Fuel and air code
P2187: System too lean at idle (bank 1)
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $5 | $60 |
| Labor: 0.8 to 2.5 hours × $125 to $175 an hour | $100 | $438 |
| Fees: shop supplies, disposal, diagnostics | $0 | $25 |
| Total, rounded | $100 | $530 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, vacuum leak repair. Which repair your car needs depends on a proper diagnosis.
At idle the engine pulls in only a small amount of air, so a small leak has a big effect. The computer says the cylinder 1 bank is running lean at idle even with the maximum fuel correction. An unmetered air leak, such as a cracked hose or a leaking gasket, is the most common reason.
- Safe to drive?
- Short trips only
- Most common cause
- Vacuum or intake leak
Usually drivable, but a lean engine can misfire and run hot, so get it looked at soon.
What you may notice
- Rough idle
- Stalling
- Hesitation
- Check-engine light
Common causes, most likely first
- Vacuum or intake leak
- Dirty MAF sensor
- Weak fuel delivery
- Leaking intake manifold gasket
Check this first
With the engine idling, look and listen for hissing, check that the oil fill cap and dipstick are seated, and look at the vacuum hoses for cracks. A small unseated cap can leak enough air to set this code.
Other repairs that sometimes fix P2187
| Repair | Typical range, Boston |
|---|---|
| Mass airflow sensor replacement | $130 to $410 |
| Fuel injector replacement (one injector) | $180 to $910 |
| PCV valve replacement | $70 to $240 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P2187 questions
Why only at idle?
Small leaks matter most when the engine pulls very little air. At idle, a leak is a large share of the total, but at higher speed it gets lost in the larger airflow, so the problem fades.
Can a smoke test help?
Yes. Shops blow harmless smoke into the intake and watch where it escapes. The test is quick and often finds the cracked hose or gasket in minutes, so it saves guessing and replacing parts.
Is it the PCV valve?
It can be. A PCV valve or hose that sticks open or cracks lets in extra air that the computer does not measure. The part is inexpensive, so shops often check it early.
How much does it cost to fix P2187?
The most common fix, vacuum leak repair, has a typical range of $100 to $530 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- P0171: Engine getting too much air or too little fuel (bank 1)
- P0507: Engine idle higher than expected
More fuel and air codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.