The second-gen MR2 runs either the naturally aspirated 5S-FE 2.2L or the turbocharged 3S-GTE 2.0L. Both engines are mid-mounted, which means access is tight. Injector failure shows up differently depending on which powerplant you have. The 5S-FE typically starts misfiring around 120,000 miles when injectors clog or stick. You'll pull P0300 random misfire codes, sometimes with P0171 or P0174 lean codes. The 3S-GTE is less forgiving. A clogged injector on a boosted engine can trigger knock under load or fuel trim codes that swing wildly. You might see P0201 through P0204 for specific cylinders. Both engines use top-feed injectors, but flow rates differ—the turbo uses higher-flow units. Swapping injectors on the MR2 requires removing the intake plenum and fuel rail. It's doable in a driveway, but you're working over the engine bay from awkward angles. If you're chasing a stumble at part throttle or a cylinder that won't fire cleanly, injectors are a common culprit once you've ruled out coils and plugs. We stock OEM-spec replacements and upgraded options for modified 3S-GTE builds.
The 5S-FE typically sees injector issues between 110,000 and 150,000 miles, especially if regular fuel system cleaning wasn't part of maintenance. The turbocharged 3S-GTE can develop problems earlier—around 90,000 miles—because higher fuel pressures and heat cycles wear the seals faster. Modified cars running more boost will kill injectors sooner. If you're still on original injectors past 120,000 miles, start budgeting for replacements.
You can do it at home if you're comfortable working in tight spaces. The mid-engine layout means you're reaching over the bay to access the fuel rail. Remove the intake plenum, disconnect the fuel lines, unbolt the rail. Main difficulty is keeping the bay clean—any dirt that falls in can damage the new injectors. Budget three to four hours if it's your first time. A shop will charge around two hours labor because they've done it enough to work efficiently.
Ignition coil failure on these cars usually shows as a hard misfire that doesn't change with throttle position—cylinder just quits. Bad injectors cause a stumble that comes and goes, often worse under light load or when the engine is cold. Check fuel trims on a scan tool. If long-term fuel trim is adding more than 10% fuel at idle, injectors are likely restricted. Coil problems won't affect fuel trims. Swap coils between cylinders to confirm if the misfire follows the coil.
Yes. The 3S-GTE runs higher fuel pressure and flow rates. If you're installing aftermarket injectors, you'll need to match impedance—most are high-impedance, but some performance sets are low-impedance and require resistor boxes. Also, the turbo engine is more sensitive to injector spray patterns. A partially clogged injector will cause lean spots under boost, which leads to detonation. Always replace all four at once on the turbo, not just the bad one. The 5S-FE is more tolerant of mismatched flow rates.