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SR20DE Tuneup and Troubleshooting Guide

By Andy Radin

So here’s the deal: I’ve spent a lot of time trying to solve a number of idle, timing, and smooth running gremlins on my car – basic tune-up stuff. "Tuning up" a feedback-controlled, fuel-injected, computer-driven engine can get pretty hairy pretty fast. This is my attempt to sort out all the relevant systems of the engine, give ideas about how to diagnose problems, and help with possible fixes. This is a work in progress, so email with any additional data is very welcome.

What will NOT be welcome are questions like, "what step do I start with?" "I can’t afford to do all this, what should I do?" "What’s a torque wrench?" "Can I use generic filters, plugs, wires, oil, sensors, etc instead of Nissan?" I will continue to try to make this guide very easy to follow and understand, but it presumes a good tool set, a little mechanical experience, a lot of determination, and one brain in good working order. This page will contain the sum total of my knowledge, so anything I can tell you about your problem is probably in here. If you have new data that extends or contradicts something I’ve written, then let me know. Otherwise, you’ll have to do like I did – use your brain, try some experimentation, try to be objective, LEARN, and remember what you learn.

For reference, my car is a 1993 G20 (120,000 miles) with Jim Wolf ECU and POP Charger, Hotshot header and CAI, and JUN extra-light flywheel. It’s OBD-I, so there’s fewer items diagnosable by the car’s ECU than with the later OBD-II cars. However, my experience has been that most of the normal complaints that we have are not severe enough to trigger the "check engine" light anyway. Those that do trigger it are often misidentified by mechanics, so this should help that too.

Some common symptoms of tune-up problems that can be dealt with by your typical driveway mechanic:

  • Idle speed wrong
  • Stumbling when cold or hot
  • Hesitation at particular RPMs when cold or hot
  • Trying to stall when braking or cornering
  • Car starts, hunts wildly, then stalls
  • Runs rough all the time or at particular RPMs
  • Surge/jerking while rolling at very low RPMs
  • and the dreaded "just doesn’t feel right." The dealer service guys love this one!


This page talks about the main systems that a tune-up needs to cover, and how they work. These are:

  • EGR system
  • Idle control system
  • Ignition system
  • Fuel delivery system.


A step-by-step process for finding problems. Might not make sense until you've read the Background Info page.