Before you buy
Even the earliest C4s had lively performance – though the later examples make them feel tame. The very hard ride on early cars (especially the Euro-spec Z51 pack) was unsettling on rough roads; it was gradually softened and the advanced alloy and composite suspension components have proved durable in service.
On the L98, check for oil leaks from the front and rear crank seals (£300-plus to sort). With the LT1, inlet-manifold leaks cause poor running and the Opti-spark distributor (used up to 1994) suffers if the water pump above it weeps and the moisture corrodes the electrics – budget £1000plus to replace both. ZR-1S can be troublesome if neglected, but are great when working well and they thrive on use. A high tickover indicates a vacuum leak under the plenum chamber.
Upgrades are popular; the best for the L98 is a dual exhaust, and on pre-’92s losing the cats gives 20bhp+ more and takes heat away from the engine. On LT1S, cat-back systems are best.
Most cars have auto transmissions. Check the fluid is red: if it’s black or smells burnt, budget £7-900 for a rebuild. The manual ‘4+3’ (with overdrive on 2/3/4) is robust; ensure overdrive cuts in both automatically and on the gearlever switch. The six-speed ZF is also strong, but beware of clattering from its dual-mass flywheel.
Electrics are the most likely problem area, and Japanese imports can suffer major issues due to being overloaded with extras. Diagnostics are OBD I up to 1995, then OBD II. If buying from the US, get a CARFAX vehicle history report.