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Lexus RX 300 P1354 Code and Misfire Solutions: Common Causes and Fixes

Model: Lexus RX 300 Fault Code: P1354 Posted: 2011-06-15 20:29

I've seen numerous posts with the same symptoms I'm experiencing, but no definitive solutions. It's frustrating—after researching everything possible, once a problem is fixed, people rarely share their resolution. My 1999 Lexus RX300 has 143,000 miles on it. As soon as the engine reaches operating temperature, the Check Engine Light (CEL) triggers a P1354 fault code. This occurs every time, without exception. If I continue driving, additional misfire codes appear: P0300, P0302, P0304, and P0306. Occasionally, the CEL flashes, indicating severe misfiring. The engine runs smoothly above 1500 RPM, but idles very roughly. I've already replaced the spark plugs (which were original), installed a K&N air filter five years ago, and cleaned the MAF sensor with spray cleaner. The vehicle also leaks a small amount of oil—just enough to be noticeable in the driveway, not enough for visible smoke. I’ve replaced the PCV valve and reconnected most vacuum lines during my last spark plug service. A mechanic suggested engine sludge may be clogging the oil control sensor, potentially disrupting the VVT system. While this seems plausible, I've changed the oil twice in the past 5,000 miles, and the second oil was not dirty. Additionally, when I pulled a length of rope from the oil pan during the last service, there was no visible sludge. I’m hesitant to replace sensors randomly without clear evidence. Are there any proven solutions or diagnostic steps for this specific issue on the 1999 Lexus RX300?

Related fault codes

P1354

Comments (4)

Anonymous 2011-06-16 04:48

You should check the engine's idle vacuum at operating temperature—how many inches of vacuum is it reading? A low reading could point to a timing issue. Also, consider whether the catalytic converter might be restricted. If misfires are primarily logged on one bank of a V6 engine, inspect for a slipped camshaft, exhaust restriction on that bank, or a vacuum leak on the intake side of that bank.

Anonymous 2011-06-16 08:19

Great suggestions—thanks! I hadn't considered the catalytic converter and didn’t know how to test it. I’ve avoided checking for vacuum leaks because I’ve never had any past issues, but I do have a vacuum gauge. I’ll pull it out this weekend and check idle vacuum levels. I can already feel low vacuum at low RPM through the brake pedal. While I suspect a timing issue, the engine runs fine when cold, which makes me think the serpentine belt hasn’t slipped—though it should be replaced eventually. It’s a major job in terms of time and cost, so I wanted to resolve the CEL issues first before tackling that. Thanks for the input!

Anonymous 2011-08-04 20:06

I’ve found that a faulty VVT-i sensor is a common cause on both my GS430 and RX300 models. One sensor fails, then after about six months, the second one fails too. Replacement is straightforward—just one 10mm bolt and a plug. It’s worth checking if either of these sensors has failed.

Anonymous 2011-11-28 13:41

Hi rxkevin—I have the same issue on my 2001 Lexus RX300 with P1354 and misfire codes. What did you end up doing to fix it? Any specific steps or parts you used?