DIY Guides › Engine & Idle
A small leak at the MAP line can cause big drivability problems on Renix rigs.
When to use this guide: 1987 to 1990 XJ with rough running, hesitation, or brittle elbow failures.
On a Renix, the MAP sensor reads intake vacuum to calculate fuel delivery. A tiny crack in the rubber elbow at the throttle body, which hardens and crumbles with age, leaks vacuum and sends the ECU a false reading. The engine runs lean, hesitates, and idles rough in ways that look exactly like a sensor problem. Check that elbow first, it's a $1 fix.
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