Dealing with car troubles can be frustrating, especially when the dreaded check engine light illuminates your dashboard. For many car owners, error codes related to the catalytic converter efficiency, such as “catalyst system Below Threshold Bank 1,” are a common source of anxiety. This code often points towards issues within your vehicle’s emission control system, potentially impacting performance and fuel economy. One DIY mechanic faced this very problem, coupled with excessive oil consumption, in their Honda Integra. This is their journey to resolving these issues, offering valuable insights for anyone encountering similar automotive challenges.
The saga began with classic symptoms: a persistent check engine light and a noticeable drop in miles per gallon (MPG). Further investigation revealed the culprit – a clogged catalytic converter. Initially, a temporary fix was attempted by removing the restrictive components within the catalytic converter housing, essentially gutting it. To manage the “catalyst system below threshold bank 1” error that arises when the downstream oxygen sensor detects insufficient catalytic activity, an angled O2 sensor adapter was installed. This trick often fools the ECU into thinking the catalytic converter is working efficiently. While this eliminated the check engine light and restored MPG, it was far from a permanent or environmentally sound solution. The car would not pass an emissions test, and the underlying problem remained unaddressed.
A used, working catalytic converter was then installed to pass emissions testing. This proved successful initially, but unfortunately, history repeated itself. The replacement catalytic converter eventually succumbed to clogging, bringing back the check engine light and poor MPG. The root cause was becoming clearer: excessive oil burning. The engine was consuming a significant amount of oil – 1.25 quarts per 1000 miles. This excess oil combustion was overwhelming the catalytic converter, leading to its repeated failure and triggering the “catalyst system below threshold bank 1” code. The engine control unit (ECU), in an attempt to compensate for the extra oil being burned, was enriching the fuel mixture, further contributing to poor fuel economy. Moreover, the modified O2 sensor adapter, while masking the error, would not pass a visual emissions inspection, and the environmental impact of running without a properly functioning catalytic converter was a concern.
Faced with these recurring issues and the desire for a lasting solution, the DIY mechanic explored repair options. Quotes from various Midwest automotive shops for a ring job and valve seal replacement ranged from $2,500 to $3,300. Considering the age and mileage (around 120,000 miles) of the Honda Integra, a more cost-effective approach was sought. The decision was made to replace the entire engine with a used, low-mileage unit.
Research led to hmotorsonline dot com, where a JDM (Japanese Domestic Market) B18B engine was sourced for $900, including shipping. This engine was a Japanese variant of the USDM (United States Domestic Market) B18B1 engine originally in the Integra. To ensure compatibility, a local mechanic was found through Facebook to handle the engine swap. For $500, they transferred all necessary USDM sensors, oil pump, brackets, intake manifold, and other components to the JDM engine. This also included replacing the timing belt as preventative maintenance. The cost of new parts required for the swap amounted to $600, bringing the total project cost to approximately $2,000.
This engine replacement proved to be the definitive solution. Since 2012, the Honda Integra, now equipped with the used JDM engine, has driven an additional 25,000 miles without issue. Fuel economy improved to a respectable 27 MPG, and crucially, the car now passes emissions regulations, resolving the “catalyst system below threshold bank 1” concern by addressing the underlying oil burning problem. While the car is now primarily used for occasional drives and stored in a garage, this experience highlights the effectiveness of a used engine replacement as a viable and cost-saving alternative to extensive engine repairs when facing issues like oil consumption and catalytic converter inefficiency.
