process. The problem wasn't in the machine work either. The thing fired right up, and the oil-pressure gauge showed 65 psi. What's more, the 350 sounded great at idle and drove like new at part throttle on surface streets.
But at anything over half throttle, which is where Corvettes come to life, the motor would hiccup, the SES light would turn on, and the engine would turn into a pig. Oh, it'd run up to its 5,000-rpm shift point, but it was laboring and sure didn't feel like 230 net horsepower. Clearly it was in "limp home mode," a self-preservation tactic where the ECM triggers stinky-rich fuel metering and retards the spark curve to prevent damage. Worse, the dash-mounted instantaneous fuel-economy readout showed single digits. With a fresh set of piston rings, I knew the obvious gas wash would quickly dilute the oil, making every mile traveled equal to 1,000 miles of wear. I parked it after two frustrating days of repeatedly disconnecting the battery to clear the codes and defeat the SES.